@conference {4662,
	title = {Dynamic Bandwidth Allocation in MIMO 5G Networks},
	booktitle = {The 20th International Wireless Communications \& Mobile Computing Conference (IWCMC 2024), May 27 {\textendash} 31, 2024, Ayia Napa, Cyprus},
	year = {2024},
	abstract = {The advent of 5G technology has ushered in a new era of wireless communication, characterized by its promise of high data rates, low latency, and enhanced connectivity. In this context, Multiple-Input Multiple-Output (MIMO) systems have emerged as a key enabler, leveraging advanced antenna arrays to simultaneously serve multiple users with increased spectral efficiency. This paper investigates the dynamic resource allocation problem in a MIMO 5G environment, where each user possesses distinct bandwidth requirements. The focus is on optimizing user allocation while considering the limited bandwidth and user capacity of base stations. By harnessing the
power of deep learning techniques, the proposed solution aims to efficiently manage the allocation of users to base station antennas, thereby maximizing overall network performance while accommodating heterogeneous user demands.},
	author = {Nikolaos Prodromos and Damianos Diasakos and Vasileios Kokkinos and Apostolos Gkamas and Christos Bouras and Philippos Pouyioutas}
}
@conference {4664,
	title = {Energy Efficiency Analysis of DUDe 5G Networks},
	booktitle = {The 15th International Conference on Ubiquitous and Future Networks (ICUFN 2024), Jyly 2 {\textendash} 5, 2024, Budapest, Hungary},
	year = {2024},
	abstract = {In this paper we evaluate the energy efficiency of Downlink/Uplink Decoupling (DUDe) systems by considering the energy consumption of each Base Station (BS) and the communication overhead between the BSs and User Equipment (UE). Through extensive simulations, the energy efficiency of DUDe systems is evaluated under various scenarios, such as different UE densities, Base Stations (BSs) configurations, and traffic patterns. The simulation results indicate that the proposed DUDe system can achieve significant energy savings compared to traditional centralized 5G systems. The impact of various parameters on energy efficiency is also analyzed, providing guidelines for designing energy-efficient DUDe systems. The paper emphasizes the significance of energy-efficient design in 5G networks, as it can significantly reduce the operational costs and carbon footprint of the network.},
	author = {Chrysostomos-Athanasios Katsigiannis and Konstantinos Tsachrelias and Vasileios Kokkinos and Christos Bouras and Apostolos Gkamas and Philippos Pouyioutas}
}
@conference {4680,
	title = {Enhancing Real {\textendash} Time IoT Applications: Latency Reduction Techniques in 5G MIMO Networks},
	booktitle = {The 19th International Conference on Broadband and Wireless Computing, Communication and Applications (BWCCA 2024), November 13 {\textendash} 15, 2024, San Benedetto del Tronto, Italy },
	year = {2024},
	abstract = {In the ever-growing field of 5G technology, Massive Multiple Input Multiple Output (MIMO) systems hold the promise of substantial improvements in network capacity and efficiency. However, the demand for low latency, im-posed by real-time Internet of Things (IoT) applications presents some significant obstacles. This study delves into novel approaches to reducing latency within 5G MIMO setups, focusing particularly on the integration of shortened Transmission Time Intervals (TTIs) and preemptive scheduling tactics. Through simulations involving a small-scale MIMO configuration servicing multiple IoT devices, this study thoroughly evaluates the effects of these methods on transmission latency. The desired result is to demonstrate that the adoption of reduced TTIs notably mitigates overall latency, thereby augmenting the efficacy of time-sensitive IoT tasks such as industrial automation and healthcare monitoring systems. This re-search not only contributes to the theoretical progression of 5G communications but also furnishes practical insights for network operators and system designers trying to fine-tune 5G networks for evolving IoT environments. The simulation results indicate that the proposed techniques significantly reduce latency by ap-proximately 30\% compared to standard configurations, particularly benefiting high-priority IoT applications. These findings highlight the effectiveness of shortened TTIs and preemptive scheduling in enhancing the performance of real-time IoT tasks within 5G MIMO networks.},
	author = {Chrysostomos-Athanasios Katsigiannis and Konstantinos Tsachrelias and Vasileios Kokkinos and Christos Bouras and Apostolos Gkamas and Philippos Pouyioutas}
}
@article {4672,
	title = {The Nexus between Wind Energy, Biodiversity Protection and Social Acceptance: Evidence of Good Practices from Greece, Latvia and Poland},
	journal = {International Journal of Environmental and Ecological Engineering , World Academy of Science, Engineering and Technology},
	volume = {18},
	year = {2024},
	pages = {85-94},
	abstract = {Wind power represents a major pathway to curtailing greenhouse gas emissions and thus reducing the rate of climate change. A wind turbine runs practically emission-free for 20 years, representing one of the most environmentally sustainable sources of energy. Nevertheless, environmental and biodiversity concerns can often slow down or halt the deployment of wind farms due to local public opposition. This opposition is often fuelled by poor relationships between wind energy stakeholders and civil society, which in many cases led to conflictual protests and property damage. In this context, addressing these concerns is essential in order to facilitate the proliferation of wind farms in Europe and the phase-out of fossil fuels from the energy mix. The aim of this study is to identify a number of good practices and cases to avoid increasing biodiversity protection at all stages of wind farms{\textquoteright} lifecycle in three participating countries, namely Greece, Latvia, and Poland. The results indicate that although available technological solutions are already being exploited worldwide, in these countries, there is still room for improvement. To address this gap, a set of policy recommendations is proposed to accomplish the wind energy targets in the near future while simultaneously mitigating the pertinent biodiversity risks.},
	author = {Christos Bouras and Eirini Stergiou and Charitini Karakostaki and Vasileios Tzanos and Vasileios Kokkinos}
}
@conference {4663,
	title = {Optimizing Resource Allocation in 5G MIMO Networks Using DUDe Techniques},
	booktitle = {14th IEEE/IET International Symposium on Communication Systems, Networks and Digital Signal Processing (CNDSP 2024), July 17 {\textendash} 19, 2024, Rome Italy},
	year = {2024},
	pages = {454 - 459},
	abstract = {In the landscape of 5G networks, efficient resource allocation stands as a critical factor in meeting the diverse demands of applications and users. This paper delves into optimizing resource allocation within 5G Multiple Input Multiple Output (MIMO) networks by leveraging Downlink/Uplink Decoupling (DUDe) techniques. MIMO technology, enabling the simultaneous transmission of multiple data streams, holds promise for boosting spectral efficiency. However, accommodating the dynamic and diverse user requirements poses a significant challenge in resource allocation. By employing advanced DUDe techniques, this research aims to dynamically allocate resources in 5G MIMO networks, seeking to enhance throughput, minimize latency, and optimize user satisfaction. Through simulation-based analysis, this paper highlights the efficacy of the proposed approach in significantly improving network performance and resource utilization.},
	author = {Konstantinos Tsachrelias and Chrysostomos-Athanasios Katsigiannis and Vasileios Kokkinos and Apostolos Gkamas and Christos Bouras and Philippos Pouyioutas}
}
@conference {4674,
	title = {Power Consumption Analysis in DUDe 5G MIMO Networks},
	booktitle = {15th  International Conference on Network of the Future (NoF 2024), October 2 {\textendash} 4, 2024, Barcelona, Spain },
	year = {2024},
	abstract = {The advent of 5G technology has brought unprecedented advancements in wireless communication, promising higher data rates and improved user experiences. However, the implementation of Multiple-Input Multiple-
Output (MIMO) techniques in 5G networks has significantly increased power consumption, posing a challenge to sustainability and operational costs. This study conducts a comparative analysis of energy efficiency in 5G MIMO networks, specifically between Downlink Uplink Coupling (DUCo) and Downlink Uplink Decoupling (DUDe) techniques. By examining the remaining power in the Base Stations (BSs) of the implemented Heterogeneous Network (HetNet), this analysis evaluates the potential of DUDe over DUCo in managing power consumption. The findings of this study aim to assist network operators, researchers, and policymakers in developing greener
and more sustainable 5G infrastructures for a cleaner, energyefficient future.},
	author = {Chrysostomos-Athanasios Katsigiannis and Apostolos Gkamas and Konstantinos Tsachrelias and Christos Bouras and Vasileios Kokkinos and Philippos Pouyioutas}
}
@conference {4661,
	title = {Simulation Based Energy Efficiency Analysis of DUDe 5G Networks},
	booktitle = {The Twentieth Advanced International Conference on Telecommunications (AICT 2024), April 14 {\textendash} 18, 2024, Venice, Italy},
	year = {2024},
	abstract = {To be able to respond to the explosively increased data traffic demand of 5G and beyond networks (Internet of Things (IoT) , Voice/Video calls, Peer2Peer (P2P) software, etc.), one of the most promising technologies are densified Heterogeneous Networks (HetNets). In HetNets, base stations are brought closer to users with the placement of small base stations, which results in better spectral and energy efficiency for cellular systems. However, the HetNet topology challenges traditional cellular systems. One of the most important challenges is user association. Aiming to avoid the drawback caused by Downlink/Uplink Coupling (DUCo) access in HetNets user association, a Downlink/Uplink Decoupling DUDe Access approach has emerged. By allowing access points in the uplink and downlink association to be different, DUDe greatly improves the uplink performance of HetNets. In this paper, we evaluate energy efficiency and resource allocation of DUDe approach.},
	author = {Chrysostomos-Athanasios Katsigiannis and Apostolos Gkamas and Konstantinos Tsachrelias and Christos Bouras and Vasileios Kokkinos and Philippos Pouyioutas}
}
@article {4671,
	title = {Analyzing mmWave Bands from a techno {\textendash} economic perspective in 5G networks},
	journal = {International Journal of Business Data Communications and Networking (IJBDCN), IGI Global},
	year = {2023},
	abstract = {The data rates used by mobile network subscribers have been augmented the last few years either via excessive social media usage or video-streams. Thus, most traffic is exchanged in video form online. The next decade almost 7-10 devices per person will be connected via the Internet. The Internet of Things (IoT) is a technology contributing in this direction, as simplistic domestic devices such as cookers, fridges etc. are going to be connected in the Internet and will offer the chance of remote managing of these appliances via applications in mobile phones.
Nowadays, mobile subscribers require augmented demands in terms of mobile service experience, which require large network resources. Users are not extremely content by network{\textquoteright}s efficiency and ask for better services in lower prices. They also require coverage on the most remote places, such as high mountains, beaches etc. as social media are a huge part of the everyday life and thus, users want to stay connected as much as possible},
	author = {Christos Bouras and Anastasia Kollia}
}
@conference {4659,
	title = {Bandwidth Optimization Techniques in Heterogeneous 5G Networks Using DUDe},
	booktitle = {The 6th International Conference on Advanced Communication Technologies and Networking (CommNet 2023), December 11 {\textendash} 13, 2023, Rabat, Morocco},
	year = {2023},
	abstract = {The deployment of 5G networks has led to a significant increase in demand for high-speed data rates and improved overall network performance. HetNets are a promising solution for providing coverage and capacity
enhancements for 5G networks. However, one of the key  challenges in HetNets is the optimization of bandwidth allocation. Traditional resource allocation techniques are limited in their ability to provide efficient and effective solutions for 5G networks. To address this challenge, a novel technology called DUDe (Downlink/Uplink Decoupling) has been proposed. DUDe optimizes bandwidth allocation in HetNets by dynamically adjusting the allocation of network resources to user demand and network conditions. The motivation of this paper is to highlight the importance of DUDe technology in macro cell offloading in 5G HetNets. The paper evaluates the
performance of DUDe in comparison to traditional resource allocation techniques and provides insights into the key factors that influence its effectiveness. Moreover, this paper presents a detailed analysis of simulations results and provides recommendations for future research. The findings of this study will be useful for network operators and researchers in developing more efficient and effective resource allocation strategies for 5G networks.},
	author = {Konstantinos Tsachrelias and Chrysostomos Katsigiannis and Vasileios Kokkinos and Apostolos Gkamas and Christos Bouras and Philippos Pouyioutas}
}
@conference {4657,
	title = {A Chatbot Generator for Improved Digital Governance},
	booktitle = {20th European Mediterranean \& Middle Eastern Conference on Information Systems (EMCIS 2023), December 11 {\textendash} 12, 2023, Dubai, UAE,},
	year = {2023},
	pages = {123-134},
	abstract = {Chatbots, the pioneering conversational artificial intelligence (AI) agents, have experienced remarkable growth and integration in various domains. In modern societies, chatbots have emerged as transformative digital entities, revolutionizing the way humans interact with technology. These conversational AI agents have transcended their initial applications to become integral parts of various industries and daily life. One of the most prominent roles of chatbots is in customer service, where they offer round-the-clock assistance, swift issue resolution, and personalized interactions.By handling routine queries and tasks, chatbots free up human agents to focus on complex and specialized issues, thus optimizing overall efficiency and customer satisfaction. To this end, this paper aims to present and describe the architecture of a novel chatbot generator with improved functionality in terms of quality of communication with end users and level of provided services, with a specialized infrastructure understanding the Greek language. The chatbot generator was developed in the framework of a research project and will
be pilot tested by two end-users, the National Bank of Greece (NBG) and the General Secretariat for Information Systems \& Digital Governance (GSIS-DG).},
	author = {Christos Bouras and Damianos Diasakos and Chrysostomos Katsigiannis and Vasileios Kokkinos and Apostolos Gkamas and Nikos Karacapilidis and Yannis Charalabidis and Zoi Lachana and Charalampos Alexopoulos and Theodoros Papadopoulos and Georgios Karamanolis and Michail Psalidas}
}
@conference {4658,
	title = {Chatbot technology asseeement: 40 cases from Greece},
	booktitle = {20th European Mediterranean \& Middle Eastern Conference on Information Systems (EMCIS 2023), December 11 {\textendash} 12, 2023, Dubai, UAE,},
	year = {2023},
	pages = {167-181},
	abstract = {In recent years, the field of Artificial Intelligence has seen significant progress, particularly in the development of chatbots via Natural Language Processing (NLP) technology. Recently, however, there has been a real race in this sector with major technology companies constantly presenting new improved solutions. However, the Greek reality presents several peculiarities and difficulties in adopting modern solutions, both due to the diosyncrasies and rarity of the language and the limited funding capabilities of the Greek economy. The purpose of this research is to evaluate the performance of chatbots in terms of the quality of their responses regarding relevance, naturalness, cohesion, accuracy, vocabulary, as well as to assess the user experience and satisfaction. Another goal is to gain a comprehensive comparative picture of chatbot operation in Greece, both
per question and in comparison, between relevant questions. A guided interview with closed-type questions was chosen as the method of evaluation. The aim is to obtain structured and quantified data in an area where the average internet user is not fully familiarized and does not have previous relevant evaluation experience. Conclusions were drawn per question in order to evaluate the level of solutions in a focused and comparative way to identify possible trends and to confirm the consistency of the responses.},
	author = {Yannis Charalabidis and Thanos Anagnou and Charalampos Alexopoulos and Theodoros Papadopoulos and Zoi Lachana and Christos Bouras and Nikos Karacapilidis and Vasileios Kokkinos and Apostolos Gkamas}
}
@conference {4655,
	title = {On the Development of a Novel Chatbot Generator Architecture: Design and Assessment Issues},
	booktitle = {8th IEEE International Conference on Mathematics and Computers in Sciences (MCSI 2023), October 14 - 16, 2023, Athens, Greece},
	year = {2023},
	abstract = {Chatbots are witnessing remarkable growth in various fields. In modern society, chatbots have evolved into innovative digital entities that have revolutionized the way people interact with technology. These conversational AI agents have gone beyond their initial uses to become an integral part of various industries. One of the most important roles of chatbots is customer service, providing 24/7 support, quick problem resolution, and personalized interactions. Chatbots free up human agents by handling routine queries and tasks, allowing them to focus on complex and specific issues, optimizing the overall efficiency and customer satisfaction. To this end, this paper aims to present the architecture of a novel chatbot generator with improved functionality in terms of quality of communication with end users and level of provided services. In addition, the paper presents the results of two pilot chatbots assessment by users with experience in artificial intelligence and chatbot technology.},
	author = {Christos Bouras and Damianos Diasakos and Chrysostomos Katsigiannis and Vasileios Kokkinos and Apostolos Gkamas and Nikos Karacapilidis and Yannis Charalabidis and Zoi Lachana and Charalampos Alexopoulos and Theodoros Papadopoulos and Georgios Karamanolis and Michail Psalidas}
}
@conference {4654,
	title = {Evaluation of User Allocation Techniques in Massive MIMO 5G Networks},
	booktitle = {The 10th International Conference on wireless Networks and Mobile Communications (WINCOM 2023),  October 26 {\textendash} 28,  2023, Istanbul, Turkey},
	year = {2023},
	abstract = {Massive MIMO (Multiple Input Multiple Output) is a fundamental technique for improving the efficiency of 5G wireless networks. At the base station, it calls for the use of numerous antennas{\textemdash}usually in the dozens or even hundreds. In addition to better coverage and less interference, this enables a large increase in the amount of data that can be delivered and received simultaneously. By enabling more precise signal transmission and reception, Massive MIMO can also result in significant energy savings. The use of optimization techniques can further improve the performance of 5G networks. The aim of this paper is to investigate a signal quality optimization technique for MIMO in which users are allocated to antennas according to different algorithms. For our research, the DeepMIMO simulator produced a dataset that sets up all necessary parameters. In our study, we examine different techniques for user allocation in 5G MIMO Networks. We conclude that transforming the problem of user allocation to a linear assignment problem in order to find the most efficient connection between the users and the base stations is one of the best ways to optimize user allocation.},
	author = {Christos Bouras and Damianos Diasakos and A Apostolopoulos and Vasileios Kokkinos and Philippos Pouyioutas and Nikolaos Prpdromos}
}
@article {4670,
	title = {Long Range Based IoT Search and Rescue System, a Human- Computer Interaction Preliminary Study and Implementation},
	journal = {Computer Networks and Communications, Universal Wiser},
	year = {2023},
	abstract = {Nowadays, IoT has been introduced in different aspects of our lives giving solutions to several problems, one of which is the Search and Rescue (SAR) operations. People that suffer from dementia or people with disease in the autism spectrum tend to elope from their caretaker{\textquoteright}s attention, a fact that can lead to serious problems. Thus, a system that takes into consideration of the multiple requirements is of paramount importance. In this paper, a LoRa based SAR system is proposed in order to help in the localization of people with high risk of going missing. In contrast to most of the related systems, in this research article a different approach has been followed. Instead of focusing on the technology, in our approach a human-centered design has been used, leveraging the knowledge of Human-Computer Interaction (HCI) domain. Thus, the technologies used, are an outcome of the initial study. Finally, the system is evaluated using heuristic evaluation and questionnaires},
	author = {Christos Bouras and Apostolos Gkamas and Spyridon Aniceto Katsampiris Salgado}
}
@conference {4656,
	title = {The Nexus Between Wind Energy, Biodiversity Protection and Social Acceptance: Evidence of Good Practices from Greece, Latvia and Poland},
	booktitle = {17th International Conference on Renewable Energy and Environent (ICREE 2023), October 16 {\textendash} 17, 2023, Athens, Greece,},
	year = {2023},
	pages = {83-88},
	abstract = {Wind power represents a major pathway to curtailing greenhouse gas emissions and thus to reducing the rate of climate change. A wind turbine runs practically emission-free for 20 years, representing one of the most environmentally sustainable sources of energy. Nevertheless, environmental and biodiversity concerns can often slow down or halt the deployment of wind farms due to local public opposition. This opposition is often fueled by poor relationships between wind energy stakeholders and civil society, which in many cases led to conflictual protests and property damage. In this context, addressing these concerns is essential in order to facilitate the proliferation of wind farms in Europe and the phase out of fossil fuels from the energy mix. The aim of this study is to identify a number of good practices and cases to avoid for increasing biodiversity protection at all stages of wind farms{\textquoteright} lifecycle in three participating countries, namely Greece, Latvia and Poland. The results indicate that although available technological solutions are already being exploited worldwide, in these countries there is still room for improvement. To address this gap, a set of policy recommendations is proposed to accomplish the wind energy targets in the near future while simultaneously mitigating the pertinent biodiversity risks.},
	author = {Christos Bouras and Eirini Stergiou and Charitini Karakostaki and Vasileios Tzanos and Vasileios Kokkinos}
}
@conference {4652,
	title = {On the Optimization of User Allocation in Heterogeneous 5G Networks Using DUDe Techniques},
	booktitle = {The 14th International Conference on Ubiquitous and Future Networks (ICUFN 2023), July 4 {\textendash} 7, 2023, Paris France},
	year = {2023},
	abstract = {In previous years, 3G and 4G cellular homogeneous networks configured with macro Base Stations (BSs) relied only on the downlink signal, even though transmission power and interference levels differ significantly between uplink and downlink. In 5G Heterogeneous Networks (HetNet), a new generation which have multiple BSs of different types such as Femto BS and Macro BS, there is the possibility of choosing to receive the data from one BS and transmit them to a different BS, and therefore decoupling the uplink and downlink. Especially, the increasing demand for faster, more reliable, and efficient connectivity has made the optimization of User Equipment (UE) allocation in 5G networks a crucial task. To tackle the challenges posed by heterogeneous 5G networks, this study compares and evaluates the performance of Downlink/Uplink Decoupling (DUDe) and traditional Downlink/Uplink Coupled (DUCo) user allocation approaches. Simulation results show that DUDe UE allocation outperforms DUCo by providing improved network performance and more efficient utilization of network resources in diverse network conditions. These findings have important implications for the design and optimization of 5G networks and provide valuable insights for researchers and practitioners in the field.},
	author = {Konstantinos Tsachrelias and Apostolos Gkamas and Chrysostomos-Athanasios Katsigiannis and Christos Bouras and Vasileios Kokkinos and Philippos Pouyioutas}
}
@conference {4660,
	title = {Optimizing Network Performance in 5G Systems with Downlink and Uplink Decoupling},
	booktitle = {The 6th International Conference on Advanced Communication Technologies and Networking (CommNet 2023), December 11 {\textendash} 13, 2023, Rabat, Morocco},
	year = {2023},
	abstract = {This research paper presents a comprehensive investigation into the optimization of resource allocation in 5G networks through the technique of Downlink and Uplink Decoupling (DUDe). With the growing need for accurate modeling and scenario planning in 5G systems, DUDe allows for the configuration of an additional, lower frequency signal on the uplink to complement the existing uplink signal, rebalancing the uplink/downlink difference at the cell edge and enhancing coverage and network capacity. Drawing on extensive literature and industry trends, this study explores the benefits and challenges of DUDe, considering its impact on network performance, user experience, and future developments. The paper also introduces a simulation-based methodology and experiments to evaluate the  effectiveness of DUDe in improving coverage, capacity, latency, and energy efficiency. The findings contribute to the understanding of DUDe{\textquoteright}s potential in optimizing 5G networks, providing valuable insights for researchers and network operators in designing and deploying efficient resource allocation strategies for enhanced network performance in various scenarios.},
	author = {Christos Bouras and Charalampos Chatzigeorgiou and Vasileios Kokkinos and Apostolos Gkamas and Philippos Pouyioutas}
}
@conference {4653,
	title = {Optimizing Resource Allocation in 5G Networks through Downlink and Uplink Decoupling},
	booktitle = {The 15th International Congress on Ultra Modern Telecommunications and Control Systems and Woorkshops (ICUMT 2023), October 30 {\textendash} November 1, 2023, Ghent, Belgium,pp. 225 -230},
	year = {2023},
	abstract = {This research paper sets out to explore the multifaceted and complex topic of decoupling downlink and uplink in 5G networks, with a view to optimizing resource allocation. Drawing on an extensive range of current literature and industry trends, the authors conduct a comprehensive and in-depth analysis of the potential benefits and drawbacks of decoupling, taking into account the impact on network capacity, flexibility, and user experience. Additionally, the article offers valuable insights into the practical implementation of decoupling in real-world 5G networks, including an exploration of the challenges and considerations that may arise, and potential future developments in this field. Through a rigorous and meticulous examination of the topic, the authors aim to provide an understanding of the subject, offering valuable guidance and insights to future researchers and developers working in this area. With a focus on depth and detail, this paper represents a vital contribution to the ongoing dialogue surrounding decoupling in 5G networks and has the potential to drive significant advancements in the
field in the years to come.},
	author = {Christos Bouras and Charalampos Chatzigeorgiou and Vasileios Kokkinos and Apostolos Gkamas and Philippos Pouyioutas}
}
@conference {4649,
	title = {Reinforcement Learning Approach for Resource Allocation in 5G HetNets},
	booktitle = {The 37th International Conference on Information Networking (ICOIN 2023), January 11 {\textendash} 14, 2023, Bangkok, Thailand},
	year = {2023},
	abstract = {Heterogeneous Networks (HetNets) have been hailed as a critical technology for 5G communications, allowing for the rapid expansion of mobile traffic. HetNets can increase network capacity and serve additional users by installing small cells inside macrocells. However, resource allocation for such networks becomes more challenging than for conventional cellular networks due to interference between small-cells and macrocells, making it more difficult to provide quality of service. Deep Reinforcement Learning (DRL) has opened the door for applications in resource allocation for 5G HetNets, because of recent breakthroughs in the field. We present a unique resource allocation technique based on DRL that may be used to both small and macro cells. According to the resource allocation process, an autonomous {\textquotedblleft}agent{\textquotedblright}, in our case a cell, makes judgments to determine the appropriate BS to assign to a user, and the optimal number of Resource Blocks that should be allocated, while not needing or waiting for any information.},
	author = {Fivos Allagiotis and Christos Bouras and Vasileios Kokkinos and Apostolos Gkamas and Philippos Pouyioutas}
}
@conference {4650,
	title = {State of the Art Analysis of Resource Allocation Techniques in 5G MIMO Networks},
	booktitle = {The 37th International Conference on Information Networking (ICOIN 2023), January 11 {\textendash} 14, 2023, Bangkok, Thailand},
	year = {2023},
	abstract = {The industry is shifting from 4G to 5G, which  promises a tenfold increase in data throughput. However, 5G is about much more than simply higher bandwidth. 5G is basically a re-architecture of network infrastructure that incorporates a number of significant technology advancements. One important aspect of 5G networks is the Resource Allocation (RA), where many promising technologies are implemented, like Multi-User Multiple-Input Multiple-Output (MU-MIMO) and Downlink and Uplink Decoupling (DUDe) and many new technologies like Machine Learning (ML) and Game Theory (GT) must be investigated. This paper presents state of art research for RA
using MU-MIMO, DUDe, ML and GT. The above will be the base for proposing guidance for effective RA algorithm design and implementation for 5G and beyond networks.},
	author = {Christos Bouras and Ioannis Caragiannis and Apostolos Gkamas and Nikos Protopapas and Tasos Sardelis and Kyriakos Sgarbas}
}
@conference {4651,
	title = {Techno-Economic Analysis of IoT Networks in 5G},
	booktitle = {This article evaluates the Techno-economic analysis of IoT networks in 5G. The study analyzed the proposed model for the Internet of Things and the Femtocell in ascertaining the feasibility of the models for the 5G network. The study entirely majors on th},
	year = {2023},
	abstract = {This article evaluates the Techno-economic analysis of IoT networks in 5G. The study analyzed the proposed model for the Internet of Things and the Femtocell in ascertaining the feasibility of the models for the 5G network. The study entirely majors on the analysis of the LoRa WAN network because of its adequate characteristics of low power consumption, easy scalability, and high coverage. It is license-free, which facilitates reduced costs and fast developments. Compared with the expected revenue to be collected during the growth period, the cost elements were Operating Expenditure (OPEX) and Capital Expenditure (CAPEX). The analysis of the results shows that the 5G network is more significant than the 4G LTE because of the lower cost associated with it and the increase in the data transferability that the 5G offers, and the increased number of users.},
	author = {Christos Bouras and Charalampos Chatzigeorgiou and Anastasia Kollia and Philippos Pouyioutas}
}
@conference {4580,
	title = {Applying Machine Learning and Dynamic Resource Allocation Techniques in Fifth Generation Networks},
	booktitle = {The 36th International Conference on Advanced Information Networking and Applications (AINA {\textendash} 2022),  April 13 - 15, 2022, Sydney, Australia},
	volume = {1},
	year = {2022},
	pages = {662-673},
	abstract = {According to Internet of Things (IoT) Analytics, soon, the online devices in IoT networks will range from 25 up to 50 billion. Thus, it is expected that IoT will require more effective and efficient analysis methods than ever before with the use of Machine Learning (ML) powered by Fifth Generation (5G) networks. In this paper, we incorporate the K-means algorithm inside a 5G network infrastructure to better associate devices with Base Stations (BSs). We use multiple datasets consisting of user distribution in our area of focus and propose a Dynamic Resource Allocation (DRA) technique to learn their movement and predict the optimal position, RB usage and optimize their resource allocation. Users can experience significantly higher data rates and extended coverage with minimized interference and in fact, the DRA mechanism can mitigate the need for small cell infrastructure and prove a cost-effective solution, due to the resources transferred within the network.},
	author = {Christos Bouras and Evangelos Michos and Ioannis Prokopiou}
}
@conference {4642,
	title = {A Game Theoretic Approach for Efficient Resource Allocation in 5G Networks},
	booktitle = {The 14th International Congress on Ultra Modern Telecommunications and Control Systes (ICUMT 2022), October 11 {\textendash} 13, 2022, Valencia, Spain},
	year = {2022},
	abstract = {Heterogeneous Networks (HetNets) have been lauded as a key technology for 5G communications, enabling fast growth in mobile traffic. HetNets may also expand the network{\textquoteright}s capacity and serve more users. However, interference between small cells and macro-cells makes Quality of Service (QoS) more difficult to achieve, and thus novel protocols, new technologies, and future trends should also be included in order to provide efficiency in Resource Allocation (RA). Game Theory (GT) concepts have been widely used in a variety of engineering design challenges in which one component{\textquoteright}s activity affects and perhaps conflicts with the actions of other components. As a result, game formulations are utilized, and the idea of equilibrium is applied to find a stable solution for the participants. In this paper, we compare two algorithms used for RA, the first being a classical RA algorithm and the second being a game theoretic one. The game implemented is called {\textquotedblleft}Tragedy of the Commons{\textquotedblright}, and is applied in a non-cooperative network.},
	author = {Aspasia Koukouvela and Christos Bouras and Vasileios Kokkinos and Apostolos Gkamas and Philippos Pouyioutas}
}
@article {4568,
	title = {Honey discrimination based on the bee feeding by Laser Induced Breakdown Spectroscopy},
	journal = {Food Control, Elsevier Science},
	year = {2022},
	abstract = {In the present work, the effects of artificial feeding of bees on the honey are investigated by employing for the first time, Laser Induced Breakdown Spectroscopy (LIBS) by analyzing the emission spectral characteristics of the plasma created on the surface of honey samples. Correlation plots indicating the importance of spectral lines of elements as e.g., Calcium (Ca), Magnesium (Mg), Sodium (Na) and Potassium (K) are constructed, while machine learning algorithms based on Linear Discriminant Analysis (LDA) and Random Forest Classifiers (RFC) are employed to classify the honey samples in terms of the bee food used. The constructed machine learning
models were validated by both cross-validation and external validation, while the obtained accuracies exceeded 90\% of correct classification, indicating the potential of LIBS technique for honey discrimination. The obtained results by LIBS were also validated by HPLC-RID, which is the standard technique used for the analysis of the main honey sugars.},
	author = {Dimitris Stefas and Nikolaos Gyftokostas and Panagiotis Kourelias and Eleni Nanou and Chrysoula Tananaki and Dimitrios Kanelis and Vasileios Liolios and Vasileios Kokkinos and Christos Bouras and Stelios Couris}
}
@inbook {4569,
	title = {An Introduction of Upcoming Radio Resource Management Techniques for 5G Networks},
	booktitle = {Advances in Engineering Research, Nova Science Publishers},
	volume = {46},
	year = {2022},
	pages = {147-188},
	chapter = {3},
	abstract = {5G networks are the next generation of mobile internet connectivity, that are able to offer vastly increased speeds, more reliable connections, minimal latency and more supported devices. 5G networks are expected to supercharge Internet of Things (IoT) technology, so as to provide the infrastructure needed in order to support and transfer large data amounts that will enable a smarter and more connected world. To this direction, 5G incorporates many technologies and mechanisms that aid towards the overall goal, such as Multiple-Input and Multiple-Output (MIMO), Downlink (DL) and Uplink (UL) Decoupling (DUDe) and Machine Learning (ML). These technologies can significantly help towards more efficient resource allocation inside the next generation networks, offering increased spectral efficiency and data rates, better signal coverage, reduced latencies and many more. In this chapter, we will provide insights over the aforementioned technologies through firstly a literature review and later on by analyzing their architecture and their models. We will explain how these technologies can be taken advantage of in order to support the 5G networks and why they are core components of future networks, as it is expected that also 5G and Beyond networks will capitalize on them.},
	author = {Christos Bouras and Vasileios Kokkinos and Apostolos Gkamas and Evangelos Michos and Ioannis Sina and Ioannis Prokopiou and Foivos Allayiotis}
}
@conference {4640,
	title = {A Machine Learning Approach to User Assignment in 5G Networks},
	booktitle = {Global Information Infrastructure and Networking Symposium (GISS 2022), September 26-28, Argostoli, Greece},
	year = {2022},
	abstract = {With the advancement of wireless networks the data needs of the wireless internet have become so great, and the use of 4G and 5G so ubiquitous, that challenges arise in the availability and distribution of resources. In this paper we examine an application of Machine Learning and subsequently Neural Networks to offer a solution to this problem. The, now more than ever, profound availability of processing power greatly empowers and makes the deployment of these tools easier than ever, even in problems where in the past their application would not be feasible. The use of machine learning techniques to distribute resources in wireless networks is investigated and contrasted to a traditional algorithmic method. Scenarios are also entertained in which such approaches might be applicable.},
	author = {Michael Kouris and Vasileios Kokkinos and Apostolos Gkamas and Philippos Pouyioutas and Christos Bouras}
}
@conference {4587,
	title = {An online real-time face recognition system for police purposes},
	booktitle = {The 36th International Conference on Information Networking (ICOIN), Jan. 12 {\textendash} 15, 2022, Bangkok, Thailand},
	year = {2022},
	abstract = {In general, face recognition algorithms are often utilized in order to identify or authenticate a human through a camera feed. However, face recognition algorithms must adapt to real-life uncertainties and noisy environments. This work targets upon extending the existing work of facial recognition algorithms by proposing an online platform that can be used from the police forces towards effective real-time human recognition. The approach on facial recognition is to use and extend the Haar Cascade algorithm for real-time purposes, which is widely considered one for the most efficient and used algorithms for that cause. As for the criminal identification, it will made possible through image pattern recognition between the provided criminal{\textquoteright}s image and snapshots of identified faces from the livestream feed. The platform will include a live feed section with different options for video filters, enabling the user to select the best filter, depending on relevant situation of the physical surroundings for better recognition.},
	author = {Christos Bouras and Evangelos Michos}
}
@conference {4585,
	title = {Performance Analysis of MIMO using Machine Learning in 5G Networks},
	booktitle = {The Eighteenth International Conference on Wireless and Mobile Communications (ICWMC 2022), May 22 {\textendash} 26, 2022, Venice, Italy},
	year = {2022},
	abstract = {Massive Multiple-Input Multiple-output (MIMO) is an important radio antenna technology for mobile wireless networks, such as 5th Generation (5G) with high potential. The use of hybrid analog and digital precoding to minimize the energy consumption as well as the hardware complexity of mixed signal components is an essential strategy. Machine Learning (ML) could be able to boost 5G technologies due to the rising difficulty of configuring cellular networks. More than ever, a ML computational framework focused on successfully processing the expected huge data generated normally by 5G networks with high subscriber cell density, is required. In the Ultra-Dense Networks (UDNs) of 5G and beyond high demanding networks paired with beamforming and massive MIMO technologies, ML struggles to define network traffic aspects distinctively, especially when they are projected to be much more dynamic and complicated. This paper presents a state-of-the-art analysis of the combined and multiple uses of ML along with MIMO technology in 5G Networks.},
	author = {Christos Bouras and Ioannis Prokopiou and Apostolos Gkamas and Vasileios Kokkinos}
}
@article {4547,
	title = {Prediction Mechanisms to Improve 5G Network User allocation and Resource management},
	journal = {Wireless Personal Communications, Springer Verlang},
	year = {2022},
	abstract = {As technology rapidly advances, the number of devices constantly communicating, transmitting and receiving data through the cellular networks keeps rising, posing an unprecedented load on them. Such an increase calls for establishing new methods to manage these devices as well as utilize the data produced by them to establish network architectures that can prevent cellular networks from overloading. To achieve the desired results, we need to optimally allocate network resources to existing users. Resource allocation has traditionally been considered an optimization problem where proposed solutions are hard to implement in real time, resulting in the use of inferior solutions with reduced produced performance. With the introduction of Machine Learning, we propose three mechanisms, intending to utilize network data to improve real time network performance. The first mechanism, a Decision Trees based mechanism aims to improve real time decision making by predicting the optimal matching of users and Base Stations. The second mechanism, a K-means based mechanism intends to tackle network congestion and ensure uninterrupted Quality of Service by predicting the optimal coordinates for placing Base Stations along the network based on traffic data. Finally, a Regression based mechanism manages to predict user movement along the network, resulting in improved resource management and reduced energy waste. These mechanisms can work cooperatively, essentially establishing a network architecture that utilizes prediction to efficiently allocate users and manage available resources.},
	author = {Christos Bouras and Rafail Kalogeropoulos}
}
@conference {4584,
	title = {Resource Allocation In 5G and Beyond Networks for Mu-MIMO Systems},
	booktitle = {The Twenty - First International Conference on Networks (ICN 2022), April 24 - 28, 2022, Barcelona, Spain },
	year = {2022},
	abstract = {The resource allocation problem focuses on finding an optimal allocation of a specific number of resources to maintain Quality of Service (QoS). That is where Multiple-Input Multiple-Output (MIMO) come in as a radio antenna technology. In order to, optimize data speed, minimize errors and improve the radio transmission capacity MIMO utilizes multiple antennas at both the transmitter and the receiver. This technology uses a variety of antennas and paths that carry the data. Each antenna uses different paths. Multi-user MIMO (mu-MIMO) stands for a technology that allows routers to communicate simultaneously with multiple endpoint devices and it is the next evolutionary step of single user MIMO. Over the past decade, significant advances have been made to improve the performance of mu-MIMO. Although non-negligible progress has been achieved so far, optimal algorithms for Resource Allocation (RA) will help better the performance of mu-MIMO by increasing the system{\textquoteright}s performance in terms of throughput, fairness, and QoS. The purpose of this paper is to provide a comparison of different beamforming techniques used for resource allocation and list them in ascending order depending on their efficiency.},
	author = {Eirini Barri and Christos Bouras and Apostolos Gkamas and Vasileios Kokkinos and Aspasia Koukouvela}
}
@conference {4641,
	title = {Techno-economic analysis of Cloud Computing supported by 5G: A Cloud vs On Premise based solutions comparison},
	booktitle = {Broadband and Wireless Computing, Communication and Applications (BWCCA 2022), October 27 {\textendash} 29, Tirana , Albania},
	year = {2022},
	abstract = {Cloud computing has gotten a lot of press in the IT world because it allows users to have instant access to a shared pool of configurable computer resources with no effort on their part. It is now being discussed as an enabler for more flexible, cost-effective, and powerful mobile network implementations in the communication technology (CT) sector.In this paper, a techno-economic analysis of a Cloud-based solution compared to an On-premise based one is developed. The technologies are analyzed in a technical way. Mathematical models that help determine the models{\textquoteright} pricing is analyzed. What is more, several experiments are conducted determining if the advantages and profits outweigh the disadvantages of each proposed solution. Also, the way 5G helps scale all these processes is analyzed. Finally, this article analyzes the conclusions of the work, as well as the result of the techno-economic study that was carried out, to explain to the reader the overall benefits provided to users by exploiting the Cloud Computing technology.},
	author = {Christos Bouras and Charalampos Chatzigeorgiou and Anastasia Kollia and Philippos Pouyioutas}
}
@conference {4588,
	title = {Techno-economic analysis of providers{\textquoteright} profit using Ultra-density in 5G networks},
	booktitle = {20th  Mediterranean Communication and Computer Networking Conference (MedComNet 2022), June 1 {\textendash} 3, 2022, Paphos, Cyprus },
	year = {2022},
	abstract = {Fifth generation of mobile networks plays an important role internationally for the scientific community, as well as for everyday life. The challenges are rising, therefore, it is crucial to study technologies that can meet most requirements. Ultra-density is one of the technologies that appear to be a solution to the problems that arise. In this paper, authors present a techno-economic analysis of ultra-dense implementations and macrocellular deployments. In addition to structural analysis and benefits, authors develop economic models, based on parameters and factors that most affect these technologies. Furthermore, they conduct Sensitivity Analysis (SA) experiments based on those economic models, thus leading to important conclusions. Finally, there are proposals for future research and ways to reduce the higher costs of ultra-density.},
	author = {Christos Bouras and Aikaterini Florou and Anastasia Kollia}
}
@conference {4589,
	title = {Α Machine Learning Mechanism for improved Energy Consumption in 5G Small Cells},
	booktitle = {The 27th  IEEE Symposium on Computers and Communications (ISCC 2022), June 30 {\textendash} July 3, 2022, Rhodes, Greece},
	year = {2022},
	abstract = {By introducing 5G networks in our lives, we are faced with the challenge to lower energy consumption, which is expected to increase significantly. As a result, the communications sector must devise solutions to improve the energy efficiency of 5G networks while maintaining spectrum performance. We propose a Machine Learning Mechanism that provides new sleep mode functionalities, that reduce energy consumption during idle hours, on small cells. We will describe our model and examine its performance using data collected from a simulated environment. Furthermore, we present the results of our findings and conclude that such models are necessary for the introduction of 5G networks. Lastly, possible future steps, are discussed.},
	author = {Foivos Allayiotis and Christos Bouras and Vasileios Kokkinos}
}
@inbook {4497,
	title = {An agent-based simulation model for energy saving in large passenger and cruise ships},
	booktitle = {CRC Press},
	year = {2021},
	abstract = {Undoubtedly, energy saving is of paramount importance in the shipping industry, as far as both the protection of environment and the reduction of the associated operating costs are concerned. In this direction, the
International Maritime Organization aims to reduce ship emissions by at least 50\% by 2050, while ships to be built by 2025 are expected to be a massive 30\% more energy efficient than those built some years ago [IMO,
2018].},
	author = {Christos Bouras and Eirini Barri and Apostolos Gkamas and Nikos Karacapilidis and Dimitris Karadimas and Giorgos Kournetas and Yiannis Panaretou}
}
@article {4521,
	title = {Classification of Greek olive from different regions by machine learning - aided Laser - Induced Breakdown Spectroscopy and Absorption Spectroscopy},
	journal = {Open Access Journal, MDPI, Special Issue Characterization of Olive Products from Greece},
	volume = {26},
	year = {2021},
	abstract = {In the present work, the emission and the absorption spectra of numerous Greek olive oil samples and mixtures of them, obtained by two spectroscopic techniques, namely Laser-Induced Breakdown Spectroscopy (LIBS) and Absorption Spectroscopy, and aided by machine learning algorithms, were employed for the discrimination/classification of olive oils regarding their geographical origin. Both emission and absorption spectra were initially preprocessed by means of Principal Component Analysis (PCA) and were subsequently used for the construction of predictive models, employing Linear Discriminant Analysis (LDA) and Support Vector Machines (SVM). All
data analysis methodologies were validated by both {\textquotedblleft}k-fold{\textquotedblright} cross-validation and external validation methods. In all cases, very high classification accuracies were found, up to 100\%. The present results demonstrate the advantages of machine learning implementation for improving the capabilities of these spectroscopic techniques as tools for efficient olive oil quality monitoring and control.},
	author = {Nikolaos Gyftokostas and Eleni Nanou and Dimitrios Stefas and Vasileios Kokkinos and Christos Bouras and Stelios Couris}
}
@conference {4525,
	title = {Clustering Based User Allocation in 5G Networks},
	booktitle = {The 2021 IEEE International Symposium on Networks, Computers and Communications (ISNCC 2021), October 31 {\textendash} November 2, 2021, Dubai - UAE },
	year = {2021},
	abstract = {Machine Learning is an extremely efficient technique for solving complex problems without the use of traditional programming but rather enabling machines to learn from an input of data and train them to cope with various problems. The rapid growth in the number of active mobile devices, mobile applications and services dictate an efficient utilization of mobile and wireless networking infrastructure. Communication networks need to evolve and valorize Machine Learning methods in order to process large volumes of data without introducing excessive time delay in these computations. Upcoming 5G systems are expected to be the first network infrastructure to support exploding mobile traffic volumes and Machine Learning techniques can be used in order to help manage the rise in data volumes. We present a mechanism for resource allocation in mobile and wireless networks, that effectively utilizes Machine Learning techniques.},
	author = {Christos Bouras and Rafail Kalogeropoulos and Ioannis Sina}
}
@article {4519,
	title = {A Comparative Study of Machine Learning Models for Spreading Factor Selection in LoRa Networks},
	journal = {Journal of Wireless Networks and Broadband Technologies (IJWNBT), IGI Global},
	volume = {10},
	year = {2021},
	pages = {100-121},
	abstract = {Low Power Wide Area Networks (LPWAN) technologies offer reasonably priced connectivity to a large number of low-power devices spread over great geographical ranges. Long Range (LoRa) is a LPWAN technology that empowers energy-efficient communication. In LoRaWAN networks collisions are strongly correlated with Spreading Factor (SF) assignment of end-nodes which affects network performance. In this work, SF assignment using Machine Learning models in simulation environment is presented. This work examines three approaches for the selection of the SF during LoRa transmissions a) random SF assignment b) Adaptive Data Rate (ADR) and c) SF selection through Machine Learning (ML). The main target is to study and determine the most efficient approach as well as to investigate the benefits of using ML techniques in the context of LoRa networks. In this research a library that enables the communication between ML libraries and OMNeT++ simulator was created. The performance of the approaches is evaluated for different scenarios, using the delivery ratio and energy consumption metrics.},
	author = {Christos Bouras and Apostolos Gkamas and Spyridon Katsampiris and Nikolaos Papachristos}
}
@conference {4539,
	title = {Comparison of Techno-Economic Solutions for 5G Networks and Beyond},
	booktitle = {The Seventeenth International Conference on Wireless and Mobile Communications (ICWMC 2021),  July 18 {\textendash} 22, 2021, Nice, France },
	year = {2021},
	abstract = {The fifth-generation (5G) envisions a society that is constantly interconnected with a large number of devices, anywhere and anytime. The developed technologies play a substantial role, allowing low latency, large volumes of data traffic, and improved Quality of Service (QoS). The advent of 5G encourages providers and investors to develop innovative services that meet consumer demands. However, the viability of a new service should be investigated from an economic perspective. Therefore, the introduction of effective techniques concerning the financial evaluation of such services is essential. This paper analyzes 5G technologies and evaluates them in a techno-economic point of view using pricing models. In particular, the main factors used to estimate the different types of costs are Capital Expenditures (CAPEX) and Operational Expenditures (OPEX), which define the viability of each investment. Based on the results obtained, 5G is a profitable investment due to its low cost and increase in the average data consumption of each consumer. Finally, using metrics, it is found that reusing existing sites is less costly than to develop a dense macro-cell network.},
	author = {Christos Bouras and Fotios Kaisoudis and Anastasia Kollia}
}
@article {4538,
	title = {Discrimination of olive oils based on the olive cultivar origin by machine learning employing the fusion of emission and absorption spectroscopic data},
	journal = {Food Control, Elsevier Science},
	volume = {130},
	year = {2021},
	pages = {1-8},
	abstract = {In this work Laser-Induced Breakdown Spectroscopy (LIBS) and absorption spectroscopy aided by machine learning are employed for discriminating some extra virgin Greek olive oils of different olive cultivars for the first
time. LIBS and absorption spectra of extra virgin olive oils belonging to Kolovi and Koroneiki cultivars, as well as mixtures of them, were collected, analyzed, and used to develop classification schemes employing Linear
Discriminant Analysis and Gradient Boosting, the latter allowing the determination of the most important spectral features. Both algorithms were found to provide efficient classification of the olive oil spectra with
accuracies exceeding 90\%. Furthermore, for the first time, the emission spectra of LIBS were fused with the absorption spectra to create predictive models and their accuracies were found to be significantly improved. This
work demonstrates the enhanced capabilities of LIBS and absorption spectroscopy and the potential of their combination for olive oil quality monitoring and control.},
	author = {Christos Bouras and Dimitrios Stefas and Nikolaos Gyftokostas and Panagiotis Kourelias and Eleni Nanou and Vasileios Kokkinos and Stelios Couris}
}
@article {4510,
	title = {Energy efficient mechanism for LoRa networks},
	journal = {Internet of Things: Engineering Cyber Physical Human Systems, Elsevier Science, 2021},
	volume = {13},
	year = {2021},
	pages = {1-13},
	abstract = {Internet of Things (IoT) is the ability of communication between objects and refers to a wide range of applications, such as the Search and Rescue (SAR) operations. SAR applications need long distance connectivity, thus can be benefited by Low Power Wide Area Networks (LPWAN). One LPWAN technology is called LoRa (Long Range). In this context, the WeSAR project has been created that provides a system for locating and rescuing people, especially those who belong to population groups with a very high probability of getting lost. The energy consumption of the wearable devices is important factor in the SAR operations, as the battery should last more than 45 50 hours. Therefore, the proposed system is based on LoRa technology, the user localization is based on LoRa using trilateration and Time Difference of Arrival (TDoA) instead of Geolocation Positioning System (GPS), as GPS increases the energy consumption, and we created an energy-efficient mechanism to tackle the problem of energy consumption. In this paper, an energy efficient mechanism for LoRa networks is presented, that is based on the user{\textquoteright}s state and the battery level of the wearable device. Realistic simulations have been conducted to evaluate the system for both one wearable device, and multiple wearable devices, using different mobility models. The results from the simulations have shown a decrease in the energy consumption in various node mobility models that were tested, without compromising the delivery ratio of the network, something important as the LoRa packets are used for the localization of the lost person.},
	author = {Christos Bouras and Apostolos Gkamas and Spyridon Katsampiris}
}
@conference {4526,
	title = {Energy Efficient Mechanism over LoRa for Search and Reuse operations},
	booktitle = {The 2021 IEEE International Symposium on Networks, Computers and Communications (ISNCC 2021): Smart Cities and the Internet of Everything, October 31 {\textendash} November 2, Dubai - UAE},
	year = {2021},
	abstract = {Search and Rescue (SAR) operations can be vastly benefited by the use of IoT and especially by Low Power Wide Area Networks (LPWAN) technologies, such as Long Range (LoRa). In this framework, the wearable device-based Search And Rescue system (WeSAR) project has been created. The main goals that WeSAR tries to improve are the localization accuracy and the energy efficiency of the wearable device. In this paper, the authors propose an energy-efficient mechanism for LoRa networks, taking into consideration the energy of a real wearable device, containing multiple sensors in a SAR scenario. In this work, we simulate the LoRa network, taking into consideration the various states of a wearable device and the impact of the sensors on the energy consumption, in order to have insights into the mechanism{\textquoteright}s efficiency with multiple nodes, up to 500 nodes. The experiment results reveal significant reductions in the energy consumption of the wearable device and improvement of battery life, in urban and suburban conditions, and in stationary and no stationary node mobility models.},
	author = {Christos Bouras and Apostolos Gkamas and Spyridon Katsampiris}
}
@inbook {4513,
	title = {Exploring SDN \& NFV in 5G Using ONOS \& POX Conytollers},
	booktitle = {Research Anthology on Developing and Optimizing 5G Networks and the Impact on Society, IGI Global 2021},
	year = {2021},
	pages = {187-203},
	chapter = {9},
	abstract = {This article describes how novel functionalities will take advantage of the cloud networking and will gradually replace the existing infrastructure of mobile networks with a virtualized one. Two technologies, namely software defined networking (SDN) and network function virtualization (NFV), offer their important benefits and a combination of them is an answer to the demands raised, such as central office re-architected as a data center (CORD). Open network operating system (ONOS) and POX are SDN controllers and offer an option to combine SDN and NFV addressing many ongoing problems in the field of mobile networks. In this paper, technologies and both controllers are compared and contrasted. Indicative cases of topologies are simulated and help evaluating both controllers. According to the experimental findings, ONOS is one of the most important controllers for practical, theoretical, research and educational purposes, while POX is a useful and simpler controller for other educative applications.},
	author = {Christos Bouras and Anastasia Kollia and Andreas Papazois}
}
@conference {4523,
	title = {Exploring the energy efficiency for Search and Rescue operations over LoRa},
	booktitle = {11th IFIP International Conference on New Technologies, Mobility and Security (NTMS{\textquoteright} 2021), April 19 - 21, 2021, Paris, France },
	year = {2021},
	month = {April 19 - 21},
	abstract = {The Internet of Things (IoT) is one of the pioneering domains of Computer Science and Engineering, that comes to solve a plethora of real-life problems. One of the most promising technologies that aim to provide long-distance transmission while retaining energy consumption at low levels, is Long Range (LoRa). In this paper, a thorough study of the energy efficiency in LoRa based Search and Rescue (SAR) project for people with special needs, called Wearable based Search And Rescue system (WeSAR) is presented. After research the authors propose a LoRa based system, taking into consideration the energy efficiency. The results of the proposed mechanism are encouraging in terms of energy consumption, and the battery can last enough for the majority of the SAR operations, even when the battery is not fully charged. Also, there is no deterioration in terms of the delivery ratio of the network which is important for localization algorithms.},
	author = {Christos Bouras and Apostolos Gkamas and Spyridon Katsampiris}
}
@conference {4528,
	title = {GuideMe: A system for Indoor Orientation and Guidance},
	booktitle = {The Seventh International Conference on Smart Portable, Wearable, Implantable and Disability - oriented Devices and Systems (SPWID 2021), May 30 - June 3, 2021, Valencia, Spain },
	year = {2021},
	abstract = {The demand for indoor navigational systems is increasing daily. The use of navigational systems is ranging from smart cities and robots to visually impaired people support to navigate safely. The GuideMe Project aims to provide guidance and security for people suffering from blindness, and in the time being it is in the final development stage. This paper presents GuideMe Project goals GuideMe Project architecture and GuideMe final prototype. GuideMe Project architecture consists of the wearable device curried the user has, the anchors with which the wearable device works to determine the position of the user, the smartphone that is informed by the system for the route the user must follow and converts the message into audio information through the user{\textquoteright}s headset. The headset in order to guide the user in indoor places and the local server who controls the protocols, and the information are the last parts of the architecture. It is clear that the system is quite complex, it consists of several entities and requires them to work together harmoniously to provide the prescribed functionality, in real-time. All the technologies developed to this final system, each of which has multiple sub-entities as mentioned, handle the required functionality that is the provision orientation of users who are located and moving indoors.},
	author = {Eirini Barri and Christos Bouras and Apostolos Gkamas and Spyridon Katsampiris}
}
@conference {4536,
	title = {GuideMe: A system for Indoor Orientation and Guidance},
	booktitle = {The Seventh International Conference on Smart Portable, Wearable, Implantable and Disability - oriented Devices and Systems (SPWID 2021), May 30 - June 3, 2021, Valencia, Spain},
	year = {2021},
	abstract = {The interest for indoor navigational systems is expanding daily, and concerns among others visually impaired people that cannot navigate safely indoors. The main goal of such systems is to localize and direct the individual that has a wearable device and provide voice commands to navigate indoor buildings. This paper{\textquoteright}s aims to present the design and the implementation of the GuideMe project. GuideMe project{\textquoteright}s goal is the design, implementation and evaluation of a navigation system focused on people that face troubles in indoor moving, utilizing a wearable device. Specifically, the focus group is people suffering from visual impairment. The person carrying the wearable device takes guidelines about the location from indoor UltraWide Band (UWB) anchors. The commands provided are about indoor direction through voice commands, assisting him to avoid obstacles in his route. We present the architecture and the details of the various modules which consist of the proposed indoor navigation system, and finally, some initial evaluations of the proposed system yield promising results.},
	author = {Eirini Barri and Christos Bouras and Apostolos Gkamas and Spyridon Katsampiris}
}
@conference {4572,
	title = {HCI preliminary study and implementation for a LoRa based SAR system},
	booktitle = {The 12th International Conference on Sensor Device Technologies and Applications (SENSORDEVICES 2021), November 14 {\textendash} 18, 2021, Athens, Greece },
	year = {2021},
	abstract = {The subject of this paper is the study and implementation of a Long Range (LoRa) based Search and Rescue system that can help in the localization of people having a high risk of going missing. These people may suffer from dementia, attention disturbance, and distraction, or disease in the autism spectrum, and it is of great importance to be found in a specific time frame, as their life can be in danger. The system is based on LoRa network architecture that enables both long-range communication and low energy consumption. In this paper aspects of the human-computer interaction were taken into consideration in contrast to the majority of the related papers, and is the proposed system is evaluated using heuristic evaluation and questionnaires.},
	author = {Christos Bouras and Apostolos Gkamas and Spyridon Katsampiris}
}
@article {4520,
	title = {Laser-Induced Breakdown Spectroscopy coupled with machine learning as a tool for olive oil authenticity and geographic discrimination},
	journal = {Scientific Reports, Nature Research Journals},
	volume = {11},
	year = {2021},
	abstract = {Olive oil is a basic element of the Mediterranean diet and a key product for the economies of the Mediterranean countries. Thus, there is an added incentive in the olive oil business for fraud through practices like adulteration and mislabeling. In the present work, Laser Induced Breakdown Spectroscopy (LIBS) assisted by machine learning is used for the classification of 139 virgin olive oils in terms of their geographical origin. The LIBS spectra of these olive oil samples were used to train different machine learning algorithms, namely LDA, ERTC, RFC, XGBoost, and to assess their classification performance. In addition, the variable importance of the spectral features was calculated, for the identification of the most important ones for the classification performance and to reduce their number for the algorithmic training. The algorithmic training was evaluated and tested by means of classification reports, confusion matrices and by external validation procedure as well. The present results demonstrate that machine learning aided LIBS can be a powerful and efficient tool for the rapid authentication of the geographic origin of virgin olive oil.},
	author = {Nikolaos Gyftokostas and Dimitrios Stefas and Vasileios Kokkinos and Christos Bouras and Stelios Couris}
}
@article {4546,
	title = {A Laser-Based Method for the Detection of Honey Adulteration},
	journal = {Applied Sciences, MPDI, Special Issue Chemical Composition, Properties and Applications of Honey},
	year = {2021},
	abstract = {In the present work, laser-induced breakdown spectroscopy, aided by some machine learning algorithms (i.e., linear discriminant analysis (LDA) and extremely randomized trees (ERT)), is used for the detection of honey adulteration with glucose syrup. In addition, it is shown that instead of the entire LIBS spectrum, the spectral lines of inorganic ingredients of honey (i.e., calcium, sodium, and potassium) can be also used for the detection of adulteration providing efficient discrimination. The constructed predictive models attained high classification accuracies exceeding 90\% correct classification.},
	author = {Dimitrios Stefas and Nikolaos Gyftokostas and Panagiotis Kourelias and Eleni Nanou and Vasileios Kokkinos and Christos Bouras and Stelios Couris}
}
@article {4524,
	title = {MAES_GR: A Web-Based, Spatially Enabled Field Survey Platform for the MAES Implementation in Greece},
	journal = {Land, MDPI 2021},
	volume = {10},
	year = {2021},
	abstract = {This study presents a standardized approach to collecting, registering, and reporting field-survey data for baseline MAES (Mapping and Assessment of Ecosystems and their Services) information in Greece. This is accomplished through a web-based platform (MAES_GR) exclusively developed under the relevant, nation-wide LIFE-IP 4 NATURA project. Based on the European Commission{\textquoteright}s guidance for ecosystem condition (EC) and ecosystem services (ES) MAES studies, we conceptualized and structured an online platform to support EC and ES assessments, integrating all relevant fields of information needed for registering EC and ES parameters. A novel algorithm calculating EC was also developed and it is available as an integral part of the platform. The use of the MAES_GR platform was evaluated during nationwide field surveys efforts, increasing time efficiency and reducing costs. Field recording of EC and ES pinpoint spatial priorities for ecosystem restoration, conservation and sustainable development. This work highlights that MAES implementation can be favored by the use of technology tools such as mobile survey platforms, developed according to scientific needs and policy guidelines. Such tools, apart from the data inventory phase, can be used for data analysis, synthesis and extraction, providing timely, standardized information suitable for reporting at the local, regional, national and European Union scale.},
	author = {Ioannis Kokoris and Vasileios Kokkinos and Evangelos Michos and Rafail Kalogeropoulos and Marios Charalambides and Agisilaos Kounelis and Eleni Iliadou and Christos K. Damianidis and Giorgos Mallinis and Christos Bouras and Panayotis Dimopoulos}
}
@conference {4571,
	title = {A mechanism for 5G MIMO performance optimization and evaluation},
	booktitle = {The 13th IFIP Wireless and Mobile Networking Conference (WMNC 2021),  October 20 {\textendash} 22, 2021, Montreal, Canada },
	year = {2021},
	abstract = {MIMO (Multiple-Input Multiple-Output) technology has become a fundamental technique in current wireless communications, both in cellular and Wi-Fi networks. Fifth generation networks (5G) are expected to support extremely high data rates and more reliable services. The performance of 5G networks can be significantly improved with MIMO; yet the integration of optimization algorithms can further improve its performance. The purpose of this paper is to study an optimization technique for Channel State Prediction in a MIMO environment. We will examine a specific interconnection between 5G and optimization algorithms, to produce a feasible Channel State Prediction mechanism. For our experiments, we use a Dataset produced by the DeepMIMO simulator, which sets up all necessary parameters for our experiment. On this dataset we apply the Hungarian Algorithm to optimize the total throughput and based on the results we conclude that such mechanism is feasible and required for the introduction of 5G Networks in day-to-day tasks.},
	author = {Dimosthenis Tzanakos and Foivos Allayiotis and Vasileios Kokkinos and Christos Bouras}
}
@conference {4570,
	title = {A Mechanism for Improving the Spectral Efficiency in mu-MIMO for 5G and Beyond Networks},
	booktitle = {The 19th International Symposium on Mobility Management and Wireless Access (ACM Mobiwac 2021), November 22 {\textendash} 26, 2021, Alicante, Spain },
	year = {2021},
	abstract = {The ultimate challenge that arises in 6G and 5G and beyond networks is how the mobile networks of the future will be able to cope with the constantly increasing number of devices. In Multiuser Multiple-Input and Multiple-Output (mu-MIMO), the base station basically serves many users at the same time using the same frequency. The topic considered in this paper is the spectral performance in Downlink mu-MIMO. This paper{\textquoteright}s goal is to improve the achieved spectral efficiency of the communication system, as well as the achieved reliability of the communication link. An algorithm based on downlink scheduling and the resource allocation is proposed to achieve maximum spectral use of the system. Considering user{\textquoteright}s demands, this paper{\textquoteright}s mechanism is able to allocate the potential user of the queue to the {\textquotedblright}best antenna{\textquotedblright} based on its demands and distance. That provokes a larger number of devices that can be supported, always according to the specifications stated in IEEE 802.11ax.},
	author = {Eirini Barri and Christos Bouras and Vasileios Kokkinos and Aspasia Koukouvela}
}
@inbook {4498,
	title = {A Novel Approach to Energy Management in Large Passenger and Cruise Ships: Integrating Simulation and Machine Learning Models},
	booktitle = {Springer Book of SIMULTECH 2020},
	year = {2021},
	abstract = {It has been broadly admitted that the prediction of energy consumption in large passenger and cruise ships is a complex and challenging issue. Aiming to address it, this chapter reports on the development of a novel approach that builds on a sophisticated agent-based simulation model, which takes into account diverse parameters such as the size, type and behavior of the different categories of passengers onboard, the energy consuming facilities and devices of a ship, spatial data concerning the layout of a ship{\textquoteright}s decks, and alternative ship operation modes. According to the proposed approach, outputs obtained from multiple simulation runs are then exploited by prominent Machine Learning algorithms to extract meaningful patterns between the composition of passengers and the corresponding energy demands in a ship. In this way, our approach is able to predict alternative energy consumption scenarios and trigger meaningful insights concerning the overall energy management in a ship. Overall, the proposed approach may handle the underlying uncertainty by blending the process centric character of a simulation model and the data-centric character of Machine Learning algorithms. The chapter also describes the overall architecture of the proposed solution, which is based on the microservices approach.},
	author = {Christos Bouras and Eirini Barri and Apostolos Gkamas and Nikos Karacapilidis and Dimitris Karadimas and Georgios Kournetas and Yiannis Panaretou}
}
@conference {4579,
	title = {An Online Real {\textendash} Time Face Recognition System for Police Purposes},
	booktitle = {The 36th International Conference on Information Networking (ICOIN), Jan. 12 {\textendash} 15, 2022, Bangkok, Thailand (to appear)},
	year = {2021},
	abstract = {In general, face recognition algorithms are often utilized in order to identify or authenticate a human through a camera feed. However, face recognition algorithms must adapt to real-life uncertainties and noisy environments. This work targets upon extending the existing work of facial recognition algorithms by proposing an online platform that can be used from the police forces towards effective real-time human recognition. The approach on facial recognition is to use and extend the Haar Cascade algorithm for real-time purposes, which is widely considered one for the most efficient and used algorithms for that cause. As for the criminal identification, it will made possible through image pattern recognition between the provided criminal{\textquoteright}s image and snapshots of identified faces from the livestream feed. The platform will include a live feed section with different options for video filters, enabling the user to select the best filter, depending on relevant situation of the physical surroundings for better recognition.},
	author = {Christos Bouras and Evangelos Michos}
}
@article {4576,
	title = {Performance Evaluation of Monitoring IoT Systems using LoRaWan},
	journal = {Telecommunication Systems, Springer Verlang},
	year = {2021},
	abstract = {The proliferation of smart devices, or even better, IoT devices, has led to the widespread development of applications that take advantage of these devices. Of particular interest is the precise localization of such a device. However, these use cases become extremely difficult when connectivity to end-devices is required even in areas where the signal is too low or different technologies co-exist for the transmission of the data. In this research work, we study LoRaWan and Wi-Fi as two possible candidates for data transmission. We are particularly focused on the study of the above technologies in terms of performance as well as application development that can be used as rescue monitoring systems. For this reason, we start by describing LoRa as an ideal low power and long-distance communication protocol on the IoT devices compared to the Wi-Fi network. We perform various simulations in terms of time on air transmission, bit error rate by changing important metrics to study the behavior of the whole mechanism. Based on our simulations, the main findings highlight that the contribution of a Spreading Factor (SF) and bandwidth (BW) optimizations can be applied to real hardware for real Search and Rescue (SAR) cases giving improved results in case of coverage and battery extension applications. As a continuation of our research, we developed a monitor application that collects and visualizes data from end-nodes (wearables). These data are processed gateway and network server to The Things Network (TTN) for further analysis. The proposed solution can be used in different rescue monitor scenarios such as identifying and find individuals of vulnerable groups or those belonging to group of people with a high probability of being lost. The purpose of the above solution is to overcome monitor problems on SAR cases, compare with WiFi and suggest a module supporting both technologies in order to be used in real experiments.},
	author = {Christos Bouras and Apostolos Gkamas and Vasileios Kokkinos and Nikolaos Papachristos}
}
@conference {4504,
	title = {Real - Time Geolocation Approach through LoRa on Internet of Things},
	booktitle = {The 35th International Conference on Information Networking (ICOIN 2021), January 13 - 16, 2021, Jesu Island},
	year = {2021},
	month = {January 13 - 16,},
	pages = {186-191},
	abstract = {Internet of Things (IoT) and wireless technologies like LoRa brought more opportunities for application development in a plethora of different fields. One of these is location estimation of real-time objects and people. In this study, we focus on monitoring user{\textquoteright}s location through a wearable IoT device with LoRa connectivity. The paper presents the development and integration of an loT ecosystem (Hardware and Software) which can be used in Search and Rescue (SAR) use cases. The proposed IoT ecosystem is evaluated and deployed inreal-scenarios with established gateways. After that we compare  the existed location-estimation methods in terms of attenuation problem, cost and operation as well to conclude to the most suitable solution that can be integrated in LoRaWAN environments. Finally, the conclusions of this work and improvements for possible future activity are described.},
	author = {Christos Bouras and Apostolos Gkamas and Vasileios Kokkinos and Nikolaos Papachristos}
}
@conference {4507,
	title = {Spreading Factor Analysis for LoRa networks: A supervised learning approach},
	booktitle = {9th World Conference on Information Systems and Technologies (WorldCIST{\textquoteright}21), March 30 - 31 and 1-2 April 1 - 2, 2021, Azores, Portugal},
	year = {2021},
	abstract = {Today, the Internet of Things (IoT) has been introduced in our lives, giving a variety of solutions and applications. The critical requirements for de-vices connected to the IoT are long battery life, long coverage, and low de-ployment cost. Some applications require the transmission of data over long distances, thus Low Power Wide Area Networks (LPWAN) have emerged, with LoRa being one of the most popular players of the market. In order, to improve energy consumption and connectivity problems, machine learning can be used in LoRa networks. In this paper, we intend to improve the energy consumption of end nodes by using machine learning models. For this reason, we present a comparison of classification algorithms, specifically, the k-NN, the Na{\"\i}ve Bayes, and Support Vector Machines (SVM), for the Spreading Factor (SF) as-signment in LoRa networks. The simulation results indicate that, both energy efficiency and reliability in IoT communications could be significantly im-proved using the proposed learning approach. These promising results, which are achieved using lightweight learning, make our solution favorable in many low-cost low-power IoT applications.},
	author = {Christos Bouras and Apostolos Gkamas and Spyridon Katsampiris and Nikolaos Papachristos}
}
@conference {4531,
	title = {Spreading Factor Selection Mechanism for Transmission over LoRa Networks},
	booktitle = {28th International Conference on Telecommunications (ICT 2021), June 1 - 3, 2021, London, UK },
	year = {2021},
	pages = {344-353},
	abstract = {This paper presents a mechanism for Spreading Factor (SF) prediction in LoRa networks for more optimized data transmissions. The proposed mechanism is based on Machine Learning (ML) algorithms and assigns the node{\textquoteright}s SF value based on prior transmission data. This paper examines three different approaches for the selection of the SF during LoRa transmissions a) Random SF assignment b) Adaptive Data Rate (ADR) and c) ML based SF selection. The main target is to study and determine the most efficient approach, as well as to investigate the exploitation of ML techniques in the context of LoRa networks. We created a simple library based on ML libraries, such as Scikit Learn that can be used with the FLoRa an OMNeT++ based LoRa simulator. With the use of this library, it is possible to predict the node{\textquoteright}s SF using ML techniques. Two classification algorithms were tested, the k Nearest Neighbors (k-NN) and Na{\"\i}ve Bayes classifier. Finally, we compared the ML mechanisms with two variants of the ADR mechanism. The approaches performance is evaluated for different scenarios, using the delivery ratio and energy consumption metrics.},
	author = {Christos Bouras and Apostolos Gkamas and Spyridon Katsampiris and Nikolaos Papachristos}
}
@conference {4518,
	title = {User Allocation in 5G Networks Using Machine Learning Methods for Clustering},
	booktitle = {The 35th International Conference on Advanced Information Networking and Applications (AINA - 2021), May 12 - 14, 2021, Toronto, Canada },
	volume = {1},
	year = {2021},
	month = { May 12 - 14, },
	pages = {13-24},
	abstract = {The rapid increase in the volume of devices connected to mobile networks poses unprecedented demands on existing networking infrastructures. Machine Learning is a promising technique, already applied in various sectors of our everyday lives. It enables decision making not with the use of traditional programming but rather by using data to train models to cope with various problems without explicit programming on how to do so. The integration of Machine Learning techniques is deemed necessary in as many processes as possible to help the network face congestion and enable efficient real time decision making. In this paper we present two Machine Learning based mechanisms for improving real time user allocation on the network as well as predicting the best positioning scheme for Smallcell Base Stations to provide effective utilization of the network{\textquoteright}s resources.},
	author = {Christos Bouras and Rafail Kalogeropoulos}
}
@conference {4573,
	title = {Using NOMA scheme for the management of interference and the improvement of performance in 5G networks},
	booktitle = {The 13th International Congress on Ultra Modern Telecommunications and Control Systems and Workshops (ICUMT 2021), October 25 {\textendash} 27, 2021 Virtual event  },
	year = {2021},
	pages = {32-37},
	abstract = {The new generation of 5G networks, compared to 4G networks, is a very important example of change in achieving very high frequencies in the carrier with huge bandwidth, high densities with a huge number of antennas and improved quality of services, making effective interference management necessary. In this paper, we present the contribution of the Non-Orthogonal Multiple Access (NOMA) scheme to improving the performance of 5G networks. We refer to the technique of sequential interference cancellation applied to some NOMA formats, compare NOMA and Orthogonal Multiple Access (OMA) formats in terms of the capabilities they offer users and NOMA{\textquoteright}s significant contribution to Multiple-Input Multiple-Output (MIMO) technology and compare three basic NOMA formats in three different resource and user reporting scenarios. Finally, we present the results of the simulations of the above comparisons and analyze the contribution of each scheme to the improvement of the system performance.},
	author = {Christos Bouras and Vasileios Kokkinos and Georgios Tzioumanis}
}
@conference {4457,
	title = {Blending simulation and Machine Learning models to advance energy management in large ships},
	booktitle = {10th International Conference on Simulation and Modeling Methodologies, Technologies and Applications (SIMULTECH 2020)},
	year = {2020},
	pages = {101-109},
	abstract = {The prediction of energy consumption in large passenger and cruise ships is certainly a complex and challenging issue. Towards addressing it, this paper reports on the development of a novel approach that builds on a sophisticated agent-based simulation model, which takes into account diverse parameters such as the size, type and behavior of the different categories of passengers onboard, the energy consuming facilities and devices of a ship, spatial data concerning the layout of a ship{\textquoteright}s decks, and alternative ship operation modes. Outputs obtained from multiple simulation runs are then exploited by prominent Machine Learning algorithms to extract meaningful patterns between the composition of passengers and the corresponding energy demands in a ship. In this way, our approach is able to predict alternative energy consumption scenarios and trigger meaningful insights concerning the overall energy management in a ship. Overall, the proposed approach may handle the underlying uncertainty by blending the process-centric character of a simulation model and the data-centric character of Machine Learning algorithms.},
	author = {Eirini Barri and Christos Bouras and Apostolos Gkamas and Nikos Karacapilidis and Dimitris Karadimas and Georgios Kournetas and Yiannis Panaretou}
}
@article {4467,
	title = {A comparative study of 4G and 5G Network Simulators},
	journal = {International Journal on Advances in Networks and Services, IARIA},
	volume = {13},
	year = {2020},
	pages = {11-20},
	abstract = {Network simulation is a technique of utmost importance to evaluate new network performance, verify new algorithms and analyze various network topologies. It is used to find results to be expected from a hardware setup without the need for actual implementation. For this reason, there is a plethora of Network Simulation Software applied to different scenarios to evaluate theories and hypotheses. A cellular network is an example of an extremely complex system in which different components impact the overall performance in different ways. The aim of this paper is to study the most common Simulators regarding the deployment of 4G and 5G networks, provide a detailed comparison featuring their main advantages and showcasing potential defects and support the academic community, offering the required data to help choose the necessary one.},
	author = {Christos Bouras and Georgios Diles and Apostolos Gkamas and Andreas Zacharopoulos}
}
@conference {4434,
	title = {Efficient Mechanism of eNB bandwidth in D2D communication in 5G},
	booktitle = {The 34th International Conference on Advanced Information Networking and Applications (AINA - 2020), Caserta, Italy},
	year = {2020},
	abstract = {The device to device (D2D)communication will be a big part of 5G and is responsible for the direct communication between users in range without the relay of Base Station (BS). There are three modes that work in D2D communication based on radio resources and how they are used. In D2D the radio resources that are the same with cellular users the mode is named as reuse mode. The other option is to specify an amount of resources only for D2D users and it is called dedicated mode. In this paper will provide how the Users Equipments (UEs) and the D2D communication itself respond in a D2D communication when an eNB serving only in dedicated mode has to change to reuse mode in order to serve more users. Considering two scenarios, reuse and dedicated the mechanism will provide the values of interference and throughput of eNB in each scenario indicating which mode is better under specific circumstances.},
	author = {Christos Bouras and Eirini Barri}
}
@article {4487,
	title = {Geolocation analysis for SAR systems using LoRaWAN},
	journal = {International Journal of Communication Systems, Wiley InterScience},
	year = {2020},
	abstract = {Low Power Wide Area Network (LPWAN) technologies aiming to provide power-efficient solutions to the field of
Internet of Things (IoT). Over the last years we have seen a significant development within the area of IoT applications.
For many applications, the problem of localization (i.e. determine the physical location of nodes) is critical. An area
study of such use case is also the rescue monitor systems. In this study, we start by describing a solution designed for the
Long Range Wide Area Network (LoRaWAN) to localize position of IoT modules such as wearables used from
vulnerable groups. Through performance study of the behavior of a LoRaWAN channel and using trilateration and RSSI
information, the localization of an IoT wearable can be acquired within a small range. Routing people in need is one of
the use cases the above mechanism could be integrated so as to be able to be tracked by familiar people. After that, we
evaluate the usage of mathematical model of multilateration algorithms using Time Difference of Arrival (TDoA) as a
solution for positioning over LoRaWAN. The research is carried out using simulations in Python by configuring the
constant positions of the Gateways inside an outdoor area. The proposed algorithms can be integrated in application for
tracking people at any time and especially routing people from vulnerable groups. Through multilateration and
algorithm{\textquoteright}s prediction, we can have an accuracy of 40-60m in location positioning, ideal for search and rescue use cases.
We finally summarize the above algorithms{\textquoteright} estimation and general behavior in a SAR system.},
	author = {Christos Bouras and Apostolos Gkamas and Vasileios Kokkinos and Nikolaos Papachristos}
}
@article {4567,
	title = {GuideMe: A Complete System for Indoor Orientation and Guidance},
	journal = {International Journal of Smart Sensor Technologies and Applications (IJSSTA), IGI Global},
	volume = {1},
	year = {2020},
	pages = {36-53},
	abstract = {The interest for indoor navigational systems is expanding daily with concerns among visually impaired people who cannot navigate safely indoors. The main goal of such systems is the localization and direction of the individual who has a wearable device that provides voice commands to navigate indoor buildings. This paper aims to present the design and the implementation of the GuideMe project. The GuideMe project{\textquoteright}s goal is the design, implementation, and evaluation of a navigation system focused on people who face troubles in indoor moving utilizing a wearable device. Specifically, the focus group is people suffering from visual impairment. The person carrying the wearable device takes guidelines about the location from indoor ultrawide band (UWB) anchors. The commands provided are about indoor direction through voice commands, assisting him to avoid obstacles in his route. The authors present the architecture and the details of the various modules, which consist of the proposed indoor navigation system, and some initial evaluations of the proposed system yielding promising results.},
	author = {Eirini Barri and Christos Bouras and Apostolos Gkamas and Spyridon Katsampiris}
}
@conference {4500,
	title = {GuideMe: A Networked Application for Indoor Orientation and Guidance},
	booktitle = {The Sixteenth International Conference on Networking and Services (ICNS 2020), September 27, 2020 - October 01, 2020, Lisbon, Portugal },
	year = {2020},
	abstract = {Today{\textquoteright}s indoor navigational systems are more and more in demand, commonly used for applications such as smart cities, robots and visually impaired people. As far as outdoor navigation is concerned, the Global Positioning System (GPS) technology is still one of the most (if not the most) commonly used approaches. Even though it is still considered an ideal solution for navigating in outdoor areas, challenges and problems arise when GPS is considered for navigation inside buildings due to obstacles (e.g., shopping malls, hospitals, etc.) and because signals cannot be absorbed by the building walls. To tackle the aforementioned issue, other technologies have emerged aimed at indoor navigation, such as Wireless-Fidelity (Wi-Fi), Bluetooth and sensors. This paper{\textquoteright}s contribution is towards indoor navigation and, more specifically, it targets designing and developing a tracking and navigation system aimed at people that experience difficulties in indoor orientation using a wearable device. The user takes direction from the wearable device for the indoor orientation through voice commands helping him to avoid obstacles. The central part of the system is a device that provides the ability to navigate and find a route by voice commands, based on the device{\textquoteright}s location and orientation capabilities.},
	author = {Christos Bouras and Eirini Barri and Apostolos Gkamas and Christina Koulouri and Evangelos Michos and Spyridon Katsampiris}
}
@conference {4462,
	title = {GuideMe: A Networked Application for Indoor Orientation and Guidance},
	booktitle = {The Sixteenth International Conference on Networking and Services (ICNS 2020), September 27, 2020 - October 01, 2020 , Lisbon, Portugal (to appear)},
	year = {2020},
	abstract = {Today{\textquoteright}s indoor navigational systems are more and more in demand, commonly used for applications such as smart cities, robots and visually impaired people. As far as outdoor navigation is consider, the Global Positioning System (GPS) technology is still one of the most (if not the most) commonly used approaches. Even though it is still considered an ideal solution for navigating in outdoor areas, challenges and problems arise when GPS is considered for navigation inside buildings due to obstacles (e.g., shopping malls, hospitals, etc.) and because signals cannot be absorbed by the building walls. To tackle the aforementioned issue, other technologies have emerged aimed at indoor navigation, such as Wireless-Fidelity (Wi-Fi), Bluetooth and sensors. This paper{\textquoteright}s contribution is towards indoor navigation and more specifically, it targets at designing and developing a tracking and navigation system aimed at people that experience difficulties in indoor orientation using a wearable device. The user takes direction from the wearable device for the indoor orientation through voice commands helping him to avoid obstacles. The central part of the system is a device that provides the ability to navigate and route by voice commands, based on the device{\textquoteright}s location and orientation capabilities.},
	author = {Eirini Barri and Christos Bouras and Apostolos Gkamas and Christina Koulouri and Evangelos Michos and Spyridon Katsampiris}
}
@conference {4433,
	title = {IoT Geolocation Performance Using LoRaWAN},
	booktitle = {The 34th International Conference on Advanced Information Networking and Applications (AINA - 2020), Caserta, Italy},
	year = {2020},
	abstract = {Low Power Wide Area Network (LPWAN) technologies aiming to provide power-efficient solutions to the world of IoT. This paper describes a solution based on the Long Range Wide Area Network (LoRaWAN) technology to geolocalise IoT modules such as wearables used from vulnerable groups. Through estimation of the behavior of a LoRaWAN channel and using trilateration and RSSI information, the localization of an IoT wearable can be obtained within a small range. Routing people in need is one of the use cases the above mechanism could be integrated so as to be able to be tracked by familiar people.},
	author = {Christos Bouras and Apostolos Gkamas and Vasileios Kokkinos and Nikolaos Papachristos}
}
@conference {4460,
	title = {A Novel Approach for Handling Diverse Energy Consumption Issues in Large Passenger and Cruise Ships},
	booktitle = {7th International Conference on Energy, Substainability and Climate Change (ESCC 2020), Skiathos, Greece},
	year = {2020},
	abstract = {The prediction of energy consumption in large passenger and cruise ships is certainly a complex and challenging issue. Towards addressing it, this paper reports on the development of a novel approach that builds on a sophisticated agent-based simulation model, which takes into account diverse parameters such as the size, type and behavior of the different categories of passengers onboard, the energy consuming facilities and devices of a ship, spatial data concerning the layout of a ship{\textquoteright}s decks, and alternative ship operation modes. Outputs obtained from multiple simulation runs are then exploited by prominent Machine Learning algorithms to extract meaningful patterns between the composition of passengers and the corresponding energy demands in a ship. In this way, our approach is able to predict alternative energy consumption scenarios and trigger meaningful insights concerning the overall energy management in a ship. Overall, the proposed approach may handle the underlying uncertainty by blending the process-centric character of a simulation model and the data-centric character of Machine Learning algorithms.},
	author = {Eirini Barri and Christos Bouras and Apostolos Gkamas and Georgios Kournetas and Nikos Karacapilidis}
}
@article {4502,
	title = {An online tool on sustainable water management},
	journal = {Tourism: An International Interdisciplinary Journal, Institute for Tourism, Zagreb, Croatia, 2020},
	volume = {68, Νο4},
	year = {2020},
	pages = {450-465},
	abstract = {Water demand strains supply capacity in the Mediterranean coastal areas, affecting negatively the maintenance of natural and cultural heritage. Tackling this subject, the {\textquotedblleft}Coastal areas sustainable tourism water management in the Mediterranean - CASTWATER{\textquotedblright} project aims to support sustainable tourism water management in Mediterranean (MED) coastal areas, by improving the monitoring and assessment of the water sustainability performance of tourism. To this end, the elaboration of an online tool to monitor and assess sustainable tourism water management was envisaged and developed, primarily addressed to tourism sector small and medium-sized enterprises (SMEs). The CASTWATER online tool was designed to so as to provide two different functionalities. On the one hand, SMEs can self-evaluate their performance in sustainable water management and efficiently acknowledge possible actions that promote water efficiency in their tourism establishments. On the other hand, the tool measures, at both regional and local level, the levels of good governance and the effectiveness of water-tourism policies in order to improve sustainable water management. The approach presented in this work is heavily based on the initial technical specifications and end-user feedback, aiding SMEs in understanding, comparing, assessing and rating their performance regarding water efficiency and sustainable water manag},
	author = {Christos Bouras and Vasileios Kokkinos and Evangelos Michos}
}
@article {4466,
	title = {A QoS driven adaptive mechanism for Downlink and Uplink Decoupling in 5G},
	journal = {Internet of Things: Engineering Cyber Physical Human Systems, Elsevier Science},
	volume = {11},
	year = {2020},
	pages = {1-11},
	abstract = {In current cellular networks, cell association is heavily based on the Downlink signal power and all devices are associated with the same Base Station (BS) in Downlink (DL) and Uplink (UL). While as of now this technique has been proved adequate in homogeneous networks where all BSs have similar transmission levels, in increasingly dense heterogeneous networks (HetNets) rate is heavily dependent on the load, which can significantly vary from BS to BS. Due to increased demands for usage over several devices in HetNets, large disparities in the DL pose a threat to the quality of services (QoS) rendered by the network and this technique seems obsolete. Decoupling Uplink and Downlink is the proposed solution, where the UL cell association is not necessarily based on the same criteria as the DL association. We propose using Signal to Noise Ratio (SINR) and Path Loss with Range Extension (PLRE) as factors for choosing the appropriate BS for connection in DL and UL respectively for every user, taking into consideration the BS{\textquoteright}s Resource Block availability, to avoid overloading BSs. We will use simulations to test our approach, with different Path Loss offsets for PLRE, to note the importance of adaptive mechanisms.},
	author = {Christos Bouras and Rafail Kalogeropoulos}
}
@conference {4465,
	title = {Resource Allocation Mechanism for Massive MIMO},
	booktitle = {The Sixteenth International Conference on Networking and Services (ICNS 2020), September 27, 2020 - October 01, 2020 , Lisbon, Portugal},
	year = {2020},
	abstract = {Nowadays, mobile users need faster data speeds and more reliable service. The next generation of wireless networks 5G pledges to commit that, and much more. Multiple-Input, Multiple-Output (ΜΙΜΟ) technology in 5G networks is studied in this paper, with emphasis on the achieved performance in terms of achieved Bandwidth. Multi-antenna technologies, such as MIMO, are anticipated to play a key role in 5G systems, as they will have to handle much higher speeds than today{\textquoteright}s cellular networks and greater network traffic. Specifically, we will refer to Massive MIMO (Ma-MIMO) technology. In this paper, a resource allocation mechanism is proposed from the Base Station (BS) to the available antennas, using the Knapsack Problem (KP) algorithm. Our goal is to evaluate user access throughput to the antennas and to study the case where the BS allocates resources, according to the channel rate it receives from each User Equipment (UE). The scenario executed is about serving the maximum number of UE connected to the BS, in high quality services. Finally, we simulate the results in MATLAB, in order to be able to evaluate the Quality of Service (QoS) that is provided to the UE by the BS, with the resource allocation technique that is proposed.},
	author = {Christos Bouras and Vasileios Kokkinos and Christina Koulouri}
}
@article {4439,
	title = {A Resource - efficient Approach on User Association in 5G Networks using Downlink and Uplink Decoupling},
	journal = {International Journal of Wireless Networks and Broadband Technologies (IJWNBT), IGI Global},
	volume = {9},
	year = {2020},
	pages = {43 - 59},
	abstract = {A user-centered network model can significantly optimize connectivity issues between a user and the corresponding Base Station (BS). This paper shall evaluate the User Centric (UC) model targeted for Fifth Generation telecommunication systems and will attempt to optimize communication between users and BSs. The authors suggest a resource-aware mechanism that targets at improving coverage through the network decoupling into two separate and independent uplink and downlink networks. Our mechanism shall fully respect each user{\textquoteright}s initially requested throughput demands and aims to solve the network user {\textendash} BS association problem with efficient resource management techniques. Simulations revealed that the mechanism perfectly preserves Quality of Service (QoS) and offers increased data rates in favor of ultimate user coverage, in both scenarios. Additionally, Frequency Range 2 offers an increased amount of resources, both increased data rates and higher amounts of devices that are covered by the overall network.},
	author = {Christos Bouras and Evangelos Michos}
}
@inbook {4496,
	title = {Search and Rescue System Based on NB-IoT Wearable Device},
	booktitle = {Principles and Applications of Narrowband Internet of Things (NBIoT), IGI Global},
	year = {2020},
	pages = {195-222},
	chapter = {9},
	abstract = {This chapter presents the design and development of a search and rescue (SAR) system, for the location and provision of aid to people who are missing or in imminent danger, especially those belonging to population groups with a particularly high probability of getting lost. With the use of Low-Power Wide Area Network (LPWAN) technology, such as Narrow Band Internet of Things (NB-IoΤ), authors are able to provide search and rescue solutions for individuals, especially those belonging to groups of people who are more likely to get lost. The central part of the system is a modular {\textquotedblleft}wearable (portable){\textquotedblright} device, while in the framework of the implementation of this system authors have seriously taken into consideration the aspects of energy efficiency in order to provide better battery life.},
	author = {Christos Bouras and Apostolos Gkamas and Spyridon Katsampiris and Nikolaos Papachristos}
}
@conference {4432,
	title = {Techno - economic analysis of MMWave vs Mid - Band Spectrum in 5G networks},
	booktitle = {The 34th International Conference on Advanced Information Networking and Applications (AINA - 2020), Caserta, Italy},
	year = {2020},
	abstract = {Nowadays, users rapidly augment and need more efficient and better-quality network coverage. Therefore, the available spectrum is not able to meet these excessive demands. Several novel technologies and approaches are introduced into the 5G networks. One of these is the MiliMeter Wave (MMWave) spectrum. In this paper, a techno-economic analysis of the MMWave compared to the Mid-Band Spectrum (MBS) is developed. The technologies are analyzed in a technical way. Mathematical models that help determining the models{\textquoteright} pricing are analyzed. What is more, several experiments are conducted using the Sensitivity Analysis (SA) technique determining if the advantages and profits outweigh the disadvantages.},
	author = {Christos Bouras and Anastasia Kollia}
}
@article {4468,
	title = {Techno - economic comparison of Cognitive Radio and Software Defined Network (SDN) cost models in 5G networks},
	journal = {Wireless Personal Communications, Springer Verlang},
	volume = {114},
	year = {2020},
	pages = {1403{\textendash}1430},
	abstract = {5G is anticipated in 2020. In this generation of mobile networks, a great deal of requirements have been set. Although, there are many strong technologies in the telecommunications{\textquoteright} sector they do not respond to the 5G goals. On the other hand, telecommunication operators and providers do not want to invest in new equipment/architectures. Cognitive Radio (CR) and Software Defined Networking (SDN) are two technologies with special and vigorous advantages. In this paper, several technical and economic models are developed. The CR is combined with the Stackelberg game. A Sensitivity Analysis (SA) is implemented and the parameters that impact mostly on the model are pinpointed. It is shown that the CR technology could offer all its fundamental cognitive advantages and even financial profits to the telecommunication companies.},
	author = {Christos Bouras and Anastasia Kollia and Eleftheria Maligianni}
}
@conference {4464,
	title = {Techno-economic analysis of cognitive radio models in 5G networks},
	booktitle = {15th International Conference on Future Networks and Communications (FNC 2020)},
	year = {2020},
	abstract = {The first commercial products of 5G will be released within 2020 and therefore, it becomes an absolute necessity to research whether the key enabling technologies are advantageous for the operators to invest in. One of the most fundamental technologies Cognitive Radio (CR), since there is not much research in the field. This paper develops a techno-economic framework for the CR technology and is contrasted with an already existing model for Software Defined Networks (SDN). A Sensitivity Analysis (SA) indicates the cost parameters that are the most expensive ones and should be reconsidered for the model{\textquoteright}s wide adoption and viability.},
	author = {Christos Bouras and Anastasia Kollia and Andreas Papazois}
}
@article {4311,
	title = {Techno-economic comparison of MIMO and DAS cost models in 5G networks},
	journal = {Wireless Networks, Springer Verlang},
	volume = {26},
	year = {2020},
	pages = {1-15},
	abstract = {High communicational standards have been set for the 5G mobile networks. Therefore, it is of great importance that technological solutions that include all the significant features, such as the high coverage and capacity and low round-trip delays, are adopted for the next generation of mobile networks. Except for their technical efficiency, these technologies should be profitable for providers as well. As a result, the need for limiting the costs spent for the development of these technologies emerges. In this papers, four models two for each one of the two solutions for 5G networks are developed, namely the Multiple Input Multiple Output (MIMO) and the Distributed Antenna System. The architectural models assumed for the techno-economic analyses are presented. The mathematical models for both technologies are developed. Experiments are conducted using prices of the Greek market and also Sensitivity Analysis (SA) is used to pinpoint, which cost parameters are the most expensive ones and therefore it is likely that they discourage providers to invest in them. To our knowledge there are not many studies comparing and contrasting these technologies and there is no SA for MIMO. Therefore, it is considered that research for these models is of vital importance for the next generation of mobile communication networks, as they are foundation stonesfor the formation of 5G.},
	author = {Christos Bouras and Stylianos Kokkalis and Anastasia Kollia and Andreas Papazois}
}
@conference {4459,
	title = {Text to Speech through Bluetooth for People with Special Needs Navigation},
	booktitle = {The Sixteenth International Conference on Networking and Services (ICNS 2020), September 27, 2020 - October 01, 2020 , Lisbon, Portugal},
	year = {2020},
	abstract = {As far as outdoor navigation is considered, the Global Positioning System (GPS) technology is still one of the most (if not the most) commonly used approaches. Even though it is still considered an ideal solution for navigating in outdoor areas, challenges and problems arise when GPS is considered for navigation inside buildings due to the fact that GPS signals cannot penetrate walls/ceilings (e.g., shopping malls, hospitals, etc.) and because signals can be absorbed by the building walls. This paper{\textquoteright}s contribution is navigation system that assists people with special needs using an audio guidance system that incorporates input from a voice recognition system. The central part of the system is a device that is able to identify the position and orientation of the person that carries it and provide the ability to navigate and route by voice commands. The suggested voice synthesis system is used, so as to guide the user through obstacles in indoor locations. The information of the precise location and.orientation of the device is made available to the whole system, through the building{\textquoteright}s network infrastructure, so that the user{\textquoteright}s mobile phone, been connected to the same network and also to the user{\textquoteright}s headset through BLE, is able to send audio commands. For the voice commands, Google Cloud Text-ToSpeech (TTS) will be used, supposed that an online connection is active on the user{\textquoteright}s device.},
	author = {Eirini Barri and Christos Bouras and Apostolos Gkamas and Christina Koulouri and Evangelos Michos and Spyridon Katsampiris}
}
@conference {4461,
	title = {Time Difference of Arrival Localization Study for SAR Systems over LoRaWAN},
	booktitle = {15th International Conference on Future Networks and Communications (FNC 2020)},
	year = {2020},
	abstract = {Over the last years we have seen a rapid expansion within the area of Internet of Things (IoT) applications. For many applications{\textquoteright} use cases, such as rescue monitor systems, the problem of localization (i.e. determine the physical location of nodes) is critical. This paper studies and evaluates the usage of mathematical model of multilateration algorithms using Time Difference of Arrival (TDoA) as a solution for positioning over Long Range Wide Area Network (LoRaWAN). The research is carried out using simulations in Python by configuring the constant positions of the Gateways inside an outdoor area. The proposed algorithms can be integrated in application for tracking people at any time and especially routing people from vulnerable groups. Through multilateration and algorithm{\textquoteright}s prediction, we can have an accuracy of 40-60m in location positioning ideal for search and rescue use cases.},
	author = {Christos Bouras and Apostolos Gkamas and Vasileios Kokkinos and Nikolaos Papachristos}
}
@conference {4463,
	title = {Towards an informative simulation-based application for energy saving in large passenger and cruise ships},
	booktitle = {6th IEEE International Energy Conference (ENERGYCon 2020), Gammarth, Tunisia},
	year = {2020},
	abstract = {Over the years, the need to save energy and efficiently manage its consumption becomes increasingly imperative. This paper reports on the development of a novel application for handling diverse energy consumption issues in large passenger and cruise ships. Our overall approach is based on a comprehensive agent-based simulation model, which takes into account spatial data concerning a ship{\textquoteright}s decks and position of energy consuming facilities, as well as data concerning the ship{\textquoteright}s passengers and their behavior during the operation of the vessel. The proposed application may predict energy consumption for a particular vessel and passenger group and accordingly facilitate informed decision making on energy saving matters.},
	author = {Eirini Barri and Christos Bouras and Apostolos Gkamas and Nikos Karacapilidis and Dimitris Karadimas and Georgios Kournetas and Yiannis Panaretou}
}
@conference {4368,
	title = {5G Νetworks: Advancement and Challenges},
	booktitle = {The Fifteenth International Conference on Wireless and Mobile Communications (ICWMC 2019)},
	year = {2019},
	month = {June 30 - July 4},
	pages = {33-38},
	abstract = {Nowadays, mobile networks consist an indispensable part of everyday life. Although, the advent of 5G is imminent, given that the 2020 is approaching, there are still a lot of addressable questions. It becomes of great significance that the Advancements and Challenges of the 5th generation of mobile networks are presented. The Strong points and the Weak parts should be indicated so that they will be treated. In this paper, a review of the current foundational stones of the 5G networks is completed. The state of all different technologies is noted.},
	author = {Christos Bouras and Paraskevi Fotakopoulou and Anastasia Kollia}
}
@conference {4364,
	title = {Capacity guaranteed sleep mode algorithm for 5G femtocell tier},
	booktitle = {International Symposium on Networks, Computers and Communications (ISNCC{\textquoteright} 19) - Wireless and Mobile Networks},
	year = {2019},
	month = {June 18-20},
	abstract = {The upcoming 5G networks require an advanced planning in terms of coordinating various mechanisms to achieve the highly expected performance growths that they pledge. This coordination becomes more challenging due to the increased density in urban environments of the deployment of small radius base stations, such as femtocells. In this paper we test our proposed mechanism for sleep mode power control in femtocell networks, over a widely used simulated traffic model, adjusted to our scenario. Our sleep mode strategy has been developed for femtocell clusters with the goal of reducing the number of operating femtocells without compromising the data rate performance of their subscribers. Our simulations reaffirm the benefits of our algorithm, especially the reduced number of operating femtocells and the increased offered capacity, when tested in realistic environments.},
	author = {Christos Bouras and Georgios Diles and Konstantinos Nikolareas}
}
@conference {4369,
	title = {Comparison of 4G and 5G Network Simulators},
	booktitle = {The Fifteenth International Conference on Wireless and Mobile Communications (ICWMC 2019)},
	year = {2019},
	month = {June 30 - July 4},
	pages = {13-18},
	abstract = {Network simulation is a technique of utmost importance to evaluate new network performance, verify new algorithms and analyze various network topologies. It is used to find results to be expected from a hardware setup without the need for actual implementation. For this reason, there is a plethora of Network Simulation Software applied to different scenarios to evaluate theories and hypotheses. The aim of this paper is to study the most common Simulators regarding the deployment of 5G networks, provide a detailed comparison featuring their main advantages and showcasing potential defects and support the academic community, offering the required data to help choose the necessary one.},
	author = {Christos Bouras and Georgios Diles and Apostolos Gkamas and Andreas Zacharopoulos}
}
@conference {4414,
	title = {Comparison of LoRa Simulation Environments},
	booktitle = {The 14th International Conference on Broad - Band Wireless Computing, Communication and Applications (BWCCA - 2019), Antwerp, Belgium},
	year = {2019},
	month = {November 7 - 9},
	pages = {374-385},
	abstract = {Internet of Things (IoT) is used more and more in our everyday life, connecting different wireless devices, and their distance can vary from some centimeters to many kilometers. New IoT technologies such as Long Range (LoRa) are emerging enabling power efficient wireless communication over very long distances. Simulation of LoRa networks is quite important, because can be used for the design and the evaluation of LoRa based application without the need of costly implementations or before to proceed to the actual implementation of the system. Choosing the right parameters of the systems like spreading factor can improve the energy consumption of the wireless devices. This paper presents the most important LoRa simulation environments available in the literature and after that, we present a comparative evaluation of LoRa simulation environments. The benefits, the disadvantages and the highlights of each LoRa simulation environment is presented.},
	author = {Christos Bouras and Apostolos Gkamas and Spyridon Katsampiris and Vasileios Kokkinos}
}
@conference {4413,
	title = {Efficient 5G Network Decoupling using dynamic Modulation and Coding Scheme Selection},
	booktitle = {The 14th International Conference on Broad - Band Wireless Computing, Communication and Applications (BWCCA - 2019), Antwerp, Belgium},
	year = {2019},
	month = {November 7 - 9},
	pages = {253-265},
	abstract = {The transmission power limitations in telecommunication systems are tackled by using low code rates and high order modulation schemes, thus achieving high spectral efficiency with lower costs per bit. This paper evaluates the User-Centric model for Fifth Generation wireless telecommunication systems, attempting to efficiently improve user terminal-Base Station communication aspects. We propose a resource-aware method of improving network coverage across all layers by choosing to decouple the overall network into two separate uplink and downlink networks. The algorithm fully respects each user{\textquoteright}s throughput demands and solves the User Equipment {\textendash} Base Station association problem efficiently by choosing the appropriate Modulation and Coding Scheme that maximizes spectral efficiency inside each macro cell coverage area. Results are evaluated for both acceptable frequency ranges defined in 5G New Radio protocol interfaces (namely, Frequency Range 1 and Frequency Range 2) and show that the proposed Modulation and Coding Scheme-based mechanism offers perfect Quality of Service preservation and augmented data rates in favor of ultimate user coverage, in both scenarios. Additionally, due to the extended resources Frequency Range 2 provides, the equivalent simulation not only offers increased data rates compared to Frequency Range 1, but also a lower number of devices unsupported by the mechanism.},
	author = {Christos Bouras and Vasileios Kokkinos and Evangelos Michos}
}
@conference {4415,
	title = {An Energy Efficient Mechanism for Downlink and Uplink Decoupling in 5G Networks},
	booktitle = {The 14th International Conference on Broad - Band Wireless Computing, Communication and Applications (BWCCA - 2019), Antwerp, Belgium},
	year = {2019},
	month = {November 7 - 9},
	pages = {241-252},
	abstract = {In current cellular networks, cell association is heavily based on the Downlink signal power and all devices are associated with the same Base Station in Downlink and Uplink. While as of now this technique has been proved adequate in homogeneous networks where all BSs have similar transmission levels, in increasingly dense heterogeneous networks rate is heavily dependent on the load, which can significantly vary from Base Station to Base Station. Due to increased demands for usage over several devices in heterogenous networks, large disparities in the Downlink pose a threat to the quality of services rendered by the network and this tecnhique seems obsolete. Uplink and Downlink decoupling is the proposed solution, where the Downlink cell association is not necessarily based on the same criteria as Uplink . We propose using SINR and Path Loss with Range Extension as factors for choosing the appropriate Base Station for connection in Downlink and Uplink respectively, taking into consideration the Base Stations{\textquoteright} Resource Block availability, to avoid overloading Base Stations and we will use simulations to test our theory.},
	author = {Christos Bouras and Georgios Diles and Rafail Kalogeropoulos}
}
@conference {4365,
	title = {Resource-Efficient Decoupling in Ultra-Dense 5G Networks},
	booktitle = {International Symposium on Networks, Computers and Communications (ISNCC{\textquoteright} 19) - Wireless and Mobile Networks},
	year = {2019},
	month = {June 18-20},
	abstract = {The evolution of 5G mobile networks is expected to be comprised of small cell deployments within spitting distance of existing macrocell infrastructures. The small cells adoption, which promises to offer an economical solution for improved coverage and data rate, appears to be the key factor at improving network cooperation and system performance. In this paper, we evaluate the User-Centric model for 5G networks, targeted at improving communication between user terminal and Base Stations across all layers. We suggest a cost-effective, resource-aware method for improved mobile outdoor coverage and overall network capacity while fully respecting the user{\textquoteright}s Quality of Service, by decoupling the overall network into downlink and uplink networks. The proposed algorithm determines how the network users in both networks will efficiently connect to a Base Station. The network performances are evaluated in terms of data rates enhancements, association outcome and preservation of the Quality of Service for each user. Our low-complexity algorigthm ultimately manages to serve the vast majority of the users placed inside an ultra-dense network and achieve perfect preservation of Quality of Service, regardless of the number of active users.},
	author = {Christos Bouras and Vasileios Kokkinos and Evangelos Michos}
}
@article {4404,
	title = {Techno - economic analysis for programmable networks},
	journal = {Wiley 5G Ref: The Essential 5G Reference Online, Wiley InterScience},
	year = {2019},
	abstract = {The forthcoming advent of the fifth generation of mobile networks (5G) will boost technology, as new solutions are needed to meet the growing demands of 5G. These novelties are pinpointed both by scientists and elecommunication providers. Programmable logic solutions are going to be used, as they accumulate financial, performance and environmental benefits. The programmable logic nowadays is represented by the combination of the Software Defined Networking (SDN) technology with the Network Function Virtualization (NFV). This combination not only reduces hardware as most network components are replaced by Network Functions or Virtual Machines (VMs), but also offers better resource allocation and provides more bandwidth, CPU etc. to the parts of the network that become more congested. Solutions, such as SDN, may concentrate fundamental advantages and profits, but they appear to face basic problems and therefore, key questions are raised concerning their cost and safety. One of these issues contains all the expenses that need to be made for the acquisition of the technology and the adjustments that need to be incorporated into current infrastructure so that it is able to cover SDN networks as well. This paper analyses a programmable model of SDN combined with NFVs. A Sensitivity Analysis (SA) is held to enable determining the factors, that largely influence the pricing so as to propose ways to significantly reduce several types of costs and propose solutions or research directions to cut down on the expenses of these network factors.},
	author = {Christos Bouras and Anastasia Kollia}
}
@conference {4370,
	title = {The techno-economic models for CR and SDN in 5G},
	booktitle = {12th IFIP Wireless and Mobile Networking Conference (WMNC 2019) Paris, France},
	year = {2019},
	month = {September 11-13 },
	abstract = {5G is closer than ever, considering that in 2020 it will have been released. Existing technologies do not adequately cover the 5G demands, therefore new or modified versions of the existing technologies should be introduced. Telecommunication operators remain skeptical about the costs induced by 5G technologies. In this context, it is fundamental that 5G enabling technologies are analyzed in a techno-economic way. In this paper, authors present models of Cognitive Radio (CR) and Software Defined Networking (SDN). They develop economic models based on the Stackelberg competition, opt for the experimentation parameters and conduct Sensitivity Analysis (SA) experiments that show which are the most influential factors for each technology proposing ways to limit them.},
	author = {Christos Bouras and Anastasia Kollia and Eleftheria Maligianni}
}
@conference {4412,
	title = {Using LoRa Technology for IoT Monitoring Systems},
	booktitle = {10th International Conference on the Network of the Future (NoF 2019), Rome, Italy},
	year = {2019},
	month = {October 1 - 3},
	pages = {134-137},
	abstract = {This paper presents technology comparison scenarios for Internet of Things (IoT) concepts on rescue monitoring. The study starts by comparing WiFi \& LoRa as wireless technologies able to be used by smart devices for data transmission. The IoT end-devices used in these concepts have high requirements in battery saving and for this reason the usage of low-power modules is advisable. This paper focus in rescue monitoring and the goal in the current study is the usage of the two wireless technologies used for data transmission from IoT devices: the already known WiFi and the upcoming LoRa technology. During rescue monitoring, important concepts are
the identification and individuals{\textquoteright} rescue of particularly vulnerable groups or individuals belonging to population groups with a high probability of being lost. A LoRa based gateway and WiFi Router is used to connect the end-devices used in our scenarios to the Internet. The collected data on server application as captured from installed sensors on the IoT modules can be displayed to authorized users through a web or mobile application. The results through simulation and real time experiments indicate that LoRa could be an ideal candidate for rescue monitoring. This study is a first step in creating a more general ecosystem for rescue concepts including all the hardware and software using the LoRa technology as transmission method.},
	author = {Christos Bouras and Apostolos Gkamas and Vasileios Kokkinos and Nikolaos Papachristos}
}
@article {4405,
	title = {WiFiMon - A Tool for Wi-Fi Performance Monitoring and Verification},
	journal = {International Journal of Wireless Networks and Broadband Technologies (IJWNBT), IGI Global},
	volume = {8},
	year = {2019},
	pages = {1-18},
	abstract = {Measuring network quality of a wireless network as experienced by end-users is quite difficult, as there isn{\textquoteright}t a single tool available that can record measurements on all sides of the system. The approach presented in this research work is based on the end-user feedback, giving the opportunity of visualization of network performance in real time. We initially present an overview of the developed tool, called WiFiMon, which has the ability to capture, record measurements and export statistics on the quality of Wi-Fi network as perceived by the end-users. The measurements are initiated by the end-users - without their intervention {\textendash} after they visit a web page or use a mobile application. WiFiMon aims to give a clear understanding of the Wi-Fi network conditions by measuring specific parameters of the network, such as download/upload throughput, and correlate these measurements with raw data from various log files to obtain additional information regarding the performance of specific access points. The results reveal the functionality of the proposed tool and its scalability.},
	author = {Kurt Baumann and Christos Bouras and Vasileios Kokkinos and Nikolaos Papachristos and Kostas Stamos}
}
@conference {4280,
	title = {AL-FEC application on NGMN-Edge computing integrated systems},
	booktitle = {10th International Conference on Ubiquitous and Future Networks (ICUFN 2018), Prague, Chech Rebuplic},
	year = {2018},
	month = {July 3 - 6},
	pages = {364-369},
	abstract = {Edge computing or edge networking is an architecture that uses one or more collaborative multitude of enduser clients or near-user edge devices to carry out a substantial amount of communication, control, management or other operations. Edge Computing for mobile networks is a new technology which is currently under standardization providing an IT service environment and cloud-computing capabilities at the edge of the mobile network in close proximity to the mobile end users. The aim of this technology is to reduce latency, ensure highly efficient network operation and service delivery, providing improved user experience. All of these can be translated into value and can create opportunities for operators, application and content providers enabling them to better utilize the mobile broadband capabilities. Furthermore, edge computing enables a new value chain for end users but also for industries allowing to efficient deliver their applications over the mobile network providing fresh business opportunities and new use cases. FEC is a feedback free error recovery method where the sender introduces redundant data in advance with the source data enabling the recipient to recover from different arbitrary packet losses. Recently, the adoption of FEC error control method has been boosted by the introduction of the powerful RaptorQ Application Layer FEC (AL-FEC) codes. In this work we propose the integration of AL-FEC error protection application at the edge layer. We propose a novel AL-FEC application architecture scheme based on RaptorQ codes and we analyze the performance enhancements such an error control architecture can introduce on NGMN-edge computing integrated systems.},
	author = {Christos Bouras and Nikolaos Kanakis}
}
@conference {4277,
	title = {DAS modifications for more efficient network cost in 5G},
	booktitle = {14th International Wireless Communications and Mobile Computing Conference, Limassol, Cyprus},
	year = {2018},
	month = {June 25 - 29},
	pages = {1110 - 1115 },
	abstract = {Demanding goals have already been described concerning the next generation of mobile networks. In order to address these requirements, novel technologies are introduced or new concepts are integrated into conventional ones. In this paper, a modified Distributed Antenna System (DAS) architecture is described. Several hardware components are replaced with Network Function Virtualization (NFV) techniques, which are introduced in modern architectures so as to contribute in reducing capital and operational expenses. The model is described mathematically, is compared and contrasted with the conventional model proposed by authors in past research activity. Simulation scenarios help concluding into fundamental results concerning which are the most dissuasive cost factors e.g. bandwidth, frequency, capacity, coverage, etc. Several conclusions are summarized.},
	author = {Christos Bouras and Anastasia Kollia and Andreas Papazois}
}
@article {4326,
	title = {Evolving AL-FEC application on 5G NGMN-Edge computing systems},
	journal = {Technology and Engineering Systems Journal, Special Issue on Multidisciplinary Sciences and Engineering (ASTEJS), Advances in Science},
	volume = {3},
	year = {2018},
	pages = {152-160},
	abstract = {Fifth generation of mobile networks (5G) comes to cope with the context of the new mobile telecommunications era. Edge computing is a new collaborative technology under standardization utilizing end-user devices or near-end-user edge devices to operate processing, communication, or control operations. The achievement of efficient error control is a very critical aspect in the successful development of 5G Next Generation Mobile Networks (NGMN). Especially utilizing Forward Error Correction (FEC) codes on the application level is an efficient approach on improving error control on NGMN since it is adopted in several mobile multicast standards. FEC is a feedback free error control technique where redundant data are introduced with the source data to enable the recipient recovering from packet losses with an interesting approach on applying AL-FEC error protection introduces deterministic or randomized online algorithms. Based on this we present a novel online scheme on applying AL-FEC application on the context of the AL-FEC policy online problem. In this work we present an online algorithm based on feedback received from mobile end-users which adapts the introduced protection based on this. Another aspect of this work is the utilization of AL-FEC protection on the edge level based on RaptorQ FEC codes.},
	author = {Christos Bouras and Nikolaos Kanakis}
}
@conference {4224,
	title = {Evolving AL-FEC application towards 5G NGMN},
	booktitle = {9th IFIP International Conference on New Technologies, Mobility and Security, Paris, France},
	year = {2018},
	month = {February 26-28},
	pages = {1-15},
	abstract = {The fifth generation of mobile technology (5G) is positioned to address the demands and business contexts of 2020 and beyond. Therefore, in 5G, there is a need to push the envelope of performance to provide, where needed, for example, much greater throughput, much lower latency, ultra-high reliability, much higher connectivity density, and higher mobility range. A crucial point in the effective provisioning of 5G Next Generation Mobile Networks (NGMN) lies in the efficient error control and in more details in the utilization of Forward Error Correction (FEC) codes on the application layer. FEC is a method for error control of data transmission adopted in several mobile multicast standards. FEC is a feedback free error recovery method where the sender introduces redundant data in advance with the source data enabling the recipient to recover from different arbitrary packet losses. Recently, the adoption of FEC error control method has been boosted by the introduction of powerful Application Layer FEC (AL-FEC) codes. Furthermore, several works have emerged aiming to address the efficient application of ALFEC protection introducing deterministic or randomized online algorithms. In this work we propose a novel AL-FEC scheme based on online algorithms forced by the well stated AL-FEC policy online problem. We present an algorithm which exploits feedback capabilities of the mobile users regarding the outcome of a transmission, and adapts the introduced protection respectively. Moreover, we provide an extensive analysis of the proposed ALFEC algorithm accompanied by a performance evaluation against common error protection schemes.},
	author = {Christos Bouras and Nikolaos Kanakis}
}
@article {4223,
	title = {Exploring SDN \& NFV in 5G Using ONOS \& POX Controllers},
	journal = {International Journal of Interdisciplinary Telecommunications and Networking, (IJITN), IGI Global 2018},
	volume = {10},
	year = {2018},
	pages = {46-60},
	abstract = {Novel functionalities will take advantage of the cloud networking and will gradually replace the existing infrastructure of mobile networks with a virtualized one. Two technologies, namely Software Defined Networking (SDN) and Network Function Virtualization (NFV), offer their important benefits and a combination of them is an answer to the demands raised, such as Central Office Re-architected as a Data Center (CORD). Open Network Operating System (ONOS) and POX are SDN controllers and offer an option to combine SDN and NFV addressing many ongoing problems in the field of mobile networks. In this paper, technologies and both controllers are compared and contrasted. Indicative cases of topologies are simulated and help evaluating both controllers. According to the experimental findings, ONOS is one of the most important controllers for practical, theoretical, research and educational purposes, while POX is a useful and simpler controller for other educative applications},
	author = {Christos Bouras and Anastasia Kollia and Andreas Papazois}
}
@article {4259,
	title = {MCS Selection Exploiting Femtocells Utilization in Multicast Transmissions},
	journal = {International Journal of Communication Systems, Wiley InterScience},
	volume = {31},
	year = {2018},
	abstract = {Multicast-Broadcast over Single Frequency Network (MBSFN) technology, as introduced by the Long Term Evolution Advanced (LTE-A) group, is expected to be part of the upcoming cellular systems offering resource efficiency to broadcast services. MBSFN transmission is suitable to serve multicast groups searching the same content. In addition, the fast emerging technology of femtocells networks and their hybrid nature can lead to efficient resource sharing between non-subscribed users when located inside their coverage. The focus of this manuscript is twofold; firstly, we have contacted simulation experiments to compare the MBSFN transmission with the traditional PTP transmission for various femtocell distributions and network topology changes; secondly, a novel multicast transmissions mechanism is proposed from non-subscribed users who exploit femtocells resources for broadcast services, without limiting user{\textquoteright}s data requirements. The simulation results lead to a significant system{\textquoteright}s performance in terms of average throughput, total capacity and energy consumption.},
	author = {Christos Bouras and Nikolaos Kanakis and Vasileios Kokkinos and Nikolaos Papachristos and Demosthenes Vouyioukas}
}
@article {4132,
	title = {Peer-to-peer live video streaming with rateless codes for massively multiplayer online games},
	journal = {Peer-to-Peer Networking and Applications, Springer Verlang},
	volume = {11},
	year = {2018},
	pages = {44-62},
	abstract = {<p class="rtejustify">We present a multi-level multi-overlay hybrid peer-to-peer live video system that enables players of Massively Multiplayer Online Games to simultaneously stream the video of their game and watch the game videos of other players. Each live video bitstream is encoded with rateless codes and multiple trees are used to transmit the encoded symbols. Trees are constructed dynamically with the aim to minimize the transmission rate at the source while maximizingthe number of served peers and guaranteeing on-time delivery and reliability. ns-2 simulations and real measurements on the Internet show competitive performance in terms of start-up delay, playback lag, rejection rate, used bandwidth, continuity index, and video quality.</p>
},
	author = {Shakeel Ahmad and Christos Bouras and Eliya Buyukkaya and Muneeb Dawood and Raouf Hamzaoui and Vaggelis Kapoulas and Andreas Papazois and Gwendal Simon}
}
@conference {4324,
	title = {Performance evaluation of LoraWan physical layer integration on IoT devices},
	booktitle = {Global Information Infrastructure and Networking Symposium (GIIS 2018), Thessaloniki, Greece},
	year = {2018},
	abstract = {Due to the constant motion of wireless devices in the Internet of Things (IoT), infrastructure wireless networks cannot provide connectivity at all times, in comparison with ad hoc networks, which are more easy to use and are based on abstract and continuously altering topologies. LoraWan, as a Long Range Wide Area Network specification recommended by the LoRa Alliance, is a low power and long distance communication protocol suitable for IoT environments and applications to different domains such as healthcare and smart farming. This IoT concept is gaining a rapid growth on the IoT market and is simultaneously improving our living environment. In this paper, we first briefly introduce LoRa as an efficient solution of physical layer integration on the IoT devices. We then conduct a performance evaluation taking into consideration metrics such as bit error rate, time on air transmission based on Signal to Noise Ratio (SNR) and Spreading Factors modifications for different bandwidth values.},
	author = {Christos Bouras and Vasileios Kokkinos and Nikolaos Papachristos}
}
@conference {4325,
	title = {Sleep mode strategies for dense small cell 5G networks},
	booktitle = {The 10th International Congress on Ultra Modern Telecommunications and Control Systems (ICUMT 2018), Moscow, Russia},
	year = {2018},
	pages = {28 - 33},
	abstract = {The evolution of the fifth generation (5G) of mobile networks tends towards the prevalence of dense femtocell deployments, which offer improvements in data rate and overall network{\textquoteright}s capacity. Small cell deployments and particularly femtocells provide an attractive, cheap and flexible solution for the increased traffic demand. However, the resulting dense networks are characterized by challenges, too, such as increased interference and resource allocation. In this paper, we propose ways to address these difficulties by combining hybrid access, sleep mode and a power control mechanism. Simulations show that the above mechanism leads to improved capacity and throughput for subscribers, along with improved energy efficiency, without compromising the non-subscribers performance.},
	author = {Christos Bouras and Georgios Diles and Dimitrios Ntoutsos}
}
@conference {4323,
	title = {Techno-economic analysis of MIMO \& DAS in 5G},
	booktitle = {11th IFIP Wireless and Mobile Conference, Prague, Chech Rebuplic},
	year = {2018},
	pages = {73-80},
	abstract = {2020 will be the year, in which 5G is going to be put into operation, therefore, it is fundamental that all enabling technologies are analyzed in a technical and economic way. The business sector is not very favorable in investing into novel technologies. In this paper, authors propose a techno-economic model for the Multiple Input Multiple Output (MIMO) tech- nology and compare it to the previously developed model for the Distributed Antenna Systems (DAS). Firstly, the experimentation models are analyzed. Secondly, the mathematical models are presented and the specific parameters are opted. Several experiments help comparing and contrasting the two different technologies. There are not many works concerning the technoeconomic perspectives of MIMO comparing it with the DAS, this research contributes in this direction.},
	author = {Christos Bouras and Stylianos Kokkalis and Anastasia Kollia and Andreas Papazois}
}
@article {4191,
	title = {Analyzing Small - cells and Distributed Antenna Systems from Techno - economic Perspective},
	journal = {International Journal of Wireless Networks and Broadband Technologies (IJWNBT), IGI Global},
	volume = {6},
	year = {2017},
	pages = {45-64},
	abstract = {<p class="rtejustify">Next-generation of mobile technologies is expected to largely augment the system{\textquoteright}s peak data rates and cut down on the round-trip delays. The main idea of using ultra-density or DAS (Distributed Antenna Systems) based on their properties, is that they are able to increase efficiency and expand network capacity without the need for more spectrum resources by redistributing the existing ones, depict them as the key solutions for the future mobile networks. Small cells and DAS were launched mainly for addressing the issue of limited connectivity indoors.<br />
There are several other important benefits of these technologies, which constitute them as bases for future generations of mobile networks, such as 5G (5G-PPP, 2014). Femtocells{\textquoteright} benefit is that they provide ultra-density, which is expected to be one of the essential features of 5G. Ultra-dense networks coexist with the existing macrocellular ones forming altogether heterogeneous networks and fulfill the requirements and the network{\textquoteright}s future demands. Scientists and researchers have decided to move towards this direction by conducing several research activity in the area (Networld2020 ETP, 2014; IWPC, 2014).<br />
The future mobile networks are going to demand a large network coverage. DAS would be an ideal solution to deal with the limited spectrum, because it provides repeaters, that are connected to the antenna system. It also serves the augmenting numbers of the smart devices, that in the future will be connected to the Internet or the smart home devices of the owner{\textquoteright}s home network as we move dynamically to the Internet of Things.<br />
This paper studies the techno-economic aspects of ultra-dense and DAS deployments. It presents the characteristics and advantages for all their parts, as well as a techno-economic modeling of these deployment types. The defined models are used for the investigation of the upper technologies from an economic point of view. They provide an insight in the future financial and pricing aspects of these solutions and consist a useful tool for the definition of financing and pricing policies towards economically viable deployments. The authors define models for selecting the most appropriate network architectural solution for public buildings{\textquoteright} indoor coverage. Cost, investment, materials, coverage and capacity are the parameters that are taken into account for the definition of their models. The main scientific contribution of this paper is that it includes multiple case-study examples of the techno-economic models as well as results of conducted experiments. It also analyzes and presents a techno-economic model and summarizes the main research activity in the particular field.<br />
The remaining part of this paper is structured as follows: the second section refers to the related research that has been conducted so far. The third section presents the architectures of ultra-dense and DAS deployments used in the models. In the following section we describe cost models for ultra-dense and DAS deployments. In the next section we define the parameterization of the cost models. In the sixth section we conduce some experimental scenarios and analyze the corresponding results. Finally, in the seventh section we conclude our paper with the most fundamental conclusions realized in the experimental procedure and in the final section we list some ideas for future research work in the field of mobile network technologies.</p>
},
	author = {Christos Bouras and Vasileios Kokkinos and Anastasia Kollia and Andreas Papazois}
}
@article {4139,
	title = {Dense deployments and DAS in 5G: a techno-economic comparison},
	journal = {Wireless Personal Communications, Springer Verlang},
	volume = {19},
	year = {2017},
	month = {1777-1797},
	abstract = {<p class="rtejustify">5G wireless telecommunications require rapid data traffic and high network speed. Thus, it is important to focus on technologies that are capable of meeting these high demands. On the other hand, the cost calculation of installing, maintaining and operating a network deployment, plays an important role for its adoption by an enterprise or a network provider. In this paper, there is a presentation of cost models for Distributed Antenna Systems (DAS) and small cells, because these two technologies offer significant benefits and meet the needs of the next generation of mobile networking. A Sensitivity Analysis (SA) of several network components, such as the allocated bandwidth, the running costs, the periodical interest rate, the base station, the equipment, the power consumption, the backhauling, the implementation costs and throughput density is analyzed. Throughput density and several important information are listed and calculated, according to public data. All these components are tested, using parameters and variables to represent them in mathematical equations model resulting in a cost provision for the next five years. Then, the overall and the individual costs are computed, namely the Total Cost of Ownership (TCO), the Capital (CAPEX) and the Operational (OPEX) expenditures for several throughput density prices according to the suggested pricing models. The paper concludes by drawing fundamental conclusions for the expenses and as a result, for the viability of each technological suggestion and it ends up offering ideas for future research activity in the field.<br />
\&nbsp;</p>
},
	author = {Christos Bouras and Anastasia Kollia and Andreas Papazois}
}
@conference {4196,
	title = {Distributed Sleep Mode Power Control in 5G Ultra Dense Networks},
	booktitle = {15th International Conference on Wired \& Wireless Internet Communications (WWIC 2017), St. Petersburg, Russia},
	year = {2017},
	month = {June 21 - 23},
	pages = {65-76},
	abstract = {<p class="rtejustify">The upcoming 5G networks are characterized by ultra dense deployments of small cells. These structures are capable of providing the much desired increase in capacity and data rates. The limited resources though present challenges on how they will be shared among the high number of base stations. Distributed coordination will play a big part in resource allocation. In this paper, we present a power control mechanism for dense femtocell deployments which utilizes sleep mode strategies and spectrum sharing among users. The mechanism exhibits increased throughput for the femtocell subscribers, preserving non-subscribers performance and increasing the network{\textquoteright}s energy efficiency.</p>
},
	author = {Christos Bouras and Georgios Diles}
}
@conference {4187,
	title = {Energy efficiency in sleep mode for 5G femtocells},
	booktitle = {Wireless Days Conference 2017 (WD 2017)},
	year = {2017},
	month = {March 29 - 31},
	pages = {143-145},
	abstract = {<p class="rtejustify">Energy efficiency is a major requirement for next generation mobile networks both as an end to reduce operational expenses and to increase the systems{\textquoteright} ecological friendliness. Another integral part of 5G networks is the increased density of the deployment of small radius base stations, such as femtocells. Based on the design principle that demands a system to be active and transmitting only when and where it is needed, we evaluatethe energy savings harvested when sleep mode techniques are enforced in dense femtocell deployments. We present our novel variations of sleep mode combined with hybrid access strategies and we estimate capacity and energy benefits. Our simulations show significant advantages in performance and energy efficiency.</p>
},
	author = {Christos Bouras and Georgios Diles}
}
@conference {4220,
	title = {Energy savings in power control fro 5G dense femtocells},
	booktitle = {12th International Conference on Broa-Band Wireless Computing, Communication and Applications (BWCCA - 2017)},
	year = {2017},
	month = {November 8-10},
	pages = {299-308},
	abstract = {The dramatic increase in traffic observed in the recent years in mobile networks is not expected to slow down. Increasing the number of deployed base stations of different range and capabilities creating ultra dense networks is one of the solutions that will be adapted in order to cover the demand. Energy efficiency schemes are needed in order to keep the energy impact of such an approach limited. In this paper we focus on densely deployed femtocells (clusters) evaluating the power savings resulted from a power controlled sleep mode mechanism. The mechanism tries to reduce the number of operating closed access femtocells, by providing perfofmance incentives to the clusters subscribers to coordinate reducing energy consumption without compromising their throughput. Simulations investigate the different levels of power savings depending on the chosen configuration
and the deployment density.},
	author = {Christos Bouras and Georgios Diles and Theodoros Moulias}
}
@conference {4192,
	title = {Extension to Middleware for IoT Devices, with Applications in Smart Cities},
	booktitle = {2nd  EAI International Conference on ICT Infrastructures and Services for Smart Cities (IISSC 2017), Brindesi, Italy},
	year = {2017},
	month = {April 20 - 21},
	abstract = {<p class="rtejustify">This work proposes extensions toWubby (a device-level software platform for IoT devices, a technology developed by Econais A.E.) to support wireless modules for mobile networks (4G / LTE-A, and also supporting the forthcoming 5G). The proposed extension leverages the use of such modules, as it allows easy programming and existing code re-use. It thus adds a compatibility layer across the di erent modules as it a common set of classes for the wireless modules. The system can be used to support the networking aspects of a variety of IoT applications, including applications for Smart Cities, using a variety of IoT devices. This work suggests such a case focusing on air quality monitoring.</p>
},
	author = {Christos Bouras and Vaggelis Kapoulas and Vasileios Kokkinos and Dimitris Leonardos and Costas Pipilas and Nikolaos Papachristos}
}
@article {4059,
	title = {Improving news articles recommendations via user clustering},
	journal = {International Journal of Machine Learning and Cybernetics, Springer Verlang},
	volume = {8},
	year = {2017},
	pages = {223-237},
	abstract = {<p>Although commonly only item clustering is suggested by Web mining techniques for news articles recommendation systems, one of the various tasks of personalized recommendation is categorization of Web users. With the rapid explosion of online news articles, predicting<br />
user-browsing behavior using collaborative filtering (CF) techniques has gained much attention in the web personalization area. However common CF techniques suffer from problems like low accuracy and performance. This research proposes a new personalized recommendation approach that integrates both user and text clustering based on our developed algorithm, W-kmeans, with other information retrieval (IR) techniques, like text categorization and summarization in order to provide users with the articles that match their profiles. Our system can easily adapt over time to divertive user preferences. Furthermore, experimental results show that by aggregating item and<br />
user clustering with multiple IR techniques like categorization and summarization, our recommender generates results that outperform the cases where each or both of them are used, but clustering is not applied.</p>
},
	author = {Christos Bouras and Vassilis Tsogkas}
}
@article {4195,
	title = {Interference Management Strategy for 5G Femtocell Clusters},
	journal = {Wireless Personal Communications, Springer Verlang},
	volume = {96},
	year = {2017},
	pages = {323-339},
	abstract = {<p class="rtejustify">With the next generation of mobile networks closing in, its main characteristics have already been proposed and adapted. Ultra-dense heterogeneous networks seem to be one of the main drivers to answer the need for larger device connectivity and increased data rate. Multiple Base Stations with different specifications will be deployed to achieve these targets. Femtocells are a type of Base Station that is expected to dominate, due to their low cost and easy deployment and maintenance. However, trying to increase spectral efficiency with the use of femtocells, by multiple base stations utilizing the same spectrum will lead to severe interference phenomena. This can be tackled by sharing spectrum strategies and power control techniques. In this manuscript, we propose a full scheme of resource management that can be applied in instances of femtocell deployments of increased density. The mechanism is based on coordination among the femtocells to achieve better spectrum usage, on power control and on hybrid access configuration aiming to fairness in resource allocation and to the improvement of overall capacity. Conducted simulations showed that our algorithm increases the overall capacity, protects non-subscribed users and balances the hybrid access effect on subscribers.</p>
},
	author = {Christos Bouras and Georgios Diles}
}
@article {4193,
	title = {Online AL - FEC Policy Problem on Mobile Unicast Services},
	journal = {Physical Communication, Elsevier Science},
	volume = {23},
	year = {2017},
	pages = {95-102},
	abstract = {<p class="rtejustify">Forward error correction (FEC) is a method for error control of data transmission adopted in several mobile multicast standards. FEC is a feedback free error recovery method where the sender introduces redundant data in advance with the source data enabling the recipient to recover from different arbitrary packet losses. Recently, the adoption of FEC error control method has been boosted by the introduction of powerful Application Layer FEC (AL-FEC) codes, e.g. RaptorQ codes. Furthermore, several works have emerged aiming to address the shortcomings of AL-FEC protection application utilizing deterministic or randomized online algorithms to enhance the efficiency of AL-FEC error control method. In this work, since the investigation of AL-FEC application as primary or auxiliary error protection method over mobile multicast environments is a well investigated field but the opportunity of utilizing the AL-FEC over mobile unicast services as the only method for error control replacing common feedback based methods that are now considered to be obsolete, we provide an analysis on the feasibility of AL-FEC protection over unicast delivery utilizing online algorithms in conjunction with AL-FEC codes with exceptional recovery performance.</p>
},
	author = {Christos Bouras and Nikolaos Kanakis}
}
@conference {4186,
	title = {SDN \& NFV in 5G: Advancements and Challenges},
	booktitle = {20th Conference on Innovations in Clouds, Internet and Networks (ICIN 2017)},
	year = {2017},
	month = {March 7 - 9},
	pages = {107-111},
	abstract = {<p class="rtejustify">The next generation of mobile networks has risen the expectations and has induced a whole new approach in the networking future. This study summarizes solutions, that meet all the existing requirements integrating Software Defined Network (SDN) and Network Function Virtualization (NFV) in mobile networking. The main contribution of this research activity is that it is a tool for literature reference for scientists and engineers, because it presents and compares the most fundamental existing solutions and the future directions. In this paper, the main characteristics of SDN and NFV are summarized as fundamental alternatives contributing to succeed the goals set by 5G. The main demands and challenges faced by these solutions and the most beneficial applications of the combination of SDN with NFV are described. Finally, the main conclusions of this research and suggestions for possible future activity in the field are described.</p>
},
	author = {Christos Bouras and Anastasia Kollia and Andreas Papazois}
}
@conference {4197,
	title = {Teaching 5G Networks Using the ONOS SDN Controller},
	booktitle = {The Ninth International Conference on Ubiquitous and Future Networks, (ICUFN 2017), Milan, Italy},
	year = {2017},
	month = {July 4 - 7},
	pages = {312-317},
	abstract = {<p class="rtejustify">Software Defined Networks (SDN) and Network Functions Virtualization (NFV) are two significant answers to the demands raised by the next generation of mobile networks. Teaching 5G, wireless and mobile networking is becoming an absolute necessity as virtualization and SDN generate a whole new approach for these types of networks and are candidate solutions for the fifth generation. We present several ideas for teaching the combination of SDN and NFV in future mobile networks using the Open Network Operating System (ONOS) and its use cases. The architectural scheme which is experimentedis thoroughly explained. There are several network simulations using the use cases vRouter (Virtual Router), IPRAN (InternetProtocol Radio Access Network) and MCORD\&nbsp; (Mobile Central Office Re-architected as a data center) of the ONOS controller, which show how important the ONOS is and how it contributes in explaining 5G and SDN in the teaching process. Finally, experiments indicate that ONOS is suitable for teaching SDN and NFV in 5G. Future activity in the field is suggested.</p>
},
	author = {Christos Bouras and Anastasia Kollia and Andreas Papazois}
}
@conference {4198,
	title = {Teaching network security in mobile 5G Using the ONOS SDN controller},
	booktitle = {The Ninth International Conference on Ubiquitous and Future Networks, (ICUFN 2017), Milan, Italy},
	year = {2017},
	month = {July 4 - 7},
	pages = {465-470},
	abstract = {<p class="rtejustify">Software Defined Networking (SDN) constitutes a fundamental technological solution which responds to the most essential challenges in 5G and beyond networks. Security still remains one of its most controversial issues. Security should be ensured in order to create reliable and consistent networks and on line applications and satisfy the demands of Service Level Agreements (SLAs). Therefore, teaching security of SDN and NFV is fundamental for academia these days. In this paper, we are going to summarize the most fundamental issues related to SDN security challenges and problems appearing alongside with the key back-doors in future SDN mobile networks. Several solutions utilizing SDN capabilities are suggested to avoid SDN security issues. We are also presenting experiments of network topologies using well-known network attack scenarios performed to showcase how networks{\textquoteright} security could be taught using SDN controllers. Experiments are conducted using the Open Network Operating System (ONOS) controller indicating that security teaching using ONOS controller is easy and offers many benefits. Future research activity in the field is proposed.</p>
},
	author = {Christos Bouras and Anastasia Kollia and Andreas Papazois}
}
@article {4131,
	title = {Video transmission in mobile ad hoc networks using multiple interfaces and multiple channels},
	journal = {International Journal of Communication Systems, Wiley InterScience},
	volume = {8},
	year = {2017},
	month = {May 2017},
	pages = {1-28},
	abstract = {<p class="rtejustify">Mobile Ad hoc NETworks (MANETs) are an important part of wireless communications and the increasing use of mobile devices is confirming that. MANETs can be of great value in Emergency Response situations where communication between mobile deployed units is critical and wired or wireless infrastructures may not be present or functional. In emergency scenarios, multimedia communication is very important for decision making and situation assessment. This requires up-to-date (on-line) information feed on the situation, including voice and video from the affected zone. However, MANETs do not seem to efficiently support multimedia applications, and this is quite evident in video transmission. One way to remedy this is to use more (wireless) interfaces per mobile node and consequently more communication channels. In this work, we perform an analytical study on the use of multiple interfaces and multiple channels (MIMC) in video transmission with respect to the requirements of Emergency Response Ad hoc Networks. More specifically, we examine and present the impact of using MIMC on MANETs during video transmission applications, we evaluate the performance of three basic routing protocols in MANETs, and we propose a channel selection mechanism in MANET nodes with MIMC for enhanced video transmission. In addition, we evaluate video transmission streams with rate adaptation and present comparative results. The proposed mechanism is evaluated using the ns-2 network simulator and the simulations are performed for a variety of topologies. Simulation results show that the different routing protocols respond differently when MIMC is introduced. The Ad hoc On-Demand Multipath Distance Vector and (especially) the Ad hoc On-Demand Distance Vector routing protocols benefit significantly, while the Destination Sequenced Distance Vector shows fewer improvements. The proposed mechanism is shown to be beneficial for transmitting video streams and enhances the network{\textquoteright}s ability to accommodate more streams and reduce packet delay.</p>
},
	author = {Christos Bouras and Apostolos Gkamas and Vaggelis Kapoulas and Dimitra Politaki and Enea Tsanai}
}
@conference {4194,
	title = {WiFiMon App Measuring Wi-Fi Performance as Experienced by End - Users},
	booktitle = {24th International Conference on Telecommunication (ICT 2017)},
	year = {2017},
	month = {May 3 - 5},
	abstract = {<p class="rtejustify">The measurement of quality and efficiency of a wireless Wi-Fi network is particularly difficult, as there is not a single tool that can record measurements from all sides of the system, i.e. from both the access point and the end-user. Existing tools are able to monitor the overall quality of the wireless network; although they cannot determine how end-users experience the quality of Wi-Fi in a particular part of the network at a given time. In this paper we present a novel tool, named WiFiMon, which enables measuring, recording and exporting statistics regarding the quality of a Wi-Fi network as experienced by the end-users. The measurements are triggered by the end-users when they visit WiFiMon-enabled websites and/or run WiFiMon-enabled mobile applications and are recorded without users{\textquoteright} intervention. Main goal of WiFiMon is to give network administrators a better overview on how the endusers experience the conditions of the Wi-Fi network.</p>
},
	author = {Kurt Baumann and Christos Bouras and Vasileios Kokkinos and Nikolaos Papachristos and Kostas Stamos}
}
@article {3437,
	title = {Assisting cluster coherency via N-grams and clustering as a tool to deal with the new user problem},
	journal = {International Journal of Machine Learning and Cybernetics, Springer Verlang},
	volume = {7},
	year = {2016},
	pages = {171-184},
	abstract = {<p class="rtejustify">Collaborative filtering systems typically need to acquire some data about the new user in order to start making personalized suggestions, a situation commonly referred to as the {\textquotedblleft}new user problem{\textquotedblright}. In this work we attempt to address the new user problem via a unique personalized strategy for prompting the user with articles to rate. Our approach makes use of hypernyms extracted from the WordNet database and proves to be converging fast to the actual user interests based on minimal user ratings, which are provided during the registration process. In addition, we explore the possible enhancement of the document clustering results, and in particular clustering of news articles from the web, when using word-based n-grams during the keyword extraction phase. We present and evaluate a weighting approach that combines clustering of news articles derived from the web, using n-grams that are extracted from the articles at an offline stage. This technique is then compared with the single minded {\textquotedblleft}bag-of-words{\textquotedblright} representation that our clustering algorithm, W-kmeans, previously used. Our experimentation reveals that via fine tuning the weighting parameters between keyword and n-grams, as well as the n value itself, a significant improvement regarding the clustering results metrics can be achieved.</p>
},
	author = {Christos Bouras and Vassilis Tsogkas}
}
@conference {4136,
	title = {Comparison of Point to Point and MBSFN transmissions in Next Generation Mobile Networks},
	booktitle = {The 14th  ACM International Symposium on Mobility Management and Wireless Access (Mobiwac 2016)},
	year = {2016},
	month = {November 13 - 17},
	pages = {169-172},
	abstract = {<p class="rtejustify">Multicast/Broadcast Multicast Service over Single Frequency Network (MBSFN) technology has introduced advanced broadcast capabilities to cellular systems. In Long Term Evolution Advanced (LTE-A) systems, MBSFN transmission accommodates multicast groups in search of the same data. In this paper we compare the traditional Point-to-Point (PTP) communication with the MBSFN services through simulation experiments for various femtocell distributions and network configurations. The comparison takes into account the average throughput, overhead cost, energy consumption and capacity gain, concluding that MBSFN through multicast transmission may guarantee performance improvement even for users in the cell boundaries.</p>
},
	author = {Christos Bouras and Nikos Kanakis and Vasileios Kokkinos and Nikolaos Papachristos and Demosthenes Vouyioukas}
}
@conference {4146,
	title = {Coordination strategy for dense 5G femtocell deployments},
	booktitle = {8th IFIP International Conference on New Technologies, Mobility and Security},
	year = {2016},
	month = {November 21-23},
	address = {Larnaca, Cyprus},
	abstract = {<p>The demand of next generation mobile networks for high connectivity for multiple devices with tenfold data rate<br />
requires the deployment of multiple base stations of different range and capacity and their optimal management. Femtocells will play a major role in these heterogeneous networks, being a low-cost and effective solution. In this paper we propose a mechanism on management of femtocells{\textquoteright} resources, based on spectrum allocation policies, power control and user classification. We combine hybrid access operation with user redistribution to provide a complete mechanism for resource allocation in dense femtocell deployments. Simulations show that the proposed scheme increases the capacity provided by the involved femtocells, it guarantees service to non-subscribers and balances the performance of the subscribed users improving the worst cases.</p>
},
	author = {Christos Bouras and Georgios Diles}
}
@conference {4133,
	title = {Cost Modeling for SDN/NFV Based Mobile 5G Networks},
	booktitle = {8th International Congress on Ultra Modern Telecommunications and Control Systems - ICUMT 2016},
	year = {2016},
	month = {October 18 - 20},
	pages = {87-92},
	abstract = {<p class="rtejustify">This paper presents a techno-economic analysis on the integration of new technologies in 5G mobile networks, in order to fulfil the requirements provided by ETSI organization. Therefore {\textquotedblleft}softwarization{\textquotedblright} of 5G networks is imperative and becomes a reality through new technologies, such as Software Defined Networking (SDN), Network Function Virtualization (NFV) and Cloud Computing. In this context, this paper provides a cost model in order to estimate the Capital Expenditure (CAPEX), the Operational Expenditure (OPEX) and the Total Cost of Ownership (TCO) for the proposed architecture. Furthermore, the proposed techno- economic model is used in order to estimate the above-mentioned network costs for the proposed network architecture and these costs are compared with the corresponding costs of a traditional network architecture. The experimental results verify and even exceed the ambitious predictions for cost reduction, due to the integration of those state of the art technologies in next-generation architectures.</p>
},
	author = {Christos Bouras and Panagiotis Ntarzanos and Andreas Papazois}
}
@article {4119,
	title = {Efficient Mechanism and Performance Analysis of Routing   Protocols in VANETs for Realistic Scenarios},
	journal = {International Journal of Interdisciplinary Telecommunications and Networking, IGI Global},
	volume = {8},
	year = {2016},
	pages = {20-49},
	abstract = {<p class="rtejustify">Vehicular Ad Hoc Networks (VANETs) are considered as a special case of mobile Ad Hoc Networks (MANETs) and are recently gaining a great attention from the research community. The need for improved road safety, traffic efficiency and direct communi-cation along with the great complexity in routing, makes VANETs a highly challeng-ing field. Routing in VANETs has to adapt to special characteristics such as high speed and road pattern movement as well as high linkage break probability. In this work, we show that traditional MANET routing protocols cannot efficiently handle the challeng-es in a VANET environment and thus need further modifications. For this reason, we propose and implement an enhancement mechanism, applied to the GPSR routing pro-tocol that adapts to the needs of a VANET. The proposed mechanism{\textquoteright}s performance is evaluated through simulation sets for urban and highway scenarios and compared to the performance of the most common MANET routing protocols adopted in VANETs. The proposed enhancement is shown to be considerably beneficial and it significantly outperforms the rest of the tested routing protocols for almost every topology setting</p>
},
	author = {Christos Bouras and Vaggelis Kapoulas and Enea Tsanai}
}
@conference {4117,
	title = {Evaluation of Power Control Mechanism on OLSR Routing Protocol},
	booktitle = {The 11th International Workshop on the Performance Analysis and Enhancement of Wireless Networks (PAWEN 2016), Crans - Montana, Switzerland},
	year = {2016},
	month = {March 23 - 25},
	pages = {766 - 771},
	abstract = {<p class="rtejustify">The mobility that characterizes the wireless networks, is leading to the use of ad hoc networks for wireless communications. Due to the constant motion of wireless devices, infrastructure wireless networks cannot provide connectivity at all times, in comparison with ad hoc networks, which are more easy to use and are based on abstract and continuously altering topologies. The use of specialized routing protocols is improving the performance of these networks, concluding to lower power consumption and faster communication. However, routing is not enough to preserve the battery power of the mobile devices. By using a power control mechanism on top of the routing protocols, further power savings can be achieved. In this paper, we present a power control mechanism which relies on the routing protocol in<br />
order to make decisions about power management and the behavior and the performance of the network. The mechanism is based on using SNR (Signal-to-Noise Ratio) as a metric for adjusting the transmission power accordingly and eventually saving a respectable amount of energy to prolong life time of mobile devices and benefit the performance ad hoc networks.</p>
},
	author = {Christos Bouras and Vaggelis Kapoulas and Kostas Stamos and Nikos Stathopoulos}
}
@conference {4135,
	title = {Mechanisms for enhancing the performance of routing protocols in VANETs},
	booktitle = {13th  ACM International Symposium on Performance Evaluation of Wireless, Ad Hoc, Sensor and Ubiquitous Networks (PE - WASUN)},
	year = {2016},
	month = {November 13 - 17},
	pages = {11-18},
	abstract = {<p class="rtejustify">Vehicular Ad Hoc Networks (VANETs) are considered as a special case of Mobile Ad Hoc Networks (MANETs) and are recently gaining a great attention from the research community. Routing in VANETs has to adapt to special characteristics such as high speed and road pattern movement as well as high linkage break probability. In an urban setting the problem becomes more difficult as the existence of buildings blocks the wireless signal and hinders communication, resulting in only few nodes with increased connectivity (mostly in the intersections) that can act as true routing nodes rather than just forwarding nodes. In this paper, we compare the performance of GPCR (Greedy Perimeter Coordinator Routing), GPSR (Greedy Perimeter Stateless Routing) as well as the modified GPSR (GPSR-M) routing protocols. GPSR-M is an enhancement for the GPSR protocol that focuses on routing a message to an intermediate vehicle moving in the line of movement of the final destination, as soon as possible. Based on the performance evaluation we propose enhancements to GPSR-M in order to improve performance.</p>
},
	author = {Christos Bouras and Vaggelis Kapoulas and Nikos Stathopoulos and Apostolos Gkamas}
}
@article {3438,
	title = {Mobility - aware Power Control in MBSFN},
	journal = {Telecommunications Systems, Springer Verlang (Special Issue on WMNC 2012)},
	volume = {61},
	year = {2016},
	pages = {77-91},
	abstract = {<p class="rtejustify">Multimedia Broadcast/Multicast Service (MBMS) over a Single\&nbsp;Frequency Network (MBSFN) within LTE systems is a feature that allows\&nbsp;synchronous broadcasting of common data among neighboring cells. With\&nbsp;MBSFN operation, mobile broadcast/multicast users are able to use inter-cell\&nbsp;interference in a constructive way and to achieve increased bit-rates compared\&nbsp;to when conventional broadcasting is used. In this manuscript, we present our\&nbsp;work on the optimization of the power control for future mobile networks that\&nbsp;employ MBSFN transmission. We propose a novel simulator and system optimizer\&nbsp;that can minimize the individual cell{\textquoteright}s transmission power by taking\&nbsp;into account the changing positions of users. The system optimizer is based\&nbsp;on a novel genetic algorithm, which is resistant to entrapment in local optima\&nbsp;and makes use of mutations over the previous solutions in order to optimize<br />
the power consumption given the new users{\textquoteright} positions. The optimizer{\textquoteright}s engine\&nbsp;can be used in conjunction with the simulator or can be easily modied to\&nbsp;receive real-time measurements from a real LTE network as an input. In order<br />
to read descriptions of the various scenarios, the simulator uses the eXtendable\&nbsp;Temporal Network Description Language (XTNDL), a language that is also\&nbsp;specied in this manuscript.</p>
},
	author = {Konstantinos Asimakis and Christos Bouras and Vasileios Kokkinos and Andreas Papazois}
}
@article {4130,
	title = {Power-Aware and QoS Provisioned Real Time Multimedia Transmission in Small Cell Networks},
	journal = {International Journal of Wireless Networks and Broadband Technologies, IGI Global},
	volume = {5},
	year = {2016},
	pages = {24-45},
	abstract = {<p class="rtejustify">The recent emergence of ultra-high-speed and high-definition data and video services has pushed wireless network capacity to its limits. Cellular network capacity is therefore a valuable resource, whereas indoor coverage poses itself as a challenging issue. At the same time, real-world paradigms of multimedia transmission require effective Quality-of-Service (QoS) provisioning as well as power admission. To confront issues like delay-sensitive QoS requirements and traffic provisioning, as well as meet the mobile customer needs, this paper presents a traffic-aware Orthogonal Frequency-Division Multiple-Access (OFDMA) hybrid small-cell deployment for QoS provisioning and an optimal admission control strategy for 4G cellular systems. The traffic awareness in the proposed framework is provided by a utility function, which differentiates the traffic QoS levels with the user{\textquoteright}s grouping priority indexes, channel conditions, and traffic characteristics. To further enhance the proposed framework, an admission power control algorithm based on an efficient algorithm handover is also proposed.</p>
},
	author = {Antonios Alexiou and Anastasios Bikos and Dimitrios Bilios and Christos Bouras}
}
@article {4109,
	title = {Science parks and regional innovation performance in fiscal austerity era: Less in more},
	journal = {Special Issue on GCW 2014, Small Business Economics, Springer Verlang},
	volume = {47},
	year = {2016},
	month = {August 2016},
	pages = {313-330},
	abstract = {<p class="rtejustify">European financial crisis has raised questions about the sustainability and the contribution of innovation anchors especially in Southern European countries such as Greece. This paper utilizes the concept of regional innovation systems (RISs) and introduces a methodological approach that allows for evaluating an Science and Technology Park{\textquoteright}s (STP) contribution into the corresponding RIS performance, taking into consideration (1) the RIS idiosyncrasies, (2) the dominant role of government expenditures on R\&amp;D and (3) the underlying complexity of knowledge production and management, under alternative sets of restrictions imposed by fiscal consolidation on the preferences of authorities which design and implement Science, Technology and Innovation (STI) policies. Our framework relies on the estimation of a multi-input{\textendash}multi-output latent knowledge production function approach and the corresponding efficiency indices. Data requirements are sourced from the Regional Innovation Scoreboard, for the four Greek regions and from a small-scale case study, with respect to the examined regional STP covering the period from 2000 to 2012. The main empirical findings highlight that the contribution of the examined STP in the corresponding RIS performance diminishes alongside with the decrease in GERD investment levels, with respect to all the efficiency indices. These findings are attributed to the structural characteristics of both the RIS and the STP under investigation, and capture their dependence on managing public financial resources for STI activities.</p>
},
	author = {Areti Gkypali and Vasileios Kokkinos and Christos Bouras and Kostas Tsekouras}
}
@conference {4116,
	title = {Sensitivity Analysis of Small Cells and DAS Techno-economic Models in Mobile 5G},
	booktitle = {IEEE Wireless Communications and Networking Conference (WCNC 2016) Doha, Qatar},
	year = {2016},
	month = {April 3 - 6},
	pages = {2742 - 2747},
	abstract = {<p class="rtejustify">Next generation of mobile technologies demands high date rates and low round trip times. Therefore, we analyze deployments that offer these performance capabilities. We consider the fundamental issue of the expenses of the network{\textquoteright}s installation, maintenance and operation. We calculate the costs of Distributed Antenna Systems (DAS) and small cells by describing updated cost models for each one. We present a Sensitivity Analysis of certain types of cost variables and parameters including the existing bandwidth, the running costs, the interest rate, the base station, the equipment, the power consumption, the backhaul, the implementation costs and Throughput Density. We include a variable cost provision for the year 2016 and beyond, and conduce several experiments, based on the upper analysis, by considering many different parameter prices and introducing the Throughput Density. We calculate the Total Cost of Ownership (TCO), the Capital (CAPEX) and the Operational (OPEX) expenditures. Finally, we are led to important conclusions by comparing the two main technologies costs and evaluating the cost parameters and variables that will lead future researchers to suggest ways to reduce the higher costs.</p>
},
	author = {Christos Bouras and Anastasia Kollia and Andreas Papazois}
}
@conference {4134,
	title = {Sleep Mode Performance Gains In 5G Femtocell Clusters},
	booktitle = {8th International Congress on Ultra Modern Telecommunications and Control Systems - ICUMT 2016},
	year = {2016},
	month = {October 18 - 20},
	pages = {106-111},
	abstract = {<p class="rtejustify">Femtocells present an efficient, low cost solution to help reach the traffic and data rate targets of 5G mobile networks. However, their ad-hoc nature, the expected great density of deployment and their closed\&nbsp; registration policy may result in multi-layered networks with base stations{\textquoteright} ranges constantly overlapping and non-registered users struggling from the accumulative interference. In this paper, we propose a mechanism where femtocells operate in clusters, and may decide to turn to sleep mode if capacity demand of its users is met adequately by the remaining awake femtocells. We propose a special version of hybrid access targeting only users of neighboring femtocells, in order to reduce the number of active base stations and thus, to reduce interference. We enforce sleep mode under conditions that ensure the increased throughput of each involved registered user and the increased capacity provided by the entire cluster with the extra benefit of reduced energy.</p>
},
	author = {Christos Bouras and Georgios Diles}
}
@article {4108,
	title = {Transmission optimizing on dense femtocell deployments in 5G},
	journal = {International Journal of Communication Systems, Wiley InterScience},
	volume = {29},
	year = {2016},
	pages = {2325 - 2438},
	abstract = {<p class="rtejustify">In the upcoming generation of mobile networks, femtocells will play a major role because they provide cost-efficient improvement in data rates and coverage. High penetration is expected in the upcoming ultradense 5G networks, increasing the probability of femtocells{\textquoteright} clusters. This, in turn, will require interference mitigation techniques to protect nearby non-subscribed users, especially in weak macrocell signal areas. In this paper, we present a mechanism where multiple femtocells coordinate their transmission to serve multiple non-subscribed users through hybrid access. First, we introduce an algorithm that determines the spectrum allocation of femtocells{\textquoteright} hybrid access. The algorithm aims to compensate for the performance reduction of subscribed users, due to reduced spectrum. For the second step of the mechanism, we introduce a power control algorithm that balances the impact of hybrid access among all the members of the femtocell cluster. First, we investigate the case where only one femtocell operates in hybrid access, and then we refine the power control algorithm by allowing multiple femtocells in the same cluster to operate in hybrid mode and by taking into account the effect that any change in power transmission will have on neighbouring femtocells. Simulations for the evaluation of the hybrid access algorithm compared with closed and other hybrid access schemes show improvement in the throughput of the non-subscribed users connected to femtocell and the most impacted subscribed users at weak macrocell signal areas and in the fairness of the hybrid access application scheme.</p>
},
	author = {Christos Bouras and Georgios Diles and Vasileios Kokkinos and Andreas Papazois}
}
@conference {4118,
	title = {Utilization of Hybrid Access Femtocells During Multicast Transmissions in Mobile Networks},
	booktitle = {European Conference on Networks and Communications, Athens, Greece},
	year = {2016},
	month = {June 27 - 30},
	pages = {190-194},
	abstract = {<p class="rtejustify">Femtocells enhance indoor coverage of mobile services using the owner{\textquoteright}s broadband connection. They were initially designed to serve a number of subscribed User Equipments within their range. This design however, resulted in underutilization of the femtocells resources, and simultaneously in high interference levels for nearby non-subscribed users. Nowadays, femtocells can support multicast transmissions, while their hybrid operation allows non-subscribed users to use a portion of their resources. In this paper we propose a novel mechanism that is based on the selection of the appropriate Modulation and Coding Scheme. The mechanism allows non-subscribed users to utilize a portion of the femtocells{\textquoteright} resources for multicast transmissions when located inside their coverage, without affecting the owners{\textquoteright} satisfaction. The simulation results show that depending on the portion of the femtocells{\textquoteright} resources allocated to non-subscribed users, the mechanism may significantly increase the average user throughput.</p>
},
	author = {Christos Bouras and Nikolaos Kanakis and Vasileios Kokkinos and Nikolaos Papachristos and Demosthenes Vouyioukas}
}
@article {4060,
	title = {Broadband and e - Government Services in South East Europe:   Comparative Analysis, Impact and Policy Recommendations},
	journal = {International Journal of Interdisciplinary Telecommunications and Networking, IGI Global},
	volume = {6},
	year = {2015},
	pages = {39-56},
	abstract = {<p>The European Commission acknowledging the significance of broadband for the improvement of citizen welfare and its economic benefits, has put in place targets for the diffusion of broadband to all citizens and businesses in the European Union. This manuscript comparatively assesses the current state of affairs in broadband and digital public services in selected South East Europe (SEE) countries in order to identify weaknesses and highlight strengths, and attempts to measure the impact and effectiveness of broadband on the economy. To this direction, the authors focus on evaluating the correlation between broadband and growth and employment. They also estimate the savings achieved by the usage of e-services and the potential savings that will follow their increased utilization over the next years. The analysis is followed by a number of recommendations that aim to support informed decision making. The manuscript builds on four surveys that took place during the second quarter of 2013.</p>
},
	author = {Konstantinos Antonis and Christos Bouras and Fabrizio D{\textquoteright}Elia and Annalisa Di Vincenzo and Georgios Diles and Vasileios Kokkinos and Andreas Koskeris}
}
@article {4058,
	title = {Cross-platform Mobile Applications with Web Technologies},
	journal = {International Journal of Computing and Digital Systems, (Special Issue on MobiApps 2014)},
	volume = {4},
	year = {2015},
	pages = {153-163},
	abstract = {<p class="rtejustify">The extended use of smart mobile devices has become an integral part of daily life leading to the expansion of mobile application development. Currently, the majority of mobile applications are native applications that need an initial installation prior to being utilized. In addition, for a given application, a separate software development process could be required for each mobile platform, which subsequently increases dramatically the corresponding effort and cost. With the emergence of HTML5 these issues can be addressed efficiently, since web technologies allow the application development in a cross-platform manner. An important benefit is that users can have easy and immediate access the application without any need for downloading and installation. In this manuscript, we investigate the potentials of mobile application development with web technologies and we present a development framework that we have designed and implemented. This framework utilizes the most important state-of-art web technologies for the support of mobile devices. It can be used for the implementation of mobile web applications and also for the investigation and experimentation on the main features that HTML5 offers for this specific type of devices.</p>
},
	author = {Christos Bouras and Andreas Papazois and Nikolaos Stasinos}
}
@article {3436,
	title = {Deploying AL-FEC Protection with Online Algorithms for Multicast Services over Cellular Networks},
	journal = {Wireless Networks, Springer Verlang},
	volume = {20},
	year = {2015},
	pages = {2109-2122},
	abstract = {<p class="rtejustify">Reliability control is a key concern on the evolution of mobile multicast services. To this direction, the use of forward error correction (FEC)\&nbsp;on the application layer is widely adopted in several mobile multicast standards. FEC is a feedback free error control method, where the transmitter\&nbsp;introduces in advance redundant information within the source data to enable receivers recovering arbitrary data erasures. On multicast delivery where\&nbsp;retransmission-based error recovery methods are not ecient, the most suitable error control method is the use of application layer forward error correction (AL-FEC) codes. In this work, we introduce novel AL-FEC deployment\&nbsp;policies over mobile multicast environments utilizing online algorithms. We\&nbsp;aim at the ecient application of AL-FEC protection with RaptorQ codes over multicast delivery in the context of competitive analysis. We provide a\&nbsp;competitiveness analysis model of AL-FEC application over mobile multicast\&nbsp;environments. Furthermore, we propose two online algorithms adjusting the introduced redundancy of AL-FEC protection according to several FEC encoding parameters and constraints of mobile multicast delivery.</p>
},
	author = {Christos Bouras and Nikos Kanakis and Vasileios Kokkinos and Andreas Papazois}
}
@conference {4071,
	title = {A GPSR Enhancement Mechanism for Routing in VANETs},
	booktitle = {The 13th International Conference on Wired \& Wireless Internet Communications (WWIC{\textquoteright} 2015), Malaga, Spain},
	year = {2015},
	month = {May 25-27},
	pages = {94 - 107 },
	abstract = {<p class="rtejustify">Vehicular Ad Hoc Networks (VANETs) are considered as a special case of mobile Ad Hoc Networks (MANETs) and are recently gaining a great attention from the research community. The need for improved road safety, traf-fic efficiency and direct communication along with the great complexity in rout-ing, makes VANETs a highly challenging field.. Routing in VANETs has to adapt to special characteristics such as high speed and road pattern movement as well as high linkage break probability. In this paper, we propose an enhancement mechanism for the GPSR routing protocol and present its performance for urban and highway scenarios. Its performance is compared to the performance of the most common MANET routing protocols adopted in VANETs. The proposed enhancement is shown to be beneficial in most occasions as it outperforms the rest of the tested routing protocols.</p>
},
	author = {Christos Bouras and Vaggelis Kapoulas and Enea Tsanai}
}
@article {3434,
	title = {Mobile Ad hoc networks (MANETs) for multimedia transmission},
	volume = {9},
	year = {2015},
	pages = {6239-6248},
	publisher = {Encyclopedia of Information Science and Technology (3rd Ed.), IGI Global},
	edition = {3rd},
	chapter = {614},
	abstract = {<p class="rtejustify">Mobile Ad hoc Networks (MANETs) are becoming more essential to wireless communications due to growing popularity of mobile devices. A node in MANETs could act as a router while having also the possibility of being the sender or receiver of information. MANETs offer the freedom to use mobile devices and move independently of the location of base stations (and outside their coverage) with the help of other network devices. The ability of MANETs to be self-configured and form a mobile mesh network, by using wireless links, make them very suitable for a number of cases that other type of networks cannot operate. In addition, MANETs do not require vast technological investments.\&nbsp;An ideal application area for the utilization of MANET technology is for instance any disaster scenario in which the fixed infrastructure is incapacitated or non-existent. In this case it is important to ensure that a suitable communication solution is established within the very first critical hours of an incident, considering national or cross-border emergency incidents.\&nbsp;What is missing, however, from this type of networks is the so called a {\textquotedblleft}killer application{\textquotedblright} that could boost its utilizations in the real world. Real time multimedia applications have the potential to turn MANETs into a very attractive solution in wireless networks taking into account its unique characteristics.\&nbsp;Our motivation for this article is to present the shortcomings and the current state of the art in MANETs in regards to the transmission of multimedia data, which is a promising application area.</p>
},
	author = {Apostolos Gkamas and Christos Bouras and G Kioumourtzis}
}
@conference {4115,
	title = {A Mobile Learning Application for Self-Management of Health and Disease},
	booktitle = {2015 International Conference on Interactive Mobile Communication Technologies and Learning, Thessaloniki, Greece},
	year = {2015},
	month = {November 19 - 20},
	pages = {101-105},
	abstract = {<p class="rtejustify">Supporting self-management of patients is a highly challenging task, which needs to meaningfully exploit and interrelate approaches and technologies concerning interactive communication, personalized health and mobile learning. In line with these remarks, this paper reports on the development of an innovative clinical decision support platform for selfmanagement of health and disease purposes. Work presented focuses on two basic components of the platform, namely a webbased collaboration support tool and a mobile application, both aiming to augment the interaction of all types of stakeholders with the platform. The functionality of the above components is sketched through a realistic use case.</p>
},
	author = {Christos Bouras and Vaggelis Kapoulas and Nikos Karacapilidis and Vasileios Kokkinos and Andreas Papazois}
}
@conference {4070,
	title = {A Novel Tool for Cost-Efficient Broadband Development through Infrastructure Sharing},
	booktitle = {The 20th IEEE Symposium on Computers and Communications, Larnaca, Cyprus},
	year = {2015},
	month = {July 6-9},
	pages = {323-328},
	abstract = {<p class="rtejustify">Broadband is a public utility with positive effects on competitiveness, employment and growth. Although evidence shows that broadband development is increasing, this increment is not homogeneous between urban and rural areas. The main cause is the high cost for deploying next generation networks in rural areas, and especially the cost linked to civil engineering works. In order to overcome the investment challenges arising in the context of broadband deployment, the European Commission made mandatory the sharing of existing telecommunication and non-telecommunication infrastructures and facilities. This paper proposes and presents a novel tool that enables the estimation of the expected savings from exploiting existing infrastructures when deploying a broadband network. This is followed by a number of general principles and recommendations that policy makers and national authorities could embrace to diminish deployment costs and promote broadband deployment.</p>
},
	author = {Christos Bouras and Georgios Diles and Vasileios Kokkinos and Konstantinos Antonis and Leonidas Loukopoulos}
}
@conference {4069,
	title = {Online AL-FEC protection over Mobile Unicast Services},
	booktitle = {European Conference on Networks and Communications, Paris, France},
	year = {2015},
	month = {June 29 - July 2},
	pages = {234-238},
	abstract = {<p class="rtejustify">Forward error correction (FEC) is a method for error control of data transmission adopted in several mobile multicast standards. FEC is a feedback free error recovery method where the sender introduces redundant data in advance with the source data enabling the recipient to recover from different arbitrary packet losses. Recently, the adoption of FEC error control method has been boosted by the introduction of powerful Application Layer FEC (AL-FEC) codes i.e., RaptorQ codes. Furthermore, several works have emerged aiming to address the efficient application of AL-FEC protection introducing deterministic or randomized online algorithms. The investigation of ALFEC application as primary or auxiliary error protection method over mobile multicast environments is a well investigated field. However, the opportunity of utilizing the AL-FEC over mobile unicast services as the only method for error control, replacing common feedback based methods that are now considered to be obsolete, is not yet examined. In this work we provide an analysis on the feasibility of AL-FEC protection over unicast delivery utilizing online algorithms on the application of AL-FEC codes with exceptional recovery performance.</p>
},
	author = {Christos Bouras and Nikolaos Kanakis}
}
@conference {4113,
	title = {Optimizing hybrid access femtocell clusters in 5G networks},
	booktitle = {10th International Conference on Broadband and Wireless Computing, Communication and Apllications (BWCCA 2015), Krakow, Poland},
	year = {2015},
	month = {November 4 - 6},
	pages = {220-226},
	abstract = {<p class="rtejustify">Femtocells are an efficient way of reducing infrastructure costs while providing better data rates and coverage. High penetration is expected in the upcoming ultra dense 5G networks, increasing the probability of femtocells{\textquoteright} clusters. Strong resulting interference for nearby non-subscribed users will require interference mitigation techniques. In this paper we present a mechanism where multiple femtocells coordinate their transmission to serve multiple non-subscribed users through hybrid access. First, the spectrum allocation of non-subscribed users by femtocells is determined. Then, we introduce a power control algorithm that is based on two factors. The need for compensation for the subscribed users, due to reduced spectrum, and the effect that any change in power transmission will have on neighbouring femtocells. We evaluate the effectiveness of the algorithm through simulations on individual throughput and overall achieved capacity.</p>
},
	author = {Christos Bouras and Georgios Diles and Vasileios Kokkinos and Andreas Papazois}
}
@inbook {4105,
	title = {Performance Evaluation of Routing Mechanisms for VANETs in Urban Areas},
	booktitle = {Algorithms, Probability, Networks, and Games: Scientific Papers and Essays},
	year = {2015},
	pages = {133-135},
	abstract = {<p class="rtejustify">Mobile Ad hoc Networks (MANETs) and especially Vehicular Ad hoc Networks (VANETs) have recently gained large interest and their performance is heavily studied. A great challenge in VANETs, especially in an urban setting, is the routing scheme used and the subsequent performance obtained. This work presents an experimental performance evaluation of routing mechanisms in VANETs, using simulation, within<br />
an urban Manhattan grid like environment. It also describes and evaluates an enhancement of the Greedy Perimeter Stateless Routing (GPSR) protocol that takes into account the motion of the vehicles and the nature of the urban environment. The simulation results demonstrate that the proposed enhancement to the GPSR protocol manages to significantly increase the delivery ratio without increasing the power consumption; nevertheless, in some cases the improvement on delivery ratio is achieved at the expense of slightly increased end-to-end delay.</p>
},
	author = {Christos Bouras and Vaggelis Kapoulas and Enea Tsanai}
}
@conference {4111,
	title = {Power Management and Rate Control Mechanism for Wi-Fi Infrastructure Networks},
	booktitle = {The 6th  International Workshop on Wireless Networks and Multimedia (WNM - 2015), Liverpool, UK},
	year = {2015},
	month = {October 26 - 28},
	pages = {731-736},
	abstract = {<p class="rtejustify">The advances in wireless networks have encouraged the use of mobile devices in everyday life. However, one of the main problems of these devices is the limited amount of energy they have available to use in order to function and the extended energy consumption of wireless adapters. A lot of research has been done to reduce the amount of energy spent on wireless communications. On the other hand, the extended use of wireless networks causes interference problems in communications, which affect the overall performance of each network. The purpose of this work is to provide a mechanism, which can reduce the power consumption on the station side and increase the mobile devices{\textquoteright} operation time, and in combination with a rate adaptation mechanism on the access point side, improve the overall performance of the network.</p>
},
	author = {Christos Bouras and Vaggelis Kapoulas and Kostas Stamos and Nikos Stathopoulos and Nikolaos Tavoularis}
}
@conference {4112,
	title = {Power-Aware QoS Provisioning in OFDMA Small Cell Networks},
	booktitle = {The 6th  International Workshop on Wireless Networks and Multimedia (WNM - 2015), Liverpool, UK},
	year = {2015},
	month = {October 26 - 28},
	pages = {725-730},
	abstract = {<p class="rtejustify">Orthogonal frequency-division multiple-access (OFDMA) small-cell networks of next-generation Long-Term Evolution (LTE-Advanced) standard, is perhaps a key factor to efficiently provide beneficial usage of expensive radio resources, while maintaining adequate network capacity. Network capacity is without doubt a critical resource for LTE networks. At the same time, real-time multimedia transmission requires effective quality-of-service (QoS) provisioning, as well as power admission. This paper proposes a traffic-aware OFDMA hybrid small-cell deployment for QoS provisioning and an optimal power admission control strategy for 4G cellular systems. By performing real-case scenario simulations of user-type multimedia transmission, we show that the implemented framework achieves high QoS levels of performance, increased<br />
throughput capacity, lower delay levels and optimally adapted network traffic.</p>
},
	author = {Christos Bouras and Antonios Alexiou and Anastasios Bikos}
}
@conference {4114,
	title = {Resource management in 5G femtocell networks},
	booktitle = {10th International Conference on Broadband and Wireless Computing, Communication and Apllications (BWCCA 2015), Krakow, Poland},
	year = {2015},
	month = {November 4 - 6},
	pages = {353-358},
	abstract = {<p class="rtejustify">Small cells are expected to contribute to the targets of next generation mobile networks. Ultra dense networks through the form of heterogeneous structures of multiple RAT technologies and small cells present a flexible, economical way for better coverage and data rates. In this paper, we investigate particularly how femtocells may best utilize their available resources in order to increase their provided capacity when neighbouring femtocells are present. We propose a spectrum policy, according to which femtocell deployments are forming clusters and the femtocells adopt hybrid access policy versus users subscribed to other femtocells members of the same cluster. We also determine the spectrum allocation for non-subscribed users in the range of the femtocell. We evaluate the performance of the set up through simulations showing that the mechanism offers better overall capacity.</p>
},
	author = {Christos Bouras and Georgios Diles}
}
@article {4107,
	title = {A Signal Adaptation Mechanism for power optimization of wireless adapters},
	journal = {International Journal of Wireless Networks and Broadband Technologies, IGI Global},
	volume = {4(3)},
	year = {2015},
	pages = {48-72},
	abstract = {<p class="rtejustify">This manuscript introduces, implements and evaluates a feedback-based adaptation mechanism that adjusts the transmission power of a wireless card on commodity mobile devices. Main focus of this work is to minimize the power consumption by adjusting the transmission power of the wireless card, thus extending the battery life, while negative effects on connection quality are avoided. To achieve that, a mechanism that optimizes the power depending on the quality of the connection is presented, which measures the quality of the transmission and adjusts the transmission power, by utilizing an expanded array of metrics, for more accurate estimation. The mechanism has been implemented and tested on actual wireless adapters. In order to evaluate, fine-tune and improve the mechanism, a list of real environment experiments has been performed. The results indicate that power consumption can be significantly reduced for nodes that are either almost stationary or slowly moving, without any significant increase in packet loss.</p>
},
	author = {Christos Bouras and Vaggelis Kapoulas and Georgios Kioumourtzis and Kostas Stamos and Nikos Stathopoulos and Nikolaos Tavoularis}
}
@conference {4110,
	title = {Techno-economic Analysis of Ultra-dense and DAS Deployments in Mobile 5G},
	booktitle = {Twelfth International Symposium on Wireless Communication Systems, Brussels, Belgium},
	year = {2015},
	month = {August 25 - 28},
	pages = {241-245},
	abstract = {<p class="rtejustify">Ultra-dense and Distributed Antenna Systems (DAS) technology consist fundamental means for achieving the data rates and round-trip times promised by future mobile networks, because they promise to assure excellent indoor coverage and offer the potential to meet the target key performance indicators at a lower cost. In this paper, we study the techno-economic aspects of ultra-dense and DAS deployments. Apart from the presentation of their architectures and advantages, we present a techno-economic modeling of these deployment types. The defined models are used for the investigation of the upper technologies from an economic perspective and therefore, they provide an insight in the future financial and price aspects of these technologies by consisting a useful tool for the definition of financing and pricing policies towards an economically viable ultra-dense femtocell-based or DAS deployment. Finally, it is confirmed that the Total Cost of Ownership (TCO) is lower for the femtocells compared to the DAS.</p>
},
	author = {Christos Bouras and Vasileios Kokkinos and Anastasia Kollia and Andreas Papazois}
}
@conference {3449,
	title = {An Adaptive Weighted Online AL -FEC Algorithm over Mobile Multicas Networks},
	booktitle = {IEEE Wireless Communications and Networking Conference, Istanbul, Turkey},
	year = {2014},
	month = {April 6 - 9},
	pages = {1602-1607},
	abstract = {<p class="rtejustify">A crucial point on the delivery of multicast content\&nbsp;over mobile multicast networks is the utilization of Forward Error Correction (FEC) codes on the application layer (AL-FEC) so as to introduce robustness against arbitrary erasures on different recipients without the need of inefficient common error control\&nbsp;methods based on data retransmission. FEC is a feedback free error recovery method where the sender introduces redundant data in advance with the source data enabling the recipients to recover from different arbitrary packet losses. The main issue on the efficient application of AL-FEC protection is the adaptation\&nbsp;of the introduced redundancy to the current network conditions, in order to avoid network resources wastage ensuring at the same time sufficient transmission robustness. Based on this, in this work we present an adaptive weighted online algorithm aiming at the efficient application of RaptorQ AL-FEC codes over mobile multicast services. The proposed algorithm adapts the introduced AL-FEC transmission overhead exploiting at first the reception reports ability defined by several mobile multicast standards and thereafter the performance properties of the newly introduced RaptorQ FEC codes. We introduce the competitive\&nbsp;framework of the efficient application of AL-FEC protection over mobile multicast networks, in the context of which, we design and analyze the adaptive online weighted algorithm and we further\&nbsp;provide a series of simulation results to analyze the performance of the proposed scheme.</p>
},
	author = {Christos Bouras and Nikos Kanakis}
}
@conference {3447,
	title = {Comperative analysis of broadband penetration and digital services in South East Europe},
	booktitle = {The 19th IEEE Symposium on Computers and Communications (ISCC 2014), Madeira Island, Portugal},
	year = {2014},
	month = {June 23-26},
	abstract = {<p class="rtejustify">Broadband is starting to be deemed by many as a\&nbsp;public utility and several countries have already recognized it as<br />
a civil right. The European Commission (EC) acknowledging the\&nbsp;significance of broadband services for the improvement of citizen\&nbsp;welfare and its economic benefits, has put in place targets for the\&nbsp;diffusion of broadband to all citizens and businesses in the\&nbsp;European Union. This paper, comparatively assesses the current\&nbsp;state of affairs in broadband and digital public services in\&nbsp;selected South East Europe countries in order to identify\&nbsp;weaknesses and highlight strengths and to produce knowledge\&nbsp;resources and provide insights that will support informed\&nbsp;decision making including strategy and policy planning. It builds\&nbsp;on three surveys that took place in the second quarter of 2013\&nbsp;and evidence gathered from seven South East Europe countries.</p>
},
	author = {K Antonis and Christos Bouras and D Elia and A. Di Vincenzo and Georgios Diles and Vasileios Kokkinos and A. Koskeris}
}
@article {3441,
	title = {Cross Layer Design for Video Streaming in MANETs},
	journal = {Journal of Networks, Academy Publishers},
	volume = {9, No. 2},
	year = {2014},
	pages = {328-338},
	abstract = {<p class="rtejustify">Mobile Ad hoc NETworks (MANETs) are\&nbsp;becoming more essential to wireless communications due to<br />
growing popularity of mobile devices. However, MANETs\&nbsp;do not seem to effectively support multimedia applications<br />
and especially video transmission. In this work, we propose\&nbsp;a cross-layer design that aims to improve the performance\&nbsp;of video transmission using TCP Friendly Rate Control\&nbsp;(TFRC). Our design provides priority to video packets and\&nbsp;exploits information from the MAC layer in order to\&nbsp;improve TFRC?s performance. The proposed cross-layer\&nbsp;design utilizes SNR measurements along the routing path, in\&nbsp;order to make the route reconstruction procedure more\&nbsp;efficient. Simulation results show that both the use of traffic\&nbsp;classification and the SNR utilization lead to important\&nbsp;improvements in terms of end-to-end Quality of Service\&nbsp;(QoS).</p>
},
	author = {George Adam and Christos Bouras and Apostolos Gkamas and Vaggelis Kapoulas and G Kioumourtzis}
}
@article {4106,
	title = {Economic Broadband Development through Infrastructure Sharing},
	journal = {International Journal of Business Data Communications and Networking, IGI Global},
	volume = {10},
	year = {2014},
	pages = {21-42},
	abstract = {<p class="rtejustify">Broadband is a public utility with positive effects on competitiveness, employment and growth. Although evidence shows that broadband development is increasing, this increment is not homogeneous between urban and rural areas. The main factor is the high cost for deploying next generation networks in rural areas, and especially the cost linked to civil engineering works. In order to overcome the investment challenges arising in the context of broadband deployment, the European Commission made mandatory the sharing of existing telecommunication and non-telecommunication infrastructures and facilities. This manuscript proposes and presents a novel tool that enables the estimation of the expected savings from exploiting existing infrastructures when deploying a broadband network. This is followed by a number of general principles and recommendations that policy makers and national authorities could embrace to diminish deployment costs and promote broadband deployment.</p>
},
	author = {Christos Bouras and Konstantinos Antonis and Georgios Diles and Vasileios Kokkinos and Leonidas Loukopoulos}
}
@inbook {3435,
	title = {Enhancing simulation environment with TRAFIL},
	booktitle = {Simulation Technologies in Networking and Communications: Selecting the Best Tool for the Test},
	year = {2014},
	pages = {391-415},
	publisher = {CRC Press},
	organization = {CRC Press},
	chapter = {14},
	abstract = {<p>This chapter presents TRAFIL, a comprehensive tool for enhancing execution of simulations. It provides an overview of the tool, its architecture and its functionalities. It explains how TRAFIL en-hances the entire simulation procedure including graphical setup of simulation scenarios, automated execution of simulations, flexible handling and storage of simulation trace files and presentation of plots based on processing of simulation results. It presents the concept of metafiles that provides TRAFIL with the flexibility to handle heterogeneous simulation environments. The chapter also compares TRAFIL performance with other similar tools and finds that it offers significantly im-proved performance. It therefore concludes that TRAFIL offers both a rich set of simulation en-hancement functionalities and top performance.</p>
},
	author = {Christos Bouras and Savvas Charalambides and Michalis Drakoulelis and G Kioumourtzis and Kostas Stamos}
}
@conference {4063,
	title = {Evaluating the Unification of Multiple Information Retrieval Techniques into a News Indexing Service},
	booktitle = {3rd International Conference on Data Management Technologoes and Applications (DATA 2014)},
	year = {2014},
	month = {29-31 August},
	pages = {33-40},
	abstract = {<p>While online information sources are rapidly increasing in amount, so does the daily available online news content. Several approaches have being proposed for organizing this immense amount of data. In this work we explore the integration of multiple information retrieval techniques, like text preprocessing, n-grams expansion, summarization, categorization and item/user clustering into a single mechanism designed to consolidate and index news articles from major news portals from around the web. Our goal is to allow users to seamlessly and quickly get the news of the day that are of appeal to them via our system. We show how, the application of each one of the proposed techniques gradually improves the precision results in terms of the suggested news articles for a number of registered system users and how, aggregately, these<br />
techniques provide a unified solution to the recommendation problem.</p>
},
	author = {Christos Bouras and Vassilis Tsogkas}
}
@conference {4061,
	title = {Femtocells Coordination in Future Hybrid Accesss Deployments},
	booktitle = {The Eleventh International Symposium on Wireless Communication Systems, Barcelona, Spain},
	year = {2014},
	month = {26-29 August},
	pages = {313-317},
	abstract = {<p>Femtocells provide an attractive solution to locally improve the data rates and the coverage of future mobile networks including 5G. However, nearby non-subscribed users may experience severe interference. Hybrid access operation allows femtocells to serve non-subscribers by allowing them access to part of the spectrum. In this work, we propose a distributed process that allows the hybrid femtocell to defines the<br />
spectrum access for the two types of users. The mechanism takes into account the prior condition of the users and tries to minimize the femtocell{\textquoteright}s impact to the rest of the network. We also introduce a power control mechanism within clusters of femtocells. The mechanism relieves the femtocell operating in hybrid access mode and its subscribed users, by coordinating accordingly the nearby femtocells{\textquoteright} transmission.</p>
},
	author = {Christos Bouras and Georgios Diles and Vasileios Kokkinos and Andreas Papazois}
}
@conference {3448,
	title = {Financing and Pricing Small Cells in Next - Generation Mobile Networks},
	booktitle = {12th International Conference on Wired and Wireless Internet Communications (WWIC{\textquoteright}2014), Paris, France},
	year = {2014},
	month = {May 26-28},
	pages = {41-54},
	abstract = {<p class="rtejustify"><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">Small cells technology has also strong potentials for enhancing cell coverage and network capacity of next-generation cellular net</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">works including 5G. From mobile network operators{\textquoteright} perspective, small\&nbsp;</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">cell deployment will additionally achieve large reduction to the network\&nbsp;</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">costs in both elds of capital expenditure and operational expenditure.\&nbsp;</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">In this study, we analyze the benets of small cells{\textquoteright} deployment for oper</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">ators and we list the subscriber incentives for choosing small cells instead\&nbsp;</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">of other access types, such as WiFi, for indoor deployment. Furthermore,\&nbsp;</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">we provide a nancial analysis of the small cell costs for deployment and\&nbsp;</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">operation against the corresponding macrocellular costs. We also exam</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">ine pricing models that could be used to incentivize subscribers and to\&nbsp;</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">expedite the small cells{\textquoteright} penetration into the market so as to become an\&nbsp;</span><span style="color:rgb(0, 0, 0); font-family:times new roman; font-size:medium">economically viable solution. Finally, we present our experimental results\&nbsp;demonstrating possible use cases of our cost and pricing models.</span></p>
},
	author = {Christos Bouras and Vasileios Kokkinos and Andreas Papazois}
}
@conference {3445,
	title = {A Framework for Cross - platform Mobile Web Applications Using HTML5},
	booktitle = {2014 International Workshop on Mobile Applications (MobiApps 2014), Barcelona, Spain},
	year = {2014},
	month = {August 27-29},
	pages = {420-424},
	abstract = {<p class="rtejustify">In recent years the use of smart mobile devices has become\&nbsp;an integral part of everyday life leading to the expansion of applications\&nbsp;development for the various mobile platforms. Each of these platforms\&nbsp;requires separate software development process, which subsequently increases\&nbsp;dramatically the corresponding eort. With the emergence of<br />
HTML5 these issues can be addressed eciently since application development\&nbsp;is allowed in a cross-platform manner. An additional important\&nbsp;benet is that users can access the application immediately without\&nbsp;any need for installation. In this paper, we investigate the potentials of\&nbsp;mobile application development with web technologies and we present<br />
a development framework that utilizes the most important state-of-art\&nbsp;web technologies for the support of mobile devices. This framework can\&nbsp;be used for the implementation of mobile web applications and also for\&nbsp;the investigation and experimentation on the main features that HTML5\&nbsp;oers for this specic type of devices.</p>
},
	author = {Christos Bouras and Andreas Papazois and Nikos Stasinos}
}
@inbook {4067,
	title = {IMPACT OF BROADBAND ON ECONOMY},
	booktitle = {Policies and Tools for Efficient Design of Broadband Development},
	year = {2014},
	pages = {28-42},
	chapter = {2},
	abstract = {<p>In this chapter, we investigate the impact of broadband on the growth and employment in SEE countries, namely Austria, Bulgaria, the former Yugoslav Republic of Macedonia (FYROM), Greece, Montenegro, Slovenia. Specifically, we define the macroeconomic evidence required for the analysis. We then enforce regression analysis on data collected by the respective countries in order to find the correlation between broadband, growth and employment. The period of the examination was set to be the last decade in order to obtain an extended amount of data, and take into account possible influences on the results by the economic crisis and the subsequent recession of the last years in the area. We also estimate the cost savings to companies and the state by the usage of broadband-based e-government services. We then forecast these benefits to 2015 when the respective countries are expected to have reached the e-government usage level which is set by the European digital agenda (Digital agenda, 2013).</p>
},
	author = {Christos Bouras and Vasileios Kokkinos and Georgios Diles and Lefteris Topaloglou and Christos Bouras and Andrej Kos and Andrew Frank}
}
@article {3111,
	title = {Implementing Advanced Characteristics of X3D Collaborative Virtual Environments for supporting e - Learning: The Case of EVE Platform},
	journal = {International Journal of Distance Education Technologies, IDEA Group Publishing},
	volume = {12},
	year = {2014},
	pages = {13-37},
	abstract = {<p>Three dimensional Collaborative Virtual Environments are a powerful form of collaborative telecommunication applications, enabling the users to share a common three-dimensional space and interact with each other as well as with the environment surrounding them, in order to collaboratively solve problems or aid learning processes. Such an environment is {\textquotedblleft}EVE Training Area tool{\textquotedblright} which is supported by {\textquotedblleft}EVE platform{\textquotedblright}. This tool is a three-dimensional space where participants, represented by three-dimensional humanoid avatars, can use a variety of e-collaboration tools. This paper presents advanced functionality that has been integrated on {\textquotedblleft}EVE Training Area tool{\textquotedblright} in order to support: (a) multiple collaborative learning techniques (b) Spatial audio conferencing, which is targeted to support principle 3 (augmenting user?s representation and awareness). Furthermore the paper presents technological and implementation issues concerning the evolution of {\textquotedblleft}EVE platform{\textquotedblright} in order to support this functionality.</p>
},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Vasileios Triglianos}
}
@article {3442,
	title = {Multi - domain Information Exchange in a Bandwidth on Demand Tool},
	journal = {Journal of Networks, Academy Publishers},
	volume = {9, No. 5},
	year = {2014},
	pages = {1075-1085},
	abstract = {<p class="rtejustify">Abstract{\textemdash}In this paper we describe the multi-domain\&nbsp;information exchange aspects of the AutoBAHN tool, which<br />
is used for implementing a Bandwidth on Demand service as\&nbsp;part of the GEANT project. This project was driven by the\&nbsp;increasing demand for reliable and guaranteed data\&nbsp;transportation for scientific purposes. In order to\&nbsp;implement the process of information exchange in a multidomain\&nbsp;heterogeneous environment several design decisions\&nbsp;have to take place, in order to balance and satisfy by the\&nbsp;needs of information security, fast information\&nbsp;dissemination, efficient request processing, reliability and\&nbsp;robustness. The paper describes how AutoBAHN\&nbsp;implements a flexible AAI in a distributed environment,\&nbsp;how it exchanges and updates information and how it\&nbsp;handles incoming requests in an efficient and timely manner.\&nbsp;The multi-domain aspect of this effort stems from the fact\&nbsp;that the tool is used in the production environment of\&nbsp;several cooperating National Research and Educational\&nbsp;Networks (NRENs) across Europe. Each NREN may have\&nbsp;different underlying technologies, different policies and\&nbsp;different use cases, but they all have to coordinate through\&nbsp;usage of the AutoBAHN tool in order to produce a multidomain\&nbsp;service of circuit reservation.</p>
},
	author = {George Adam and Christos Bouras and Ioannis - Christos Kalligeros and Kostas Stamos and Giannis Zaoudis}
}
@book {4064,
	title = {Policies and Tools for Efficient Design of Broadband Development},
	year = {2014},
	abstract = {<p>Broadband is the fourth strategic pillar of the Digital Agenda for Europe. The connectivity and internet access it provides is a key enabler for a number of important services for citizens, businesses and the public sector. The ambitious targets set in the Digital Agenda indicate the importance of broadband for the economy of the EU and citizen welfare.</p>

<p>The SIVA project supports the goals of EU{\textquoteright}s strategy on digital technologies (namely the Digital Agenda for Europe) and aims to contribute to the improvement of virtual accessibility in South East Europe through the promotion of broadband access, supplementing physical accessibility and thus narrowing the digital gap in the SEE area.</p>
},
	author = {Lefteris Topaloglou and Christos Bouras and Andrej Kos and Andrew Frank, Andrew (editors)}
}
@article {3443,
	title = {Policy recommendations for public administrators on free and open source software usage},
	journal = {Telematics and Informatics, Elsevier Science},
	volume = {31},
	year = {2014},
	abstract = {<div>\&nbsp;</div>

<div>
<p>Free and open source software, holding a strategic position in knowledge economy, reaffirms\&nbsp;the critical role of governments and regional authorities in establishing strategies for integrating\&nbsp;effective and sustainable Information Technology solutions in the public sector\&nbsp;towards economic growth and social welfare. Moreover, public services, organisations and\&nbsp;territorial administrations collectively represent a major software user with great impact\&nbsp;on the software market. In this sense, software selection in the public sector is a highly political\&nbsp;and strategic process; various collateral implications and policy aspects should be considered\&nbsp;in order to reach the best possible decisions. Within this context, this manuscript\&nbsp;provides policy recommendations on issues and challenges pertaining to the use of free\&nbsp;and open source software by European public administrations. The recommended policy\&nbsp;actions are mainly based on review of the current policy framework. The main goal of this\&nbsp;manuscript is to contribute in providing policy orientations and proposing actions that can\&nbsp;help governments, public administrations and European institutions fully harvest the benefits\&nbsp;of open source.</p>
</div>
},
	author = {Christos Bouras and Anestis Filopoulos and Vasileios Kokkinos and Sotiris Michalopoulos and Dimitris Papadopoulos and Georgia Tseliou}
}
@conference {4062,
	title = {Power Efficient Group Communication in Small Cell Networks},
	booktitle = {Fourth International Conference on Selected Topics in Mobile \& Wireless Networking (MoWNET{\textquoteright} 2014)},
	year = {2014},
	month = {8-10 September},
	pages = {102-109},
	abstract = {<p>Small Cell Networks (SCNs) constitute a new promising way for increasing coverage, boosting data rates and lowering capital and operating expenditures (CAPEX and OPEX) of today{\textquoteright}s mobile networks. In this paper, we deal with the problem of efficient power control in SCNs. We propose and evaluate an efficient power control mechanism for SCNs, which efficiently controls the available power resources of the network, while on the other hand guarantees home users{\textquoteright} Quality of Service. We introduce the methodology of Priority Grouping, in which home users in the topology, are assigned to one of a number of predefined groups, with different priorities, in terms of traffic requirements. Furthermore, the<br />
mechanism dynamically updates the power setting of home base stations, based on the topology of the macro and home users in real time.</p>
},
	author = {Christos Bouras and Antonios Alexiou and Dimitrios Billios}
}
@conference {3446,
	title = {Power management for wireless adapters using multiple feedback metrics},
	booktitle = {The 10th International Wireless Communications and Mobile Computing Conference (IWCMC 2014), Nicosia},
	year = {2014},
	month = {4-8 August},
	pages = {262-267},
	abstract = {<p class="rtejustify">The main focus of this work is the effort to minimize the power consumption on mobile devices such as notebooks, netbooks, tablets, tablets, smartphones, etc. by adjusting the transmission power of the wireless card, thus extending the battery life. In order to achieve that, we provide a mechanism (which we call Signal Adaptation Mechanism {\textendash} SAM) that optimizes the power depending on the quality of the connection. This mechanism measures the quality of the transmission and adjusts the transmission power accordingly, by utilizing an expanded array of metrics along the Received Signal Strength Indicator (RSSI), for more accurate estimation. It also aims at easy implementation on various wireless adapters. In order to evaluate, fine-tune and improve the mechanism, a list of experiments has been performed. These experiments were conducted on a real (as opposed to simulated) ad-hoc network, where the nodes of the networks followed varying moving patterns.</p>
},
	author = {Christos Bouras and Vaggelis Kapoulas and Kostas Stamos and Nikos Stathopoulos and Nikos Tavoularis}
}
@conference {4066,
	title = {Revisiting the role of Incubators during Fiscal Austerity Times: The Case of PSP, Greece.},
	booktitle = {3rd Edition of the International Conference Governance of a Complex World 2014 (GCW 2014), Turin, Italy},
	year = {2014},
	month = {18 - 20 June },
	pages = {1-44},
	abstract = {<p class="rtejustify">European financial crisis has raised questions about the sustainability and the contribution of Innovation anchors especially in Southern European countries such as Greece. Based on the concept of Regional Innovation Systems we introduce a methodological approach which allows for the evaluation of the performance of Science and Technology Parks performance under different intensity levels of Government Expenditures on R\&amp;D which is considered as the dominant a policy instrument. Our framework relies on the estimation of efficiency indices which come out of a multi input - multi output knowledge production function approach. The region under scrutiny is Western Greece and its corresponding Science Park for the period from 2000-2009. The main empirical finding suggests that, due to institutional and other factors, the contribution of PSP, as it has been formed in last decade, is negative in fostering innovation activitie</p>
},
	author = {Christos Bouras and Kostas Tsekouras and Vasileios Kokkinos and Areti Gkypali}
}
@article {3440,
	title = {A Simulation Framework for Evaluating Interference Mitigation Techniques in Heterogeneous Cellurar Environments},
	journal = {Wireless Personal Communications, Springer Verlang},
	volume = {77},
	year = {2014},
	pages = {1213-1237},
	abstract = {<p class="rtejustify">Femtocells present an attractive solution for the improvement of a mobile network?s\&nbsp;services providing better data rates and coverage. Since their deployment results to a\&nbsp;heterogeneous network where two layers must utilize the available spectrum, issues of interference\&nbsp;arise. A method to address this challenge, is investigating the locations of the newly\&nbsp;installed FBS, and enforcing a power controlled transmission of all FBSs that achieves optimal\&nbsp;and fair overall performance. Another option that becomes available in inter-cell interference\&nbsp;cancellation (ICIC) macrocell environments, is utilizing the available spectrum to complete\&nbsp;or partly avoid co-channel operation. In this work, we provide a simulation framework that\&nbsp;allows the creation of custom, high configurable, user defined topologies of femtocells with\&nbsp;power control and frequency allocation capabilities. It allows the investigation of the margin\&nbsp;of improvement in interference when these methods are applied and may work as a decision\&nbsp;tool for planning and evaluating heterogeneous networks. To showcase the framework?s\&nbsp;capabilities, we evaluate and study the behaviour of custom deployed femtocells/macrocells\&nbsp;networks and examine the cross-tier interference issues. Facilitated by the framework, we\&nbsp;enforce and evaluate each interference mitigation technique for different femtocells? deployment<br />
densities. Finally, we compare the results of each method in terms of total throughput,\&nbsp;spectral efficiency and cell-edge users? performance.</p>
},
	author = {Christos Bouras and Georgios Diles and Vasileios Kokkinos and Konstantinos Kontodimas and Andreas Papazois}
}
@article {3439,
	title = {A Simulation Framework for the Evaluation of Frequency Reuse in LTE - A Systems},
	journal = {International Journal of Wireless Networks and Broadband Technologies, IGI Global},
	volume = {3},
	year = {2014},
	pages = {56-83},
	abstract = {<p class="rtejustify">Long Term Evolution Advanced (LTE-A) technology is considered as the most possible candidate for next generation mobile communications. LTE-A networks offer high capacity and are specified and designed to accommodate small, high performance, power-efficient end-user devices. Similarly to its predecessor LTE, LTE-A incorporates inter-cell interference mitigation methods in order to mitigate interference and to enhance efficiency in bandwidth usage. These methods include power and frequency allocation schemes that allow neighbouring cells and femtocells in heterogeneous networks to co-ordinately share and reuse available spectral resources, in order to avoid performance degradation for interference suffering cell-edge users. In this paper, we study the LTE-A multi-cell systems? performance using a simulation framework, which integrates several frequency reuse techniques and provides a user-friendly graphical presentation of the evaluation results. The optimal Fractional Frequency Reuse (FFR) configuration for the user-defined network instance is also determined, based on overall performance and fairness index metrics. Finally, we examine FFR techniques in two-tier femtocell/macrocell environments and evaluate them based on the optimization of different metrics, depending on the network operator?s needs.</p>
},
	author = {Dimitrios Bilios and Christos Bouras and Georgios Diles and Vasileios Kokkinos and Andreas Papazois and Georgia Tseliou}
}
@article {3113,
	title = {Application Layer Forward Error Correction for Multicast Streaming over LTE Networks},
	journal = {International Journal of Communication Systems, Wiley InterScience},
	volume = {26},
	year = {2013},
	pages = {1459-1574},
	abstract = {<p>The next step beyond third generation (3G) mobile networks is the Third Generation Partnership Project (3GPP) standard, named Long Term Evolution (LTE). A key feature of LTE is the enhancement of Multimedia Broadcast/Multicast Services (MBMS), where the same content is transmitted to multiple users located in a specific service area. To support efficient download and streaming delivery, 3GPP included an application layer Forward Error Correction (AL-FEC) technique based on the systematic fountain Raptor code, in the MBMS standard. In order to achieve protection against packet losses, Raptor codes introduce redundant packets to the transmission, i.e., the FEC overhead. In this work, we investigate the application of AL-FEC over MBMS streaming services. We consider the benefits of AL-FEC for a continuous multimedia stream transmission to multiple users and we examine how the amount of FEC redundancy can be adjusted under different packet loss conditions. For this purpose, we present a variety of realistic simulation scenarios for the application of AL-FEC and furthermore we provide an in-depth analysis of Raptor codes performance introducing valuable suggestions to achieve efficient use of Raptor codes.</p>
},
	keywords = {FEC, LTE, MBMS},
	author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Nikos Kanakis}
}
@conference {3013,
	title = {Bandwidth on Demand over Carrier Grade Ethernet Equipment},
	booktitle = {The Twelfth International Conference on Networks (ICN 2013), Seville, Spain},
	year = {2013},
	month = {January 27 - February 1},
	pages = { 204 - 208 },
	abstract = {This paper presents the prototype implementation of
a Bandwidth on Demand (BoD) service over equipment using
Carrier Grade Ethernet. The BoD multi-domain service is
based on AutoBAHN (Automated Bandwidth Allocation across
Heterogeneous Networks) software. The paper describes the
steps that have taken place for designing and implementing a
prototype technology proxy that is able to match the Carrier
Grade Ethernet equipment with AutoBAHN, based on the
implementations of the relevant standards and technologies by
Extreme Networks. The equipment in particular is comprised
of BlackDiamond 12804 switches, running ExtremeXOS
version 12. The paper demonstrates how a suitable testbed can
be created and utilized and how a new technology at the data
plane can be supported by a Bandwidth on Demand tool.},
	author = {Christos Bouras and Kostas Stamos and Theoni-Katerina Spuropoulou}
}
@conference {3019,
	title = {A Competitive AL-FEC Framework over Mobile Multicast Delivery},
	booktitle = {The 9th International Wireless Communications and Mobile Conference (IWCMC 2013), Cagliari, Italy},
	year = {2013},
	month = {July 1 - 5},
	pages = {305-310},
	abstract = {<p>Reliability control is a key concern on the evolution of real-time mobile multicast services. To this direction the use of forward error correction (FEC) on the application layer is widely adopted in several mobile multicast standards. FEC is a feedback free error control method where the transmitter introduces in advance redundant information to enable receivers recovering data erasures. On multicast delivery and especially on the time constrained streaming delivery where retransmission-based error recovery methods are not feasible, the most suitable error control method is the use of application layer forward error correction (AL-FEC) codes. In this work, we introduce a novel AL-FEC deployment policy over mobile multicast standards utilizing online algorithms. We aim on the efficient application of ALFEC protection with RaptorQ codes over multicast streaming delivery in the context of competitive analysis. We provide a competitiveness analysis model of AL-FEC application over mobile multicast real-time environments and we introduce an innovative online algorithm adjusting the introduced redundancy of AL-FEC protection according to the FEC encoding parameters in order to satisfy the individual constraints of a multicast streaming delivery.</p>
},
	keywords = {FEC},
	author = {Christos Bouras and Nikos Kanakis}
}
@conference {3431,
	title = {Deploying AL - FEC with Online Algorithms},
	booktitle = {7th International Conference on Next Generation Mobile Applications, Services and Technologies (NGMAST{\textquoteright}13), Prague, Czech},
	year = {2013},
	month = {September 25-27},
	pages = {175-180},
	abstract = {<p class="rtejustify">Application Layer Forward Error Correction (ALFEC)\&nbsp;schemes are the most suitable mechanism for error control in mobile multicast services. AL-FEC introduces redundant information in advance with the source data to provide reliability control in the multicast transmission. Due to this fact the introduced\&nbsp;redundancy must be carefully selected with respect to the current network conditions to avoid channel bandwidth wastage and achieve an efficient and reliable multicast delivery. However, the efficient selection of the introduced redundancy is not a trivial issue for the multicast source, due to the individual constraints\&nbsp;of a multicast environment. In this work, we present a novel way to face the AL-FEC deployment utilizing online algorithms for selecting the appropriate amount of redundancy introduced in the multicast transmission. We provide an efficient way to apply AL-FEC protection on mobile multicast environments with randomized online algorithms eliminating the need for prior\&nbsp;knowledge of the network conditions. To this direction, we present a competitive framework under which, we state the problem of the efficient deployment of AL-FEC protection and provide a randomized online algorithm for the AL-FEC application over mobile multicast environments.</p>
},
	author = {Christos Bouras and Nikos Kanakis and Vasileios Kokkinos and Andreas Papazois}
}
@article {3119,
	title = {Embracing RaptorQ FEC in 3GPP multicast services},
	journal = {Wireless Networks, Springer Verlang},
	volume = {19},
	year = {2013},
	pages = {1023-1035},
	abstract = {<p>Multimedia Broadcast/Multicast Services (MBMS) have been introduced by Third Generation Partnership Project (3GPP) aiming to efficiently deliver data to mobile users in a one-to-many way. In order to provide reliable multicast transmission, 3GPP recommends exclusively for MBMS the use of a Forward Error Correction (FEC) mechanism on the application layer. Raptor codes are standardized as the Application Layer FEC (AL-FEC) scheme over 3GPP MBMS. However, the 3GPP standardized systematic fountain Raptor code is nowadays considered obsolete, since a new variation of the Raptor codes has emerged. This enhanced AL-FEC scheme, named RaptorQ, promises higher protection efficiency and superior flexibility on the provision of demanding mobile multicast services. In this work, we provide an extensive performance evaluation presenting at first a theoretical performance comparison of the newly introduced RaptorQ FEC scheme with its predecessor Raptor code, examining the enhancements that RaptorQ introduces on the AL-FEC protection robustness. Thereafter, to verify the enhanced performance of RaptorQ, we present several simulation results considering the modeling of the AL-FEC protection over multicast services for next generation mobile networks, utilizing the ns-3 simulation environment. Investigating several mobile system parameters in conjunction with FEC encoding parameters, we provide valuable results regarding the impacts of the examined AL-FEC schemes application on the multicast services performance.</p>
},
	keywords = {FEC, MBMS},
	author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Nikos Kanakis}
}
@conference {3020,
	title = {Enhancing news articles clustering using word n - grams},
	booktitle = {2nd Intenational Conference on Data Management Technologies and Applications, Reykjavvk, Iceland},
	year = {2013},
	month = {July 29 - 31},
	pages = {53-60},
	abstract = {<p>In this work we explore the possible enhancement of the document clustering results, and in particular clus-tering of news articles from the web, when using word-based n-grams during the keyword extraction phase. We present and evaluate a weighting approach that combines clustering of news articles derived from the web using n-grams, extracted from the articles at an offline stage. We compared this technique with the sin-gle minded bag-of-words representation that our clustering algorithm, W-kmeans, previously used. Our ex-perimentation revealed that via tuning of the weighting parameters between keyword and n-grams, as well as the n itself, a significant improvement regarding the clustering results metrics can be achieved. This re-flects more coherent clusters and better overall clustering performance.</p>
},
	author = {Christos Bouras and Vassilis Tsogkas}
}
@conference {3427,
	title = {Enhancing video transmission in MANETs utilizing multiple interfaces and multiple channels per node},
	booktitle = {5th International Conference on Ad Hoc Networks, Barcelona, Spain},
	year = {2013},
	month = {October 16 - 18 },
	abstract = {<p>Mobile Ad hoc NETworks (MANETs) are becoming more essential to wireless communications due to growing popularity of mobile devices. MANETs are also essential in Emergency Response situation where network information flow between deployed units is vital. In such cases voice and video transmission is essential to form a global view of the situation and decide on action. However, MANETs do not seem to effectively support multimedia applications and especially video transmission. In this work we propose a simple and efficient channel selection mechanism for enhancing Video Transmission in MANETS that have nodes with multiple interfaces, and can utilize multiple channels at the same time. The mechanism is implemented and tested in the ns-2 network simulator. Simulation results indicate that the mechanism improves the networks capacity for video transmission and reduces the video streams? packet delay.</p>
},
	author = {Christos Bouras and Apostolos Gkamas and Vaggelis Kapoulas and Dimitra Politaki and Enea Tsanai}
}
@conference {3432,
	title = {Evaluating ICIC Performance in LTE - A Systems},
	booktitle = {The Tenth International Symposium on Wireless Communication Systems (ISWCS 2013), Ilmenau, Germany},
	year = {2013},
	month = {August 27 - 30},
	pages = {400-404},
	abstract = {<p class="rtejustify">LTE-A technology incorporates Inter-Cell Interference Coordination (ICIC) methods in order to enhance performance and mitigate interference. These methods include frequency allocation techniques that allow neighboring cells and femtocells in heterogeneous networks, to coordinately share and reuse available spectral resources, in order to avoid performance degradation for interference suffering cell-edge users. In this paper we evaluate the performance of the ICIC methods in LTE-A multi-cell systems using a simulation framework integrating several frequency reuse techniques and providing a user-friendly graphical presentation of the results. The optimal frequency\&nbsp;reuse configuration for the examined network instance is also determined, based on overall performance and fairness index metrics.</p>
},
	author = {Dimitrios Bilios and Christos Bouras and Georgios Diles and Vasileios Kokkinos and Andreas Papazois}
}
@conference {3429,
	title = {Evaluation of Femtocells Interference Mitigation Techniques over ICIC Coordinated LTE - A Networks},
	booktitle = {Wireless Days 2013, Valencia Spain},
	year = {2013},
	month = {November 13 - 15},
	abstract = {<p class="rtejustify">Abstract{\textemdash}Femtocells offer an attractive solution to locally\&nbsp;improve the data rates and coverage of mobile networks, however interference issues may rise when they are deployed to nearby non-subscribed macro users. Power control and radio management are the most prominent ways to tackle the problem. In this work, we provide a simulation framework that is capable to simulate the behaviour of femtocells deployment over Long\&nbsp;Term Evolution Advanced (LTE-A) macrocells networks. With the help of the tool, we evaluate several available interference mitigation techniques for femtocells, when applied in Inter-Cell Interference Cancellation (ICIC) macrocell environments.</p>
},
	author = {Christos Bouras and Georgios Diles and Vasileios Kokkinos and Andreas Papazois}
}
@conference {3426,
	title = {Evaluation of Routing Protocols for Video Transmission over MANETs that use Multiple Interfaces and Multiple Channels per node},
	booktitle = {19th IEEE International Conference on Networks (ICON 2013), Singapore},
	year = {2013},
	month = {December 11 - 13},
	abstract = {<p class="rtejustify">Mobile Ad hoc NETworks (MANETs) are becoming\&nbsp;more essential to wireless communications due to growing popularity of mobile devices. Many researchers have committed effort to enhance the Multimedia (video) transmission over MANETs. Various algorithms and mechanisms concerning the optimization of multimedia transmission have been presented. In\&nbsp;this work we evaluate the effect of using multiple interfaces and multiple channels per node in the performance of already existing MANET routing protocols during video transmission. The\&nbsp;evaluation shows that all routing protocols benefit from using multiple interfaces and multiple channels per node, and the video transmission over MANETs is improved.</p>
},
	author = {Christos Bouras and Apostolos Gkamas and Vaggelis Kapoulas and Dimitra Politaki and Enea Tsanai}
}
@conference {3433,
	title = {Evaluation of video transmission in emergency response ad - hoc networks},
	booktitle = {4th International Conference on Data Communication Networking - DCNET 2013, Reykjavvk, Iceland},
	year = {2013},
	month = {July 29 - 31},
	pages = {27-35},
	abstract = {<p class="rtejustify">Mobile Ad hoc NETworks (MANETs) are becoming more essential to wireless communications due to\&nbsp;growing popularity of mobile devices. MANETs are also essential in Emergency Response situation where\&nbsp;network information flow between deployed units is vital. In such cases voice and video transmission is\&nbsp;essential to form a global view of the situation and decide on action. However, MANETs do not seem to\&nbsp;effectively support multimedia applications and especially video transmission. In this work we evaluate the\&nbsp;use of multiple interfaces and multiple channels for Video Transmission in Emergency Response Ad hoc\&nbsp;Networks. We also evaluate the video transmission with rate adaptation. Aim of this paper is to tune multiinterfaces\&nbsp;and multi-channels video transmission mechanisms in order to support better emerging situations\&nbsp;and offer a solution to have acceptable transmission of the necessary video streams so that the control can\&nbsp;get a complete overall picture of the situation and decide on the action to be taken. The simulation\&nbsp;evaluation performed shows that multi-interfaces and multi-channels video transmission offers many\&nbsp;advantages in Video Transmission in Emergency Response Ad hoc Networks.</p>
},
	author = {Christos Bouras and G Kioumourtzis and Apostolos Gkamas and Vaggelis Kapoulas and Dimitra Politaki and Enea Tsanai}
}
@conference {3015,
	title = {Feedback-based Adaptation for Improved Power Consumption},
	booktitle = {27th IEEE Intenational Conference on Advanced Information Networking and Applications (AINA - 2013),  Barcelona, Spain},
	year = {2013},
	month = {March 25 - 28},
	pages = { 562 - 568 },
	abstract = {In this paper we present a feedback-based
adaptation mechanism that adjusts the transmission power of
a wireless card on commodity PCs depending on the quality of
the connection. Our purpose is to manage the available power
in order to achieve lower power consumption without
negatively affecting the user?s perception of connection quality.
We based our implementation on an existing theoretical model
and focused on resolving problems and removing assumptions
which made it inefficient in real life implementation. The initial
model manages to minimize the power consumption in
networks with exactly two nodes. In this paper, we extend the
model to consider the possibility of the existence of a base
station, where any number of nodes can be connected. Our
objectives for the base station are to minimize the power
consumption and guarantee continuous connectivity for all
mobile nodes. We implement the adaptation mechanism for a
specific adapter with open sources drivers thus allowing
necessary modifications. We conduct a number of real world
experiments. The results indicate that power consumption can
be significantly reduced for nodes that are either almost
stationary or slowly moving (e.g. at walking speed), without
any significant increase in packet loss. The results are quite
important as nowadays mobile devices with limited battery life
time use tethering to become base stations for other devices
like in ad-hoc networks.},
	author = {Christos Bouras and Vaggelis Kapoulas and Kostas Stamos and G Kioumourtzis and Nikos Tavoularis and Nikos Stathopoulos}
}
@conference {3017,
	title = {Fractional Frequency Reuse in Integrated Femtocell/Macrocell Environments},
	booktitle = {11th International Conference on Wired/Wireless Internet Communications (WWIC 2013), Saint - Petersbourg, Russia},
	year = {2013},
	month = {June 5-7},
	pages = { 229 - 240},
	abstract = {<p>Femtocells have a strong potential for increasing the efficiency, cell coverage and network capacity of next-generation mobile networks. In Long Term Evolution technology, the adaptation of Fractional Frequency Reuse techniques has been proposed in order to overcome the co-channel interference and augment the total throughput of the network. In this work, we propose a Fractional Frequency Reuse method that on the one hand calculates the optimal inner region radius and frequency allocation of a macrocell and on the other hand assigns frequency resources to the femtocells in order to mitigate the co-channel interference. We apply this method in an integrated femtocell/macrocell environment and evaluate it based on the optimization of three metrics, depending on the network operator?s needs.</p>
},
	keywords = {FFR},
	author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Georgia Tseliou}
}
@conference {3018,
	title = {Handling Topology Updates in a Dynamic Tool for Support of Bandwidth on Demand Service},
	booktitle = {The Ninth Advnaced International Conference on Telecommunications (AICT 2013), Rome, Italy},
	year = {2013},
	month = {June 23 ?- 28},
	pages = {161-165},
	abstract = {<p>Automated Bandwidth Allocation across Heterogeneous Networks (AutoBAHN) is a tool under active development that supports a Bandwidth on Demand (BoD) service, intended to operate in a multi-domain environment using heterogeneous transmission technologies. The AutoBAHN system aims at providing a guaranteed capacity, connection-oriented service between two end points. Due to the distributed nature of the system and the fact that AutoBAHN has access to critical parts of the network, the importance of a robust, secure and dynamic mechanism for handling and distributing topology information cannot be underestimated. We will present how AutoBAHN manages to create an abstract representation of the physical network topology by hiding information such as IP addresses, port values, VLAN, MTU, link capacities etc., how this abstract topology is merged among domains and how AutoBAHN system handles topology changes in terms of their influence on reservation processing.</p>
},
	author = {Christos Bouras and Kostas Stamos and Ioannis - Christos Kalligeros}
}
@conference {3428,
	title = {Impact of broadband public infrastructures and services on SEE countries{\textquoteright} economy},
	booktitle = {Global Information Infrastructure and Networking Symposium (GIIS 2013), Trento Italy},
	year = {2013},
	month = {October 28 - 31},
	abstract = {<p class="rtejustify">Broadband is an important tool for increasing\&nbsp;productivity and competitiveness. This paper attempts to measure the accumulative impact and effectiveness of broadband public infrastructures and services on the economy of South East Europe (SEE) areas. To this direction, we focus on evaluating the correlation between broadband and each country?s growth and\&nbsp;employment. Moreover, we estimate the cost savings achieved by the extended usage of e-services, and we evaluate the potential cost savings that will follow the increase of e-services utilization the next years. The results of our analysis show that broadband\&nbsp;may have positive impact on growth and employment and that the possible savings are substantial.</p>
},
	author = {Christos Bouras and Georgios Diles and Vasileios Kokkinos}
}
@article {3115,
	title = {Methodology for Public Administrators for Selecting between Open Source and Proprietary Software},
	journal = {Journal of Telematics
and Informatics, Elsevier Science},
	year = {2013},
	pages = {  100 - 110},
	abstract = {The public sector needs to change over to communicating digitally. This development makes great demands both on work processes in the public sector and on the Information Technology systems, on which e-government is based. From the economic perspective, the change-over poses great challenges, as huge investments will have to be made in Information Technology in the public sector. It is therefore natural, in connection with these investments, for a detailed assessment to be made of what forms of technology it is anticipated to be used, and who controls the development and ownership of this technology. The question is: to what extent Free and Open Source Software can supplement or completely replace proprietary software? This work constitutes a review of literature on pre-existing comparative studies regarding the technical, social, economic and organizational factors on Free and Open Source Software usage. Furthermore, this work includes guidelines that Public Administrations should follow for the selection between open source and proprietary software. Our goal is to help public stakeholders understand the technical/social/economic/organizational environment and therefore reach informed decisions when selecting the appropriate software. The manuscript can also be useful for Free and Open Source Software developers, users and communities who are either directly or indirectly involved in the software market.},
	author = {Christos Bouras and Vasileios Kokkinos and Georgia Tseliou}
}
@conference {3016,
	title = {Mobility MCS Selection Mechanisms for Multicasting over LTE Networks},
	booktitle = {6th Joint IFIP Wireless and Mobile Networking Conference (IFIP WMNC{\textquoteright} 2013), Dubai, UAE},
	year = {2013},
	month = {April 23 -? 25},
	abstract = {<p>In Long Term Evolution (LTE) networks, the Multimedia Broadcast/Multicast Services over Single Frequency Network (MBSFN) operation enables the delivery of the same multimedia content to a set or all the users in a cell, leading in this way to efficient utilization of the network resources. This is achieved through a time-synchronized common waveform that is transmitted from multiple cells for a given duration, which enables over-the-air combining, and therefore significantly improves the spectral efficiency. However, the performance of MBSFN is directly connected to the Modulation and Coding Scheme (MCS) and the transmission mode that will be selected for the delivery of the multimedia data. This paper proposes three different approaches for the selection of the MCS during MBSFN transmissions. Main target is to determine the most efficient approach depending on the target that the operator may set, i.e. the approach that either maximizes the spectral efficiency or achieves a target spectral efficiency for various user distributions. The performance of the approaches is evaluated for scenarios that include users? mobility and for three different transmission modes in order to also examine the effectiveness of Multiple Input Multiple Output (MIMO) techniques.</p>
},
	keywords = {MCS},
	author = {Christos Bouras and Vasileios Kokkinos and Stavroula Bochrini}
}
@conference {3014,
	title = {Mobility-Sensitive Power Control for MBSFN Cellular Networks},
	booktitle = {The Ninth International Workshop on Heterogeneous Wireless Networks (HWISE - 2013), Barcelona, Spain},
	year = {2013},
	month = {March 25 - 28},
	pages = { 483 - 487 },
	abstract = {Cellular networks? Multimedia Broadcast/Multicast
Service (MBMS) over a Single Frequency Network (MBSFN)
allows broadcasting cell signals to constructively interfere and
users to take advantage of increased bitrates compared to other
broadcasting technologies. In this paper, we present our work on
the optimization of the power control for future cellular networks
that employ MBSFN transmission scheme. We propose a novel
simulator and optimizer that can minimize the transmission
power of individual cells taking into account the changing
positions of users. In order to read descriptions of the various
scenarios, the simulator uses the eXtendable Temporal Network
Description Language (XTNDL), a language that is defined in this
paper. The optimizer?s engine can be used in conjunction with
the simulator or can be modified to read real time measurements
from a real network.},
	keywords = {Power Control},
	author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Konstantinos Asimakis}
}
@article {3105,
	title = {Modulation and coding scheme selection in multimedia broadcast over a single frequency network-enabled long-term evolution networks},
	journal = {International Journal of Communication Systems, Wiley InterScience},
	volume = {25},
	year = {2013},
	pages = {1603-1619},
	abstract = {<p>Long term evolution constitutes the next generation cellular network beyond 3G that is designed to support the explosion in demand for bandwidth-hungry multimedia services in wireless networks by providing an extremely high performance radio access technology. To support multimedia broadcast/multicast services (MBMS), long term evolution offers the functionality to transmit MBMS over a single frequency network, where a time-synchronized common waveform is transmitted from multiple cells for a given duration. This enables over-the-air combining, thus significantly improving the spectral efficiency (SE) compared with conventional MBMS operations. In MBMS over a single frequency network transmissions, the achieved SE is mainly determined by the modulation and coding scheme selected. This study proposes and evaluates four approaches for the selection of the modulation and coding scheme. Each approach corresponds to different users? distribution and multimedia traffic conditions. On the basis of SE measurements, we determine the approach that either maximizes or achieves a target SE for the corresponding users? distribution and traffic conditions. Copyright {\textcopyright} 2011 John Wiley \&amp; Sons, Ltd.</p>
},
	keywords = {LTE, MBSFN, MCS},
	author = {Christos Bouras and Antonios Alexiou and Andreas Papazois and Vasileios Kokkinos and George Tsichritzis}
}
@conference {3430,
	title = {A Power Control Mechanism Based on Priority Grouping for Small Cell Networks},
	booktitle = {8th International Conference on Broadband and Wireless Computing, Communication and Applications (BWCCA 2013), Paris, France},
	year = {2013},
	month = {October 28 - 30},
	pages = {170-176},
	abstract = {<p class="rtejustify">Future mobile networks following Long Term Evolution (LTE) will be characterized by demanding services, in terms of bandwidth and delay, already dominant in wired networks, such as cloud-computing, High Definition of anything (HDOA) and highly-interactive online games. Small Cell technology is one of the key-technologies aiming to address the need for ultra-high performance in future mobile networks. This paper is focused on efficient power control in Small Cell Networks (SCNs). In particular, we propose a power control mechanism for efficient power allocation in SCNs. The proposed mechanism efficiently controls systems? interference while on the other hand guarantees home user QoS. We introduce the methodology of Priority Grouping, in which home users in the topology is assigned to one of the available groups with different priorities in terms of power requirements and requested traffic load. The mechanism dynamically updates the Home evolved Node B power setting based on the topology of the macro and home users in real time. Additionally, depending on the examined traffic scenario the mechanism can provide better protection (in terms of interference) either on macro users or on home users.</p>
},
	author = {Antonios Alexiou and Dimitrios Bilios and Christos Bouras}
}
@article {3120,
	title = {Power Management Mechanism Exploring Network and Video Information over Wireless Links},
	journal = {Journal of Networks, Academy Publishers},
	year = {2013},
	pages = { 15 - 25},
	abstract = {This article examines the ways in which crosslayer
information from higher network layers may be
utilized for more efficient power management in wireless
networks and energy constrained mobile devices. In
particular, we present and evaluate mechanisms that finetune
transmission power according to information received
from the transport (feedback reports from TFRC) and
application (type of the video frame encoded) layers.
Further improvements may be applied if the video encoding
is done using capabilities of the SVC standard. We also
describe power management adaptation techniques for
wireless video transmission using the TFRC protocol that
take into account feedback about the received video quality
and try to adapt transmitting power accordingly. The
purpose of the mechanisms is to utilize TFRC feedback and
thus achieve a beneficial balance between the power
consumption and the received video quality. The
mechanisms proposed, offer significant improvements when
used in terms of both power consumption and received
video quality. All proposals are compared and evaluated
using simulation.},
	author = {Christos Bouras and Kostas Stamos and Giannis Zaoudis and Stamatis Stroumpis and Savvas Charalambides}
}
@article {3121,
	title = {Selecting the Optimal Fractional Frequency Reuse Scheme in Long Term Evolution Networks},
	journal = {Wireless Personal Communications, Springer Verlang},
	volume = {71},
	year = {2013},
	pages = {2693-2712},
	abstract = {<p>Long Term Evolution (LTE) networks offer high capacity and are specified and designed to accommodate small, high performance, power-efficient end-user devices. One limiting factor that influences LTE performance is the interference from neighbouring cells, the so called Inter-Cell Interference (ICI). The investigation of ICI mitigation techniques has become a key focus area in achieving dense spectrum reuse in next generation cellular systems. Fractional Frequency Reuse (FFR) has been proposed as a technique to overcome this problem, since it can efficiently utilize the available frequency spectrum. This manuscript proposes a dynamic mechanism that selects the optimal FFR scheme based on a custom metric, which is called user satisfaction. In detail, the proposed mechanism divides the cell into two regions, the inner and outer region, and selects the optimal size as well as the optimal frequency allocation between these regions with main target to maximize the user satisfaction metric. The proposed mechanism is evaluated through several simulation scenarios that incorporate users? mobility and its selected FFR scheme is compared with other frequency reuse schemes in order to highlight its performance.</p>
},
	keywords = {FFR},
	author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Georgia Tseliou and Dimitrios Bilios}
}
@conference {3021,
	title = {Simulation design and execution: The case of TRAFIL},
	booktitle = {3rd Intenational Conference on Simulation and Modeling Methodologies, Technologies and Applications, Reykjavvk, Iceland},
	year = {2013},
	month = {29-31 July },
	pages = {27-34},
	abstract = {<p>This paper presents the enhancements that we have done on the TRAFIL (TRAce FILe) framework, which significantly extend its capabilities in the areas of simulation design and execution. In particular, TRAFIL now offers the possibility to design, create, execute and review NS-2 simulation scenarios, on top of its ex-isting post-simulation trace analysis functionalities. The enhancements make TRAFIL a complete wrapper around the NS-2 simulator, allowing the user to perform all steps from pre-simulation design to actual simu-lation execution in an automated way and fast and convenient post-simulation analysis of potentially large amount of data. The paper describes the new TRAFIL architecture and how these enhancements were im-plemented with the goal of relieving NS-2 users from the often cumbersome tasks of script writing and vali-dating, while also enabling them at to go behind the TRAFIL environment and into the simulator internals at any time. The paper presents the new GUI functionalities developed for that purpose, the approach that we took for their design and how these fit in the overall TRAFIL architecture.</p>
},
	author = {Christos Bouras and Kostas Stamos and G Kioumourtzis and Savvas Charalambides and Michalis Drakoulelis}
}
@article {3118,
	title = {A tool for automatic network simulation and processing tracing data files},
	journal = {Simulations Modelling Practice and Theory Journal, Elsevier Science},
	year = {2013},
	pages = { 90 - 110},
	abstract = {<p class="rtejustify">One of the most highly regarded discrete event simulators used for network simulation is NS-2 (Network Simulator). NS-2 executes simulation scenarios producing various data of which trace files are considered the most beneficial for evaluating a simulation. In this paper we present the design considerations and implementation of a new tool that can be used both in TRAce FILe analysis and execution of simulations using NS-2. Although TRAFIL is primarily based on NS-2 trace files it can be extended to support a number of different other simulation trace file formats. It aims to make the execution of a great number of network simulations quicker, and the extraction of results from a large amount of data more flexible and productive. In order to accomplish the above tasks TRAFIL presents a novel way of interpreting, parsing, reading and eventually using NS-2 trace files. It introduces the notion of ??metafiles?? and ??sub metafiles?? throughout the procedures of trace file recognition and parsing, making the overall analysis operation substantially efficient and faster than alternative approaches. Metafiles and sub metafiles are used to encode NS-2 trace file structures enabling a more abstract approach to the trace file processing operation. Furthermore, TRAFIL facilitates the overall trace file analysis task by offering the opportunity to store each trace file as well as every Quality of Service (QoS) measurement produced for each trace file. Following the trace file recognition and processing operations, the information contained in a trace file is presented through a Graphical User Interface (GUI) offered by TRAFIL along with a variety of data, metrics and statistics related to simulation results. Finally, the tool offers the opportunity to execute custom Structured Query Language (SQL) queries to the local database and to completely automate the simulation procedure by enabling the user to execute NS-2 scripts as well as perform a simulation of a video transmission using the Evalvid-RA framework.</p>
},
	author = {Christos Bouras and Kostas Stamos and G Kioumourtzis and Savvas Charalambides and Michalis Drakoulelis}
}
@article {3116,
	title = {Building community and collaboration applications for MMOGs},
	journal = {International Journal of Computer Games Technology, Hindawi Publishing Corporation, Vol. 2012, Article ID 969785},
	year = {2012},
	abstract = {Supporting collaborative activities among the online players are one of the major challenges in the area of Massively  multiplayer Online Games (MMOG), since they increase the richness of gaming experience and create more engaged communities. To this direction, our study has focused on the provision of services supporting and enhancing the players{\textquoteright} in-game community and collaboration activities. We have designed and implemented innovative tools exploiting a game adaptation technology, namely the In-game Graphical Insertion Technology (IGIT), which permits the addition of web-based applications without any need from the game developers to modify the game at all, nor from the game players to change their game installation. The developed tools follow a design adapted to the MMOG players{\textquoteright} needs and are based on the latest advances on Web 2.0 technology. Their provision is performed through the core element of our system, which is the so-called Community Network Game (CNG) Server. One of the important features provided by the implemented system{\textquoteright}s underlying framework is the utilization of enhanced Peer-to-Peer (P2P) technology for the distribution of user-generated live video streams. In this paper, we focus on the architecture of the CNG Server as well as on the design and implementation of the online community and collaboration tools.},
	author = {Christos Bouras and Vaggelis Kapoulas and Andreas Papazois and George Adam}
}
@article {3117,
	title = {A clustering technique for news articles using WordNet},
	journal = {Knowledge-Based Systems Journal, Elsevier Science, Vol. 36},
	year = {2012},
	pages = {115 - 128 },
	abstract = {The Web is overcrowded with news articles, an overwhelming information source both with its amount and diversity. Document clustering is a powerful technique that has been widely used for organizing data into smaller and manageable information kernels. Several approaches have been proposed which, however, suffer from problems like synonymy, ambiguity and lack of a descriptive content marking of the generated clusters. In this work, we are investigating the application of a great spectrum of clustering algorithms, as well as similarity measures, to news articles that originate from the Web. Also, we are proposing the enhancement of standard k-means algorithm using the external knowledge from WordNet hypernyms in a twofold manner: enriching the ??bag of words?? used prior to the clustering process and assisting the label generation procedure following it. Furthermore, we are examining the effect that text preprocessing has on clustering. Operating on a corpus of news articles derived from major news portals, our comparison of the existing clustering methodologies revealed that k-means, gives better aggregate results when it comes to efficiency. This is amplified when the algorithm is accompanied with preliminary steps for data cleaning and normalizing, despite its simple nature. Moreover, the proposed WordNetenabled W-k means clustering algorithm significantly improves standard k-means generating also useful and high quality cluster tags by using the presented cluster labeling process.},
	author = {Christos Bouras and Vassilis Tsogkas}
}
@conference {3011,
	title = {Clustering to Deal with the New User Problem},
	booktitle = { 15th IEEE International Conference on Computational Science and Engineering, Paphos, Cyrus},
	year = {2012},
	month = {5 - 7 December},
	pages = { 58 - 65},
	abstract = {Collaborative filtering (CF) techniques attempt to alleviate information overload by identifying which items a user will find interesting to browse. It focuses on identification of other users with similar tastes and usage of their opinions in order to recommend items. Commonly, however, CF suffers from the so-called new user problem which occurs when a new user is added to the system and there is not enough information to make a good suggestion. The system has to acquire some data about the new user in order to start making personalized recommendations. In this paper, we present a novel algorithm that combines previously acquired knowledge from article and user clustering in order to quickly determine the new user{\textquoteright}s interests. We attempt to address the new user problem by providing a personalized strategy for prompting the user with articles to rate. Our approach makes use of hypernyms extracted from the WordNet database and proves to be converging fast to the actual user interests based on minimal user ratings which are provided during the registration process.},
	author = {Christos Bouras and Vassilis Tsogkas}
}
@article {3109,
	title = {Cost Optimization of MBSFN and PTM Transmissions for Reliable Multicasting in LTE Networks},
	journal = {Wireless Networks, Springer Verlang},
	year = {2012},
	pages = {277-293},
	abstract = {Long Term Evolution (LTE) systems have been specified and designed to accommodate small, high performance, power-efficient, end-user devices. The evolved Multimedia Broadcast/Multicast Service (e-MBMS) feature is introduced by the 3rd Generation Partnership Project (3GPP) as a complement to the existing MBMS service in order to accommodate multicast groups that are interested in receiving the same data. MBMS service is provided by MBMS over a Single Frequency Network (MBSFN) and/or Point-To-Multipoint (PTM) transmission methods. One of the challenges of MBMS is the complete error recovery of the transmitted files, a matter of great importance since the distribution of binary data must result in 100\% error-free download. To fulfill this tight requirement, Forward Error Correction (FEC) mechanism has been proposed by 3GPP. In this work, we investigate the reliable multicasting by introducing a transmission method that combines the advantages of MBSFN and PTM transmission methods. We compare several FEC-based file recovery methods and evaluate them against various network parameters in a realistic simulation environment. The comparison is based on a cost-oriented analysis of MBMS service that takes into account the transmission cost over all the interfaces and nodes of the LTE architecture. The simulation results are performed with the aid of a new simulation tool and show that the performance of the file repair schemes depend on the network configuration.
KEYWORDS: multimedia multicasting; cellular networks; forward error correction; reliability; single frequency network; optimization; point to multipoint;},
	keywords = {Cost analysis, LTE, MBSFN},
	author = {Christos Bouras and Antonios Alexiou and Andreas Papazois and Vasileios Kokkinos and Konstantinos Asimakis and Georgia Tseliou}
}
@conference {3005,
	title = {A cross - layer design for video transmission with TFRC in MANETS},
	booktitle = {International Conference on Data Communication Networking - DCNET 2012, Rome, Italy},
	year = {2012},
	month = {24-27 July},
	pages = {5-12},
	abstract = {<p>Mobile Ad hoc NETworks (MANETs) are becoming more essential to wireless communications due to growing popularity of mobile devices. However, MANETs do not seem to effectively support multimedia applications and especially video transmission. In this work, we propose a cross-layer design that aims to improve the performance of video transmission using TCP Friendly Rate Control (TFRC). Our design provides priority to video packets and exploits information from the MAC layer in order to improve TFRC?s performance. The proposed cross-layer mechanism utilizes Signal to Noise Ratio (SNR) measurements along the routing path, in order to make the route reconstruction procedure more efficient. Simulation results show that both the use of traffic categorization and the SNR utilization lead to important improvements of video transmission over the mobile Ad hoc network. More specifically, simulations indicate increased average Peak Signal to Noise Ratio (PSNR) for the received video, increased throughput and packet delivery ration, as well as reduced average end-to-end delay.</p>
},
	author = {Christos Bouras and Vaggelis Kapoulas and Apostolos Gkamas and G Kioumourtzis and George Adam}
}
@article {3108,
	title = {Enhancing Meta   Portals using Dynamic User Context Personalization Techniques},
	journal = {Journal of Network and Computer
Applications, Elsevier Science},
	year = {2012},
	pages = {1446-1453},
	abstract = {The Internet is 
ooded with Information and the last decade its size has
grown so many times that information search and presentation have become
tedious tasks even for experienced users. Minor changes to existing resources
can alter the situation and lead to major changes to the end user experi-
ence. In this manuscript we present the dynamic web personalization and
document grouping infrastructure for meta-portals and the evaluation of our
mechanism on a meta-portal. A meta-portal is an informational node where
articles from dierent sources are collected and presented in a categorized
and personalized manner. The web personalization mechanism is based on
dynamic creation and update of user proles according to the users prefer-
ences when browsing. In parallel a user{\textquoteright}s prole is aected by user grouping
details, which are constructed by users with similar proles. Assuming that
required information, such as article tagging, keywords to categories match-
ing and articles to categories relation is already part of the meta-portal we present a novel mechanism that can build and maintain a user prole which is
formed without disturbing the user. Furthermore, we describe the real-time
user-centred document grouping mechanism that is implemented to support
the web personalization system and present the experimental evaluation of
the whole system.
Keywords: personalization, web personalization, on-line document
grouping, user proling, meta-portal},
	author = {Christos Bouras and Vassilis Poulopoulos}
}
@conference {3000,
	title = {Enhaning Reliable Mobile Multicasting with RaptorQ FEC},
	booktitle = {17th IEEE Symposium on Computers andCommunication (ISCC), Cappadocia, Turkey},
	year = {2012},
	month = {1-4 July},
	pages = {82-87},
	abstract = {A crucial point on the successful deployment of
multicast services is the enhanced reliability by means of advanced
error control schemes. To this direction Third Generation
Partnership Project (3GPP) has standardized exclusively for
Multimedia Broadcast/Multicast Services (MBMS) the use of a
Forward Error Correction (FEC) mechanism on the application
layer based on Raptor codes. Since the standardized systematic,
fountain Raptor code is now considered obsolete, the emergence
of a new variant of Raptor codes, named RaptorQ, provides
enhanced capabilities for mobile multicast services. In this paper,
we provide a performance comparison of the standardized
Raptor Application Layer FEC (AL-FEC) scheme with the very
promising RaptorQ FEC code. We examine the enhancements
that RaptorQ introduces on the AL-FEC protection robustness,
providing a thorough performance analysis in comparison with
the current Raptor FEC scheme. Furthermore, in order to
verify the improved performance of RaptorQ, we provide several
simulation results utilizing the ns-3 environment, considering the
application of both the examined AL-FEC schemes over multicast
services for next generation mobile networks.},
	keywords = {FEC, LTE, MBMS},
	author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Nikos Kanakis}
}
@conference {2999,
	title = {Evaluating RaptorQ FEC over 3GPP Multicast Services},
	booktitle = {The 8th International Wireless
Communications \& Mobile Computing Conference (IWCMC 2012), Limassol, Cyprus},
	year = {2012},
	month = {August 27-31},
	pages = {257 - 262},
	abstract = {Third Generation Partnership Project (3GPP) introduced
Multimedia Broadcast/Multicast Services (MBMS), in
order to efficiently deliver the same content to multiple users over
mobile cellular networks. To enhance the download and streaming
delivery robustness against packet losses, 3GPP proposes
the use of Forward Error Correction (FEC) on the application
layer. The Application Layer FEC (AL-FEC) scheme that 3GPP
standardized is based on the systematic, fountain Raptor code.
In this work, in response to the emergence of an enhanced
FEC scheme, we provide a performance evaluation of the
existing standardized AL-FEC scheme with the newly introduced
RaptorQ code. Introducing a variety of simulation experiments,
we analyze the performance behavior of each AL-FEC scheme
considering several FEC encoding parameters. Furthermore, we
try to verify the improvements that have emerged in AL-FEC
providing enhanced capabilities in multicast services over next
generation mobile networks.},
	keywords = {FEC, LTE, MBMS},
	author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Nikos Kanakis}
}
@conference {3010,
	title = {Genetic Optimization for Spectral Efficient Multicasting in LTE Systems},
	booktitle = {Fifth IFIP Wireless and Mobile Networking Conference, Bratislava, Slovakia},
	year = {2012},
	month = {19-21 September},
	pages = {54-59},
	abstract = {<p>Past research has proposed the usage of assisting cells with Multimedia Broadcast/Multicast Service (MBMS) over a Single Frequency Network (MBSFN) to increase the Spectral Efficiency (SE) of LTE. In this paper we propose and investigate a method for optimizing the power consumption of the network while retaining an acceptable SE for most users. We design an algorithm that makes use of genetic optimization and analytical estimation of the SE. The algorithm is implemented in a novel simulation tool that allows experimentation over various user distributions and LTE deployments similar to the real-world ones. This simulation tool estimates the SE of each user and is able to optimize the network deployment by adjusting the individual transmission power levels for each cell.</p>
},
	keywords = {LTE, MBMS, MBSFN},
	author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Konstantinos Asimakis}
}
@conference {3002,
	title = {Guidelines for the procurement of free and open source software in public administrators},
	booktitle = {IADIS International Conference Information Systems Post-Implementation and Change Management 2012, Lisbon, Portugal},
	year = {2012},
	month = {17-19 July},
	pages = {29-36},
	abstract = {<p>This paper provides a concise guide on Free and Open Source Software procurement for European Public Administrations to be used by elected representatives and decision makers, procurement and Information Technology managers and staff in addition to any existing national or European Union guidelines and regulations. This work provides definitions of basic terms, outlines the legal context and the main principles of software procurement and highlights good practices and recommended actions for Public Administrations. Although the adoption of Free and Open Source Software as a strategic choice has certain advantages for public organisations, the guidelines and resources provided in this paper also apply to both open source and proprietary software procurement procedures and scenarios, such as downloading and purchasing, in-house development and outsourcing. The main aspects addressed and guidelines provided include: planning and defining a procurement method, estimating costs and benefits, setting interoperability and the use of open standards as a priority, avoiding discriminating practices such as naming trademarks, understanding and assessing licensing schemes, software provision models and suppliers, and establishing fair tendering processes.</p>
},
	author = {Christos Bouras and Vasileios Kokkinos and Georgia Tseliou and Anestis Filopoulos and Sotiris Michalopoulos and Dimitris Papadopoulos}
}
@conference {2997,
	title = {Interference Management in LTE Femtocell Systems Using an Adaptive Frequency Reuse Scheme},
	booktitle = {Wireless Telecommunications Symposium (WTS 2012), London, UK},
	year = {2012},
	month = {18-20 April},
	abstract = {Long Term Evolution (LTE) has developed a new
technology in order to enhance indoor coverage. This new
technology is called femtocells and is achieved with the use of
access points installed by home users. However, interference
problem between the femtocell and the macrocell decreases the
system{\textquoteright}s capacity and as a result users{\textquoteright} throughput. In this paper
we study the interference mitigation techniques in
femtocell/macrocell networks and we propose a frequency reuse
mechanism that leads to increased overall system performance.
In particular, the mechanism aims to maximize throughput via a
variety of combinations between inner cell radius and frequency
allocation to the macrocell. Additionally, a position minded
frequency allocation to the femtocells targets to further optimize
the total throughput of the cell.},
	keywords = {Femtocell, FFR, LTE},
	author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Georgios Kavourgias}
}
@inbook {3145,
	title = {Multimedia Broadcasting in LTE Networks},
	booktitle = {Access Environments and Quality of Service Provisioning: Solutions and Applications},
	year = {2012},
	pages = {269-289},
	publisher = {IGI Global},
	organization = {IGI Global},
	chapter = {11},
	abstract = {<p>Long Term Evolution (LTE) constitutes the latest step before the 4th generation (4G) of radio technologies designed to increase the capacity and speed of mobile communications. To support Multimedia Broadcast/Multicast Services (MBMS), LTE offers the functionality to transmit MBMS over Single Frequency Network (MBSFN), where a time-synchronized common waveform is transmitted from multiple cells for a given duration. In MBSFN transmissions, the achieved Spectral Efficiency (SE) is mainly determined by the Modulation and Coding Scheme (MCS) selected. This study proposes and evaluates four approaches for the selection of the MCS that will be utilized for the transmission of the MBSFN data. The evaluation of the approaches is performed for different users? distribution and from SE perspective. Based on the SE measurement, we determine the approach that either maximizes or achieves a target SE for the corresponding users? distribution.</p>
},
	keywords = {LTE, MBMS},
	author = {Christos Bouras and Antonios Alexiou and Andreas Papazois and Vasileios Kokkinos and George Tsichritzis}
}
@conference {2995,
	title = {Optimization of Fractional Frequency Reuse in Long Term Evolution Networks},
	booktitle = {2012
IEEE Wireless Communications and Networking Conference (WCNC 2012), Paris,
France},
	year = {2012},
	month = {1-4 April},
	pages = {1875-1879},
	abstract = {In cellular systems, Fractional Frequency Reuse (FFR)
partitions each cell into two regions; inner region and outer
region and allocates different frequency band to each region.
Since the users at the inner region are less exposed to inter-cell
interference, the frequency resources in each inner region can be
universally used. Based on this frequency band allocation, FFR
may reduce channel interference and offer large system capacity.
This paper proposes a mechanism that selects the optimal FFR
scheme based on the user throughput and user satisfaction. In
detail, the mechanism selects the optimal size of the inner and
outer region for each cell as well as the optimal frequency
allocation between these regions that either maximizes the mean
user throughput or the user satisfaction. The mechanism is
evaluated through several simulation scenarios.},
	keywords = {FFR, LTE},
	author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Georgia Tseliou and Dimitrios Bilios}
}
@conference {3009,
	title = {Peer-to-peer live streaming for massively multiplayer online games},
	booktitle = {12th IEEE International Conference on Peer to Peer Computing 2012, Tarragona, Spain},
	year = {2012},
	month = {3 - 5 September},
	pages = {67 - 68},
	abstract = {One of the most attractive features of Massively Multiplayer Online Games (MMOGs) is the possibility for users to interact with a large number of other users in a variety of collaborative and competitive situations. Gamers within an MMOG typically become members of active communities with mutual interests, shared adventures, and common objectives. This demonstration presents a peer-to-peer live video system that enables MMOG players to stream screen-captured video of their game. Players can use the system to show their skills, share experience with friends, or coordinate missions in strategy games.},
	author = {Christos Bouras and A Shani and Andreas Papazois and S Ahmad and R Hamzaoui and G Simon and Elyia Buyukkaya and F Zhou}
}
@article {3106,
	title = {Performance Evaluation of Ad Hoc Routing Protocols for Military Communications},
	journal = {International Journal
of Network Management, Wiley InterScience},
	year = {2012},
	pages = {216 - 234},
	abstract = {Mobile Ad hoc networks (MANETs) are of much interest to both the research community and the military because of the potential to establish a communication network in any situation that involves emergencies. Examples are search-and-rescue operations, military deployment in hostile environment, and several types of police operations.
One critical open issue is how to route messages considering the characteristics of these networks. The nodes act as routers in an environment without a fixed infrastructure, the nodes are mobile, the wireless medium has its own limitations compared to wired networks, and existing routing protocols cannot be employed at least without modifications.
Over the last few years, a number of routing protocols have been proposed and enhanced to address the issue of routing in MANETs. It is not clear how those different protocols perform under different environments. One protocol may be the best in one network configuration but the worst in another. This article provides an analysis and performance evaluation of those protocols that may be suitable for military communications. The evaluation is conducted in two phases. In the first phase, we compare the protocols based on qualitative metrics to locate those that may be fit our evaluation criteria. In the second phase, we evaluate the selected protocols from the first phase based on quantitative metrics in a mobility scenario that reflects tactical military movements. The results disclose that there is no routing protocol in the current stage without modifications that can provide efficient routing to any size of network, regardless the number of nodes and the network load and mobility.},
	author = {Christos Bouras and Apostolos Gkamas and G Kioumourtzis}
}
@article {3104,
	title = {Performance Evaluation of LTE for MBSFN Transmissions},
	journal = {Wireless Networks, Springer  Verlang},
	volume = {18},
	year = {2012},
	pages = {227-240},
	abstract = {<p>Long Term Evolution (LTE) is the most promised latest step towards the 4th generation (4G) of radio technologies designed to increase the capacity and speed of mobile communications with main target the support of the so-called {\textquotedblleft}Mobile Broadband{\textquotedblright}. To support Multimedia Broadcast/Multicast Services (MBMS), LTE offers the possibility to transmit Multimedia Broadcast multicast service over a Single Frequency Network (MBSFN), where a time-synchronized common waveform is transmitted from multiple cells for a given duration. In this manuscript we analytically present the MBSFN delivery method and evaluate its performance. The critical parameters of primary interest for the evaluation of the scheme are the packet delivery cost and its scalability. To this direction, a telecommunication cost analysis of the MBMS service is presented based on the transmission cost over the air interface, as well as the costs of all interfaces and nodes of the MBSFN architecture. Based on this cost analysis we determine the ideal number of cells that should participate in the MBSFN transmission in order to improve the overall MBSFN performance. Since the performance of the MBSFN scheme mainly depends on the configuration of the LTE network that is under investigation, we consider different network topologies, MBSFN deployments and user distributions.</p>
},
	keywords = {LTE, MBSFN},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos and George Tsichritzis}
}
@article {3107,
	title = {Performance improvement of Distributed Virtual Environments by exploiting objects},
	journal = {Virtual Reality, Springer Verlang},
	year = {2012},
	pages = {187-203},
	abstract = {Distributed virtual environments need to address
issues related to the control of network traffic, resource
management, and scalability. Given the distributed nature
of these environments, the main problems they need to
overcome are the efficient distribution of workload among
the servers and the minimization of the communication
cost. In this direction, a lot of work has been done and
numerous relevant techniques and algorithms have been
proposed. The majority of these approaches mainly focus
on user entities and their interactions. However, most of
actual DVE systems include additional and non-dynamic
elements, denoted as objects, whose presence can affect
users? behavior. This paper introduces virtual objects?
attributes and proposes two approaches that exploit these
attributes in order to handle workload assignment and
communication cost in DVE systems. Both approaches
take into account scenario-specific aspects of DVE systems,
such as the impact that entities? attributes have on
each other and the way this impact can affect the system?s
state. These scenario-specific aspects are then combined
with quantitative factors of the system, such as workload,
communication cost, and utilization. The experiments
conducted in order to validate the behavior of the proposed
approach show that the incorporation of object?s presence
can improve the DVE system?s performance. More specifically,
objects? presence and their attributes can assist in
the significant reduction in the communication cost along
with effective workload distribution among the system?s
servers.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka}
}
@conference {3008,
	title = {A Performance Study of Fractional Frequency Reuse in OFDMA Networks},
	booktitle = {Fifth IFIP Wireless and Mobile Networking Conference, Bratislava, Slovakia},
	year = {2012},
	month = {19-21 September},
	pages = {38 - 43},
	abstract = {<p>Long Term Evolution (LTE) technology is considered as the most possible candidate for next generation mobile communications. LTE networks offer high capacity and are specified and designed to accommodate small, high performance, power-efficient end-user devices. One limiting factor that influences LTE performance is the interference from neighbor cells, the so called Inter-Cell Interference (ICI). Fractional Frequency Reuse (FFR) has been proposed as a technique to overcome this problem, since it can efficiently utilize the available frequency spectrum. This paper analyzes the FFR scheme and proposes a dynamic FFR mechanism that selects the optimal frequency allocation based on the cell total throughput and user satisfaction. In detail, the mechanism divides the cell into two regions (inner and outer) and selects the optimal size as well as the optimal frequency allocation between these regions with main target to maximize the overall throughput and user satisfaction. The mechanism is evaluated through several simulation scenariosthat incorporate users? mobility.</p>
},
	keywords = {FFR, LTE},
	author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Georgia Tseliou and Dimitrios Bilios}
}
@conference {3003,
	title = {Policy recommendations for free and open source software usage by public administrators},
	booktitle = {IADIS International Conference ICT, Society and Human Beings 2012, Lisbon, Portugal},
	year = {2012},
	month = {21-23 July},
	pages = {90-97},
	abstract = {Free and open source software, holding a strategic position in knowledge economy, reaffirms the critical role of governments and regional authorities in establishing strategies for integrating effective and sustainable Information Technology solutions in the public sector towards economic growth and social welfare. Moreover, public services, organisations and territorial administrations collectively represent a major software user with great impact on the software market. In this sense, software selection in the public sector is not a neutral process but highly political and strategic one; various collateral implications and policy aspects should be considered in order to reach the best possible decisions. Within this context, this paper provides policy recommendations on issues and challenges pertaining to the use of free and open source software by European public administrations. The recommended policy actions are mainly based on review of the current policy framework. Main goal of this paper is to contribute in providing policy orientations and proposed actions that can help governments, public administrations and European institutions fully harvest the benefits of open source.},
	author = {Christos Bouras and Vasileios Kokkinos and Georgia Tseliou and Anestis Filopoulos and Sotiris Michalopoulos and Dimitris Papadopoulos}
}
@conference {3012,
	title = {Power Management over Co-channel Femtocells in LTE-A Systems},
	booktitle = {IFIP Wireless Days 2012, Dublin, Ireland},
	year = {2012},
	month = {21-23 November},
	abstract = {The use of femtocells has been an attractive solution since it achieves better coverage and capacity and low cost for deployment and maintenance. However, their performance can be compromised by the cross-tier interference with existing macrocell infrastructure or between adjacent femtocells, especially in the case of co-channel deployment. One way to address this, is adjusting the transmit power of every femto base station with respect for overall performance. To this direction, we have implemented a framework that simulates femtocell overlays over LTE-Advanced (LTE-A) macrocellular systems. The framework allows power management over user-defined femtocell deployment, deciding their power levels according to three different power schemes. The resulting throughput is presented for every point of the macrocell in a user-friendly GUI. In this paper, we present the design of this framework and discuss the results.},
	keywords = {Femtocell, Power Control},
	author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Georgios Diles}
}
@conference {2998,
	title = {Providing Community and Collaboration Services to MMOG Players},
	booktitle = {IADIS International
Conference Game and Entertainment Technologies 2012, Lisbon, Portugal},
	year = {2012},
	month = {18-20 July},
	pages = {49-53},
	abstract = {Most of Massively Multiplayer Online Games (MMOGs) aim to support and improve the community activities among
their members. The Community Network Game (CNG) project has focused on services supporting players during their
in-game community and collaboration activities. The tools we offer use an innovative technology, namely the In-game
Graphical Insertion Technology (IGIT), which permits the addition of web-based applications without having to modify
the game code. These tools follow a design adapted to the needs of MMOG players. They are provided by the so-called
CNG Server and have been implemented based on recent advances in Web 2.0 technology. The in-game collaboration
activities provided by the underlying framework are also enhanced using Peer-to-Peer (P2P) technology for the
distribution of user-originated live video. In this paper, we concentrate our focus on the architecture of the server as well
as on the design and implementation of the community and collaboration tools.},
	author = {Christos Bouras and Vaggelis Kapoulas and Andreas Papazois and George Adam}
}
@conference {3004,
	title = {Security Aspects for Large Scale Distributed Environments},
	booktitle = {SECURWARE 2012: The Sixth International Conference on Emerging Security Information, Systems and Technologies, Rome, Italy},
	year = {2012},
	month = {19-24 August},
	pages = {7 - 13},
	abstract = {Heterogeneous Networks) is a tool under active development that supports a Bandwidth on Demand (BoD) service, intended to operate in a multi-domain environment using heterogeneous transmission technologies. The AutoBAHN system aims at providing a guaranteed capacity, connection-oriented service between two end points. Due to the level of access that the tool has to critical parts of the network, the importance of a trustworthy Authentication and Authorization Infrastructure (AAI) cannot be overestimated. This paper highlights the design and implementation for the Authentication and Authorization Infrastructure which is part of the AutoBAHN service and the decisions taken. The AAI is a service dedicated to enforce system security and to prevent unauthorized access and usage of resources. The BoD service modules may interact with AAI multiple times during a single request execution. After the initial authentication and authorisation check, the BoD system will apply additional, specific to BoD, rules and policies to the request. In addition, this paper presents the basic security aspects and components of the AutoBAHN system.},
	author = {Christos Bouras and Kostas Stamos and George Adam and Giannis Zaoudis and Ioannis - Christos Kalligeros}
}
@conference {2996,
	title = {Selecting between open source and proprietary software: The public administrators{\textquoteright} case},
	booktitle = {IADIS International
Conference e-Society 2012, Berlin, Germany},
	year = {2012},
	month = {10-13 March},
	pages = {185-192},
	abstract = {The necessity for the public sector to change over to communicating digitally is imminent. From the economic
perspective, the changeover poses great challenges, as huge investments will have to be made in Information Technology
(IT) in the public sector. It is therefore natural, in connection with these investments, for detailed assessment to be made
of what forms of technology it is anticipated to be used, and who controls the development and ownership of this
technology. This work constitutes a review of literature on pre-existing comparative studies regarding the technical,
social, economic and organizational factors on Free Open Source Software (FOSS) usage. Furthermore, this work
includes guidelines that Public Administrations (PAs) should follow for the selection between open source and
proprietary software. Main goal of this paper is to add to knowledge resources that can help public stakeholders
understand the technical / social / economic / organizational environment and reach informed decisions when selecting
the appropriate software. The paper can also be useful for FOSS developers, users and communities who are either
directly or indirectly involved in the software market.},
	author = {Christos Bouras and Vasileios Kokkinos and Georgia Tseliou}
}
@conference {3007,
	title = {A Simulation Framework for LTE-A Systems with Femtocell Overlays},
	booktitle = {ACM PM2HW2N 2012 Workshop, Paphos, Cyprus},
	year = {2012},
	month = {21 - 25 October},
	pages = {85 - 90},
	abstract = {The use of femtocells is an efficient way to improve cover- age and quality of service while on the other side the deployment cost for the service provider is kept in extremely low level. Long Term Evolution Advanced (LTE-A) systems with femtocell overlays aim to provide better indoor voice and data coverage and to increase network capacity. One of the major technical challenges that femtocell networks are facing nowadays, is the cross-tier interference, i.e., the interference between the femto base stations and the macrocell infrastructure. To this direction, we have designed and implemented a framework that simulates femtocell overlays integrated over LTE-A macrocellular systems. This framework focuses on the impact of cross-tier interference and furthermore is able to estimate the throughput at every point of integrated femtocell/macrocell LTE-A networks. In this paper, we present the design and implementation of this simulation framework and we provide significant experimental results obtained with the aid of this system.},
	keywords = {Femtocell, LTE},
	author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Konstantinos Kontodimas}
}
@article {3114,
	title = {A Simulation Modeling Tool for Dynamic Virtual Environments},
	journal = {Simulations Modelling Practice and Theory Journal, ElsevierScience},
	year = {2012},
	pages = {1-16},
	abstract = {<p>Distributed Virtual Environments simulate the behaviour and activities of a great number of users 22 interacting in a virtual world over a wide area network. The size of the virtual worlds and the 23 tremendous number of users that these environments are called to support require additional 24 bandwidth and computational resources. For supporting large-scale Distributed Virtual 25 Environments, extended infrastructure is needed in terms of both hardware and software. However, 26 both researchers and application designers do not always have access to such an extended 27 infrastructure and the assessment and evaluation of developed performance improvement techniques 28 becomes extremely difficult. To address this issue, this paper presents a simulation modelling tool, 29 called STEADiVE for networked servers Distributed Virtual Environments that could be used by 30 designers for evaluating the performance of their approaches under different scenarios and system 31 settings. The validation of the simulation modelling tool has showed that it achieves high accuracy in 32 representing a real DVE system. STEADiVE comes to fill in the gap in the area of simulation tools for 33 these systems.</p>
},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka}
}
@article {3112,
	title = {TFMCC vs ASMP: Lessons learned from performance evaluation},
	journal = {International Journal of Network Management, Wiley InterScience},
	volume = {22},
	year = {2012},
	pages = {349 - 372},
	abstract = {<p>In this article we present a simulation-based comparison of one of the best-known multicast congestion control schemes{\textemdash}TCP-friendly Multicast Congestion Control (TFMCC){\textemdash}against our proposed Adaptive Smooth Multicast Protocol (ASMP). ASMP consists of a single-rate multicast congestion control mechanism which takes advantage of the RTCP Sender (SR) and Receiver Reports (RR) in order to adjust the sender?s transmission rate in respect of the network conditions. The innovation in ASMP lays in the ?smooth? transmission rate, which is TCP-friendly and prevents oscillations. We use an integrated simulation environment named Multi- Evalvid-RA for the evaluation of the two congestion control schemes. Multi-Evalvid-RA provides all the necessary tools to perform simulation studies and assess video quality by using both network-centric metrics along with video quality measurements. Performance evaluation results show that ASMP is a very efficient solution for rate-adaptive multimedia applications and a serious competitor to well-known TFMCC.</p>
},
	author = {Christos Bouras and Apostolos Gkamas and G Kioumourtzis}
}
@conference {3001,
	title = {TRAFIL: A tool for enhancing simulation TRAce FILes processing},
	booktitle = {International Conference on Data Communication Networking - DCNET 2012, Rome, Italy},
	year = {2012},
	month = {24 -27 July},
	pages = {61-64},
	abstract = {NS-2 (Network Simulator) is one of the most popular discrete event simulators used for network simulation. Trace files produced by NS-2 provide very useful information for post simulation analysis. This paper presents the architecture and development considerations for a TRAce FILe analysis tool, which intends to simplify the management of trace files generated during network simulations. The tool is focused on NS-2 trace files, but can be extended to handle a variety of simulation trace files formats. Its purpose is to make the execution of a large number of network simulations faster, and the extraction of results from a large amount of data more flexible and productive. TRAFIL introduces a novel way of interpreting, parsing, reading and eventually utilizing NS-2 trace files by using "metafiles" and "sub-metafiles" during the trace file recognition and process procedures, making the overall operations more abstract, substantially efficient and faster than alternative approaches. Furthermore, TRAFIL facilitates the whole trace file analysis task, offering the opportunity to store each trace file as well as every measurement produced for each trace file. The tool aims to aid the analysis of simulation results offering features that other tools in this area have been missing.},
	author = {Christos Bouras and Kostas Stamos and G Kioumourtzis and Savvas Charalambides}
}
@conference {3006,
	title = {User Personalization via W - kmeans},
	booktitle = {KES2012 - The 16th International Conference on Knowledge Based \& Intelligent Information \& Engineering Systems, San Sebastian, Spain},
	year = {2012},
	month = {10-12 September},
	pages = {555 - 564},
	abstract = {With the rapid explosion of online news articles, predicting userbrowsing
behavior using collaborative filtering techniques has gained much attention
in the web personalization area. However, common collaborative filtering
techniques suffer from low accuracy and performance. This research proposes
a new personalized recommendation approach that integrates user and
text clustering based on our developed algorithm, W-kmeans, with other information
retrieval techniques, like text categorization and summarization in order
to provide users with the articles that match their profiles. Our system can easily
adapt over time to divertive user preferences. Furthermore, experimental results
show that by aggregating multiple other information retrieval techniques
like categorization, summarization and clustering, our recommender generates
results that outperform the cases when clustering is not applied.},
	author = {Christos Bouras and Vassilis Tsogkas}
}
@article {3097,
	title = {Adaptive Smooth Simulcast Protocol (ASSP) for Video Applications: Description and Performance Evaluation},
	journal = {Journal of Network and Systems Management, Springer Verlang},
	year = {2011},
	pages = { 143 - 177},
	abstract = {In this paper, we present Adaptive Smooth Simulcast Protocol (ASSP)
for simulcast transmission of multimedia data over best-effort networks. ASSP is a
new multiple-rate protocol that implements a single rate TCP-friendly protocol as
the underlying congestion control mechanism for each simulcast stream. The key
attributes of ASSP are: (a) TCP-friendly behavior, (b) adaptive per-stream trans-
mission rates, (c) adaptive scalability to large sets of receivers and (d) smooth
transmission rates that are suitable for multimedia applications. We evaluate the
performance of ASSP under an integrated simulation environment which combines
the measurements of both network and video performance metrics. We also com-
pare ASSP against other proposed solutions and the results demonstrate that the
performance of ASSP is significantly better than the tested solutions. Finally, ASSP
is a practical solution with very low implementation complexity for video trans-
mission over best-effort networks.
},
	author = {Christos Bouras and Apostolos Gkamas and G Kioumourtzis}
}
@conference {2990,
	title = {AL-FEC for Streaming Services over LTE Systems},
	booktitle = {14th International Symposiumon Wireless Personal Multimedia Communications, Brest, France},
	year = {2011},
	month = {October 3 - 6},
	pages = {284-288},
	abstract = {<p>The Third Generation Partnership Project (3GPP), recently introduced the evolution of the third generation (3G) cellular networks, the Long Term Evolution (LTE) telecommunication system. A key aspect of LTE specifications is the enhancement of Multimedia Broadcast/Multicast Services (MBMS), where the same content is transmitted to multiple users located in a specific service area. A significant point of the demanding multimedia services is the enhancement of the robustness against packet losses. To this direction, in order to support the efficient point-to-multipoint download and streaming delivery, 3GPP has included an Application Layer Forward Error Correction (AL-FEC) scheme in the MBMS standard. The standardized AL-FEC scheme is based on the systematic, fountain Raptor codes. In this paper, we investigate the application of AL-FEC over the MBMS streaming delivery method. We consider the benefits of AL-FEC for a seamless multimedia streaming transmission to multiple mobile users and we examine how the amount of FEC overhead can be adjusted under different packet loss conditions. For this purpose, we present a variety of realistic simulation scenarios for the performance evaluation of FEC considering several network and FEC encoding parameters. Furthermore, we provide suggestions in order to achieve efficient use of Raptor codes over LTE MBMS streaming services.</p>
},
	keywords = {FEC, LTE, MBMS},
	author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Nikos Kanakis}
}
@inbook {3141,
	title = {Broadband Infrastructures as a Common and the Role of Local Governments},
	booktitle = {Public Sector Reform Using Information Technologies : Trandforming Policy into Practice},
	year = {2011},
	pages = { 298-319},
	publisher = {IGI Global},
	organization = {IGI Global},
	author = {Christos Bouras and Vaggelis Kapoulas and Petros Ganos}
}
@conference {2994,
	title = {Clustering user preferences using W - kmeans},
	booktitle = {The 7th International Conference on Signal Image Technology \& Internet   Based Systems (SITIS 11), Dijion - France},
	year = {2011},
	month = {November 28 - December 1},
	pages = { 75 - 82},
	abstract = {Abstract{\textemdash} Although commonly only document clustering is
suggested by Web mining techniques for recommendation
systems, one of the various tasks of personalized
recommendation is categorization of Web users. In this paper,
a method for clustering navigation patterns of Web users is
proposed. We adapt the WordNet-enabled W-kmeans
algorithm, an enhancement of standard k-means algorithm
which uses the external knowledge from WordNet hypernyms
and that has been previously used for document clustering, to
user profile clustering by analyzing the users? historical data.
We also investigate the effects this approach has on the
recommendation engine by evaluating the overall performance
it has in terms of precision {\textendash} recall on our online
recommendation system.},
	author = {Christos Bouras and Vassilis Tsogkas}
}
@conference {2984,
	title = {Combining MBSFN and PTM Transmissions Schemes for Resource Efficiency in LTE Networks},
	booktitle = {9th International Conference on Wired/Wireless Internet Communications,
Vilanova I la Geltru, Barcelona, Spain, June 15 - 17, 2011},
	year = {2011},
	pages = { 56 - 67},
	abstract = {Long Term Evolution (LTE) systems allow the transmission of rich
multimedia services by utilizing the Multimedia Broadcast/Multicast Service
(MBMS) over a Single Frequency Network (MBSFN). During MBSFN
transmission a time-synchronized common waveform is transmitted from
multiple cells. The 3rd Generation Partnership Project (3GPP) has specified that
Point-to-Multipoint (PTM) transmission can be used in combination with
MBSFN to provide MBMS-based services. In this paper we evaluate the
combined transmission scheme in terms of Resource Efficiency (RE). The
evaluation is performed through simulation experiments for various user
distributions and LTE network configurations. The experiments are conducted
with the aid of a proposed algorithm, which estimates the Spectral Efficiency
(SE) of each cell and the RE of the network, and is also able to formulate the
optimal network deployment that maximizes the network?s RE. For each of the
examined scenarios, we present the most efficient solution (in terms of RE)
selected by our algorithm and we compare it with other transmission schemes.},
	keywords = {LTE, MBMS, MBSFN},
	author = {Christos Bouras and Antonios Alexiou and Andreas Papazois and Vasileios Kokkinos and Konstantinos Asimakis}
}
@article {3110,
	title = {Community Tools for Massively Multiplayer Online Games},
	journal = {International Journal on Advances in Networks and Services, IARIA,
Vol. 4, No. 3 \& 4},
	year = {2011},
	pages = {313 - 323},
	abstract = {One of the most attractive features of Massively
Multiplayer Online Games (MMOGs) is the possibility for users
to interact with a large number of other users in a variety
of collaborative and competitive situations. Gamers within
an MMOG typically become members of active communities
with mutual interests, shared adventures, and common objectives.
We present the EU funded Community Network Game
(CNG) project. The CNG project provides tools to enhance
collaborative activities between online gamers and offers new
tools for the generation, distribution and insertion of usergenerated
content in MMOGs. CNG allows the addition of new
engaging community services without changing the game code
and without adding new processing or network loads to the
MMOG central servers. The user-generated content considered
by the CNG project includes 3D objects and graphics, as well
as screen-captured live video of the game, which is shared using
peer-to-peer technology. We survey the state of the art in all
areas related to the project and present its concept, objectives,
and innovations.},
	author = {Christos Bouras and A Shani and Andreas Papazois and George Tsichritzis and S Ahmad and R Hamzaoui and E Perelman and G Simon and J Liu}
}
@conference {2993,
	title = {Cross-Layer Mechanism for Efficient Video Transmission over Mobile Ad Hoc Networks},
	booktitle = {The Third International Workshop on Cross Layer Design,  Rennes, France},
	year = {2011},
	month = {November 30 \&$\#$8211; December },
	abstract = {Abstract- Mobile ad hoc networks (MANETs) are becoming
more essential to wireless communications due to growing
popularity of mobile devices. However, MANETs do not seem to
effectively support multimedia applications and especially video
transmission. This paper presents a cross-layer mechanism for
efficient video transmission over this type of networks. The
proposed mechanism consists of a priority-scheduling algorithm,
at the network layer, and the use of the IEEE 802.11e standard at
the MAC layer. The priority-scheduling algorithm takes into
account the frame type of the MPEG-4 video file in order to
provide different priorities to the most important video packets.
At the MAC layer, the IEEE 802.11e protocol assigns the highest
priority to video applications to reduce delay and packets losses
due to other competing traffic. This design is easily implemented
in any ad hoc wireless network as an extension on the AODV
MANET routing protocol. Simulation results conducted with the
network simulator ns-2 show the advantages of the proposed
design.},
	author = {Christos Bouras and Vaggelis Kapoulas and Apostolos Gkamas and G Kioumourtzis and George Adam and Nikos Tavoularis}
}
@article {3103,
	title = {A Dynamic Management Scheme for DVEs},
	journal = {Journal of Network and Computer Applications, Elsevier Science},
	volume = {34},
	year = {2011},
	pages = {89 - 101},
	abstract = {<p>Advancesincomputertechnologyandnetworkinginfrastructuresincombinationwithadvanced applicationsandservices,haveexpandedtheadoptionofdistributedvirtualenvironmentsand promotedtheiruseinawiderangeofareas,suchaslearningandtraining,collaborativework,military applicationsandmultiplayeronlinegames.ThecharacteristicsandrequirementsofsuchDVEsdiffer significantlygiventhediverseobjectives,scopeandcontextthateachvirtualworldaimsatsupporting. However,onecommoncharacteristicofDVEsistheirdynamicstatewithusersenteringandleavingthe systemrandomly,resultinginchangesoftherequirementsfortheDVEsystem.Thesechangesrequire effectiveloaddistributionandmanagementofthecommunicationcostsothatconsistencyisalways maintained.ThispaperpresentsadynamicmanagementapproachforDVEsdrivenbythediversityof differentapplications?characteristicsandrequirements.Thisapproachexploitsthedynamicnatureof these systemsforselectingandassigning,onanon-demandbasis,theresourcesnecessaryforthe efficientoperationofthesystem.Theexperimentsconductedtovalidatethebehavioroftheapproach illustratethatitcansignificantlyminimizecommunicationcostamongthesystemserverstogether with effectiveworkloaddistribution.</p>
},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka}
}
@conference {2988,
	title = {Evaluating P2P Live Streaming Systems: the CNG Case},
	booktitle = {The Seventeenth International Conference on Distributed Multimedia Systems,
Convitto della Calza, Florence, Italy, 18 - 20 August},
	year = {2011},
	pages = { 126-129},
	abstract = {Many peer-to-peer (P2P) systems have been proposed
for the provision of scalable live video streaming services
over the Internet. While the literature contains surveys of
the architectures of these systems, there is a lack of work
on methodologies for their evaluation. We identify the main
issues in the evaluation of P2P live streaming systems and
use the Community Network Game (CNG) project as an ex-
ample to illustrate them. The evaluation of the P2P sys-
tem consists of two phases: a laboratory one using the ns-2
network simulator and an online field test with Massively
Multiplayer Online Games (MMOG) players.},
	author = {Christos Bouras and Vaggelis Kapoulas and Andreas Papazois and S Ahmad and R Hamzaoui and A Sahni and G Simon and Elyia Buyukkaya}
}
@article {3100,
	title = {Exploiting MIMO Technology for Optimal MBMS Power Allocation},
	journal = {Wireless Personal Communications, Springer Verlang},
	year = {2011},
	pages = { 447-464},
	abstract = {In mobile networks, the provision of rich multimedia services, such as Mobile TV, is considered of key importance. To this end, Multimedia Broadcast/Multicast Service (MBMS) - that was introduced in the Release 6 of Universal Mobile Telecommunication System (UMTS) - is envisaged to play an instrumental role in the proliferation of mobile market. The reason behind the design of MBMS was the need to provide multiple users with the same data at the same time in 3GPP (3rd Generation Partnership Project) cellular networks. Still, MBMS performance is limited by the base stations? transmission power. As an aftermath, efficient power allocation techniques should be implemented so as to ensure the mass provision of multimedia applications to mobile users. This paper proposes a novel mechanism for efficient radio bearer selection during MBMS transmissions. The proposed mechanism is based on the concept of transport channels combination in any cell of the network. Furthermore, the mechanism exploits the performance enhancements emerged from Multiple Input Multiple Output (MIMO) antennas and manages to efficiently deliver multiple MBMS sessions. The proposed mechanism is thoroughly evaluated and compared with the radio bearer selection mechanisms proposed by 3GPP.},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos}
}
@inbook {3144,
	title = {Forward Error Correction for Reliable e-MBMS Transmissions in LTE Networks},
	booktitle = {Cellurar Networks},
	year = {2011},
	pages = { 353 - 374},
	publisher = {InTech},
	organization = {InTech},
	keywords = {FEC, LTE, MBMS},
	author = {Christos Bouras and Andreas Papazois and Vasileios Kokkinos and Georgia Tseliou}
}
@conference {2989,
	title = {Implementation of leaky bucket module for simulations in NS - 3},
	booktitle = {Workshop on ICT - Contemporary
Communication and Information Technology, Split - Dubrovnik},
	year = {2011},
	month = {15 - 17 September },
	abstract = {Simulation has always been a valuable tool for experimentation and validation of models, architectures and mechanisms in the field of networking. In the case of the DiffServ framework, simulation is even more valuable, due to the fact that an analytical approach of mechanisms and services is infeasible because of the aggregation and multiplexing of flows. In this paper we present the implementation of a module for the extensible network simulator ns-3 in order to conduct experiments simulating a leaky bucket shaping mechanism for incoming flows, which is missing from ns-3. We describe the way the module has been implemented within the framework of the simulator and we discuss the merits of using a leaky bucket mechanism for shaping traffic. We also use the newly developed module in order to conduct experiments, verify its proper behavior and demonstrate its usefulness in studying the leaky bucket through simulation.},
	author = {Christos Bouras and Kostas Stamos and Giannis Zaoudis and Petros Baltzis}
}
@conference {2985,
	title = {An Improved GMPLS Survivability Mechanism Using Link Delay - Constrained Algorithm},
	booktitle = {International Conference on Data
Communication Networking - DCNET 2011, Seville, Spain},
	year = {2011},
	month = {July 18-21},
	pages = { 45 - 50},
	abstract = {It is widely accepted that GMPLS (Generalized MPLS) will be a key technology in the evolution of the next generation of reliable Internet Protocol (IP) backbone networks. Conventional GMPLS-based optical-switching network fault recovery only provides resiliency in terms of path segment selection instead of constraint-based calculation. This can create severe impact on the protocol?s transport plane when a fault occurs to a link or path with many optical connections attached to it. This paper proposes the implementation of an improved GMPLS recovery algorithm based on the metric of optical link delay which is achieved through the pre or post selection of a safer and more stable protection path with fewer connections attached to it, and therefore with a lesser link delay metric compared to other possible paths. The improved recovery algorithm is evaluated using the network simulator ns-2 and more particularly a specialized simulator add-on for GMPLS, called ASONS (ASONS - An Automatically Switched Optical Network Simulator). The results indicate improved resiliency, increased fault avoidance, and reduced packet loss.},
	author = {Christos Bouras and Kostas Stamos and Anastasios Bikos}
}
@conference {2991,
	title = {Interference Behavior of Integrated Femto and Macrocell Environments},
	booktitle = {IFIP Wireless Days 2011, Niagara Falls, Ontario, Canada},
	year = {2011},
	month = {October 10 \&$\#$8211; 12},
	abstract = {Abstract{\textemdash}Femtocells are data access points installed by the
subscribers to provide better indoor voice and data coverage and
to increase system capacity. The integrated femtocell/macrocell
networks offer an efficient way to increase access capacity by
improving coverage and quality of service while on the other
side the deployment cost for the service provider is kept in
extremely low levels. One of the major technical challenges that
femtocell networks are facing is their interference behavior when
they are placed within macrocells. The study presented in this
paper focuses on the impact of integrating femtocells in macrocell
networks in terms of adjacent cell interference that the macrocell
environment adds to users served by a femto base station and
vice versa. To this direction, we have designed and implemented
a simulation testbed that estimates the cross-tier interference and
the throughput in every point of an integrated femtocell/macrocell
Long Term Evolution-Advanced (LTE-A) network.},
	keywords = {Femtocell, LTE},
	author = {Christos Bouras and Antonios Alexiou and Andreas Papazois and Vasileios Kokkinos and Konstantinos Kontodimas}
}
@inbook {3146,
	title = {Learning from user{\textquoteright}s behavior - A technique for personalized news search supporting result cashing},
	booktitle = {Information Extraction from the Internet},
	year = {2011},
	pages = { 177-196},
	publisher = {iConcept Press},
	organization = {iConcept Press},
	chapter = {11},
	author = {Christos Bouras and Vassilis Poulopoulos and Panagiotis Silintziris}
}
@conference {2982,
	title = {Optimizing the Combination of MBSFN and PTM Transmissions in LTE Systems},
	booktitle = {Tenth Annual
Wireless Telecommunications Symposium (WTS 2011), New York, USA},
	year = {2011},
	month = {April 13-15},
	abstract = {The 3rd Generation Partnership Project (3GPP) has
introduced the evolved Multimedia Broadcast/Multicast Service
(e-MBMS) feature for cellular systems as an evolution to the
existing MBMS service. To support e-MBMS in Long Term
Evolution (LTE) systems, 3GPP recommends the use of Point-to-
Multipoint (PTM) transmissions and MBMS over a Single
Frequency Network (MBSFN). MBSFN is a new feature where a
time-synchronized common waveform is transmitted from
multiple cells. In this paper we investigate the provision of
MBMS service over a combination of MBSFN and PTM
transmission methods. A cost analysis of the MBMS service is
presented based on the transmission cost over all the interfaces
and nodes of the LTE architecture. We evaluate the performance
of this transmission scheme from telecommunication cost
perspective and we compare it with other transmission schemes.
The performance evaluation has been performed with the aid of a
new simulation tool that estimates the cost for the MBMS
provision under different network topologies, MBSFN
deployments and user distributions.},
	keywords = {LTE, MBMS, MBSFN},
	author = {Christos Bouras and Antonios Alexiou and Andreas Papazois and Vasileios Kokkinos and Georgia Tseliou}
}
@conference {2992,
	title = {Performance Evaluation of Routing Protocols for multimedia transmission over Mobile Ad hoc Network},
	booktitle = {4th Joint IFIP Wireless and Mobile Networks
Conference, Toulouse, France},
	year = {2011},
	month = {October 26 \&$\#$8211; 28},
	abstract = {Abstract{\textemdash} Mobile ad hoc networks (MANETs) are becoming
more essential to wireless communications due to growing
popularity of mobile devices. The integration of mobile ad hoc
devices inside vehicles has led to another type of networks, called
Vehicular Ad hoc Networks (VANETs) which are also becoming
important. These networks require specialized routing protocols
due to their ad hoc nature. The performance of these protocols
has been tested for the case of general traffic but not in respect
with to multimedia traffic and especially video transmission. In
this paper we conduct a number of simulations in order to
evaluate the performance of three of the most popular routing
protocols for MANETs and VANETs, namely AODV, DSR and
OLSR, for different number of simultaneous video transmissions.
We use the packet delivery ratio, the end-to-end delay, the packet
delay variation (jitter) and the routing overhead as evaluation
metrics. The results indicate that the DSR protocol outperforms
AODV and OLSR in terms of end-to-end delay and packet delay
variation and seems to be the most efficient routing protocol
when multimedia traffic and especially video traffic is
considered.},
	author = {Christos Bouras and Vaggelis Kapoulas and Apostolos Gkamas and G Kioumourtzis and George Adam and Nikos Tavoularis}
}
@article {3102,
	title = {Power Management Adaptation Techniques for Video transmission over TFRC},
	journal = {International Journal of Network Management, Wiley InterScience},
	volume = {25},
	year = {2011},
	pages = { 414 -431},
	abstract = {<p>In this paper, we describe power management adaptation techniques for wireless video transmission using the TFRC protocol that take into account feedback about the received video quality and try to intelligently adapt transmitting power accordingly. The purpose of the mechanisms is to utilize TFRC feedback and thus achieve a beneficial balance between the power consumption and the received video quality. There are 2 power adaptation mechanisms proposed, each one with its own advantages. They both offer significant improvements when used in terms of both power consumption and received video quality. We use simulation in order to compare and evaluate our approach.</p>
},
	author = {Christos Bouras and Vaggelis Kapoulas and Apostolos Gkamas and Kostas Stamos and Vassilis Papapanagiotou and Giannis Zaoudis}
}
@conference {2987,
	title = {Power management for SVC video over wireless networks},
	booktitle = {Sixth International Conference on Broadband, Wireless Computing, Communication and Applications (BWCCA 2011), Barcelona, Spain, October 26 - 28},
	year = {2011},
	pages = { 270 - 276},
	abstract = {The main idea of this paper is to study how the
emerging H.264 SVC standard can be utilized for more
efficient power management in wireless video transmissions.
Our proposal uses a cross-layer approach which adapts the
power transmission level of the sender according to the SVC
information regarding the priority of the SVC NAL frame.
Our aim is to improve transmission statistics, and therefore
user experience, without unnecessary power consumption. We
use extensive experimentation on the ns2 network simulator,
which we have specifically modified for this purpose, in order
to verify this approach.},
	author = {Christos Bouras and Kostas Stamos and Giannis Zaoudis and Stamatis Stroumpis and Savvas Charalambides}
}
@conference {2983,
	title = {Reliable Multicasting over LTE: A Performance Study},
	booktitle = {16th IEEE Symposioum
on Computers and Communications (ISCC 2011), Kerkyra, Greece},
	year = {2011},
	month = {June 28 - July 1},
	pages = { 603 - 608},
	abstract = {With the booming of multimedia services, the 3rd
Generation Partnership Project (3GPP) has introduced the
evolved Multimedia Multicast/Broadcast Service (e-MBMS)
feature for LTE systems. The main objective of MBMS is to
introduce real broadcast distribution capabilities into cellular
systems. This purposed 3GPP to introduce the MBMS over a
Single Frequency Network (MBSFN) operation. In this work
we investigate the provision of MBMS service over a
combination of MBSFN and PTM transmission schemes. We
focus on the file repair procedure, because the distribution of
binary data via MBMS must result in 100\% error-free
downloaded files. In order to achieve this goal, MBMS offers a
Forward Error Correction (FEC) mechanism. Our simulation
results show that there are some file repair schemes that
achieve better performance as far as different network
configurations are concerned. Furthermore, we compare all
the file recovery methods and evaluate them against various
network parameters in a realistic simulation environment.},
	keywords = {FEC, LTE, MBMS, MBSFN},
	author = {Christos Bouras and Antonios Alexiou and Andreas Papazois and Vasileios Kokkinos and Konstantinos Asimakis and Georgia Tseliou}
}
@inbook {3142,
	title = {Security issues for multi - domain resource reservation},
	booktitle = {Network Security, Administration, and Management: Advancing Technologies and Practises},
	year = {2011},
	pages = { 38 - 50},
	publisher = {IGI Global},
	organization = {IGI Global},
	abstract = {<p>In this chapter, we deal with the issue of security regarding components that are responsible for provisioning multi-domain network services, either automatically or through some form of administrator interaction. It is evident that a malicious compromise of such a component would have far-reaching implications for the stability of the network. Furthermore, trust between cooperating domains is a delicate issue and each partner in the multi-domain federation has to have some guarantees that peers in the service are not going to be security compromised. We enumerate some of the related dangers and propose ways to limit the attack surface, reduce the intrusion possibilities, and guarantee the quick resolution of any successful violations. The issue of security is studied in two main parts: Inter-domain security, for the communication between domains and the successful negotiation of resource reservations and intra-domain security, for the internal communications within a domain for the initiation of a resource reservation and its actual realization in the network devices. Resource reservation is studied both on the level of IP services based on Differentiated Services architectures, and on the level of dynamic circuit reservation based on Layer 2 technologies. The chapter is completed with a case study on the authentication and authorization framework designed in the context of a pan-european network resource reservation service, in the Geant academic and research network.</p>
},
	author = {Christos Bouras and Kostas Stamos}
}
@article {3101,
	title = {A study of Forward Error Correction for Mobile Multicast},
	journal = {International Journal of Communication Systems, Wiley InterScience},
	year = {2011},
	pages = { 607 - 627},
	abstract = {<p>3GPP has standardized the use of forward error correction for the provision of reliable data transmission in the mobile multicast framework. This error control method inevitably adds a constant overhead in the transmitted data. However, it is so simple as to meet a prime objective for mobile multicast services; that is scalability to applications with thousands of receivers. In this paper we present a study on the impact of application layer forward error correction. We examine whether it is beneficial or not, how the optimal code dimension varies based on network conditions, which parameters affect the optimal code selection, and how they achieve this. Additionally, we focus on one of the most critical aspects in mobile multicast transmission which is power control. The evaluation is performed with the aid of a novel scheme that incorporates the properties of an evolved mobile network, as they are determined by the 3GPP specifications.</p>
},
	keywords = {FEC, MBMS, Power Control, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Andreas Papazois}
}
@inbook {3143,
	title = {The TFRC protocol and its usage for wireless video transmission},
	booktitle = {Advanced CommunicationProtocol Technologies: Solutions, Methods and Applications},
	year = {2011},
	pages = { 300 - 317},
	publisher = {IGI Global},
	organization = {IGI Global},
	chapter = {14},
	abstract = {<p>The subject of this chapter is to present the TFRC (TCP-Friendly Rate Control) protocol in the area of efficient wireless video transmission and its possible usage in cross-layer power management mechanisms. The basic aspects of TFRC operation are presented, along with the suitability of TFRC usage for video transmission. The chapter examines related work and presents several mechanisms for efficient wireless video transmission using TFRC that have been proposed. These mechanisms utilize cross-layer approaches for adaptation of the power transmission level of the sender and TFRC feedback information regarding the wireless connection status from the receiver for improved transmission statistics, and therefore user experience, without unnecessary power consumption.</p>
},
	author = {Christos Bouras and Kostas Stamos and Vassilis Papapanagiotou and Giannis Zaoudis}
}
@conference {2986,
	title = {Utilizing Video Enconding for Power Management over Wireless Networks},
	booktitle = {International Conference on Data
Communication Networking, DCNET 2011, Seville, Spain, July 18 - 21, 2011},
	year = {2011},
	pages = { 57 - 62},
	abstract = {Power management is especially important in wireless networks because of the emergence of energy
constrained mobile devices. This paper examines the ways that video encoding information can be used for
more efficient power management. In particular, we propose and evaluate cross layer mechanisms that fine-
tune transmission power depending on the video frame being encoded and we examine how this mechanism
may be combined with algorithms that adjust transmission power based on feedback reports when TFRC is
used as the transport protocol. Since typical video encoding uses frames of varying importance for the
overall quality, this approach can improve received video quality and make better usage of available power.
},
	author = {Christos Bouras and Kostas Stamos and Giannis Zaoudis and Stamatis Stroumpis}
}
@article {3099,
	title = {Adaptation of RSS feeds based on the user profile and on the end device},
	journal = {Journal of Network and ComputerApplications, Elsevier Science},
	volume = {33},
	year = {2010},
	pages = { 410 - 421},
	abstract = {<p>In the last decade, the advances in technology along with the ease of access to information have dramatically changed the World Wide Web status during the last few years. The Internet acts as a means of finding useful information and more specifically news articles. Additionally, more and more people want to utilize their mobile devices towards the scope of reading news articles. The aforementioned situation generates a significant, yet almost untouched problem: easily locating interesting news articles on a dailybasis within the space that is available on the small screen device. In our work, we propose a framework that, by utilizing RSSfeeds, is able to personalize on the needs of the users and on the capabilities of their device, in order to present to them only a fraction of the news articles and merely the useful information that derives fromthem. Deploying a generalized,multi- functional mechanism that produces efficient results for the situation described, seems to be a panacea for most of the text-based, information retrieval needs. Within this framework we created PeRSSonal,a mechanism that is able to create personalized, pre-categorized,dynamically generated RSSfeeds focalized on the end user?s smal lscreen device. The system is based on algorithms that incorporate the user in to the categorization and summarization procedures, while the articles are presented back to him/her according to her interests and the client device capacity.</p>
},
	author = {Christos Bouras and Vassilis Poulopoulos and Vassilis Tsogkas}
}
@inbook {3130,
	title = {Adaptive multimedia transmission over the Internet},
	booktitle = {Chapter 20, Selected Topics in Communication Networks and Distributed Systems},
	year = {2010},
	pages = { 589 - 606},
	publisher = {World Scientific},
	organization = {World Scientific},
	abstract = {<p>The Internet is a heterogeneous network environment and the network resources that are available to multimedia applications can be modified very quickly. Multimedia applications must have the capability to adapt their operation to network changes. In order to add adaptation characteristics to multimedia applications, we can use techniques both at the network and application layers. Adaptive multimedia transmission techniques have the capability to transmit multimedia data over heterogeneous networks and adapt media transmission to network changes. In order to provide adaptive multimedia transmission, mechanisms to monitor the network conditions and mechanisms to adapt the transmission of the data to the network changes must be implemented. This chapter concentrates on the architecture and design issues of adaptive multimedia techniques that provide the capability to transmit multimedia data over heterogeneous networks and adapt the transmission of the multimedia data to the network changes.</p>
},
	author = {Christos Bouras and Apostolos Gkamas}
}
@article {3094,
	title = {Adaptive Smooth Multicast Protocol for Multimedia Transmission: Implementation Details and Performance Evaluation},
	journal = {International Journal of Communication Systems, Wiley InterScience},
	volume = {23},
	year = {2010},
	pages = { 299 - 333},
	abstract = {<p>In this article we propose a new single-rate multicast congestion control scheme named Adaptive Smooth Multicast Protocol (ASMP), for multimedia transmission over best-effort networks. The smoothness lays in the calculation and adaptation of the transmission rate, which is based on dynamic estimations of protocols? parameters and dynamic adjustment of the {\textquotedblleft}smoothness factor{\textquotedblright}, as well. ASMP key attributes are: a) TCP-friendly behavior, b) adaptive scalability to large sets of receivers, c) high bandwidth utilization, and finally d) smooth transmission rates, which are suitable for multimedia applications. We evaluate the performance of ASMP and investigate its behavior under various network conditions through extensive simulations conducted with the network simulator software (ns2). Simulation results show that ASMP can be regarded as a serious competitor of TFMCC and PGMCC. In many cases, ASMP outperforms TFMCC in terms of TCP-friendliness and smooth transmission rates, while PGMCC presents lower scalability than ASMP. We have implemented ASMP on top of RTP/RTCP protocols in ns2 by adding all the RTP/RTCP protocol?s attributes that are defined in RFC 3550 and related to QoS metrics.</p>
},
	author = {Christos Bouras and Apostolos Gkamas and G Kioumourtzis}
}
@conference {2981,
	title = {Adopting FEC for Reliable Multicasting over LTE Networks},
	booktitle = {13th ACM International Conference on Modeling Analysis and Simulation of Wireless and Mobile Systems, Bodrum, Turkey},
	year = {2010},
	month = {October 17 - 21},
	pages = { 307 - 310},
	abstract = {The key feature for the provision of Multimedia
Broadcast/Multicast Services (MBMS) in Long Term Evolution
(LTE) networks is the Multimedia Broadcast over a Single
Frequency Network (MBSFN). On the other hand, the use of
Forward Error Correction (FEC) in mobile multicast transmission
has significant advantages and the 3rd Generation Partnership
Project (3GPP) has adopted the application layer FEC in the
MBMS standard. In this paper, we investigate the impact of the
application layer FEC over the MBSFN delivery method.},
	keywords = {FEC, LTE, MBMS},
	author = {Christos Bouras and Antonios Alexiou and Andreas Papazois and Vasileios Kokkinos and George Tsichritzis}
}
@conference {2964,
	title = {Adopting forward error correction for multicasting over cellurar networks},
	booktitle = {European Wireless 2010, Lucca, Italy},
	year = {2010},
	month = {12 - 15 April },
	pages = {307-310},
	abstract = {<p>FEC is an error control method that can be used to augment or replace other methods for reliable data transmission. Such schemes inevitably add a constant overhead in the transmitted data. However, they are so simple as to meet a prime objective for UMTS multicast services, that is scalability to applications with thousands of receivers. This is the reason that 3GPP recommends the use of FEC for MBMS framework. In this paper, we use a probabilistic model for the multicast user distribution in the network and we define a scheme for multicast data delivery that combines FEC with traditional ARQ. It is important that our analysis is compliant with the 3GPP specifications and considers the latest advances in mobile networks. In this framework we investigate the impact of FEC use, we examine whether it is beneficial, how the optimal FEC code dimensioning varies based on the network conditions, which parameters affect the optimal FEC code selection, and how they do it.</p>
},
	keywords = {FEC, LTE, MBMS, MBSFN},
	author = {Christos Bouras and Antonios Alexiou and Andreas Papazois}
}
@conference {2967,
	title = {Assigning Web News to Clusters},
	booktitle = {The Fifth International Conference on Internet and Web Applications and Services, (ICIW 2010), Barcelona, Spain},
	year = {2010},
	month = {May 9 - 15},
	pages = {1-5},
	abstract = {The Web is overcrowded with news articles, an
overwhelming information source both with its amount and
diversity. Assigning news articles to similar groups, on the 
other hand, provides a very powerful data mining and
manipulation technique for topic discovery from text
documents. In this paper, we are investigating the application 
of a great spectrum of clustering algorithms, as well as 
similarity measures, to news articles that originate from the 
Web and compare their efficiency for use in an online Web
news service application. We also examine the effect of
preprocessing on clustering. Our experimentation showed that
k-means, despite its simplicity, accompanied with preliminary
steps for data cleaning and normalizing, gives better aggregate
results when it comes to efficiency.},
	author = {Christos Bouras and Vassilis Tsogkas}
}
@inbook {3140,
	title = {Best Practices and Strategies for Broadband Deployment: Lessons learned around the world},
	booktitle = {C. Bouras, A. Gkamas, T. Tsiatsos, Adoption, Usage, andGlobal Impact of Broadband Technologies: Diffusion, Practice and Policy},
	year = {2010},
	pages = { 128 - 142},
	publisher = {IGI Global},
	organization = {IGI Global},
	chapter = {8},
	abstract = {<p>Broadband deployment is a necessity nowadays. It could help each country, municipality and region to grow and offer better quality of life to the citizens. Today, the emphasis on the development of broadband networks is on fixed Fibre To The Home solutions The lessons learned from countries that are leaders in broadband penetration and Fibre To The Home deployment could be proven very useful for under-served communities, regions and countries where the broadband penetration is low. Therefore, this chapter summarises the lessons learned from implementing (a) country-wide strategies formulated at the national level, and (b) local strategies formulated by the municipalities. Concerning the role of national and local governments, it should be noted that nowadays it is very urgent the involvement of government in the development of broadband infrastructure. Proposed noteworthy remarkable cases are Japan, South Korea and Singapore.</p>
},
	author = {Christos Bouras and Apostolos Gkamas and Thrasivoulos Tsiatsos}
}
@conference {2971,
	title = {Communication Cost Analysis of MBSFN in LTE},
	booktitle = {The 21st IEEE Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC 2010), Istanbul, Turkey},
	year = {2010},
	month = {September 26 - 30},
	pages = { 1366-1371},
	abstract = {Long Term Evolution (LTE) is the latest step towards
the 4th generation (4G) of radio technologies designed to increase
the capacity and speed of mobile communications. To support
Multimedia Broadcast/Multicast Services (MBMS), LTE offers
the possibility to transmit Multimedia Broadcast multicast
service over a Single Frequency Network (MBSFN), where a
time-synchronized common waveform is transmitted from
multiple cells for a given duration. In this paper we analytically
present the MBSFN delivery method and evaluate its
performance. The critical parameters of primary interest for the
evaluation of the scheme are the packet delivery cost and its
scalability. To this direction, a telecommunication cost analysis of
the MBMS service is presented based on the transmission cost
over the air interface, as well as the costs of all interfaces and
nodes of the MBSFN architecture. Since the performance of the
MBSFN scheme mainly depends on the configuration of the LTE
network that is under investigation, we consider different
network topologies, MBSFN deployments and user distributions.},
	keywords = {Cost analysis, LTE, MBSFN},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos and George Tsichritzis}
}
@conference {2977,
	title = {The Community Network Game Project: Enhancing Collaborative Activities in Online Games},
	booktitle = {NEM Summit Towards Future Media Internet, Barcelona, Spain},
	year = {2010},
	month = {14 - 15 October},
	abstract = {The EU-funded Community Network Game (CNG)
project aims at enhancing collaborative activities between
Massively Multiplayer Online Games (MMOG) players. This
will be achieved by developing new tools for the generation,
distribution and insertion of user-generated content (UGC) into
existing MMOGs without changing the game code and without
adding new processing or network loads to the MMOG central
servers. This UGC may include items (e.g., textures, 3D objects)
to be added to the game and live video captured from the game
screen and streamed to other players. We present the objectives
of the project, focusing on its main scientific and technological
contributions.},
	author = {Christos Bouras and Andreas Papazois and S Ahmad and R Hamzaoui and E Perelman and A Sahni and G Simon}
}
@conference {2980,
	title = {The Community Network Game Project: Enriching Online Gamers Experience with User Generated Content},
	booktitle = {CONTENT 2010: The Second International Conference on Creative Content Technologies, Lisbon, Portugal},
	year = {2010},
	month = {November 21 - 26},
	abstract = {<p>One of the most attractive features of Massively Multiplayer Online Games (MMOGs) is the possibility for users to interact with a large number of other users in a variety of collaborative and competitive situations. Gamers within an MMOG typically become members of active communities with mutual interests, shared adventures, and common objectives. We present the EU funded Community Network Game (CNG) project. The CNG project will provide tools to enhance col- laborative activities between online gamers and will develop new tools for the generation, distribution and insertion of user generated content (UGC) into existing MMOGs. CNG will allow the addition of new engaging community services without changing the game code and without adding new processing or network loads to the MMOG central servers. The UGC considered by the CNG project includes 3D objects and graphics as well as video to be shared using peer-to-peer (P2P) technology. We describe the concept, innovations, and objectives of the project.</p>
},
	author = {Christos Bouras and Andreas Papazois and George Tsichritzis and S Ahmad and R Hamzaoui and E Perelman and A Sahni and G Simon}
}
@inbook {3133,
	title = {Cross Layer Design for Multimedia Transmission over Wireless Networks},
	booktitle = {Next Generation Mobile Networks and Ubiquitous Computing},
	year = {2010},
	pages = { 35 - 42},
	publisher = {Information Science Reference},
	organization = {Information Science Reference},
	chapter = {4},
	abstract = {<p>Over the last years a number of new protocols have been developed for multimedia applications in the whole OSI layer?s scale. In addition wireless communications and networking fast occupy centre stage in research and development activity in the area of communication networks. In order to support better wireless user the cross layer design paradigm has been proposed. This chapter presents the challenges in design and implementation of cross layer adaptation schemes for multimedia transmission over wireless networks. In addition this chapter presents the most important parameters and constrains that should be taken into consideration when attempting cross layer adaptation in wireless networks that involves different protocols in the overall protocol stack.</p>
},
	author = {Christos Bouras and Apostolos Gkamas and G Kioumourtzis}
}
@conference {2969,
	title = {Dynamic User Context Web Personalization in Meta - Portals},
	booktitle = {The Fifteenth IEEE Symposium on Computers and Communications (ISCC{\textquoteright}10), Riccione, Italy},
	year = {2010},
	month = {June 22 - 25},
	pages = { 925 - 930},
	abstract = {<p>We present the dynamic web personalization and document grouping infrastructure for meta-portals and the evaluation of the mechanism on peRSSonal, a system that collects articles from news portals and blogs worldwide. A meta-portal is an informational node where articles from different sources are collected and presented in a categorized and personalized manner. The web personalization mechanism is based on dynamic creation and update of user profile according to the user{\textquoteright}s preferences when browsing and on user grouping details. Assuming that required information, such as article tagging, keywords to categories matching and articles to categories relation is already part of the meta-portal we present a novel mechanism that can build and maintain a user profile which is formed without disturbing the user. Furthermore, we describe the real-time user centered document grouping mechanism that is implemented to support the web personalization system and present the experimental evaluation of the whole system.</p>
},
	author = {Christos Bouras and Vassilis Poulopoulos}
}
@conference {2974,
	title = {Efficient extraction of news articles based on RSS crawling},
	booktitle = {International Conference on Machine and Web Intelligence, Algiers, Algeria (Invited Paper)},
	year = {2010},
	month = {3 - 5 October},
	pages = {1-7},
	abstract = {<p>The expansion of the World Wide Web has led to a state where a vast amount of Internet users face and have to overcome the major problem of discovering desired information. It is inevitable that hundreds of web pages and weblogs are generated daily or changing on a daily basis. The main problem that arises from the continuous generation and alteration of web pages is the discovery of useful information, a task that becomes difficult even for the experienced internet users. Many mechanisms have been constructed and presented in order to overcome the puzzle of information discovery on the Internet and they are mostly based on crawlers which are browsing the WWW, downloading pages and collect the information that might be of user interest. In this manuscript we describe a mechanism that fetches web pages that include news articles from major news portals and blogs. This mechanism is constructed in order to support tools that are used to acquire news articles from all over the world, process them and present them back to the end users in a personalized manner</p>
},
	author = {Christos Bouras and Vassilis Poulopoulos and George Adam}
}
@conference {2978,
	title = {Efficient MCS Selection for MBSFN Transmissions over LTE Networks},
	booktitle = {IFIP Wireless Days 2010, Venice, Italy},
	year = {2010},
	month = {October 20 - 22},
	abstract = {Long Term Evolution (LTE), the next-generation
network beyond 3G, is designed to support the explosion in
demand for bandwidth-hungry multimedia services that are
already experienced in wired networks. To support Multimedia
Broadcast/Multicast Services (MBMS), LTE offers functionality
to transmit MBMS over a Single Frequency Network (MBSFN),
where a time-synchronized common waveform is transmitted
from multiple cells for a given duration. This significantly
improves the Spectral Efficiency (SE) compared to conventional
MBMS operation. The achieved SE is mainly determined by the
Modulation and Coding Scheme (MCS) utilized by the LTE
physical layer. In this paper we propose and evaluate four
approaches for the selection of the MCS that will be utilized for
the transmission of the MBSFN data. The evaluation of the
approaches is performed for different users? distribution and
from SE perspective. Based on the SE measurement, we
determine the most suitable approach for the corresponding
users? distribution.},
	keywords = {LTE, MBMS, MBSFN, MCS},
	author = {Christos Bouras and Antonios Alexiou and Andreas Papazois and Vasileios Kokkinos and George Tsichritzis}
}
@conference {2973,
	title = {An Efficient Mechanism for Stemming and Tagging: the Case of Greek Language},
	booktitle = {Advanced Knowledge - based Systems, Invited Session of the 14th International Conference on Knowledge - based and Intelligent Information \& Engineering Systems,
Cardiff Wales, UK},
	year = {2010},
	month = {8 - 10 September},
	pages = { 389 - 397},
	abstract = {In an era that, searching the WWW for information becomes a tedious task, it is obvious that mainly search engines and other data mining mechanisms need to be enhanced with characteristics such as NLP in order to better analyze and recognize user queries and fetch data. We present an efficient mechanism for stemming and tagging for the Greek language. Our system is constructed in such a way that can be easily adapted to any existing system and support it with recognition and analysis of Greek words. We examine the accuracy of the system and its ability to support peRSSonal a medium constructed for offering meta-portal news services to internet users. We present experimental evaluation of the system compared to already existing stemmers and taggers of the Greek language and we prove the higher efficiency and quality of results of our system.},
	author = {Christos Bouras and Vassilis Poulopoulos and George Adam and Konstantinos Asimakis}
}
@article {3095,
	title = {An Efficient Mechanism for UMTS Multicast Routing},
	journal = {Mobile Networks and Applications, Springer Verlang},
	volume = {15},
	year = {2010},
	pages = {802 - 815},
	abstract = {<p>In this paper, we present a novel scheme for the multicast transmission of data over Universal Mobile Telecommunications System (UMTS) networks. Apart from the normal multicast transmission over UMTS, we consider the handling of exceptional cases caused by user mobility scenarios. The proposed scheme is in accordance with the current specifications of the Multimedia Multicast/ Broadcast Service (MBMS) defined by the 3rd Generation Partnership Project (3GPP) and introduces minor modifications in the UMTS architecture and the mobility management mechanisms. The proposed scheme is implemented as an ns-2 network simulator module. The performance of the proposed scheme is validated and analyzed through ns-2 simulation experiments. This new module can be employed to investigate various aspects of UMTS multicast. Furthermore, in order to further highlight the contribution of our mechanism, we have implemented two multicast congestion control mechanisms for UMTS and we have measured their performance for MBMS transmissions.</p>
},
	keywords = {MBMS, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Andreas Papazois}
}
@inbook {3138,
	title = {Efficient Power Allocation in E-MBMS Enabled 4G Networks},
	booktitle = {Wireless Network Traffic and Quality of Service Support: Trends and Standards},
	year = {2010},
	pages = { 458 - 488},
	publisher = {IGI Global},
	organization = {IGI Global},
	chapter = {18},
	abstract = {<p>The plethora of mobile multimedia services that are expected to face high penetration, poses the need for the deployment of a resource economic scheme in Long Term Evolution (LTE) networks. To this direction, the Evolved - Multimedia Broadcast / Multicast Service (E- MBMS) is envisaged to play an instrumental role for LTE proliferation and set the basis for a successful 4th Generation (4G) standardization process. One of the most critical aspects of E- MBMS performance is the selection of the most efficient radio bearer, in terms of power consumption. This chapter presents the prevailing radio bearer selection mechanisms and examines their performance in terms of power consumption. Furthermore, it discusses problems regarding the high power requirements for the realization of E-MBMS and evaluates the proposed techniques/solutions. Finally, this chapter presents a novel mechanism for efficient power control during E-MBMS transmissions that conforms to LTE requirements for simultaneous provision of multiple multimedia sessions.</p>
},
	keywords = {LTE, MBMS, Power Control},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos}
}
@conference {2965,
	title = {Efficient Power Management Adaptation for Video Transmission over TFRC},
	booktitle = {The Sixth Advanced International Conference on Telecommunications (AICT 2010), Barcelona, Spain},
	year = {2010},
	month = {May 9 - 15},
	pages = {509-514},
	abstract = {In this paper, we describe a power management
mechanism for wireless video transmission using the TFRC
protocol that takes into account feedback about the received
video quality and tries to intelligently adapt transmitting
power accordingly. The purpose of the mechanism is to utilize
TFRC feedback and thus achieve a beneficial balance between
the power consumption and the received video quality. We use
simulation in order to compare and evaluate our approach.},
	author = {Christos Bouras and Kostas Stamos and Vassilis Papapanagiotou and Giannis Zaoudis}
}
@conference {2979,
	title = {Enhancing FEC Application in LTE Cellular Networks},
	booktitle = {IFIP Wireless Days 2010, Venice, Italy},
	year = {2010},
	month = {October 20 - 22},
	abstract = {3rd Generation Partnership Project?s (3GPP) Long
Term Evolution (LTE) is focused on enhancing the Universal
Terrestrial Radio Access (UTRA). Evolved-Multimedia
Broadcast and Multicast Service (e-MBMS) uses Multimedia
Broadcast over a Single Frequency Network (MBSFN) operation
in order to improve its performance. In MBSFN operation, data
are transmitted simultaneously over the air from multiple tightly
time-synchronized cells. Raptor codes have been standardized as
the main application layer Forward Error Correction (FEC)
method for e-MBMS due to the advanced error protection they
offer and their overall performance. In this study, we investigate
the application of FEC in MBSFN-enabled LTE cellular
networks and we propose a new scheme that takes into account
the properties of MBSFN in order to provide a more efficient
operation of FEC during e-MBMS transmissions. The proposed
scheme is compared with other file recovery methods and is
evaluated against various network parameters in a realistic
simulation environment.},
	keywords = {FEC, LTE, MBMS, MBSFN},
	author = {Christos Bouras and Antonios Alexiou and Andreas Papazois and Vasileios Kokkinos and Georgia Tseliou}
}
@inbook {3134,
	title = {Exploiting Virtual Environments and Web2.0 Immersive Worlds to Support Collaborative e-Learning Communities},
	booktitle = {Novel Approaches in Web - Based Learning Technologies: Tools for ModernTeaching},
	year = {2010},
	pages = { 20 - 45},
	publisher = {IGI Global},
	organization = {IGI Global},
	chapter = {2},
	abstract = {<p>The main goal of this chapter is to facilitate educational designers and developers by providing a point of reference for making decisions on how to incorporate 3D environments into the applications they develop as well as for extending their capabilities by integrating more functionality. Therefore, this chapter presents the design principles for virtual spaces, which aim at supporting multi-user communication in web-based learning communities. In addition the implementation of these principles is presented using as point of reference EVE Training Area. This environment constitutes a three-dimensional space where participants, represented by 3D humanoid avatars, have the ability to use a variety of 3D e-collaboration tools for learning together. Furthermore, this chapter presents how these principles could be used as criteria for validating and extending ready Web2.0 Immersive worlds for supporting collaborative e-learning. Finally, collaborative e-learning usage scenarios that could be realized by exploiting collaborative virtual environments are described.</p>
},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka}
}
@conference {2972,
	title = {HANIME: An H - Anim Compliant Avatar Editor for NVEs},
	booktitle = {International Conference on Computer
Graphics Theory and Applications, Angers, France},
	year = {2010},
	month = {May 17 - 21},
	pages = {  347 - 352},
	abstract = {This paper addresses the problem of a visual H-Anim avatar editor. Although H-Anim is a very promising
standard for interchangeable avatars and avatar?s animation, the lack of an effective yet simple to use visual
avatar editor could repel users from H-Anim compliant Networked Virtual Environments. Therefore this
paper presents an H-Anim compliant editor, called HanimE, for creating avatars for Networked Virtual
Environments. This editor is entirely based on a graphical user interface and allows users to customize H-
Anim avatars, in a simple yet effective manner. The avatars created by HanimE can be integrated in various
H-Anim compliant Networked Virtual Environments regardless of the technology they are built on, since
they are X3D files.
},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Vasileios Triglianos and Kostas Kartsakalis}
}
@conference {2963,
	title = {Image extraction from online text streams},
	booktitle = {The 2010 IEEE International Symposium on Mining and Web (MAW10), Perth, Australia},
	year = {2010},
	month = {20 - 23 April },
	pages = { 609 - 614},
	abstract = {In this paper we present an efficient system that
processes HTML pages in order to extract the useful images from them. The proposed mechanism is template independent and is focalized on HTML pages that include news articles from major portals and blogs. As useful images we define the pictures that
are relevant to the news report. In order to extract the image objects of the article we deconstruct the HTML page to its DOM model and we apply a set of algorithms in order to clean and correct the HTML code, locate and characterize each node of the
DOM model and finally keep the nodes that are characterized as useful nodes. The proposed mechanism is applied as a subsystem of peRSSonal, a web tool that is used to obtain news articles from
all over the world, process them and present them back to the end users in a personalized manner. The role of the mechanism is to feed peRSSonal?s database with digital images for browsing and searching purposes. We present the basic algorithms and experimental results on the efficiency of the proposed implementation.},
	author = {Christos Bouras and Vassilis Poulopoulos and George Adam}
}
@conference {2966,
	title = {The Impact of FEC on Mobile Multicast Power Control},
	booktitle = {The Sixth Advanced International Conference on Telecommunications (AICT 2010), Barcelona, Spain},
	year = {2010},
	month = {May 9 - 15},
	pages = {1-6},
	abstract = {3GPP has standardized the use of forward error
correction for the provision of reliable data transmission in the
mobile multicast framework. In this paper we present a study
of the impact of application layer forward error correction on
power control during mobile multicast transmission. The
evaluation is performed with the aid of a novel scheme that
allows the simulation of FEC impact on both streaming
delivery and download delivery over a multicast session. It is
important that the proposed scheme incorporates the
properties of an evolved mobile network, as they are
determined by the 3GPP specifications.},
	keywords = {FEC, LTE, MBMS, Power Control},
	author = {Christos Bouras and Antonios Alexiou and Andreas Papazois}
}
@article {3089,
	title = {An Improved MBMS Power Counting Mechanism towards Long Term Evolution},
	journal = {Telecommunication Systems Journal, Springer Verlang},
	volume = {43},
	year = {2010},
	pages = { 109 - 119},
	abstract = {<p>One of the key objectives of beyond 3rd generation mobile networks is the realization of enhanced end-user experience through the provision of rich multimedia services. Multimedia Broadcast/Multicast Services (MBMS) framework epitomizes the increasing popularity of such applications and is envisaged to play an instrumental role for the Long Term Evolution (LTE) proliferation in mobile market. For exploiting resource efficiency, MBMS specifications consider the Counting Mechanism which decides whether it is more efficient to deliver MBMS multicast traffic over Point-to-Point (PTP) or Point-to-Multipoint (PTM) bearers. However, the necessity to further improve MBMS resource efficiency and integrate new technologies in the frame of LTE stresses the need for an advanced Counting Mechanism. In this work we propose a novel Power Counting Mechanism for efficient selection of MBMS bearers. The proposed mechanism optimally utilizes power resources and exploits broadband characteristics and performance enhancements emerged from Multiple Input Multiple Output (MIMO) antennas used in LTE networks.</p>
},
	keywords = {LTE, MBMS, Power Control},
	author = {Christos Bouras and Antonios Alexiou and Evangelos Rekkas}
}
@article {3088,
	title = {An Improved Mechanism for Multiple MBMS Sessions Assignment in B3G Cellurar Networks},
	journal = {Wireless Networks, Springer Verlang},
	volume = {16},
	year = {2010},
	pages = { 671 - 686},
	abstract = {<p>In Universal Mobile Telecommunication System (UMTS), the downlink capacity is limited by the base station transmission power. Therefore, power control plays an important role to minimize the transmitted power shared among unicast and multicast users within a cell. In Multimedia Broadcast/Multicast Service (MBMS), power control targets to the efficient utilization of radio and network resources. However, the expected high demand for such services stresses the need for an efficient scheme, capable of dynamically allocating radio resources to parallel MBMS sessions. This paper proposes a power control mechanism for efficient MBMS session assignment in next generation UMTS networks. The mechanism shares efficiently the available power resources of UMTS base stations to MBMS sessions running in the network. Furthermore, the mechanism is evaluated through several realistic scenarios and the results indicate the ability of the mechanism to utilize efficiently the radio resources and to ensure the service continuity when parallel MBMS services run in the network. Our approach is compared with current 3rd Generation Partnership Project (3GPP) approaches, such as these presented in TS 25.346 and in TR 25.922, in order to highlight the enhancements that it provides.</p>
},
	keywords = {MBMS, Power Control, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos and Evangelos Rekkas}
}
@inbook {3136,
	title = {Layer 2 Quality of Service Architecture},
	booktitle = {Trends in Telecommunications Technologies},
	year = {2010},
	pages = { 399 - 412},
	publisher = {InTech},
	organization = {InTech},
	chapter = {19},
	author = {Christos Bouras and Vaggelis Kapoulas and Kostas Stamos and Dimitris Primpas and Leonidas Poulopoulos and Vassilis Papapanagiotou}
}
@inbook {3131,
	title = {The Multimedia Broadcast/Multicast Service of the Universal Mobile Telecommunications System},
	booktitle = {Selected Topics in Communication Networks and Distributed Systems},
	year = {2010},
	pages = { 43 - 78},
	publisher = {World Scientific},
	organization = {World Scientific},
	chapter = {2},
	abstract = {<p>The Universal Mobile Telecommunications System (UMTS) constitutes the premier third generation (3G) wireless technology that is dominating the global market. Multicasting is an efficient method of supporting group communication as it allows the transmission of packets to multiple destinations, using fewer network resources. The need for broadcasting and multicasting in UMTS led to the definition of the Multimedia Broadcast/Multicast Service (MBMS) framework, which targets the efficient utilization of radio and network resources of the UMTS network. This chapter introduces the key concepts of UMTS and in particular the MBMS framework of UMTS. Moreover, it investigates the power profiles of several transport channels (common and dedicated) which could be employed for the transmission of MBMS services to mobile users. Problems regarding the high power requirements for the realization of MBMS are also presented. The reader will become familiar with these problems and the proposed techniques/solutions.</p>
},
	keywords = {MBMS, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos and Evangelos Rekkas}
}
@article {3098,
	title = {Noun Retrieval Effect on Text Summarization and Delivery of Personalized News Articles to the User{\textquoteright}s Desktop},
	journal = {Data and Knowledge Engineering, Elsevier Science, Special Issue Advanced Knowledge},
	volume = {69},
	year = {2010},
	pages = { 664 - 677},
	abstract = {<p>Text summarization and categorization, as well as personalization of the results, have always been some of the most demanding information retrieval tasks. Deploying a generalized, multi-functional mechanism that produces good results for the aforementioned tasks seems to be a panacea for most of the text-based, information retrieval needs. In this article, we present the keyword extraction techniques, exploring the effects that part of speech tagging has on the summarization procedure of an existing system. Moreover, we describe the profiling features that are used as an extension to an already constructed news indexing system, PeRSSonal. We are thus enhancing the personalization algorithm that the system utilizes with various features derived from the user?s profile, such as the list of viewed articles and the time spent on them. In addition, we analyze the system?s interconnection channels that are used with the client-side desktop application that was developed and we evaluate the approaches that we propose.</p>
},
	author = {Christos Bouras and Vassilis Tsogkas}
}
@conference {2968,
	title = {Performance Evaluation of MPEG-4 Video Transmission with the Adaptive Smooth Multicast Protocol (ASMP)},
	booktitle = {The Fifteenth IEEE Symposium on Computers and Communications (ISCC{\textquoteright}10), Riccione, Italy},
	year = {2010},
	month = {June 22 - 25},
	pages = { 540 - 545},
	abstract = {We present in this work the performance
evaluation of MPEG-4 video transmission with our proposed  
single rate multicast protocol named Adaptive Smooth
Multicast Protocol (ASMP). ASMP key attributes are: a)
adaptive scalability to large sets of receivers, b) TCP-
friendly behavior, c) high bandwidth utilization, and finally
d) smooth transmission rates which are suitable for  
multimedia applications. We evaluate the performance of 
ASMP under an integrated simulation environment which
extends ns-2 and Evalvid-RA to the multicast domain with
the use of the RTP/RTCP protocols. Simulations conducted
under this environment combine the measurements of
network-centric along with video quality metrics. This
{\textquotedblleft}joint{\textquotedblright} evaluation process provides a better understanding
of the benefits and limitations of any proposed protocol for
multimedia data transmission.},
	author = {Christos Bouras and Apostolos Gkamas and G Kioumourtzis}
}
@conference {2976,
	title = {Power management of video transmission on wireless networks for multiple receivers},
	booktitle = {18th International Conference onSoftware, Telecommunications and Computer Networks (SoftCOM 2010), Split - Bol- Island Brac, Croatia,},
	year = {2010},
	month = {Sept. 23-25},
	pages = {300-304},
	abstract = {The main idea of this paper is an efficient power
management mechanism in order to transmit to multiple
receivers. The proposed mechanism consists of a module for
efficiently managing the power when transmitting video over
wireless networks by using the TFRC protocol reports and then
adjusts transmission power using a binary-like approach. In
order to extend to multiple receivers, several methods are
proposed for calculating an appropriate power transmission
level based on all TFRC reports and adjust the server?s
transmission power accordingly.},
	author = {Christos Bouras and Kostas Stamos and Giannis Zaoudis}
}
@inbook {3137,
	title = {Providing quality end-to-end videoconference services in IP networks},
	booktitle = {Videoconferencing: Technology, Impact and Applications},
	year = {2010},
	pages = { 111 - 122},
	publisher = {Nova Science Publishers},
	organization = {Nova Science Publishers},
	chapter = {5},
	abstract = {<p>The development of quality and user satisfying videoconference applications at a low cost has been hindered in the past by, among other reasons, low quality connections and a difficulty for the average user to establish end-to-end connections without hassle. In this chapter, we describe some of the latest methods and developments that overcome these problems. In particular, we discuss ways to make establishment of universal videoconference connections easier by overcoming the problem of participants that reside behind NAT routers, by deploying new protocols at the application or even the network layer. An example of the former case is the development of establishment protocols specifically designed for this purpose, while an example for the latter case is the deployment of IPv6, which aims to make NAT deployments obsolete. Furthermore, we discuss efforts to provide targeted support for quality of experience in networks that support some kind of traffic classification through the usage of dynamic mechanisms and dynamic network re-configurations. Apart from describing the state of the art in the aforementioned areas, we provide detailed insight in specific research efforts that have taken place and assess their results in the overall user experience.</p>
},
	author = {Christos Bouras and Kostas Stamos}
}
@inbook {3135,
	title = {Providing Quality of Service across multiple providers: The case of European research and academic space},
	booktitle = {Intelligent Quality of Service Technologies and Network Management: Models for Enhancing Communication},
	year = {2010},
	pages = { 280 - 296},
	publisher = {IGI Global},
	organization = {IGI Global},
	abstract = {<p>In this chapter, the authors present some of the latest developments related to the provisioning of Quality of Service (QoS) in today?s networks and the associated network management structures that are or will be deployed to support them. They first give a brief overview of the most important Quality of Service proposals in the areas of Layer 2 (L2) and Layer 3 (L3) QoS provisioning in backbone networks, and they discuss the network management structures and brokers that have been proposed in order to implement these services. As a case study, they describe the pan-european research and academic network, which is supported centrally by GEANT and which encompasses multiple independent NRENs (National Research and Education Networks). In the last few years, GEANT has developed and deployed a number of production and pilot services meant for the delivery of quality network services to the end users across Europe.</p>
},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos}
}
@inbook {3139,
	title = {Radio Resource Management for E-MBMS Transmissions towards LTE},
	booktitle = {Evolved Cellular Network Planning and Optimization for UMTS and LTE},
	year = {2010},
	pages = { 331 - 360},
	publisher = {Auerbach Publications, CRC Press, Taylor and Francis Group},
	organization = {Auerbach Publications, CRC Press, Taylor and Francis Group},
	chapter = {9},
	abstract = {<p>Long Term Evolution (LTE) constitutes a key standard that paves the way for the future mobile broadband landscape envisioned by 4th Generation (4G) wireless networks. Actu- ally, LTE addresses the emerging trend for the mass provision of rich multimedia services, such as Mobile TV, in a more power and spectral e{\textpm}cient way than its predecessors. To this direction, the Evolved - Multimedia Broadcast/Multicast Service (E-MBMS) frame- work is envisaged to play an instrumental role for the LTE proliferation in mobile. E-MBMS constitutes the evolutionary successor of MBMS, which was introduced in the Release 6 of Universal Mobile Telecommunication System (UMTS). MBMS is designed in order to deliver multimedia data from a single source entity to multiple destinations. However, downlink ca- pacity in such networks is limited by base station transmission power. As an aftermath, in MBMS e{\textpm}cient power allocation techniques should be implemented so as to ensure the mass provision of multimedia applications to mobile users. This chapter presents several techniques and mechanisms used today for MBMS power optimization in next generation cellular networks.</p>
},
	keywords = {LTE, MBMS, Power Control},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos}
}
@conference {2975,
	title = {Spectral Efficiency Performance of MBSFN-enabled LTE Networks},
	booktitle = {6th IEEE International Conference on Wireless and Mobile Computing, Networking and Communication (WiMob 2010), Niagara Falls, Canada},
	year = {2010},
	month = {October 11 - 13},
	pages = { 361 - 367},
	abstract = {Long Term Evolution (LTE) constitutes the latest step
before the 4th generation (4G) of radio technologies designed to
increase the capacity and speed of mobile communications. To
support Multimedia Broadcast/Multicast Services (MBMS), LTE
offers the possibility to transmit Multimedia Broadcast multicast
service over a Single Frequency Network (MBSFN), where a
time-synchronized common waveform is transmitted from
multiple cells for a given duration. This enables over-the-air
combining, thus improving the Signal to Interference plus Noise
Ratio (SINR) and spectral efficiency (SE) significantly compared
to conventional MBMS operation. In this paper, we analytically
calculate the SE performance achieved in a MBSFN area for a
dynamically changing user topology and different modulation
and coding schemes (MCS). Finally, based on the SE
measurement, we determine the MCS scheme that either
maximizes or achieves a target SE for the corresponding user
distribution.},
	keywords = {LTE, MBMS, MBSFN, MCS},
	author = {Christos Bouras and Antonios Alexiou and Andreas Papazois and Vasileios Kokkinos and George Tsichritzis}
}
@inbook {3132,
	title = {Squeak Etoys: Interactive and Collaborative Learning Environment},
	booktitle = {Handbook of Research on SocialInteraction Technologies and Collaboration Software: Concepts and Trends},
	year = {2010},
	pages = {417 - 427},
	publisher = {IGI Global},
	organization = {IGI Global},
	chapter = {37},
	abstract = {<p>Squeak Etoys is a free software program and media-rich authoring system with a user-friendly visual interface. The software is designed to help six to twelve year-old children learn through interaction and collaboration; it comes preinstalled on XO laptop computers distributed by the One Laptop Per Child Foundation. The goal of the One Laptop Per Child initiative is to create novel educational opportunities for the world?s children by providing each child with a book-size, light and portable computer for personal use at school and at home. This chapter elaborates on the educational dimensions of the XO laptop and the Etoys environment developed to empower teachers and students with the capacity for creative learning, exploration, interaction, and collaboration. The authors focus on how the hardware and software capabilities of XO laptops can be utilized to allow children to interact, work together on projects, and engage in computer simulations and games while learning mathematics, physics, chemistry, and geometry.</p>
},
	author = {Christos Bouras and Vassilis Poulopoulos and Vassilis Tsogkas}
}
@book {3155,
	title = {Trends in Telecommunications Technologies (Edited by C. Bouras)},
	series = {Published by In-Tech},
	year = {2010},
	author = {Christos Bouras}
}
@conference {2970,
	title = {W - kmeans: Clustering News Articles using WordNet},
	booktitle = {Advanced Knowledge - based Systems, Invited Session of the 14th International Conference on Knowledge {\textendash} based and Intelligent Information \& Engineering Systems, Cardiff Wales, UK},
	year = {2010},
	month = {September 8 - 10},
	pages = { 379 - 388},
	abstract = {Document clustering is a powerful technique that has been widely
used for organizing data into smaller and manageable information kernels.
Several approaches have been proposed suffering however from problems like
synonymy, ambiguity and lack of a descriptive content marking of the
generated clusters. We are proposing the enhancement of standard kmeans
algorithm using the external knowledge from WordNet hypernyms in a twofold
manner: enriching the {\textquotedblleft}bag of words{\textquotedblright} used prior to the clustering process and
assisting the label generation procedure following it. Our experimentation
revealed a significant improvement over standard kmeans for a corpus of news
articles derived from major news portals. Moreover, the cluster labeling process
generates useful and of high quality cluster tags.},
	author = {Christos Bouras and Vassilis Tsogkas}
}
@conference {2953,
	title = {Adaptive Smooth Simulcast Protocol for Multimedia Transmission},
	booktitle = {The Fourteenth IEEE Symposium on Computers and Communications (ISCC{\textquoteright}09), Sousse, Tunisia},
	year = {2009},
	month = {July 5 - 8},
	pages = { 437 - 442},
	abstract = {<p>We introduce Adaptive Smooth Simulcast Protocol (ASSP) for simulcast transmission over best-effort networks. ASSP is a new multiple-rate protocol that implements a single rate TCP-friendly protocol as the underlying congestion control mechanism for each simulcast stream. ASSP is build on top of the RTP/RTCP protocol and exploits the RTCP sender and receiver reports for the dissemination of feedback information. The key attributes of ASSP are: a) TCPfriendly behavior, b) adaptive per-stream transmission rates, c) adaptive scalability to large sets of receivers and finally d) smooth transmission rates that are suitable for multimedia applications. We evaluate the performance of ASSP and investigate its behavior through simulations conducted with the network simulator software (ns2).</p>
},
	author = {Christos Bouras and Apostolos Gkamas and G Kioumourtzis}
}
@article {3081,
	title = {Architectures and Performance Evaluation of Bandwidth Brokers},
	journal = {International Journal of Network Management, Wiley InterScience},
	volume = {19},
	year = {2009},
	pages = { 110 - 117},
	abstract = {<p>DiffServ is the basis of contemporary QoS-enabled networks. Setting up DiffServ QoS requires extensive engineering effort in dimensioning and provisioning, especially for adjacent networks under different administrations linked in a {\textquotedblleft}federated{\textquotedblright} hierarchy. The bandwidth broker is an entity that is responsible for the management of the resources and the QoS service operation in an automated way. In this paper, we present, test and compare 2 different architectures of bandwidth brokers, a centralized one and a distributed one. We also deal with the inter-domain operation of the bandwidth broker in order to perform end to end provisioning. The paper presents the relevant aspects for inter-domain operation of a bandwidth broker and focuses on pathfinding issues. We discuss two models for inter domain routing through bandwidth brokers, analyzing their advantages and comparing them.</p>
},
	author = {Christos Bouras and Dimitris Primpas}
}
@article {3090,
	title = {Broadband Municipal Optical Networks in Greece: A Suitable Business Model},
	journal = {Journal of Telematics and Informatics, Elsevier Science},
	year = {2009},
	pages = { 391 - 409},
	abstract = {This paper proposes a business model for the optimal exploitation of the currently developing
broadband metropolitan area networks in Greece. Having recorded and examined
relevant international practices, we describe in detail the way that these networks should
be managed, operated, maintained and expanded. Taking into consideration that these
infrastructures will widely alter the broadband map of Greece, that Greece has currently
one of the lowest broadband penetration percentages in Europe and that the proper exploitation
strategy of the networks to be deployed could boost the demand for broadband connections
and applications, the application of the optimal business model appears to be of
vital importance. We describe the proposed business model in detail, including ways for
expanding the broadband infrastructures, as well as tackling of viability issues regarding
the authority responsible for managing the broadband metropolitan networks.},
	author = {Christos Bouras and Apostolos Gkamas and Thrasivoulos Tsiatsos and J Papagiannopoulos and George Theofilopoulos}
}
@conference {2960,
	title = {Caching News Channels on the User{\textquoteright}s Desktop},
	booktitle = {IADIS International Conference Applied Computing, Rome, Italy},
	year = {2009},
	month = {November 19 - 21},
	pages = { 35 - 42},
	abstract = {The exponential growth of the Web probes for new, better filtering systems and latency diminishing applications. We are presenting the caching features that are deployed in the client-side application that is developed within the scope of PeRSSonal, the generalized, multi-functional mechanism that delivers personalized, summarized and categorized news articles. We also evaluate the caching algorithm depicting the overall improvement that it offers to the client side desktop application.},
	author = {Christos Bouras and Vassilis Tsogkas and George Tsichritzis}
}
@inbook {3129,
	title = {Congestion Control for Multicast Transmission over UMTS},
	booktitle = {Wireless Quality of Service: Techniques, Standards and Applications},
	year = {2009},
	pages = { 291 - 312},
	publisher = {Auerbach Publications, Taylor \& Francis Group},
	organization = {Auerbach Publications, Taylor \& Francis Group},
	chapter = {10},
	abstract = {<p>In this chapter, we present a novel mechanism for the multicast congestion control over Universal Mobile Telecommunications System (UMTS) networks. The proposed mechanism is based on the well known TCP-Friendly Multicast Congestion Control (TFMCC) scheme. TFMCC is an equation-based multicast congestion control mechanism intended to scale to groups of several thousand receivers. It is based on the concept of Current Limiting Receiver (CLR). The CLR is the receiver that the sender believes currently has the lowest expected throughput of the multicast group. The key challenge in the design of the new scheme lies in extending TFMCC in order to support the UMTS Terrestrial Radio-Access Network (UTRAN). Our major contribution is that the TFMCC mechanism was improved in order to cope with the packet losses caused by either the temporary or the permanent degradation of the wireless channel. One of the major advantages of the proposed scheme is that it introduces minor modifications in the UMTS nodes with respect to the computing power of the mobile terminals. Finally, we implement our approach in the ns-2 network simulator and we evaluate it under various conditions. The simulation results are presented along with their analysis.</p>
},
	keywords = {Congestion Control, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Andreas Papazois}
}
@article {3084,
	title = {Cost Analysis and Efficient Radio Bearer Selection for Multicasting over UMTS},
	journal = {Wireless Communications and Mobile Computing, Wiley InterScience},
	year = {2009},
	pages = { 1159 - 1172},
	abstract = {Along with the widespread deployment of the Third Generation (3G) cellular networks, the fast-improving
capabilities of the mobile devices, content, and service providers are increasingly interested in supporting
multicast communications over wireless networks and in particular over Universal Mobile Telecommunications
System (UMTS). To this direction, the Third Generation Partnership Project (3GPP) is currently standardizing the
Multimedia Broadcast/Multicast Service (MBMS) framework of UMTS. In this paper, we present an overview of
the MBMS multicast mode of UMTS. We analytically present the multicast mode of the MBMS and analyze its
performance in terms of packet delivery cost under various network topologies, cell types, and multicast users?
distributions. Furthermore, for the evaluation of the scheme, we consider different transport channels for the
transmission of the multicast data over the UMTS Terrestrial Radio-Access Network (UTRAN) interfaces. Finally,
we propose a scheme for the efficient radio bearer selection that minimizes total packet delivery cost.},
	keywords = {Cost analysis, MBMS, Power Control, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos and Evangelos Rekkas}
}
@conference {2941,
	title = {CUTER: An Efficient Useful Text Extraction Mechanism},
	booktitle = {The 2009 IEEE International Symposium on Mining and Web(WAM09), Bradford, UK},
	year = {2009},
	month = {26 - 29 May},
	pages = { 703 - 708},
	abstract = {In this paper we present CUTER, a system that processes HTML pages in order to extract the useful text from them. The mechanism is focalized on HTML pages that include news articles from major portals and blogs. As useful text we define the body of the article that contains the news report. In order to extract the body of the article we deconstruct the HTML page to its DOM model and we apply a set of algorithms in order to clean and correct the HTML code, locate and characterize each node of the DOM model and finally store the text from the nodes that are characterized as useful text nodes. CUTER is a subsystem of peRSSonal, a web tool that is used to obtain news articles from all over the world, process them and present them back to the end users in a personalized manner. The role of CUTER is to feed peRSSonal with the body of the articles that are collected from major news portals and blogs. In this paper we present the basic algorithms and experimental results on the efficiency of the CUTER text extractor.},
	author = {Christos Bouras and Vassilis Poulopoulos and George Adam}
}
@conference {2951,
	title = {Date - based dynamic caching mechanism},
	booktitle = {IADIS European Conference on Data Mining 2009, Algavre, Portugal},
	year = {2009},
	month = {June 18 - 20},
	pages = {67-74},
	abstract = {News portals based on the RSS protocol are becoming nowadays one of the dominant ways that Internet users follow in order to locate the information they are looking for. Search engines, which operate at the back-end of a big portion of these web sites, receive millions of queries per day on any and every walk of web life. While these queries are submitted by thousands of unrelated users, studies have shown that small sets of popular queries account for a significant fraction of the query stream. A second truth has to do with the high frequency that a particular user tends to submit the same or highly relative search requests to the engine. By combining these facts, in this paper, we design and analyze the caching algorithm deployed in our personalized RSS portal, a web-based mechanism for the retrieval, processing and presentation in a personalized view of articles and RSS feeds collected from major Internet news portals. By using moderate amounts of memory and little computational overhead, we achieve to cache query results in the server, both for personalized and non-personalized user searches. Our caching algorithm operates not in a stand-alone manner but it co-operates and binds with the rest of the modules of our Portal in order to accomplish maximum integration with the system.},
	author = {Christos Bouras and Vassilis Poulopoulos and Panagiotis Silintziris}
}
@conference {2957,
	title = {Efficient Assignment of Multiple E-MBMS Sessions toward LTE},
	booktitle = {Second Joint IFIP Wireless and Mobile Networking Conference, Gdansk, Poland},
	year = {2009},
	month = {9 - 11 September},
	pages = { 240 - 250},
	abstract = {One of the major prerequisites for Long Term Evolution (LTE) networks
is the mass provision of multimedia services to mobile users. To this end,
Evolved - Multimedia Broadcast/Multicast Service (E-MBMS) is envisaged to
play an instrumental role during LTE standardization process and ensure LTE?s
proliferation in mobile market. E-MBMS targets at the economic delivery, in
terms of power and spectral efficiency, of multimedia data from a single source
entity to multiple destinations. This paper proposes a novel mechanism for efficient
radio bearer selection during E-MBMS transmissions in LTE networks.
The proposed mechanism is based on the concept of transport channels combination
in any cell of the network. Most significantly, the mechanism manages to
efficiently deliver multiple E-MBMS sessions. The performance of the proposed
mechanism is evaluated and compared with several radio bearer selection
mechanisms in order to highlight the enhancements that it provides.},
	keywords = {LTE, MBMS},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos}
}
@conference {2940,
	title = {An Efficient Mechanism for Power Control Optimization in MBMS Enabled UTRAN},
	booktitle = {IEEE Wireless Communications and Networking Conference, Budapest, Hungary},
	year = {2009},
	month = {5 - 8 April},
	pages = { 1292 - 1297 },
	abstract = {This paper proposes a power control mechanism for
the efficient radio bearer selection in the Multimedia
Broadcast/Multicast Service (MBMS) framework of Universal
Mobile Telecommunications System (UMTS). The selection of the
most efficient transport channel in terms of power consumption
is a key point for MBMS enabled UMTS networks, since a wrong
transport channel selection for the transmission of the MBMS
data could result to a significant decrease in the total capacity of
the network. Different UMTS transport channels and power
saving techniques are examined and an algorithm that selects the
most efficient combination of the above parameters is proposed.
The proposed MBMS power control mechanism selects the
transport channel that minimizes the base station?s transmission
power in every cell of the network that serves multicast users.},
	keywords = {MBMS, Power Control, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos}
}
@conference {2950,
	title = {An Enhanced MBMS Power Control Mechanism towards Long Term Evolution},
	booktitle = {Eighth Annual Wireless Telecommunications Symposium - WTS 2009, Prague, Czech Republic},
	year = {2009},
	month = {22 - 24 April},
	abstract = {Long Term Evolution (LTE) promises the delivery
of rich multimedia services in a more power and spectral
efficient way than its predecessor Universal Mobile
Telecommunication System (UMTS). To this direction, the newly
introduced Enhanced - Multimedia Broadcast/Multicast Service
(E-MBMS) framework is envisaged to play a fundamental role
during the LTE standardization. E-MBMS constitutes the
successor of MBMS which was introduced in the Release 6 of
UMTS in order to deliver multimedia data from a single source
entity to multiple destinations. This paper proposes a novel
mechanism for efficient radio bearer selection during E-MBMS
transmissions in LTE networks. The proposed mechanism is
based on the concept of transport channels combination (pointto-
point and/or point-to-multipoint radio bearers) in any
cell/sector of the network in which multicast users are residing.
The mechanism is evaluated through several realistic scenarios
and is compared with several radio bearer selection mechanisms
in order to highlight the enhancements that it provides.},
	keywords = {LTE, MBMS, Power Control},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos}
}
@conference {2958,
	title = {An Enhanced Mechanism for Efficient Assignment of Multiple sessions towards LTE},
	booktitle = {The 12th ACM Annual Conference on Modeling, Analysis and Simulation of Wireless Mobile Systems, Tenerife, The Canary Islands, Spain},
	year = {2009},
	month = {26 - 30 October},
	pages = { 384 - 391},
	abstract = {The provision of rich multimedia services, such as Mobile TV, is considered of key importance for the Long Term Evolution (LTE) proliferation in mobile market. To this direction, Evolved - Multimedia Broadcast/Multicast Service (E-MBMS) that targets at the efficient delivery of multimedia data from a single source entity to multiple destinations, is envisaged to play an instrumental role during LTE standardization process. However, both LTE and E-MBMS performance are limited by the base station?s transmission power. As an aftermath, efficient power allocation techniques should be implemented so as to ensure the mass provision of multimedia applications to mobile users. This paper proposes a novel mechanism for efficient radio bearer selection during E-MBMS transmissions in LTE networks. The proposed mechanism is based on the concept of transport channels combination in any cell of the network. Most significantly, the mechanism exploits the performance enhancements emerged from Multiple Input Multiple Output (MIMO) antennas used in LTE networks and manages to efficiently deliver multiple E-MBMS sessions. The proposed mechanism is thoroughly evaluated and compared with several radio bearer selection mechanisms existing in bibliography.},
	keywords = {LTE, MBMS, Power Control, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos}
}
@article {3091,
	title = {Evaluation of Different Power Saving Techniques for MBMS Services},
	journal = {EURASIP Journal on Wireless Communications and Networking, Hindawi Publishing Corporation},
	year = {2009},
	abstract = {Over the last years we have witnessed an explosive growth of multimedia computing, wireless communication and applications.
Following the rapid increase in penetration rate of broadband services, the Third Generation Partnership Project (3GPP) is
currently standardizing the Evolved-Multimedia Broadcast/Multicast Service (E-MBMS) framework of Long Term Evolution
(LTE), the successor ofUniversalMobile Telecommunications System (UMTS).MBMS constitutes a point-to-multipoint downlink
bearer service that was designed to significantly decrease the required radio and wired link resources. However, several obstacles
regarding the high-power requirements should be overcome for the realization of MBMS. Techniques, such as Macrodiversity
Combining and Rate Splitting, could be utilized to reduce the power requirement of delivering multicast traffic toMBMS users. In
this paper, we analytically present several power saving techniques and analyze their performance in terms of power consumption.
We provide simulation results that reveal the amount of power that is saved and reinforce the need for the usage of such techniques.},
	keywords = {LTE, MBMS, Power Control},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos}
}
@conference {2952,
	title = {Evaluation of Single Rate Multicast Congestion Control Schemes for MPEG-4 Video Transmission},
	booktitle = {5th EURO - NGI Conference on Next Generation Internet Networks (NGI 2009), Aveiro, Portugal},
	year = {2009},
	month = {July 1 - 3},
	abstract = {We present in this paper a simulation-based
comparison of one of the best known multicast congestion
control schemes - TFMCC - against our proposed Adaptive
Smooth Multicast Protocol (ASMP). ASMP consists of a singlerate
multicast congestion control, which takes advantage of the
RTCP Sender (SR) and Receiver Reports (RR) in order to
adjust the sender?s transmission rate in respect of the network
conditions. The innovation in ASMP lays in the {\textquotedblleft}smooth{\textquotedblright}
transmission rate, which is TCP-friendly and prevent
oscillations. We use an integrated simulation environment
named Multi-Evalvid-RA for the evaluation of the two
congestion control schemes. Multi-Evalvid-RA provides all the
necessary tools to perform simulation studies and assess the
video quality by using both network related metrics along with
video quality measurements. The performance evaluation
results show that ASMP is a very efficient solution for rate
adaptive multimedia applications and a serious competitor to
well know TFMCC.},
	author = {Christos Bouras and Apostolos Gkamas and G Kioumourtzis}
}
@conference {2942,
	title = {A Framework for H-Anim Support in NVEs},
	booktitle = {International Conference on Computer Graphics Theory and Applications, Lisboa, Portugal},
	year = {2009},
	month = {5 - 9 February},
	pages = { 286 - 291},
	abstract = {Many applications of Networked Virtual Environment presuppose the users? representation by humanoid avatars
that are able to perform animations such as gestures and mimics. Example applications are computer supported
collaborative work or e-learning applications. Furthermore, there is a need for a flexible and easy way to
integrate humanoid standardized avatars in many different NVE platforms. Thus, the main aim of this paper is to
introduce a procedure of adding animations to an avatar that is complying with H-Anim standard and to present
a standardized way to integrate avatars among various NVEs. More specifically this paper presents a framework
for adding/loading custom avatars to an NVE and applying to them a set of predefined animations, using HAnim
standard.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Vasileios Triglianos and K Chatziprimou}
}
@conference {2945,
	title = {A Framework Model for DVEs using SIMUL8},
	booktitle = {Second International Conference on Simulation Tools and Techniques - SIMUTools 2009, Rome, Italy},
	year = {2009},
	month = {3 - 6 March},
	abstract = {Distributed Virtual Environment systems simulate the behaviour
and activities of a great number of users interacting in a virtual
world over a wide area network. The sizes of the virtual worlds
and the tremendous number of users that DVEs are called to
support require additional bandwidth and computational
resources. For handling these growing requirements a lot of work
has been done both to the direction of alternative architectural
solutions as well as to techniques and algorithms for handling the
limitations of these environments. For supporting large-scale
DVEs, extended infrastructure is needed in terms of both
hardware and software. However, both researchers and
application designers do not always have access to such extended
infrastructure and the assessment and evaluation of developed
techniques becomes extremely difficult. To this direction, this
paper presents a simulation modelling tool for networked servers
DVEs that could be used by designers for simulating the
performance of their approaches under different scenarios},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka}
}
@article {3092,
	title = {Identifying Best Practices for Supporting Broadbnad Growth: Methodology and Analysis},
	journal = {Journal of Network and Computer Applications, Elsevier  Science},
	year = {2009},
	pages = { 795 - 807},
	abstract = {This paperpresentsamethodologyforidentifyingbestpracticesfollowedbyvariouscountries
worldwide forsupportingbroadbandgrowth.Italsoinvestigatesandanalyzesthesepracticesusing
data concerningbroadbandpenetration,accesstechnologies,market,pricesandservicesforOECD
countriesduringtheperiod2004{\textendash}2006.Themethodologyusedtolocatethebestpracticesisbasedon
three mainsteps:(a)thepresentationofthemainfactorsthathaveamajorimpactonbroadband
growth;(b)thedefinitionofwhatisa??bestpractice??basedonquantitativecriteriaand(c)the
calculationofabestpracticeindexandagoodpracticeindex,whichindicatesthatacountryfollowed
these bestorgoodpracticestosupportitsbroadbandgrowth,respectively.Thismethodologyindicated
that Denmark,UnitedStates,Japan,CanadaandRepublicofKoreafollowedbestpracticesfortheir
broadband growth,whileUnitedKingdomandtheNetherlandsfollowedgoodpractices.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka}
}
@conference {2954,
	title = {Managing Objects in P2P DVEs},
	booktitle = {2009 International Conference on Parallel and Distributed Processing Techniques and Applications (PDPTA-09), Las Vegas, NV, USA},
	year = {2009},
	month = {July 13 - 16},
	pages = { 783 - 789},
	abstract = {Peer to Peer Distributed Virtual Environment
systems have become a scalable solution for supporting a large
number of users. One of the main challenges for these systems is
to solve the awareness problem, since it is necessary for providing
a consistent view of the environment to each participant of the
simulation. Although different strategies have been proposed,
they exclusively focus on users. Nevertheless, most of current
DVE systems include additional non-autonomous elements,
denoted as objects, whose state should also be known to system
clients. This paper studies the different attributes and
characteristics that objects can have and can affect to their
management. Based on this study, this paper presents an
extension of a previously proposed avatar awareness method
(COVER), re-designed and modified for providing object
awareness in a distributed way. The performance evaluation
results show that the resulting awareness technique allows system
users to efficiently manage objects in a distributed way without
affecting the overall performance of the system.},
	author = {Christos Bouras and Eleftheria Giannaka and S Rueda and P Morillo and J Orduna}
}
@conference {2956,
	title = {Monitoring RSS feeds},
	booktitle = {InternationalConference on Knowledge Management and Knowledge Technologies (I-KNOW 09), Gratz, Austria},
	year = {2009},
	month = {2 - 4 September},
	pages = {189-198},
	abstract = {The expansion of the World Wide Web has led to a chaotic state where the users of
the internet have to face and overcome the major problem of discovering information. For the
solution of this problem, many mechanisms were created based on crawlers who are browsing
the www and downloading pages. In this paper we describe {\textquotedblleft}advaRSS{\textquotedblright} crawling mechanism
which intends to be the base utility for systems offering collections of news in real time to
internet user. In contrast to the common crawling mechanisms our system is focused on
fetching the latest news from the major and minor portals worldwide by utilizing their RSS
feeds. The news is produced in a random order any time of the day and thus the freshness of the
offline collection can be measured even in minutes. This means that the system has to be
updated with news every single time they occur. In order to achieve this we utilize the
communication channels that exist on the modern architecture of the WWW and more
specifically in the architecture of Web 2.0. As the RSS feeds are used by every major and
minor portal it is possible to keep our crawler up to date and retain a high freshness of the
{\textquotedblleft}offline content{\textquotedblright} that is maintained in our system?s database.},
	author = {Christos Bouras and Vassilis Poulopoulos and George Adam}
}
@article {3096,
	title = {Networking and Security Issues for Remote Gaming: The Approach of G@L},
	journal = {International Journal on Advances in Security, IARIA},
	volume = {2},
	year = {2009},
	pages = { 171 - 181},
	abstract = {<p>As the evolution of computer technology introduces new advances in networks among others, online gaming becomes a new trend. Following the trends of our era, The Games At Large IST Project introduces an innovative platform for running interactive, rich content multimedia applications over a Wireless Local Area Network. The Games at Large project{\textquoteright}s vision is to provide a new system architecture for Interactive Multimedia that will enhance existing CE devices such as, Set Top Boxes (STB), Small Screen and other devices, which are lacking both the CPU power and the graphical performance to provide a rich user experience. In this study we present the controllers{\textquoteright} sub-system of the innovative mechanism that is implemented within the context of the Games at Large project. We furthermore provide information on the encryption and security of the aforementioned communication channel.</p>
},
	author = {Christos Bouras and Vassilis Poulopoulos and Vassilis Tsogkas}
}
@conference {2939,
	title = {Networking Aspects for the Security of Game Input},
	booktitle = {5th IEEE International Workshop on Networking Issues in Multimedia Entertaiment - NIME09, Las Vegas, USA},
	year = {2009},
	month = {13 January},
	abstract = {Following the trends of our era, Games At Large IST Project introduces an innovative platform for running interactive, rich content multimedia applications over a Wireless Local Area Network. Games@Large project?s vision is to provide a new system architecture for Interactive Multimedia which will enhance existing CE devices such as, Set Top Boxes (STB), Small Screen and other devices, which are lacking both the CPU power and the graphical performance to provide a rich user experience. This paper presents the input command transferring module that provides encryption capabilities for ensuring the security of the transmitted sensitive user data. In a nutshell, the client software when capturing input from a keyboard device encrypts the commands that are transmitted over a Wireless Local Area Network, using a public key encryption scheme and the server is responsible for decrypting and executing the commands to the corresponding game application.},
	author = {Christos Bouras and Vassilis Poulopoulos and Vassilis Tsogkas}
}
@conference {2943,
	title = {Optimal MBMS Power Allocation Exploiting MIMO in LTE Networks},
	booktitle = {2009 IEEE 69th Vehicular Technology Conference VTC2009 Spring, Barcelona, Spain},
	year = {2009},
	month = {26 - 29 April},
	abstract = {In the frame of the Long Term Evolution (LTE) of mobile networks, the provision of rich multimedia services, such as Mobile TV, is considered of key importance for the LTE proliferation in mobile market. To this end, Multimedia Broadcast/Multicast Service (MBMS) is envisaged to play an instrumental role during LTE standardization process. MBMS was introduced in the Release 6 of Universal Mobile Telecommunication System (UMTS) in order to deliver multimedia data from a single source entity to multiple destinations. However, downlink capacity in such networks is limited by base station transmission power. As an aftermath, in MBMS efficient power allocation techniques should be implemented so as to ensure the mass provision of multimedia applications to mobile users. In this paper we propose a power control scheme for efficient selection of MBMS bearers. The proposed mechanism on the one hand manages to economically utilize power resources during MBMS transmissions, while on the other hand exploits the performance enhancements emerged from Multiple Input Multiple Output (MIMO) antennas used in LTE networks. Simulation results indicate that the proposed scheme results to significant power and capacity improvements.},
	keywords = {LTE, MBMS, Power Control},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos and Evangelos Rekkas}
}
@conference {2946,
	title = {Optimizing MBMS Power Allocation Through HSDPA Transmissions},
	booktitle = {The Fifth Advanced International Conference on Telecommunications - AICT 2009, Venice, Italy},
	year = {2009},
	month = {24 - 28 May},
	pages = { 327 - 332},
	abstract = {Long Term Evolution (LTE) promises the delivery of rich multimedia services in a more power and spectral efficient way than its predecessor Universal Mobile Telecommunication System (UMTS). To this direction, the newly introduced Enhanced - Multimedia Broadcast/Multicast Service (E-MBMS) framework is envisaged to play a fundamental role
during the LTE standardization. E-MBMS constitutes the successor of MBMS which was introduced in the Release 6 of UMTS in order to deliver multimedia data from a single source entity to multiple destinations. This paper proposes a novel
mechanism for efficient radio bearer selection during E-MBMS transmissions in LTE networks. The proposed mechanism is based on the concept of transport channels combination (point to-point and/or point-to-multipoint radio bearers) in any cell/sector of the network in which multicast users are residing.
The mechanism is evaluated through several realistic scenarios and is compared with several radio bearer selection mechanisms in order to highlight the enhancements that it provides.},
	keywords = {MBMS, Power Control, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Evangelos Rekkas}
}
@article {3086,
	title = {Performance analysis of Relative service using TCP - aware marking and dynamic WRED},
	journal = {Journal of Communication Systems, Wiley InterScience},
	volume = {22},
	year = {2009},
	pages = { 277 - 305},
	abstract = {<p>The implementation of successful Assured Forwarding (AF) services according to the DiffServ framework remains a challenging problem today, despite the numerous proposals for AF PHB mechanisms and AF-based service implementations. The interaction of TCP and UDP traffic under an AF-based service and a number of relative issues such as fairness among flows, achievable bandwidth guarantees and qualitative performance have been taken into consideration in this work in order to address the existing limitations. We propose two modules, the TCP-Window Aware Marker (TWAM) and the Dynamic WRED (WRED) mechanism for implementing the DiffServ AF PHB. We provide analytical models and an experimental evaluation in order to demonstrate how they succeed in enhancing the quality, improving the performance and easing the deployment of a production level AF-based service.</p>
},
	author = {Christos Bouras and Afroditi Sevasti}
}
@conference {2944,
	title = {Performance Evaluation of a Dynamic Approach for Networked Servers Distributed Virtual Environments},
	booktitle = {12th Communications and Networking Simulation Symposium (CNS09), San Diego, CA, USA},
	year = {2009},
	month = {22 - 27 March},
	abstract = {Distributed Virtual Environment systems simulate the
behaviour and activities of a great number of concurrent
users interacting in a virtual world over a wide area
network. The advances both in computer technology and
networking infrastructures in combination to the advanced
applications and services developed, expanded the
popularity of DVEs and promoted their use in a wide range
of areas, such as learning and training, collaborative work,
military applications and multiplayer online games. The
sizes of the virtual worlds simulated and the tremendous
number of users that DVEs are called to support require
additional bandwidth and computational resources. For
handling these growing requirements a lot of work has been
done both to the direction of alternative architectural
solutions as well as to techniques and algorithms for
handling and overcoming the limitations of these
environments. However, recent research has shown that one
of the major limitations of networked servers DVE systems
is scalability. To this direction this paper presents on the one
hand a dynamic approach for DVEs, which exploits the
nature of these systems for the optimal resource
management and extended scalability support and on the
other hand, evaluates its performance through a series of
experiments and under various settings of the virtual world,
using Simul8 simulation tool.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka}
}
@conference {2962,
	title = {Performance Evaluation of Simulcast vs. Layered Multicasting over Best-effort Networks},
	booktitle = {The 17th International Conference on Software, Telecommunications and Computer Networks (SoftCOM 2009), Split Hvar Korcula, Croatia},
	year = {2009},
	month = {Sept. 24 - 26},
	pages = {338-348},
	abstract = {Multi-rate multicast schemes can be broadly classified
into two categories. In layered multicast, a video file is
transmitted by a base layer, which contains the most important
features of the video. Additional layers, called enhancement
layers, contain data that refine the quality of the base layer. In
simulcast, the video file is transmitted by replicated layers that
contain the same content at different quality. The benefits of
layered multicast versus simulcast are still under question, as
layered multicast presents higher complexity and more
challenging deployment than simulcast. In this paper, two multirate
multicast control schemes are compared. The layered
multicast SMCC congestion control against our proposed
solution for simulcast transmission, named ASSP. We compare
the two schemes under a controlled simulation environment
with the network simulator software (ns-2) by taking into
account the evaluation criteria in RFC 5166. The results
demonstrate that both SMCC and ASSP are TCP-friendly while
SMCC seems to suffers from small oscillations of the
transmission rate. In network topologies with low complexity
ASSP consumes no more bandwidth than SMCC for the
transmission of the different simulcast streams, while being a
simpler solution than the more complicated SMCC.},
	author = {Christos Bouras and Apostolos Gkamas and G Kioumourtzis}
}
@conference {2948,
	title = {Personalization  Mechanism for Delivering News Articles on the User{\textquoteright}s Desktop},
	booktitle = {The Fourth International Conference on Internet and Web ASpplications and Services {\textendash} ICIW 2009, Venice, Italy},
	year = {2009},
	month = {24 - 28 May},
	pages = { 157 - 162},
	abstract = {Deploying a generalized, multi-functional
mechanism that produces good results for personalizing
summarized and categorized news articles, seems to be a
panacea for most of the text-based, information retrieval
needs. In this paper, we present the personalization
algorithm, as well as a client side application that are
used as an extension to an already constructed system,
PeRSSonal, in order to deliver summarized and precategorized
news articles to the user.},
	author = {Christos Bouras and Vassilis Tsogkas}
}
@conference {2947,
	title = {Personalized News Search in WWW: Adapting on user{\textquoteright}s behavior},
	booktitle = {The Fourth International Conference on Internet and Web ASpplications and Services - ICIW 2009, Venice, Italy},
	year = {2009},
	month = {24 - 28 May},
	pages = { 125 - 130},
	abstract = {Personalized Web Search becomes nowadays a
promising option in the field of Information Retrieval and
search engines design by improving both output quality and
user experience. In this paper, we present and evaluate the
subsystem, which conducts the Advanced and Personalized
search of PeRSSonal, a web-based mechanism for the retrieval,
processing and presentation of articles and RSS feeds collected
from major news portals of the Internet. The proposed
technique uses information explicitly provided by the user in
his profile as well as information that the mechanism can learn
from the user?s behavior during his search and browsing
sessions in the system. As this behavior dynamically evolves,
the same happens to the user?s interests under the prism of the
search engine. By adopting this user-centric approach, we
manage to present the user with better-refined and more
focused results, incorporating his personal preferences to the
output. The algorithm operates not in a stand-alone manner
but it co-operates and binds with the rest of modules of
PeRSSonal in order to accomplish maximum integration with
the system. Furthermore, we introduce an enhancement in the
search function, based on cached results from past search
sessions of each user individually.},
	author = {Christos Bouras and Vassilis Poulopoulos and Panagiotis Silintziris}
}
@article {3093,
	title = {Platform for Distributed 3D Gaming},
	journal = {International Journal of Computer Games Technology, Hindawi Publishing Corporation},
	year = {2009},
	abstract = {Video games are typically executed on Windows platforms with DirectX API and require high performance CPUs and graphics
hardware. For pervasive gaming in various environments like at home, hotels, or internet cafes, it is beneficial to run games also
on mobile devices and modest performance CE devices avoiding the necessity of placing a noisy workstation in the living room or
costly computers/consoles in each room of a hotel. This paper presents a new cross-platform approach for distributed 3D gaming
in wired/wireless local networks.We introduce the novel system architecture and protocols used to transfer the game graphics data
across the network to end devices. Simultaneous execution of video games on a central server and a novel streaming approach of
the 3D graphics output to multiple end devices enable the access of games on low cost set top boxes and handheld devices that
natively lack the power of executing a game with high-quality graphical output.},
	author = {Christos Bouras and Vassilis Poulopoulos and Audrius Jurgelionis and P Fechteler and P Eisert and F Bellotti and Haggai David and Jukka - Pekka Laulajainen and Richard Carmichael and Arto Laikari and P Perala and A Gloria}
}
@article {3080,
	title = {QoS experiences in native IPv6 networks},
	journal = {International Journal of Network Management, Wiley InterScience},
	volume = {19},
	year = {2009},
	pages = { 119 - 137},
	abstract = {<p>Deployment of IPv6 technology in research and commercial networks has been accelerated in the last few years. Inevitably, as more advanced services take advantage of the new technology, IPv6 traffic gradually increases. Today, there is limited experience in the deployment of Quality of Service (QoS) for IPv6 traffic in backbone networks that support the Differentiated Services framework. As available software and hardware is designed to handle IPv4 packets, there is a need to accurately measure and validate performance of QoS mechanisms in an IPv6 environment. This paper discusses tests and technical challenges in the deployment of IPv6 QoS in core networks, namely the production dual stack gigabit-speed Greek Research \&amp; Education Network - GRNET and the IPv6-only 6NET European test network, using both hardware and software platforms. In either case, we succeeded in delivering advanced transport services to IPv6 traffic and provided different performance guarantees to portions of traffic. The deployed QoS schema was common for IPv6 and IPv4; in most cases both v4 and v6 traffic exhibited comparable performance per class while imposing no significantly different overhead on network elements. A major conclusion of our tests is that the IPv6 QoS mechanisms are efficiently supported with state-of-the-art router cards at gigabit speeds.</p>
},
	author = {Christos Bouras and Dimitris Primpas and A Liakopoulos and B Maglaris and D Kalogeras}
}
@article {3085,
	title = {Scalable Text Classification as a tool for Personalization},
	journal = {Computer Systems Science and Engineering, CRL Publishing Ltd},
	year = {2009},
	pages = { 51 - 60},
	abstract = {We consider scalability issues of the text classification problem where by
using (multi)-labeled training documents, we try to build classifiers that assign
documents into classes permitting classification in multiple classes. A new class of
classification problems; called ?scalable?, is introduced, with applications on web
mining. Scalable classification utilizes newly classified instances in order to improve the
accuracy of future classifications and capture changes in semantic representation of
different topics. In addition, definition of different similarity classes is allowed,
resulting in a ?per-user? classification procedure. Such an approach provides a new
methodology for building personalized applications. This is due to the fact that the user
becomes a part of the classification procedure. We explore solutions for the scalable text
classification problem and introduce an algorithm that exploits a new text analysis
technique that decomposes documents into the vector representation of their sentences
according to the user expertise. Finally, a web-based personalized news categorization
system that bases upon this approach is presented.},
	author = {Christos Bouras and Vassilis Poulopoulos and Ioannis Antonellis}
}
@conference {2955,
	title = {Simulcast Transmission for Video Applications: Performance Evaluation with an Integrated Simulation Environment},
	booktitle = {2009 International Symposium on Performance Evaluation of Computer and Telecommunication Systems (SPECTS 2009), Istanbul, Turkey},
	year = {2009},
	month = {July 13 - 16},
	pages = {339-346},
	abstract = {This paper presents the performance evaluation of a
multi-rate multicast protocol named Adaptive Smooth Simulcast
Protocol (ASSP) for simulcast video transmission. ASSP
implements a single rate TCP-friendly protocol as the underlying
congestion control mechanism for each simulcast stream. ASSP is
built on top of the RTP/RTCP protocol and exploits the RTCP
sender and receiver reports for the dissemination of feedback
information. The key attributes of ASSP are: a) TCP-friendly
behavior, b) adaptive per-stream transmission rates, c) adaptive
scalability to large sets of receivers and finally d) smooth
transmission rates that are suitable for multimedia applications.
We evaluate the performance of ASSP under an integrated
simulation environment, which extends ns-2 and Evalvid-RA into
the multicast domain with the use of RTP/RTCP protocols.
Simulations conducted under this environment combine the
measurements of network metrics along with objective evaluation
criteria on the perceived video quality by the end user.},
	author = {Christos Bouras and Apostolos Gkamas and G Kioumourtzis}
}
@article {3087,
	title = {A Study of Multicast Congestion Control for UMTS},
	journal = {International Journal of Communication Systems, Wiley InterScience},
	year = {2009},
	pages = { 739 - 754},
	abstract = {In this paper, we study the applicability of multicast congestion control over universal mobile telecommunications
system (UMTS) networks. We analyze two well-known multicast congestion control schemes
for fixed networks, namely TCP-friendly multicast congestion control and pragmatic general multicast
congestion control. We investigate their behavior when they are employed in UMTS networks and we
analyze the problems arose when these mechanisms are applied over the wireless links of the UMTS
terrestrial radio-access network. Additionally, we propose necessary improvements to these legacy schemes
and explain the necessity of these modifications. The proposed schemes are implemented in the ns-2
network simulator and are evaluated under various network conditions and topologies. Finally, we measure
the performance of the proposed modified schemes and compare them with the corresponding legacy
mechanisms.},
	keywords = {Congestion Control, MBMS, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Andreas Papazois}
}
@conference {2959,
	title = {Trash Article Detection using Categorization Techniques},
	booktitle = {IADIS International Conference Applied Computing, Rome, Italy},
	year = {2009},
	month = {November 19 - 21},
	pages = { 51-58},
	abstract = {We explore techniques for detecting news articles containing invalid information, using the help of text categorization technology. The information that exists on the World Wide Web is huge enough in order to distract the users when trying to find useful information. In order to overcome the large amounts of data many methodologies of text categorization have been presented. One major problem we have to deal with is that many articles fetched by a crawler, then stored in a back-end database, and finally given as an input to a categorization subsystem, may not contain valid information for the user (trashy articles). This may lead to the user losing his trust towards the system. In this paper, we analyze the special properties of trashy news articles? categorization that allows us to detect them and we propose a specific methodology for trash detection. Finally, we evaluate the proposed algorithm on a news categorization system and we depict the overall benefit of a trash detection mechanism on the system.},
	author = {Christos Bouras and Vassilis Poulopoulos and George Tsichritzis}
}
@conference {2949,
	title = {Utilizing RSS feeds for crawling the Web},
	booktitle = {The Fourth International Conference on Internet and Web ASpplications and Services - ICIW 2009},
	year = {2009},
	month = {24 - 28 May},
	pages = { 211 - 216},
	abstract = {We present {\textquotedblleft}advaRSS{\textquotedblright} crawling mechanism which
is created in order to support peRSSonal, a mechanism used to
create personalized RSS feeds. In contrast to the common
crawling mechanisms our system is focalized on fetching the
latest news from the major and minor portals worldwide by
utilizing their communication channels. The challenge between
{\textquotedblleft}advaRSS{\textquotedblright} and a usual crawler is the fact that the news is
produced in a random order any time of the day and thus the
freshness of the offline collection can be measured even in
minutes. This means that the system has to be updated with
news every single time they occur. In order to achieve this we
utilize the communication channels that exist on the modern
architecture of the WWW and more specifically in almost
every modern news portal. As the RSS feeds are used by every
major and minor portal it is possible to keep our crawler up to
date and retain a high freshness of the {\textquotedblleft}offline content{\textquotedblright} that is
maintained in our system?s database by applying algorithms in
order to observe the temporal behaviour of each RSS feed.},
	author = {Christos Bouras and Vassilis Poulopoulos and George Adam}
}
@conference {2961,
	title = {Video Transmission over TFRC using cross-layer power management},
	booktitle = {The 17th International Conference on Software, Telecommunications and Computer Networks (SoftCOM 2009), Split Hvar Korcula, Croatia},
	year = {2009},
	month = {September 24-26},
	pages = {333-337},
	abstract = {<p>This paper presents the issues related to efficient transmission of encoded video (such as H.264) over wireless links using the TFRC protocol. It proposes a novel mechanism that utilizes cross-layer approaches for adaptation of the power transmission level of the sender and feedback information regarding the wireless connection status from the receiver for improved transmission statistics and therefore user experience without unnecessary power consumption. The mechanism is tested through simulations using ns2. Compared to the operation of the video transmission without the mechanism, we observe that it has benefits in terms of video quality.</p>
},
	author = {Christos Bouras and Vaggelis Kapoulas and Apostolos Gkamas and Kostas Stamos and Vassilis Papapanagiotou and Giannis Zaoudis}
}
@conference {2927,
	title = {Adaptive Smooth Multicast Congestion Control for Adaptive Multimedia Transmission},
	booktitle = {2008 International Symposium on Performance Evaluation of Computer and Telecommunication Systems {\textendash} SPECTS 2008, Edinburgh, UK},
	year = {2008},
	month = {16 - 18 June},
	pages = { 269 - 276},
	abstract = {We introduce Adaptive Smooth Multicast Protocol
(ASMP), for multimedia transmission over best-effort networks.
The smoothness lays in the calculation and adaptation of the
transmission rate, which is based on dynamic estimation of
protocol parameters and dynamic adjustment of the {\textquotedblleft}smoothness
factor{\textquotedblright}. ASMP key attributes are: a) adaptive scalability to large
sets of receivers, b) TCP-friendly behavior, c) high bandwidth
utilization, and finally d) smooth transmission rates, which are
suitable for multimedia applications. We evaluate the
performance of ASMP and investigate its behavior under various
network conditions through extensive simulations, conducted
with the network simulator software (ns2).},
	author = {Christos Bouras and Apostolos Gkamas and G Kioumourtzis}
}
@article {3159,
	title = {Adaptive transmission of multimedia data over the Internet},
	year = {2008},
	pages = { 16 - 22},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos and Dimitris Primpas}
}
@conference {2931,
	title = {Balancing between Power Optimization and Iub Efficiency in MBMS enabled UMTS Networks},
	booktitle = {1st IFIP Wireless and Mobile Networking Conference (WMNC 2008) , Toulouse, France},
	year = {2008},
	month = {1 - 3 October},
	pages = { 355 - 368},
	abstract = {Multicast transmission is one of the major goals for Universal Mobile
Telecommunication System (UMTS) that motivated the 3rd Generation Partnership
Project (3GPP) to launch the Multimedia Broadcast/Multicast Service (MBMS)
framework. MBMS constitutes a significant step towards the so-called Mobile
Broadband, since it allows the efficient utilization of network and radio resources.
One of most important problems that MBMS is currently facing is the assignment
of the appropriate transport channel for the transmission of MBMS data. This
paper proposes an alternative solution to this problem, by introducing a cost-based
scheme for the efficient radio bearer selection that minimizes the overall delivery
cost. Our approach, calculates the telecommunication cost over the most crucial
interfaces of UMTS; and based on this cost selects the appropriate radio bearer.},
	keywords = {MBMS, Power Control, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos}
}
@conference {2916,
	title = {Bridging UMTS and Multicast Routing in ns - 2},
	booktitle = {First International Conference on Simulation Tools and Techniques for Communications, Networks, and Systems, Marseille, France},
	year = {2008},
	month = {3 - 7 March},
	abstract = {In this paper, we present the design and the implementation of a novel scheme for the multicast transmission of data over Universal Mobile Telecommunications System (UMTS) networks. The proposed scheme is implemented as an ns-2 network simulator module which can be employed to investigate various aspects of UMTS multicast. Apart from the normal multicast transmission over UMTS, we consider the handling of exceptional cases induced by user mobility scenarios. The proposed scheme is in accordance with the current specifications of the Multimedia Multicast/Broadcast Service (MBMS) defined by the 3rd Generation Partnership Project (3GPP) and introduces minor modifications in the UMTS architecture and the mobility management mechanisms. The performance of the proposed scheme is validated and analyzed through simulation experiments. Finally, the simulation results are presented along with their analysis.},
	keywords = {MBMS, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Andreas Papazois}
}
@article {3167,
	title = {Business Models For Municipal Broadband Networks},
	year = {2008},
	pages = { 457 - 465},
	author = {Christos Bouras and Apostolos Gkamas and Thrasivoulos Tsiatsos and George Theofilopoulos}
}
@conference {2936,
	title = {Challenges in Cross Layer Design for Multimedia Transmission over Wireless Networks},
	booktitle = {WWRF{\textendash} 21st Meeting WG3 {\textendash}Future Architecture, Stockholm, Sweden},
	year = {2008},
	month = {13 - 15 October},
	abstract = {This paper examines the challenges of cross layer design for multimedia transmission over wireless networks. In wireless networks multimedia data transmission inherits also all the characteristics and constrains related to the propagation to the free space. One first striking difference between wired and wireless networks is the cause of packet losses. Packet losses in wired networks occur mainly due to congestion in the path between the sender and the receiver, while in wireless networks packet losses occur mainly due to corrupted packets as a result of the low Signal to Noise Ratio (SNR), the multi-path signal fading and the interference from neighbouring transmissions. A second difference between wired and wireless networks is the {\textquotedblleft}mobility factor{\textquotedblright}. Mobility in wireless networks introduces a number of additional barriers in multimedia data transmission.},
	author = {Christos Bouras and Apostolos Gkamas}
}
@conference {2932,
	title = {Comparison of Single - Rate multicast Congestion Control protocol vs ASMP},
	booktitle = {16th International Symposium on Modeling, Analysis and Simulation of Computer and Telecommunication Systems - MASCOTS 2008, Baltimore, Maryland, USA},
	year = {2008},
	month = {8 - 10 September},
	pages = {309-316},
	abstract = {<p>We present in this paper a simulation-based comparison of two single-rate multicast congestion control schemes (TFMCC and PGMCC) against our proposed Adaptive Smooth Multicast Protocol (ASMP). ASMP consists of a single-rate multicast congestion control, which takes advantage of RTCP Sender (SR) and Receiver Reports (RR). The innovation in ASMP lays in the {\textquotedblleft}smooth{\textquotedblright} transmission rate, which is TCP-friendly and prevent oscillations. The smooth behavior is naturally well suited to multimedia applications as high oscillations of the sending rate may create distortions of Audio-Video (AV) encoders and decoders. Simulation results, which are conducted with the network simulator ns2 software, showed that ASMP can be regarded as a serious competitor of TFMCC and PGMCC. In many cases, ASMP outperforms TFMCC in terms of TCP-friendliness and smooth transmission rates, while PGMCC presents lower scalability than ASMP.</p>
},
	author = {Christos Bouras and Apostolos Gkamas and G Kioumourtzis}
}
@conference {2925,
	title = {Creating dynamic personalized RSS summaries},
	booktitle = {8th Industrial Conference on Data Mining {\textendash} ICDM 2008, , Leipzig, Germany},
	year = {2008},
	month = {16 - 18 July},
	pages = { 1 - 15},
	abstract = {Automatically generated, human-quality text summarization systems are difficult both to develop and to evaluate, partly because articles differ along several dimensions: length, writing style and lexical usage. In this paper we propose a framework that, by utilizing RSS feeds, is able to personalize on the needs of the users and on the needs of their device, in order to present to the end-user only a fraction of the news articles covering just the useful information that derives from them. The created summaries utilize a weighted combination of statistical and linguistic features which leads to sentence scoring and selection. The procedure is assisted by categorization results as well as personalization algorithms that enhance the summarization module. The mechanism is evaluated using classic precision-recall metrics together with statistical results from real users. Within this framework we have created the PeRSSonal system that is able to create personalized, pre-categorized, dynamically generated RSS feeds focalized on the end user?s small screen device.},
	author = {Christos Bouras and Vassilis Poulopoulos and Vassilis Tsogkas}
}
@book {4065,
	title = {Discrete Mathematics: A) The Mathematics of Computer Science, B) Problems and Solutions},
	year = {2008},
	author = {Christos Bouras and Lefteris Kirousis and Paul Spirakis and George Voutsadakis}
}
@article {3164,
	title = {e-Collaboration Concepts, Systems and Applications},
	year = {2008},
	pages = { 165 - 171},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka}
}
@article {3074,
	title = {An Efficient Architecture for Bandwidth Brokers in DiffServ Networks},
	journal = {International Journal of Network Management, Wiley InterScience, Vol. 18, Issue 1},
	year = {2008},
	pages = { 27 - 46},
	abstract = {In this article we examine the architecture of an entity used for automatic management and provisioning of resources for DiffServ networks. We examine the existing literature and implementations in this area, focusing on the design choices made, and we propose an architecture for the design of Bandwidth Brokers that combines an adaptive admission control algorithm for increased utilization of network resources and a mechanism for reducing the complexity overhead that intends to be both simple and effective. Specifically, we present a novel architecture for the admission control module that aims at achieving a satisfactory balance between maximizing the resource utilization for the network provider and minimizing the overhead of the module. We complement our theoretical discussion with extensive experimental simulations for the proposed Bandwidth Broker components and analysis of the results. The simulations study the possible configurations of the proposed algorithm and also compare it with alternative admission control policies.},
	author = {Christos Bouras and Kostas Stamos}
}
@conference {2928,
	title = {Efficient Assignment of Multiple MBMS Sessions in B3G Networks},
	booktitle = {2008 IEEE 68th Vehicular Technology Conference {\textendash} VTC2008 Fall, Calgary, Canada},
	year = {2008},
	month = {22 - 25 Septemer},
	pages = { 1 - 5},
	abstract = {In Universal Mobile Telecommunication System
(UMTS), the downlink capacity is limited by the base station
transmission power. Therefore, power control plays an important
role to minimize the transmitted power shared among unicast and
multicast users within a cell. In Multimedia Broadcast/Multicast
Service (MBMS), power control targets to the efficient utilization
of radio and network resources. However, the expected high
demand for such services stresses the need for an efficient
scheme, capable of dynamically allocating radio resources to
parallel MBMS sessions. This paper proposes a power control
mechanism for efficient MBMS session assignment in next
generation UMTS networks. The mechanism shares efficiently the
available power resources of UMTS base stations to MBMS
sessions running in the network. Furthermore, the mechanism is
evaluated through several realistic scenarios and the results
indicate the ability of the mechanism to utilize efficiently the
radio resources and to ensure the service continuity when parallel
MBMS services running in the network.},
	keywords = {MBMS, Power Control, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos and Evangelos Rekkas}
}
@conference {2923,
	title = {Efficient Delivery of MBMS Multicast Traffic over HSDPA},
	booktitle = {Third Workshop on multimedia Applications over Wireless Networks (MediaWiN 2008), Marrakech, Morocco},
	year = {2008},
	month = {6 July},
	pages = { 50 - 55},
	abstract = {Multimedia Broadcast/Multicast Service (MBMS) and High-Speed Downlink Packet Access (HSDPA) are two key technologies that constitute a significant step towards the Mobile Broadband. MBMS was introduced by the third Generation Partnership Project (3GPP) in order to support broadcast and multicast communication over wireless networks and in particular over Universal Mobile Telecommunications System (UMTS). Concurrently, HSDPA aims to ensure the transmission of high peak data rates and increase system capacity. In this paper we evaluate the performance of MBMS multicast transmission over the premier transport channel used in HSDPA, named High Speed-Downlink Shared Channel (HS-DSCH). Due to the fact that downlink transmission power is the scarcest resource in UMTS networks, the evaluation is performed through an analytical dimensioning of the MBMS downlink transmission power. Furthermore, the impacts of power allocation on MBMS capacity are investigated.},
	keywords = {MBMS, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Evangelos Rekkas}
}
@article {3078,
	title = {An Efficient Mechanism for Multicast Data Transmission in UMTS},
	journal = {Wireless Personal Communications Journal, Spinger Verlang, Vol. 44, No. 4},
	year = {2008},
	pages = { 455 - 471},
	abstract = {In this paper, we present an efficient scheme for the multicast transmission of the data in the Universal Mobile Telecommunications System (UMTS). We take advantage of the tree topology of the examined network and we introduce the use of Routing Lists (RLs) in the nodes of the UMTS. The adoption of these lists leads to the decrement of the transmitted packets and to the efficient use of network resources in the multicast transmission of the data. We describe in detail the appropriate steps for the successful multicast transfer of data. Furthermore, we analyze the handling of special cases such as user mobility scenarios. Especially, the various handover types are examined along with the Serving Radio Network Subsystem relocation procedure. Finally, we implement our approach in the NS-2 simulator and we present the performance of the multicast mechanism.},
	keywords = {MBMS, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Dimitrios Antonellis}
}
@conference {2938,
	title = {Evaluating PeRSSonal: A Medium for Personalized Dynamically Created News Feeds},
	booktitle = {IADIS International Conference WWW/Internet Freiburg, Germany},
	year = {2008},
	month = {13 - 15 October},
	abstract = {In this paper we present the evaluation of PeRSSonal, a system which generates personalized, dynamically created RSS feeds and is focalized on small screen devices. PeRSSonal is a complete system able to consolidate news from major news portals, categorize and summarize them, and finally syndicate them personalized to the end users. In an era where news feeds, become a part of the daily Internet life and small screen devices gain more and more attention by the end users, PeRSSonal seems the panacea that could provide fast and easy access to everyday news. The system is based on algorithms that incorporate the user into the categorization and summarization procedure of news articles, while the results are presented to the user according to his/her interests and end device.},
	author = {Christos Bouras and Vassilis Poulopoulos and Vassilis Tsogkas}
}
@conference {2937,
	title = {Evaluation of Different Radio Bearer Selection Approaches for MBMS in B3G Networks},
	booktitle = {IFIP Wireless Days Conference 2008, Dubai, United Arab Emirates},
	year = {2008},
	month = {24 - 27 November},
	abstract = {The spread of multimedia data has drastically differentiated the current landscape of Universal Mobile Telecommunication System (UMTS) networks, posing the need for further enhancements in its Radio Resource Management (RRM) strategies. Introduced in 3rd Generation Partnership Project (3GPP) Release 6, the Multimedia Broadcast/Multicast Services (MBMS) framework aims at the efficient usage of network and radio resources for the transmission of multimedia services. The main requirement during the provision of MBMS multicast services is to minimize the transmission power of UMTS base stations. To this direction, several mechanisms have been proposed that either allow a simultaneous deployment of Point-to-Point (PTP) and Point-to-Multipoint (PTM) transmissions, or a single transport channel deployment (PTP or PTM) in a cell at any given time. Main objective of this paper is to study these mechanisms, compare them in terms of power consumption, underline the advantages that they may offer; and finally to propose enhancements that will ensure the lowest possible power consumption during MBMS transmissions.},
	keywords = {MBMS, Power Control, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos and Evangelos Rekkas}
}
@article {3079,
	title = {Exploiting Virtual Environments to Support Collaborative e-Learning Communities},
	journal = {International Journal of Web-Based Learning and Teaching Technologies, IDEA GROUP PUBLISHING, Vol. 3, Issue 2},
	year = {2008},
	pages = { 1 - 22},
	abstract = {The main goal of this paper is to facilitate educational designers and developers by providing a point of reference for making decisions on how to incorporate 3D environments into the applications they develop as well as for extending their capabilities by integrating more functionality. Therefore, this paper presents the design principles for virtual spaces, which aim at supporting multi-user communication in web-based learning communities. In addition the implementation of these principles is presented using as point of reference EVE Training Area. This environment constitutes a three-dimensional space where participants, represented by 3D humanoid avatars, have the ability to use a variety of 3D e-collaboration tools for learning together. Furthermore, this paper presents collaborative e-learning usage scenarios that could be realized by exploiting collaborative virtual environments.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka}
}
@conference {2921,
	title = {Extending QoS support from Layer 3 to Layer 2},
	booktitle = {15th International Conference on Telecommunications, St. Petersburg, Russia},
	year = {2008},
	month = {16 - 19 June},
	abstract = {This paper presents some of the results
obtained by the application of Ethernet Layer 2 Quality
of Service in IP networks. IP networks traditionally
provide Quality of Service in Layer 3. However, since
there is an enormous existing Layer 2 infrastructure,
today?s networks could benefit from the deployment of
Layer 2 Quality of Service and the cooperation between
Layer 2 Quality of Service and Layer 3 Quality of
Service. In this paper, experiments are suggested and
conducted and a scheme is suggested for efficient
cooperation between Layer 2 and Layer 3 QoS
provisioning.},
	author = {Christos Bouras and Vaggelis Kapoulas and Kostas Stamos and Dimitris Primpas and Leonidas Poulopoulos and Vassilis Papapanagiotou}
}
@conference {2917,
	title = {Extending the Functionality of RTP/RTCP Implementation in Network Simulator (ns {\textendash} 2)},
	booktitle = {First International Conference on Simulation Tools and Techniques for Communications, Networks, and Systems, Marseille, France},
	year = {2008},
	month = {3 - 7 March},
	abstract = {In this paper, we present a modification of the ns2 code for the RTP/RTCP protocols. The legacy RTP/RTCP code in ns2 has not yet been validated but it provides a framework of the protocol?s specification for experimental use. We have modified the code by adding all the RTP/RTCP protocol?s attributes that are defined in RFC 3550 and related to QoS metrics. We have also implemented additional algorithms and functions in order to enhance our modified code with TCP friendly bandwidth share behavior. Our protocol, named RTPUP ({\textquotedblleft}UP{\textquotedblright} stands for the University of Patras), is offered as a package and is fully documented so that it can be used for simulations and research within the ns2 simulation environment.},
	author = {Christos Bouras and Apostolos Gkamas and G Kioumourtzis}
}
@conference {2935,
	title = {Extending the QoS provisioning in GRNET},
	booktitle = {The 16th International Conference on Software, Telecommunications and Computer Networks (SoftCOM 2008), Split - Dubrovnik, Croatia},
	year = {2008},
	month = {Sept. 25 - 27 },
	pages = {152-156},
	abstract = {This work presents the extension of QoS provisioning in GRNET, so as to include a {\textquotedblleft}second chance{\textquotedblright} mechanism for rejected premium-traffic requests. Regularly, accepted requests can be satisfied even if there is a single failure in the network and no specific path is allocated within the network core. The extended mechanism allows for rejected requests to be reconsidered for acceptance over a specific path, under the condition that if a failure occurs in this path, then the corresponding traffic will lose the premium handling and will be then considered as best effort. The extended scheme allows for more flexibility and gives a balanced alternative to the {\textquotedblleft}either full guarantees or no QoS at all{\textquotedblright} situation of the existing scheme.},
	author = {Christos Bouras and Vaggelis Kapoulas and Dimitris Primpas and Leonidas Poulopoulos}
}
@conference {2929,
	title = {Improving text summarization using noun retrieval techniques},
	booktitle = {Advanced Knowledge {\textendash} based Systems, Invited Session of the 12nd International Conference on Knowledge {\textendash} based and Intelligent Information \& Engineering Systems(KES 2008), Zagreb, Croatia},
	year = {2008},
	month = {3 - 5 September},
	pages = { 593 - 600},
	abstract = {Text Summarization and categorization have always been two of the
most demanding information retrieval tasks. Deploying a generalized, multifunctional
mechanism that produces good results for both of the aforementioned
tasks seems to be a panacea for most of the text-based, information retrieval
needs. In this paper, we present the keyword extraction techniques, exploring
the effects that part of speech tagging has on the summarization procedure of an
existing system.},
	author = {Christos Bouras and Vassilis Tsogkas}
}
@inbook {3128,
	title = {An Integrated Architecture for Supporting Vocational Training},
	booktitle = {Architecture Solutions for e-Learning Systems},
	year = {2008},
	pages = { 197 - 218},
	publisher = {IDEA Group Publishing},
	organization = {IDEA Group Publishing},
	abstract = {<p>E-learning and Web-based training have evolved over time from a newborn trend for complementing the learning process to a major form of education and training for supporting mainly geographically scattered users. The basic aim of this chapter is the description of a platform for open and distance training, which is mainly focused at supporting the needs of Vocational Training Centers as well as of institutions providing life-long adult training and learning. In particular, the issues that this chapter focuses on are vocational education and training characteristics and requirements, the current situation and technological trends in ICT-supported VET, the development framework and processes while it also proposes basic vocational training services and the system architecture of the integrated platform. The presented platform aims to provide services of both synchronous and asynchronous and collaborative distance learning.</p>
},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka}
}
@article {3161,
	title = {The IPv6 protocol},
	year = {2008},
	pages = { 257 - 262},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos and Dimitris Primpas}
}
@inbook {3127,
	title = {Metropolitan Broadband Networks: Design and implementation aspects and business models},
	booktitle = {Global Diffusion of Broadband Data Transmission: Factors Affecting the Adoption, Usage and Economics of Broadband},
	volume = {1},
	year = {2008},
	pages = { 196 - 210},
	publisher = {IDEA Group Publishing},
	organization = {IDEA Group Publishing},
	chapter = {XIII},
	abstract = {<p>This chapter presents the design principles that cover the implementation of broadband infrastructure in the region of Western Greece, by examining all the necessary parameters that arise while implementing such a critical developmental project. The broadband infrastructure that is deployed is either based on optical fiber (on big municipalities) or on wireless systems (OFDM based and WiFi cells). Furthermore, we present as two case studies, all issues of the designing of the Metropolitan Area Network of Patras, the third biggest city of Greece and the Wireless Access Network of Messatida. The major target of the broadband networks is to interconnect the buildings of the public sector in the city and also deploy infrastructure (fibers or wireless systems) that will create conditions of competition in providing both access and content services in advantage of the end consumer. The usage of the broadband infrastructure by service providers will be based on the open availability of the infrastructure in a cost effective way. Finally, we present the main characteristics of a proposed business plan that ensures financial viability of the broadband infrastructure and guarantees the administration, growth, and exploitation of infrastructure.</p>
},
	author = {Christos Bouras and Dimitris Primpas and Antonios Alexiou and J Papagiannopoulos}
}
@conference {2924,
	title = {Monitoring End to End Bandwidth on Demand Circuits over Ethernet Infrastructure},
	booktitle = {Seventh International Network Conference {\textendash} INC 2008, Plymouth, UK},
	year = {2008},
	month = {8 - 10 July},
	pages = { 3 - 13},
	abstract = {AutoBAHN (Automated Bandwidth Allocation across Heterogeneous Networks) has specified and is now prototyping a Bandwidth on Demand (BoD) service intended to operate in a multi-domain environment using heterogeneous transmission technologies. The AutoBAHN system aims at providing a guaranteed capacity, connection-oriented service between two end points. This paper highlights the architecture of the monitoring system for the AutoBAHN service, the implementations challenges and the decisions taken, focusing on monitoring end to end BoD reservations over ethernet infrastructure. In addition this paper presents the architecture and the components of the AutoBAHN monitoring system for ethernet infrastructures.},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos}
}
@article {3071,
	title = {Multicast in UMTS: Evaluation and Recommendations},
	journal = {Wireless Communications and Mobile Computing, Wiley InterScience, Volume 8, Issue 4},
	year = {2008},
	pages = {463 - 481},
	abstract = {It is known that multicasting is an efficient method of supporting group communication as it allows the transmission of packets to multiple destinations using fewer network resources. Along with the widespread deployment of the third generation cellular networks, the fast-improving capabilities of the mobile devices, content and service providers are increasingly interested in supporting multicast communications over wireless networks and in particular over Universal Mobile Telecommunications System (UMTS). Multicasting is a more efficient method of supporting group communication than unicasting or broadcasting, as it allows transmission and routing of packets to multiple destinations using fewer network resources. In this paper the three above mentioned methods of supporting group communication are analyzed in terms of their performance. The critical parameters of primary interest for the evaluation of any method are the packet delivery cost and the scalability of the method.},
	keywords = {MBMS, UMTS},
	author = {Christos Bouras and Antonios Alexiou}
}
@article {3165,
	title = {Multicast of Multimedia Data},
	year = {2008},
	pages = { 316 - 322},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos and Dimitris Primpas}
}
@article {3168,
	title = {Networked Virtual Environments},
	year = {2008},
	pages = { 2789 - 2793},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka}
}
@conference {2920,
	title = {Networking Aspects for Gaming Systems},
	booktitle = {Third International Conference on Internet and Web Applications (ICIW 2008), Athens, Greece},
	year = {2008},
	month = {8 - 13 June},
	pages = { 650 - 655},
	abstract = {<p>As the evolution of computer technology introduces new advances in networks among others, online gaming becomes a new trend. Following the trends of our era, Games At Large IST Project introduces an innovative platform for running interactive, rich content multimedia applications over a Wireless Local Area Network. Games at Large project?s vision is to provide a new system architecture for Interactive Multimedia which will enhance existing CE devices such as, Set Top Boxes (STB), Small Screen and other devices, which are lacking both the CPU power and the graphical performance to provide a rich user experience. This paper presents the controllers? subsystem of the innovative mechanism that will be implemented in the context of Games at Large project. More specifically, it presents the general architecture of the complete system and focuses on the {\textquotedblleft}capturing{\textquotedblright} and {\textquotedblleft}execution of commands{\textquotedblright} modules at the different clients and the remote execution of the commands on server side. The client software captures the input from the different input devices, sends the commands over a Wireless Local Area Network and the server is responsible for receiving and executing the commands to the corresponding application.</p>
},
	author = {Christos Bouras and Vassilis Poulopoulos and Vassilis Tsogkas and Ioannis Sengounis}
}
@conference {2934,
	title = {A Novel Mechanism for Radio Capacity Maximization during MBMS transmission in B3G Networks},
	booktitle = {The 11th ACM/IEEE International Conference on Modeling, Analysis and Simulation of Wireless and Mobile Systems (MSWiM 2008), Vancouver, British Columbia, Canada},
	year = {2008},
	month = {27 - 31 October},
	pages = { 185 - 192},
	abstract = {This paper proposes a novel mechanism for efficient power
control during multicast transmissions in Beyond 3rd Generation
(B3G) mobile networks. The mechanism utilizes optimally the
available power resources of Universal Mobile
Telecommunication System (UMTS) base stations, resulting to
network capacity maximization. The proposed mechanism is
based on the concept of transport channels combination (point-topoint
and/or point-to-multipoint radio bearers) in any cell/sector
of the network in which Multimedia Broadcast/Multicast Service
(MBMS) users are residing. In particular, the transport channel
combination that minimizes the transmission power of the base
station is selected for the transmission of the MBMS traffic to the
corresponding cell. The mechanism is evaluated through several
realistic scenarios and the results indicate the ability of the
mechanism to utilize optimally the radio resources of the network.
Furthermore, our approach is compared with several power
control mechanisms existing in the bibliography, including the 3rd
Generation Partnership Project (3GPP) approaches (presented in
3GPP TS 25.346 and 3GPP TR 25.922), in order to highlight the
enhancements that it provides},
	keywords = {MBMS, Power Control, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos and Evangelos Rekkas}
}
@conference {2930,
	title = {A Novel Power Counting Mechanism for Enhanced MBMS Performance in UMTS Networks},
	booktitle = {1st IFIP Wireless and Mobile Networking Conference (WMNC 2008) , Toulouse, France},
	year = {2008},
	month = {30 September - 2 October},
	pages = { 57 - 68},
	abstract = {One of the key objectives of Universal Mobile Telecommunications System (UMTS) is the realization of enhanced end-user experience through the provision of rich multimedia services, ensuring in parallel an economical delivery cost for service providers. Multimedia Broadcast/Multicast Services (MBMS) framework of UMTS epitomizes the increasing popularity of such applications by efficiently delivering multimedia traffic to a large number of users and optimizing the radio interface of UMTS networks. For exploiting resource efficiency, MBMS specifications consider the Counting Mechanism which decides whether it is more economic to deliver MBMS multicast traffic over point-to-point (PTP) or point-to-multipoint (PTM) bearers. However, the necessity to further improve MBMS resource efficiency and integrate new technologies such as High Speed Downlink Packet Access (HSDPA) stresses the need for an advanced Counting Mechanism. To this direction, in this paper we propose a novel Power Counting Mechanism which performs optimal power resource utilization and incorporates the HSDPA broadband extension of UMTS for enhanced performance.},
	keywords = {MBMS, Power Control, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Evangelos Rekkas}
}
@conference {2933,
	title = {Performance Evaluation of Cross Layer Adaptive Multimedia Transmission: The case of Wired Networks},
	booktitle = {13th International Telecommunications Network Strategy and Planning Symposium - NETWORKS 2008, Budapest, Hungary},
	year = {2008},
	month = {28 September - 2 October},
	abstract = {This paper presents the performance evaluation of the wired part of a proposed framework with cross layer adaptation mechanisms, for multimedia transmission over wired and wireless networks. The performance evaluation of the proposed framework is contacted through a number of simulations with the network simulator software (ns2), which has been enhanced in order to support the functionality of the proposed framework. The performance evaluation includes various simulation scenarios in order to investigate the behavior of the proposed framework under different conditions. The proposed framework can support both wired and wireless receivers in one platform in which, cross layer information are used to support the wireless users whereas TCP friendly estimations are used to support the wired users.},
	author = {Christos Bouras and Apostolos Gkamas and G Kioumourtzis}
}
@conference {2926,
	title = {Performance Study of the Mobile IPv6 Protocol and its Variations},
	booktitle = {6th International Symposium on Communication Systems, Networks and Digital Signal Processing {\textendash} CSNDSP 2008, Graz, Austria},
	year = {2008},
	month = {23 - 25 July},
	pages = { 438 - 442},
	abstract = {In this paper, we use the OMNET++ simulator in 
order to evaluate the performance of the basic Mobile IPv6 
protocol  and  some  of  its  proposed  variations.  The  most 
important  metric  we  are  interested  in  is  the  handover 
latency, which is measured for various combinations of the 
proposed Mobile  IPv6  variations  and  then  this  metric  is 
used, combined with  factors  such as  the complexity of  the 
implementation,  in order  to evaluate and  identify  the best 
possible configuration for the operation of the protocol.},
	author = {Christos Bouras and Kostas Stamos and G Aristomenopoulos}
}
@article {3077,
	title = {PeRSSonal{\textquoteright}s core functionality evaluation: Enhancing text labeling through personalized summaries},
	journal = {Data and Knowledge Engineering Journal, Elsevier Science, 2008, Vol. 64, Issue 1
},
	year = {2008},
	pages = { 330 - 345},
	abstract = {In this manuscript we present the summarization and categorization subsystems of a complete mechanism
that begins with web-page fetching and concludes with representation of the collected data to the
end users through a personalized portal. The system intends to collect articles from major news portals
and, following an algorithmic procedure, to create a more user friendly and personalized {\textquotedblleft}view{\textquotedblright}
of the articles. Before presenting the information back to the end user, the core of our mechanism automatically
categorizes data and then extracts personalized summaries. We focalize to the core of the
mechanism and more specifically, we present the algorithms used for the summarization and the categorization
of texts. The algorithms are not utilized only for producing isolated data, targeted to a specific
subsystem, but a combination of the algorithms, which achieves co-operation of the categorization and
summarization mechanisms, is introduced in order to enhance text labeling through the personalized
summaries that are constructed.},
	author = {Christos Bouras and Vassilis Poulopoulos and Vassilis Tsogkas}
}
@conference {2922,
	title = {Power Saving Methods for MBMS Transmissions in UTRAN},
	booktitle = {The Thirteenth IEEE Symposium on Computers and Communications {\textendash} ISCC 2008, Marrakech, Morocco},
	year = {2008},
	month = {6 - 9 July},
	pages = { 374 - 379},
	abstract = {The demand for wireless multimedia communications thrives in today?s consumer and corporate market. The need to evolve multimedia applications and services is at a critical point given the proliferation and integration of wireless systems. Multimedia Broadcast Multicast Services (MBMS) was introduced in Third Generation Partnership Project (3GPP) Release 6 in order to more efficiently use network and radio resources for the transmission of multimedia data, both in the core network and most importantly in the air interface of UTRAN (UMTS Terrestrial Radio Access Network). However, several obstacles, regarding the high power requirements, should be overcome for the realization of MBMS. The fact that Node B?s transmission power is a limited resource and must be shared among all MBMS users in a cell indicates the need for power control during MBMS transmissions. Several techniques, such as Dynamic Power Setting and Macro Diversity Combining, have been proposed in order to reduce the power requirements of delivering multicast traffic to MBMS users. This paper examines the efficiency of the utilization of these power saving techniques, by presenting simulation results that will reveal the amount of power that is saved.},
	keywords = {MBMS, Power Control, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos}
}
@article {3163,
	title = {Quality of Service and Service Level Agreements},
	year = {2008},
	pages = { 418 - 424},
	author = {Christos Bouras and Apostolos Gkamas and Dimitris Primpas and Kostas Stamos}
}
@article {3162,
	title = {Quality of Service architectures},
	year = {2008},
	pages = { 425 - 431},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos and Dimitris Primpas}
}
@article {3166,
	title = {Real-time protocols - RTP/RTCP},
	year = {2008},
	pages = { 463 - 468},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos and Dimitris Primpas}
}
@conference {2915,
	title = {A SIP spatial audio server for the EVE platform},
	booktitle = {3rd International Conference on Computer Graphics Theory and Applications, Funchal, Madeira, Portugal},
	year = {2008},
	month = {22 - 25 January},
	pages = { 395 - 402},
	abstract = {When it comes to 3D Virtual Environments it is well known that 3D sound is of great importance to the whole interactive experience. The percept of sound is a major counterpart for the eyesight, since it describes the location, the momentum and the attitude towards the listener, of each surrounding entity. The sound can offer precision of spatial perception that cannot be achieved by the eye itself. Thus the support of 3D surround sound of high fidelity is mandatory for a 3D Virtual platform. The evolution of Internet telephony led to the introduction of new session establishment and management protocols. The most important of them, the Session Initiation Protocol (SIP), is a robust, lightweight reliable and fast application-layer control (signaling) protocol that is highly adopted for creating, modifying and terminating sessions. This protocol can be of extreme importance in establishing audio sessions for multi-user platforms. This paper presents the work done for developing a SIP 3D spatial audio server for a multi-user virtual environments platform, called EVE, in order to support 3D spatial audio},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Vasileios Triglianos}
}
@conference {2918,
	title = {Smooth Multicast Congstion Control for Adaptive Multimedia Transmission},
	booktitle = {4th Conference on NEXT GENERATION INTERNET NETWORKS (NGI 2008), Krakow, Poland},
	year = {2008},
	month = {28 - 30 April},
	pages = {146-152},
	abstract = {In this paper we introduce an equation-based
smooth multicast congestion control for adaptive multimedia
transmission over best-effort wired networks. Target of the
proposed schema is (a) smooth transmission rate, in order to
minimize the Audio-Video (AV) encoding and decoding
distortion and (b) TCP friendly transmission. The {\textquotedblleft}smoothness{\textquotedblright}
lays in the way the TCP-Friendly transmission rate is filtered.
We integrate the congestion control functions in the RTP
protocol and use the RTCP sender and receiver reports to
provide the necessary feedback information for the sender?s
adaptive transmission rate. The performance evaluation of the
smooth adaptation and TCP-friendliness is conducted through a
number of simulations with the network simulator software
(ns2). Our intention is to use this congestion control in the context
of a proposed framework for multimedia transmission over wired
and wireless networks.},
	author = {Christos Bouras and Apostolos Gkamas and G Kioumourtzis}
}
@article {3083,
	title = {The status of broadband in western Greece: a study on the supply and the demand of Broadband Services for e-Government promotion},
	journal = {International Journal of Electronic Governance (IJEG), Interscience Publishers, Vol. 1, No. 3},
	year = {2008},
	pages = { 326 - 344},
	abstract = {Fast and reliable access technology is necessary for developing efficient and effective e-Government services. The existence of a direct relationship between the presence of a broadband network and the availability of e-Government services has frequently been debated in the literature. This paper presents the results of a study conducted by the RACTI (Research Academic Computer Technology Institute), which investigates the current status of broadband with regards to the demand for and the supply of broadband services and infrastructures that will support these services, in the Western Greece Region. Broadband promotes open effective governance and improved services to citizens while creating a new economy based on knowledge. Broadband development has a significant impact on e-Government support and diffusion. },
	author = {Christos Bouras and J Papagiannopoulos and S Katsikas and S Gritzalis}
}
@conference {2919,
	title = {Supporting Broadband Growth in an Interregional Level: The Case of Greece-Italy Partnership},
	booktitle = {Bridging the Digital Divide in Rural Communities: Practical Solutions and Policies, Athens, Greece},
	year = {2008},
	month = {15 - 16 May},
	pages = { 151 - 161},
	abstract = {Broadband is a key element of the developments that are taking place in the electronic communications markets and the European Commission has been particularly active in promoting broadband developments. This paper presents the objectives and the methodology of a project for supporting the broadband growth in an Interregional Level between regions of Italy and Greece. Main target of the project is the technology and knowhow transfer (relative to broadband) to SMEs (Small and Medium Enterprises) and the demonstration of broadband advantages and benefits.},
	author = {Christos Bouras and Apostolos Gkamas and Thrasivoulos Tsiatsos and Eleftheria Giannaka}
}
@article {3082,
	title = {A Unified Framework for Political Parties to Support e-Democracy Practices: the case of a Greek Party},
	journal = {International Journal of Electronic Democracy (IJED), Interscience Publishers, Vol. 1},
	year = {2008},
	pages = { 98 - 117},
	abstract = {E-government and e-democracy constitute a central theme
in information society policy at all levels: local, regional, national, European
and even globally. To this direction, a variety of efforts have been made, and
many systems have been developed. This paper proposes a methodology for
designing and implementing web-based services that can support e-democracy
practices. Furthermore, the paper presents and describes the effort made by
a Greek political party to this direction, for the design and development of
a unified framework for providing, supporting and managing e-democracy
services. The paper describes the actions taken and the work done according to
the proposed methodology.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka and Vassilis Poulopoulos and T Karounos and A Priftis}
}
@article {3160,
	title = {Wi-Fi Technology},
	year = {2008},
	pages = { 711 - 716},
	author = {Christos Bouras and Antonios Alexiou and Dimitrios Antonellis}
}
@article {3070,
	title = {Adaptive and Reliable Video Transmission over UMTS for Enhanced Performance},
	journal = {International Journal of Communication Systems, Wiley InterScience Vol. 20, Issue 1},
	year = {2007},
	pages = { 65 - 81},
	abstract = {This paper proposes a mechanism for the congestion control for video transmission over universal mobile telecommunications system (UMTS). Our scheme is applied when the mobile user experiences real-time multimedia content and adopts the theory of a widely accepted rate control method in wired networks, namely equation-based rate control. In this approach, the transmission rate of the multimedia data is determined as a function of the packet loss rate, the round trip time and the packet size and the server explicitly adjusts its sending rate as a function of these parameters. Furthermore, we examine the performance of the UMTS for real-time video transmission using real-time protocols. Through a number of experiments, we measure performance parameters such as end-to-end delay, delay in radio access network, delay jitter and throughput in the wireless link.},
	keywords = {Congestion Control, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Dimitrios Antonellis}
}
@article {3158,
	title = {Adaptive Transmission of Multimedia Data over UMTS},
	year = {2007},
	pages = { 20 - 24},
	keywords = {UMTS},
	author = {Christos Bouras and Antonios Alexiou and Dimitrios Antonellis}
}
@conference {2893,
	title = {AMPS - ANStool: Interoperability of automated tools for the provisioning of QoS services},
	booktitle = {TERENA Networking Conference 2007, Lyngby, Denmark},
	year = {2007},
	month = {21 - 24 May},
	author = {Christos Bouras and Kostas Stamos and Dimitris Primpas and A Varvitsiotis and V Haniotakis}
}
@article {3075,
	title = {An analytical QoS service model for delay - based differentation},
	journal = {Computer Networks Journal, Elsevier Science, Vol. 51,
Issue 12
},
	year = {2007},
	pages = { 3549 - 3563},
	abstract = {The increased need for Quality of Service (QoS) in today?s IP networks has concentrated a lot of research and implementation efforts. Carefully designed and managed priority services are essential for quality-demanding traffic, especially in large-scale IP-based environments where aggregation of flows is extensive and a variety of traffic types co-exist. Although individual mechanisms have been widely investigated, not much related work exists on integrated approaches to QoS provisioning that are also feasible to implement. This work presents a thorough approach to the design, dimensioning and provisioning of a high priority service for high-quality demanding traffic over an IP network. Our approach employs efficient scheduling and a dynamic admission control scheme while demonstrating an outstanding performance in terms of the quality offered to QoS-demanding traffic. A novel feature is also introduced: while other existing schemes only focus on provisioning of service rate guarantees, ours achieves in addition differentiation of the end-to-end delay perceived by IP flows.},
	author = {Christos Bouras and Afroditi Sevasti}
}
@conference {2914,
	title = {On the Applicability of pgmcc to UMTS Multicast},
	booktitle = {2007 International Conference on Late Advances in Networks (ICLAN-2007), Paris, France},
	year = {2007},
	month = {5 - 7 December},
	pages = { 67 - 72},
	abstract = {In this paper, we investigate the applicability of the Pragmatic General Multicast Congestion Control (pgmcc) scheme to the multicast data delivery over Universal Mobile Telecommunications System (UMTS) networks. We show that the pgmcc scheme cannot support the degradation of the radio channels in the UMTS Terrestrial Radio-Access Network (UTRAN). Our major contribution is that the legacy scheme is modified in order to cope with the packet losses caused by either the temporary or the permanent degradation of the radio channel. The proposed scheme introduces minor modifications in the UMTS nodes and respects the limited computing power of the mobile equipment. Finally, we simulate our approach and we evaluate it under various conditions. The simulation results are presented along with their analysis},
	keywords = {Congestion Control, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Andreas Papazois}
}
@conference {2897,
	title = {Business Models for Broadband Municipal Optical Networks: A proposed model for the Greek case},
	booktitle = {The Twelfth IEEE Symposium on Computers and Communications, Aveiro, Portugal},
	year = {2007},
	month = {1 - 4 July},
	pages = { 727 - 732},
	abstract = {This paper proposes an optimal business model for the successful operation of the currently developing broadband metropolitan area networks in Greece. Having recorded and examined relevant international practices, we describe in detail the way that these networks should be managed, operated, maintained and expanded. Taking into consideration that these infrastructures will alter the broadband map of Greece widely, that Greece currently has one of the lowest broadband penetration percentages in Europe and that the proper exploitation of the networks to be deployed could boost the demand for broadband connections and applications, the proposition of the optimal business model appears to be of vital importance. We present the proposed optimal business model in detail including information regarding network management and network expansion of the broadband metropolitan networks and viability issues regarding the authority which will manage the broadband metropolitan networks.},
	author = {Christos Bouras and Apostolos Gkamas and Thrasivoulos Tsiatsos and J Papagiannopoulos and George Theofilopoulos}
}
@conference {2905,
	title = {Challenges in cross layer adaptation for multimedia transmission},
	booktitle = {IADIS International Conference on Telecommunications, Networks and Systems 2007, Lisbon, Portugal},
	year = {2007},
	month = {3 - 8 July},
	pages = { 129 - 133},
	abstract = {Over the last years a number of new protocols have been developed for multimedia applications in the whole OSI layer?s scale. In order to support better wireless user the cross layer design paradigm has been proposed. This paper presents the challenges in designing and implementation of cross layer adaptation schemes for multimedia transmission over wired and wireless networks. In addition, the paper proposes the basic aspects of a cross-layer adaptation framework for multimedia transmission over wired and wireless networks. The main concept is based on a {\textquotedblleft}holistic approach{\textquotedblright} in which all layers participate to the adaptation process and make its own contributions. Finally, the proposed framework can support both wired and wireless receivers in one platform.},
	author = {Christos Bouras and Apostolos Gkamas and G Kioumourtzis}
}
@article {3157,
	title = {Content Transformation Techniques},
	year = {2007},
	pages = { 119 - 123},
	author = {Christos Bouras and Vassilis Poulopoulos and Ioannis Antonellis}
}
@conference {2896,
	title = {Cost Analysis of the MBMS Multicast Mode of UMTS},
	booktitle = {The Twelfth IEEE Symposium on Computers and Communications, Aveiro, Portugal},
	year = {2007},
	month = {1 - 4 July},
	pages = { 797 - 802},
	abstract = {Along with the widespread deployment of the third generation cellular networks, the fast-improving capabilities of the mobile devices, content and service providers are increasingly interested in supporting multicast communications over wireless networks and in particular over Universal Mobile Telecommunications System (UMTS). To this direction, the third Generation Partnership Project (3GPP) is currently standardizing the Multimedia Broadcast/Multicast Service (MBMS) framework of UMTS. In this paper, we present an overview of the MBMS multicast mode of UMTS. We analytically present the multicast mode of the MBMS and analyze its performance in terms of packet delivery cost under various network topologies, cell types and multicast users? distributions. Furthermore, for the evaluation of the scheme, we consider different transport channels for the transmission of the data over the UTRAN interfaces.},
	keywords = {Cost analysis, MBMS, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Evangelos Rekkas}
}
@conference {2908,
	title = {Design and architecture of an online system for Vocational Education and Training},
	booktitle = {10th International Conference on Interactive Computer aided Learning (ICL 2007), Villach, Austria
},
	year = {2007},
	month = {26 - 28 September},
	abstract = {E-learning and tele-training have been evolved over time from a newborn trend for complementing the learning process to a major form of education and training for supporting mainly geographically scattered users. Learning and training, can be applied to a wide variety of fields and areas, each of which is accompanied by some special characteristics related to the field of learning/training, to the tools needed for the realization of the training process as well as to the familiarization of the target audience to the selected technologies. Basic aim of this paper is the description of a platform for open and distance training, which is mainly focused at supporting the needs of Vocational Training Centres as well as of institutions providing life-long adult training and learning. In particular, the issues that this paper focuses on are vocational education and training characteristics and requirements while it also proposes basic vocational training services and the system architecture of the integrated platform.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka}
}
@conference {2900,
	title = {An efficient mechanism for adaptive multimedia transmission in 3G networks},
	booktitle = {IADIS International Conference Wireless Applications and Computing 2007, Lisbon, Portugal},
	year = {2007},
	month = {3 - 8 July},
	pages = { 11 - 18},
	abstract = {This paper proposes a mechanism for the congestion control for video transmission over Universal Mobile Telecommu-nications System (UMTS). Our scheme is applied when the mobile user experiences real time multimedia content and adopts the theory of a widely accepted rate control method in wired networks, namely equation based rate control. In this approach, the transmission rate of the multimedia data is determined as a function of the packet loss rate, the round trip time and the packet size and the server explicitly adjusts its sending rate as a function of these parameters. Through a number of simulations and experiments we validate the correctness and measure the performance and efficiency of the mechanism. The mechanism at first level is evaluated through simulations that carried out in the ns-2 simulator. At sec-ond level, in order to validate the proposed mechanism in real world traffic scenar-ios we perform some experiments in a commercial UMTS network.},
	keywords = {UMTS},
	author = {Christos Bouras and Antonios Alexiou and Konstantinos Barounis}
}
@conference {2904,
	title = {Efficient Summarization Based On Categorized Keywords},
	booktitle = {The 2007 International Conference on Data Mining (DMIN07), Las Vegas, Nevada, USA},
	year = {2007},
	month = {25 - 28 June},
	abstract = {The information that exists on the World Wide Web is enormous enough in order to distract the users when trying to find useful information. In order to overcome the large amounts of data many personalization and summarization mechanisms have been presented. In this paper we propose a mechanism that applies summarization techniques on articles extracted from the web, based on the categorization procedure (also applied on the same articles). Through extensive experiments we proved that the summarization procedure can affect the categorization mechanism and vice versa. This means that when the results of the summarization mechanism seem to be weak, then the categorization can be used in order to provide a more efficient summary and on the other hand when the categorization procedure becomes too overloaded, the summarized articles can be used in order to categorize the article more efficiently. Moreover this paper introduces that the combination of summarization and categorization can lead to more efficient results not only for both mechanisms but for a personalized portal also. Finally, we propose a complete mechanism that can be used in order to provide the users with helpful tools in order to locate more easily the information they need.},
	author = {Christos Bouras and Vassilis Poulopoulos and Vassilis Tsogkas}
}
@conference {2892,
	title = {Enhancing ns-2 with DiffServ QoS features},
	booktitle = {10th International Communications and Networking Simulation Symposium (CNS 07), Norfolk Marriott Waterside, Norfolk, VA, USA},
	year = {2007},
	month = {25 - 29 March},
	pages = { 117 - 124},
	abstract = {In this paper, we present work that we have carried out in extending the ns-2 simulator in order to study and validate Quality of Service issues and related architectures. In the case of the DiffServ framework, simulation is valuable since an analytical approach of mechanisms and services is infeasible due to the aggregation and multiplexing of flows. This paper covers work in extending ns-2 functionality towards the direction of realistic traffic generation and a series of mechanisms defined by the DiffServ architecture. We have also extended ns-2 with the functionality of Bandwidth Brokers, which are entities for managing the resources and negotiating end to end resource reservations between domains. The Bandwidth Broker ns-2 implementation is useful for studying the related architectures and admission control procedures.},
	author = {Christos Bouras and Kostas Stamos and Dimitris Primpas}
}
@conference {2906,
	title = {Evaluation of the multicast mode of MBMS},
	booktitle = {18th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, Athens, Greece
},
	year = {2007},
	month = {3 - 6 September},
	abstract = {Multicasting is an efficient way for delivering rich
multimedia applications to large user groups as it allows the
transmission of packets to multiple destinations using fewer
network resources. Content and service providers are
increasingly interested in supporting multicast
communications over wireless networks and in particular over
Universal Mobile Telecommunications System (UMTS). To
this direction, the third Generation Partnership Project (3GPP)
is currently standardizing the Multimedia Broadcast/Multicast
Service (MBMS) framework of UMTS. In this paper, we
present an overview of the MBMS multicast mode of UMTS.
We analytically present the multicast mode of the MBMS and
analyze its performance in terms of packet delivery cost under
various network topologies, cell environments and multicast
users? distributions. Furthermore, for the evaluation of the
scheme, we consider different transport channels for the
transmission of the data over the UTRAN interfaces and
propose a cost based scheme for the efficient radio bearer
selection that minimizes the packet delivery cost.},
	keywords = {MBMS, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos and Evangelos Rekkas}
}
@conference {2913,
	title = {Exploiting Virtual Objects Attributes and Avatars Behavior in DVEs Partitioning},
	booktitle = {The 17th International Conference on Artificial Reality and Telexistence - ICAT 2007, Esbjerg, Denmark},
	year = {2007},
	month = {28 - 30 November},
	pages = { 157 - 163},
	abstract = {Partitioning constitutes one of the most critical challenges a distributed virtual environment needs to handle and is related to the efficient assignment of the existing entities of the virtual world to the available resources of the system. The efficient partitioning arises from the need of high consistency maintenance among participating users? view, as virtual reality applications are characterized by the high degree of realism they aim to achieve. To the direction of partitioning algorithms, a lot of work has been done, which has been more intense due to the evolution of network technologies and the familiarization of users with virtual reality systems. This paper presents a partitioning approach, which is based on the degree of interaction of each virtual object and the behavior of the participating users, in terms of moving trends, which is usually directed by the actions they can perform on the surrounding objects. In particular, the partitioning takes place when the virtual world contains only objects, in the sense that no avatars are yet connected and objects? attributes are handled as indicators for avatars? future behavior in the system. This prediction of avatars? behavior based on objects? attributes defines the initial partitioning of the virtual space.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka}
}
@conference {2903,
	title = {A Framework for Cross Layer Adaptation for Multimedia Transmission over Wired and Wireless Networks},
	booktitle = {The 2007 International Conference on Internet Computing (ICOMP07), Las Vegas, Nevada, USA},
	year = {2007},
	month = {25 - 28 June},
	pages = { 153 - 159},
	abstract = {This paper proposes a framework for cross-layer adaptation for multimedia transmission over wired and wireless networks. The proposed framework consists of four entities: The sender, the proxy, which is located at the edge of the wired network, the access point, which co-located with the proxy and finally the wired and wireless receivers. The main concept is based on a {\textquotedblleft}holistic approach{\textquotedblright} in which all layers participate to the adaptation process and make its own contributions. In addition, the proposed framework can support both wired and wireless receivers in one platform and cross layer information are used in order to support wireless users whereas TCP friendly estimations are used in order to support wired users.},
	author = {Christos Bouras and Apostolos Gkamas and G Kioumourtzis}
}
@conference {2902,
	title = {Framework for Dynamic and On-Demand QoS to Videoconference Session},
	booktitle = {The 2007 International Conference on Multimedia Systems and Applications (MSA07), Las Vegas, Nevada, USA},
	year = {2007},
	month = {25 - 28 June},
	pages = { 110 - 116},
	abstract = {This paper deals with the design and investigation of an approach for dynamic and on demand QoS on videoconference sessions for GRNET?s (Greek NREN) network. After the activation of QoS service in GRNET, a new need for automation of mechanisms for QoS in Videoconferencing session arises. The traditional QoS workflow inserts important administrative cost when a connected institute wants to have a videoconference service with specific QoS guaranties. In such case, the network administrator must manual configure the network?s edge routers. In order to overcome the above limitation, an {\textquotedblleft}automatic{\textquotedblright} procedure for providing QoS guaranties to videoconference session was investigated. The result was an automatic solution that provides QoS using the QoS Policy Propagation via BGP mechanism for signaling. This automatic QoS deployment solution was tested successfully on the network and some performance measurement are presented in this paper.},
	author = {Christos Bouras and Apostolos Gkamas and Dimitris Primpas}
}
@article {3076,
	title = {Improvements on IP - IAPP: A fast IP handoff protocol for IEEE 802.11 wireless and mobile clients},
	journal = {WINET Journal, Special Issue on Broadband Wireless Multimedia, Kluwer Academic Publishers, Vol. 13, No. 4
},
	year = {2007},
	pages = { 497 - 510},
	abstract = {One of the most critical issues in introducingWireless
LAN (WLAN) real-time and delay sensitive applications,
such asVoice over IP (VoIP), is guaranteeing IP service
continuation during inter-subnet Basic Service Set (BSS)
transitions. Even though WLANs offer very high channel
bandwidth, they exhibit long network-layer handoff latency.
This is a restraining factor for mobile clients using interactive
multimedia applications such as VoIP or video streaming.
In a previous work, we presented a novel fast and efficient
IP mobility solution, called ?IP-IAPP?, which offers
constant IP connectivity to the 802.11 mobile users and successfully
preserves their ongoing sessions, even during subnet
handoffs (fast recovery of active connections). It is an
802.11-dependent IP mobility solution, which accelerates
the network reconfiguration phase after subnet handoffs and
significantly reduces the IP handoff latency. It restores L3
connectivity almost simultaneously to the L2 connectivity
after a subnet handoff, due to a zero-delay movement detection
method. As a result, even the most demanding next generation WLAN applications such as Voice over WLAN
(VoWLAN) suffer insignificant disruption. In this paper we
present an improved version of the IP-IAPP mobility mechanism
(new optimized protocol procedures). Certain extensions
have also been incorporated to the initial proposal, for
the provision of more advanced services: (a) secure inter-AP
IP-IAPP communications, (b) zero patching on the clients
s/w, and (c) support of clients which use a dynamic IP address.
Performance measurements out of further and more
complex testing verify that the proposed method outperforms
other existing mobility solutions, and still introduces the
lesser imperative amendments to the existing 802.11 wireless
LAN framework.},
	author = {Christos Bouras and Ioanna Sampraku and T Karoubalis}
}
@conference {2899,
	title = {Input here - Execute there through networks: the case of gaming},
	booktitle = {The 15th Workshop on Local and Metropolitan Area Networks (LANMAN 2007), Princeton, NJ, USA},
	year = {2007},
	month = {10 - 13 June},
	abstract = {As the evolution of computer technology introduces
new advances in networks (among others), online gaming
becomes a new trend. Following the trends of our era, Games At
Large introduces an innovative platform for running interactive,
rich content multimedia applications over a WAN Network.
Games@Large project?s vision is to provide a new system
architecture for Interactive Multimedia which will enhance
existing CE devices such as, Set Top Boxes (STB) and other
devices, which are lacking both the CPU power and the graphical
performance to provide a rich user experience. This paper
presents the controllers? sub-system of the innovative mechanism
that will be implemented in the context of Games at Large
project. More specifically, it presents the general architecture of
the complete system and focuses on the {\textquotedblleft}capturing{\textquotedblright} and
{\textquotedblleft}execution of commands{\textquotedblright} modules at the client and server side.
The client software captures the input from the input devices,
sends the commands over a WAN and the server is responsible
for receiving and executing the commands to the correct
application.},
	author = {Christos Bouras and Vassilis Poulopoulos and Vassilis Tsogkas and Ioannis Sengounis}
}
@conference {2898,
	title = {MBMS Power Planning in Macro and Micro Cell Envirohments},
	booktitle = {Second IEEE Workshop on multimedia Applications over Wireless Networks(MediaWiN 2007), Aveiro, Portugal},
	year = {2007},
	month = {1 July},
	pages = { 33 - 38},
	abstract = {Multimedia Broadcast Multicast Services (MBMS), introduced in Third Generation Partnership Project (3GPP) Release 6, is a point-to-multipoint downlink bearer service that addresses the need for the efficient usage of the expensive radio resources. Power control is one of the most important aspects in MBMS due to the fact that Node B?s transmission power is a limited resource and must be shared among all MBMS users in a cell. Consequently, the analysis of transmitted power plays a fundamental role in the planning and optimization process of Universal Mobile Telecommunications System (UMTS) radio access networks. This paper investigates several factors affecting Node B?s transmission power levels such as, cell deployment, propagation models, Quality of Service (QoS) requirements, users? distributions and mobility issues. Finally, different transport channels for the transmission of the multicast data over the UTRAN interfaces are considered.},
	keywords = {MBMS, Power Control, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos and Evangelos Rekkas}
}
@conference {2907,
	title = {Multicast in UMTS: Adopting TCP - Friendliness},
	booktitle = {Personal Wireless Communications (PWC07) - 12th IFIP
International Conference, Prague, Czech Republic
},
	year = {2007},
	month = {12 - 14 September},
	pages = { 433 - 444},
	abstract = {In this paper, we present a novel mechanism for the multicast congestion control over UMTS networks. The proposed mechanism is based on the well known TCP-Friendly Multicast Congestion Control (TFMCC) scheme. The key challenge in the design of the new scheme lies in improving the TFMCC mechanism to cope with the packet losses caused by either the temporary or the permanent degradation of the wireless channels. The proposed scheme introduces minor modifications in the UMTS nodes with respect to the computing power of the mobile terminals. Finally, our approach is implemented in the ns-2 network simulator and is evaluated it under various conditions.},
	keywords = {MBMS, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Andreas Papazois}
}
@proceedings {2912,
	title = {An Object Driven Partitioning Approach for Distributed Virtual Environments},
	year = {2007},
	month = {3 - 6 December},
	pages = {153-154},
	abstract = {Distributed virtual environments tend to become a de facto solution for large-scale networked virtual environments. One of the key issues and problems that need to be handled in the design of a scalable and effective distributed virtual environment system is the partitioning problem, which refers to the efficient assignment of the system?s workload to the available resources of the system. This paper presents an object driven partitioning approach based on the partitioning algorithm of Lui \& Chan, who proposed a three step technique for balancing the workload among the servers of the Distributed Virtual Environment.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka}
}
@conference {2911,
	title = {Partitioning of Distributed Virtual Environments Based on Objects{\textquoteright} Attributes},
	booktitle = { 11th IEEE International Symposium on Distributed Simulation and Real Time Applications, Chania, Crete, Greece},
	year = {2007},
	month = {22 - 24 October},
	pages = { 72 - 75},
	abstract = {The partitioning constitutes one of the basic problems that need to be handled in Distributed Virtual Environments for maintaining consistency among users? view of the virtual scene and for optimizing the performance of the system. This paper presents an approach for handling the partitioning problem, which is based on objects? attributes. In particular, the approach proposes a technique, which takes into account the degree of interaction that the objects of the virtual environment carry for predicting future avatar behavior. This prediction of avatars? behavior based on objects? attributes defines the initial partitioning of the virtual space.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka}
}
@article {3073,
	title = {Performance Analysis of Adaptive Admission Control Algorithms for Bandwidth Brokers},
	journal = {Journal of Network and Systems Management, Kluwer Academic Publishers, Vol. 15, No. 2},
	year = {2007},
	pages = { 191 - 218},
	abstract = {In this paper, we propose a novel architecture for the admission control module of a Bandwidth Broker entity that aims at achieving a satisfactory balance between maximizing the resource utilization for the managed network and minimizing the overhead of the module. We also describe, analyze and evaluate mechanisms which aim at solving the additional problems of fairly prioritizing resubmitted requests and efficiently handling requests which do not specify ending times. We use the well known network simulator ns-2, as well as a custom simulation environment in order to study the performance characteristics of the proposed mechanisms and compare them with various alternatives for the admission control module of a Bandwidth Broker. We provide the results of the experimental evaluations and the conclusions they lead us to for the relative importance of the proposed solution and the various alternatives, their advantages and drawbacks, and the environments for which each one is best suited.},
	author = {Christos Bouras and Kostas Stamos}
}
@conference {2901,
	title = {Personalizing text summarization based on sentence weighting},
	booktitle = {IADIS European First International Conference Data Mining (ECDM 2007), Lisbon, Portugal},
	year = {2007},
	month = {3 - 8 July},
	pages = { 3 - 10},
	abstract = {The amount of data that exists on the Internet is enormous enough to distract users when trying to find useful information. In addition, the expansive use of small screen devices for browsing the World Wide Web generates huge problems when trying to find and read information. A solution to these problems is to personalize the web and try to reduce algorithmically the amount of text. Many text summarizers have been presented in order to reduce the valueless information that is presented to the users and many web sites, especially news portals, introduce personalization features for the users, though, still these techniques are not often used in combination in order to create more effective results. In this paper a mechanism for creating personalized summaries for the members of a news portal that reproduces articles collected from major portals is presented, together with evaluation both of the summarizer and the personalized summaries. The evaluators of the personalized summaries are members of the news portal. The personalized summary mechanism can also be utilized by users of small screen devices, for easier reading of less but inclusive information.},
	author = {Christos Bouras and Vassilis Poulopoulos and Vassilis Tsogkas}
}
@conference {2895,
	title = {A Power Control Scheme for Efficient Radio Bearer Selection in MBMS},
	booktitle = {8th International Symposium on a World of Wireless, Mobile and Multimedia Networks, - WoWMoM 2007, Helsinki, Finland},
	year = {2007},
	month = {18 - 21 June},
	pages = { 1 - 8},
	abstract = {This paper proposes a power control scheme for the efficient radio bearer selection in the Multimedia Broadcast/Multicast Service (MBMS) framework of Universal Mobile Telecommunications System (UMTS). The choice of the most efficient transport channel in terms of power consumption is a key point for the MBMS since a wrong transport channel selection for the transmission of the MBMS data could result to a significant decrease in the total capacity of the system. Different UMTS transport channels are examined and an algorithm that defines the switching point between dedicated and common radio bearers is proposed. The proposed MBMS power control scheme selects the transport channel that minimizes the Node B?s transmission power in every cell of the network with multicast users.},
	keywords = {MBMS, Power Control, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Evangelos Rekkas}
}
@conference {2909,
	title = {Power Efficient Radio Bearer Selection in MBMS Multicast Mode},
	booktitle = {10th ACM - IEEE International Symposium on Modeling, Analysis and Simulation of Wireless and Mobile Systems - MSWIM 2007, Chania, Crete, Greece},
	year = {2007},
	month = {22 - 26 October},
	pages = { 261 - 268},
	abstract = {Multimedia Broadcast Multicast Services (MBMS) was
introduced in Third Generation Partnership Project (3GPP)
Release 6 in order to address the need for the efficient usage of
the expensive radio resources. The goal of this effort is to support
downlink streaming and download-and-play type services to large
groups of users. From the radio perspective, MBMS includes
point-to-point (PtP) and point-to-multipoint (PtM) modes. The
fact that Node B?s transmission power is a limited resource and
must be shared among all MBMS users in a cell indicates the need
for power control during an MBMS service. Consequently, the
analysis of the transmitted power plays a fundamental role in the
planning and optimization process of Universal Mobile
Telecommunications System (UMTS) radio access networks. In
this paper we investigate the factors that affect the Node B?s
transmission power levels during an MBMS session, such as, cell
deployment, propagation models, users? distributions and
mobility issues. To this direction, the transport channels in the
downlink, currently existing in UMTS which could be used to
transmit the multicast data over the UMTS Terrestrial Radio-
Access Network (UTRAN) interfaces are examined.},
	keywords = {MBMS, Power Control, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos and Evangelos Rekkas}
}
@conference {2910,
	title = {Power Saving Techniques in MBMS Multicast Mode},
	booktitle = {3rd ACM International Workshop on Wireless Multimedia Networking and Performance Modeling - ACM WMUNEP 2007, Chania, Crete, Greece,},
	year = {2007},
	month = {26 October},
	pages = { 62 - 69},
	abstract = {Multimedia Broadcast Multicast Services (MBMS) was
introduced in Third Generation Partnership Project (3GPP)
Release 6 in order to more efficiently use network and radio
resources for the transmission of multimedia services both in the
core network and, most importantly, in the air interface of
UTRAN (UMTS Terrestrial Radio Access Network). From the
radio perspective, MBMS includes point-to-point (PtP) and pointto-
multipoint (PtM) modes. The latter aims to overcome network
congestion when a large number of users request the same
content. One of the most important aspects in MBMS is power
control. The fact that Node B?s transmission power is a limited
resource and must be shared among all MBMS users in a cell
indicates the need for power control during an MBMS service.
Techniques, such us rate splitting and mixed usage of transport
channels can be used to reduce the power requirement of
delivering multicast traffic for MBMS users. To this direction,
this paper presents simulation results that will reinforce the need
for the usage of such techniques and will reveal the amount of
power that is saved.},
	keywords = {MBMS, Power Control, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Vasileios Kokkinos}
}
@article {3072,
	title = {Scalable Rate Control for Video Transmission over UMTS},
	journal = {International Journal of Communication Systems, Wiley InterScience, Vol. 20, Issue 12},
	year = {2007},
	pages = { 1315 - 1131},
	abstract = {This paper proposes a mechanism for the congestion control for video transmission over Universal Mobile
Telecommunications System (UMTS). Our scheme is applied when the mobile user experiences real time
multimedia content and adopts the theory of a widely accepted rate control method in wired networks,
namely equation-based rate control. In this approach, the transmission rate of the multimedia data is
determined as a function of the packet loss rate, the round trip time and the packet size and the server
explicitly adjusts its sending rate as a function of these parameters. Through a number of simulations and
experiments we validate the correctness and measure the performance and efficiency of the mechanism. A
first level of evaluation is carried out using the ns-2 simulator. A second level then validates the proposed
mechanism in real world traffic scenarios by performing experiments in a commercial UMTS network.},
	keywords = {Congestion Control, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Vaggelis Igglesis}
}
@conference {2889,
	title = {Sign Language Interpreters Training},
	booktitle = {10th International Conference on Interactive Computer aided Learning (ICL 2007), Villach, Austria
},
	year = {2007},
	month = {26 - 28 September},
	abstract = {Nowadays, the evolution of technology and the increasing use of computers gave the opportunity for developing new methods of education of deaf individuals and sign language interpreters. The e-learning environments that have been developed for the education of sign language provide web-based courses, designed to effectively teach to anyone the Sign Language. Recognizing the difficulties and barriers of sign language training as well as the importance of sign language interpreters for the community of deaf and hearing impaired, this paper presents the SIGN Learning Partnership, a project for sign language education. The objective of the partnership is to develop a new training method for sign language interpreter?s training together with a curriculum ready for accreditation, based on the outcome of the research in all previous-mentioned areas.},
	author = {Christos Bouras and Eleftheria Giannaka and Eirini Andriakopoulou}
}
@inbook {3126,
	title = {Using Open Source to Building and Accessing Learning Objects and Online Courses},
	booktitle = {Open Source for Knowledge and LearningManagement: Strategies beyond Tools},
	year = {2007},
	pages = { 268 - 298},
	publisher = {IDEA Group Publishing},
	organization = {IDEA Group Publishing},
	abstract = {<p>As e-learning continuously gains the interest of the scientific community, industry, and government, a wide variety of learning technology products have been incorporated into the marketplace. Advances in information and communication technologies are in favor of the incorporation of innovative services and functionalities in such systems, though content creation and delivery remain the two key factors in any e-learning system. Therefore, in this chapter, we present the design and implementation of a tool targeted at building and accessing learning objects and online courses through the Web. This tool aims to facilitate instructors and trainers to easily develop accessible, reusable, and traceable learning content that can meet their distant students? needs for anytime and anyplace learning. Learners are able to access learning content, in addition to consulting, at any time, reports on their interactions within a course and get support by subject experts. Furthermore, all users can request to upgrade their role in the system and, thus, actively participate in the learning process. Special attention has been paid on the utilization of reliable and qualitative open source technologies and Web standards so that the proposed solution can form an easily accessible system.</p>
},
	author = {Christos Bouras and Maria Nani}
}
@article {3069,
	title = {A Web Content Manipulation Technique based on Page Fragmentation},
	journal = {Journal of Network and Computer Applications, Academic Press, Vol. 30, Issue 2},
	year = {2007},
	month = {April},
	pages = { 563 - 585},
	abstract = {Web portals today offer a variety of content and services to their users. This content can be split into various categories and usually content semantically related is placed in the same area. In this paper, a software technique is presented that allows the viewers of web sites to build their own personalized portals, using specific areas of their preferred sites. This technique saves users? time and reduces the cost of browsing the web by minimizing the volume of data that has to be downloaded. It is based on an algorithm, which fragments a web page in discrete fragments using the page?s internal structure. Users utilize a web interface to define which parts of selected web pages they desire to appear in their personalized portal. No additional software needs to be installed on the users? personal computers, since this technique is designed to function centrally as a data source for a Web Server. In addition, usage of this technique reduces user perceived latency during browsing sessions, since less data must be transferred to users? personal computers.},
	author = {Christos Bouras and Ioannis Misedakis and G Kounenis}
}
@conference {2894,
	title = {X3D multi-user virtual environment platform for collaborative spatial design},
	booktitle = {The 9th International Workshop on Multimedia Network Systems and Applications (MNSA-2007), Toronto, Canada},
	year = {2007},
	month = {25 - 29 June},
	abstract = {It is well known that both space and the spatial organization play an important role in our work and learning environments as well as in everyday life. Space is neither innocent nor neutral, it has a performative aspect for whoever inhabits it and it works on its occupants. At the micro level, space prohibits, decides what may occur, lays down the law, implies a certain order, commands and locates bodies. Therefore, there is a definite need for many persons to design their space along with an expert and to preview it in order to test its functionality. Many times there is a need for the inhabitants and workers to collaborate in order to co-design their space from distance.
Multi-user three dimensional virtual environments are a powerful form of collaborative telecommunication applications, enabling the users to share a common three dimensional space and interact with each other as well as with the environment surrounding them, in order to collaboratively solve problems or aid learning processes. This paper presents the work done for extending a multi-user virtual environments platform, called EVE, in order to support collaborative spatial design applications. Furthermore, a usage scenario is presented concerning the collaborative design of a classroom for educational purposes.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Vasileios Triglianos and Ch Tegos}
}
@conference {2891,
	title = {Best Practices Worldwide for Broadband Growth},
	booktitle = {Broadband Europe 2006, Geneva, Switzerland},
	year = {2006},
	month = {11 - 14 December},
	abstract = {This paper investigates and analyses the best practices followed by various countries worldwide for supporting the broadband growth. The methodology used to locate the best practices is based on three main steps: (a) the presentation of the main factors that have a major impact on broadband growth; (b) the definition of what is a {\textquotedblleft}best practice{\textquotedblright} based on quantitative criteria; (c) the calculation of a best practice index and a good practice index, which indicates that a country followed these best or good practices to support its broadband growth respectively. This methodology indicated that Denmark, United States, Japan, Canada and Rep. of Korea followed best practices for their broadband growth, while United Kingdom and the Netherlands followed good practices.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka}
}
@conference {2883,
	title = {Comperative Evaluation of Adaptive Price-based Admission Control Algorithms for Bandwidth Allocation},
	booktitle = {Fifth International Symposium on Communication Systems, Networks and Digital Signal Processing (CSNDSP 2006), Patras, Greece},
	year = {2006},
	month = {19 - 21 July},
	pages = { 339 - 343},
	abstract = {In this paper we analyze the performance
characteristics of various alternatives for the admission
control module of a Bandwidth Broker. In particular, we
study the metrics such as acceptance rate, fairness towards
requests and computation overhead and how they are
affected when comparing a simple admission control module
and an adaptive one. Furthermore, we examine the benefits
that can arise under various circumstances through usage of
adaptive price-based admission control and enhancements
such as the ability to handle the resubmission of previously
rejected requests. We describe the results of our
experimentation using a simulated environment and the
operating circumstances that benefit each solution.
},
	author = {Christos Bouras and Kostas Stamos}
}
@conference {2874,
	title = {A delay - based analytical provisioning model for a QoS - enabled service},
	booktitle = {2006 IEEE International Conference on Communications (ICC 2006), Istanbul, Turkey},
	year = {2006},
	month = {11 - 15 June},
	abstract = {Carefully designed and managed services are essential
for quality-demanding traffic, especially in large-scale IP
networks where the aggregation of flows and the variety of traffic
types are extensive. Although individual mechanisms have been
widely investigated, not much related work exists on integrated
approaches to QoS provisioning that are also feasible to
implement. This work presents a thorough approach to the
design, dimensioning and provisioning of a high priority service
for high-quality demanding traffic over an IP network. Our
approach employs efficient scheduling and a dynamic admission
control scheme while demonstrating novel characteristics in
terms of the quality offered to IP flows.
},
	author = {Christos Bouras and Afroditi Sevasti}
}
@conference {2885,
	title = {Design Aspects of Open Municipal Broadband Networks},
	booktitle = {First International Conference on Access Networks, Athens, Greece},
	year = {2006},
	month = {4 - 6 September},
	abstract = {This paper presents the design principles that cover
the implementation of broadband infrastructure in the
region of Western Greece, by examining all the
necessary parameters that arise while implementing
such a critical developmental project. Furthermore, we
present as a case study, all issues of the designing of
the Metropolitan Area Network of Patras, the third
biggest city of Greece. The major target of the MAN of
Patras is to interconnect the buildings of the public
sector in the city and also deploy fibers that will create
conditions of competition in providing both access and
content services in advantage of the end consumer.
The usage of the broadband infrastructure by service
providers will be based on the open availability of the
fiber optics infrastructure in a cost effective way.
Finally, we present the main characteristics of a
proposed business plan that ensures financial viability
of the broadband infrastructure and guarantees the
administration, growth, and exploitation of
infrastructure.
},
	author = {Christos Bouras and Dimitris Primpas and Antonios Alexiou}
}
@conference {2880,
	title = {Distribution and Partitioning Techniques for NVEs: the case of EVE},
	booktitle = {Challenges of Large Applications in Distributed Environments, Paris, France},
	year = {2006},
	month = {19 June},
	pages = {73-82},
	abstract = {The majority of the systems and platforms developed
for supporting Distributed Virtual Environments are based on the
concept of distribution from the early beginning of their
development. In this paper we present the migration to a
distributed virtual environment from a traditional client-server
architecture. In particular, this paper describes the case of EVE,
a Networked Virtual Environment originally aimed to support
small-scale applications. EVE started as a standard client-multi
server architecture, which could support multiple concurrent
virtual worlds with a maximum number of seventeen
simultaneous participants in each of these worlds. However, the
need to support larger-scale applications revealed that the
traditional architecture, upon which EVE was based, is
insufficient to meet the needs of these applications, which are
large both in the sense of virtual space and graphics and in regard
to the number of concurrent participants. This paper discusses
the migration of EVE to a distributed platform, which will be
able to support large-scale networked virtual environments. In
particular, the paper describes the modifications realized in the
architectural model of the initial platform for supporting
effectively large-scale applications. The basic entities of the
distributed model are presented, their operations, as well as the
interconnection among them. In addition, the paper presents an
initial approach of the algorithm that will be adopted for the
efficient partitioning of the virtual world and the assignment of
the clients to the entities and resources of the distributed
platform. The approach presented is space-object driven, in the
sense that both the actual size of the virtual space along with the
number of objects with which the user can interact is taken into
account during the partitioning.
},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka and Alexandros Panagopoulos}
}
@article {3025,
	title = {Educational Virtual Environments: Design Rationale and Architecture},
	journal = {Multimedia Tools and Applications, Kluwer Academic Publishers},
	year = {2006},
	month = {June},
	pages = {Vol. 29, No. 2,  153 - 173},
	abstract = {The use of collaborative virtual environments in e-learning is one of the
most promising uses of virtual reality technology. While much research has been
done in the area of networked virtual environments corresponding to the sharing of
events, very little research has been done on specific services and functionality.
However both the requirements and the kind of the offered services affect significantly
the design of a system. In this paper we present the design and implementation
of a platform suitable for educational virtual environments, which are
collaborative virtual environments aiming at offering collaborative e-learning services
to the users. Apart from the platform itself, we present the technological
choices, and a new method for sharing virtual environments. Furthermore, we
present an e-learning environment to support e-learning services using collaborative
virtual environments from both the technical and functional point of view, along
with the end-user evaluation results.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos}
}
@conference {2887,
	title = {An Efficient Multicast Packet Delivery Scheme for UMTS},
	booktitle = {9th ACM International Symposium on Modeling, Analysis and Simulation of Wireless and Mobile Systems (MSWiM 2006), Torremolinos, Spain},
	year = {2006},
	month = {2-6 October},
	abstract = {In this paper we present an efficient scheme for the multicast transmission of the data in the Universal Mobile Telecommunications System (UMTS). We take advantage of the tree topology of the examined network and we introduce the use of Routing Lists (RLs) in the nodes of the UMTS. The adoption of these lists leads to the decrement of the transmitted packets and the efficient use of network resources during the multicast transmission of the data. We describe in detail the necessary steps for the successful multicast transfer of data. Furthermore, we analyze the handling of special cases such as user mobility scenarios. Especially, the various handover types are examined along with the Serving Radio Network Subsystem (SRNS) relocation procedure},
	keywords = {MBMS, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Dimitrios Antonellis and Andreas Papazois}
}
@article {3033,
	title = {Enhancing a Web Based Community: the case of SIG-GLUE},
	journal = { International Journal of Web Based Communities (IJWBC), Inderscience Publishers, Vol. 2, No 1},
	year = {2006},
	pages = { 112 - 130},
	abstract = {The expansion of the web has reached outrageous proportions with
the number of web communities existing and the number of those being created
daily increasing dramatically. To parallel this phenomenon is the trend
nowadays of mobile phone services. One of the most representative is the case
of Greece, where in a period of five years about five million people subscribed
for a telephone number for mobile devices. The communities are not static any
more. The philosophy is: a universal community has to be mobile. This paper
analysed the expansion of the community of SIG-GLUE in order to support
mobile users with any necessary web service.},
	author = {Christos Bouras and Vaggelis Kapoulas and Vassilis Poulopoulos and Ioannis Antonellis}
}
@conference {2873,
	title = {Equation Based Congestion Control for Video Transmission over WCDMA Networks},
	booktitle = {The IEEE 20th International Conference on Advanced Information Networking and Applications, Vienna, Austria},
	year = {2006},
	month = {18 - 20 April},
	pages = { 445 - 450},
	abstract = {   The scheme of real time streaming video is one of
the newcomers in wireless data communication,
raising a number of new requirements in both
telecommunication and data communication systems.
This scheme is applied when the user experiences real
time multimedia content. Rate control is an important
issue in video streaming applications for both wired
and wireless networks. A widely accepted rate control
method in wired networks is equation based rate
control. In this work, we focus on a mechanism for
equation based congestion control for video
transmission over WCDMA networks. With our
mechanism, the sender explicitly adjusts its sending
rate as a function of the measured rate of loss events,
the round trip time and the packet size. Furthermore,
we examine the performance of UMTS air interface for
real time video transmission using real time protocols,
through a number of experiments.
},
	keywords = {Congestion Control, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Dimitrios Antonellis}
}
@conference {2881,
	title = {Evaluating Admission Control Modules for Bandwidth Brokers in DiffServ Networks Using ns - 2},
	booktitle = {13th International Conference on Telecommunications, Madeira Island, Portugal},
	year = {2006},
	month = {9 - 12 May},
	abstract = {In this paper we use the well known network
simulator ns-2 in order to study the performance
characteristics of various alternatives for the admission
control module of a Bandwidth Broker. In particular, we
present the modifications that have to be made at the ns-2
architecture in order to simulate these architectures, the
metrics such as acceptance rate, fairness towards requests
and computation overhead and how they are affected
when comparing a simple admission control module and
more sophisticated ones. Furthermore, we examine the
benefits that can arise under various circumstances
through usage of enhancements such as the ability to
handle the resubmission of previously rejected requests.
},
	author = {Christos Bouras and Kostas Stamos}
}
@conference {2878,
	title = {Evaluating Different One to Many Packet Delivery Schemes for UMTS},
	booktitle = {7th IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks - WoWMoM 2006, Niagara - Falls/Buffalo, New York, USA},
	year = {2006},
	month = {26 - 29 June},
	pages = { 66-72},
	abstract = {It is known that multicasting is an efficient method
of supporting group communication as it allows the
transmission of packets to multiple destinations using
fewer network resources. Thus, service providers are
increasingly interested in supporting multicast
communications over wireless networks and in
particular over UMTS. Multicasting is a more efficient
method of supporting group communication than
unicasting or broadcasting, as it allows transmission
and routing of packets to multiple destinations using
fewer network resources. In this paper the three above
mentioned      methods     of     supporting      group
communication are analyzed in terms of their
performance.},
	keywords = {MBMS, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Dimitrios Antonellis}
}
@article {3022,
	title = {Implementation of 3D Mesh Streaming and Compression Techniques in NVEs},
	journal = {Computer Animation and Virtual Worlds Journal, Wiley InterScience, Vol. 17, Issue 2},
	year = {2006},
	pages = { 127 - 140},
	abstract = {<p>In this paper, we present a framework that integrates three-dimensional (3D) mesh streaming and compression techniques and algorithms into our EVE-II Networked Virtual Environments platform, in order to offer support for large-scale environments as well as highly complex world geometry. This framework allows the partial and progressive transmission of 3D worlds as well as of separate meshes, achieving reduced waiting times for the end-user and improved network utilization. We also present a 3D mesh compression method focused on network communication, which is designed to support progressive mesh transmission, offering a fast and effective means of reducing the storage and transmission needs for geometrical data. This method is integrated in the above framework and utilizes prediction to achieve efficient lossy compression of 3D geometry.</p>
},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Alexandros Panagopoulos}
}
@conference {2882,
	title = {The importance of the difference in text types to keyword extraction: Evaluating a mechanism},
	booktitle = {7th International Conference on Internet Computing 2006 (ICOMP 2006), Las Vegas, Nevada, USA},
	year = {2006},
	month = {26 - 29 June},
	pages = { 43 - 49},
	abstract = {Information exists in every aspect of our life. The expansion of the web has helped to this direction. The web
feeds us with enormous information and the widespread use of computers and other hardware appliances has lead us to a
state where we have a lot of information in our hands, but many times it is useless. People are not able to find information
that they really need but already own. How many times have you tried to find a specific article that you have, or a specific
mail that you received, or even an SMS from someone saying something specific. For this reason many information
retrieval techniques have been proposed and many information extraction mechanisms have been created. In this paper we
will provide the experimental evaluation of a keyword extraction mechanism and how we treat different types of text (news
articles, publications, e-mails). This keyword extraction mechanism is a part of a complete system that includes information
retrieval, information extraction, categorization and publication of information to a personalized portal.
},
	author = {Christos Bouras and Vassilis Poulopoulos and Charis Dimitriou and Vassilis Tsogkas}
}
@inbook {3122,
	title = {An Integrated Platform for Educational Virtual Environments},
	booktitle = {Web-Based Intelligent  e - Learning Systems: Technologies and Applications},
	year = {2006},
	pages = { 291 - 320},
	publisher = {IDEA Group Publishing},
	organization = {IDEA Group Publishing},
	chapter = {XV},
	abstract = {<p>In this chapter, we present the design and implementation of an integrated platform for Educational Virtual Environments. This platform aims to support an educational community, synchronous online courses in multi-user three-dimensional (3D) environments, and the creation and access of asynchronous courses through a learning content management system. In order to offer synchronous courses, we have implemented a system called EVE-II, which supports stable event sharing for multi-user 3D places, easy creation of multi-user 3D places, H.323-based voice- over IP services fully integrated in a 3D space, as well as many concurrent 3D multi-user spaces.</p>
},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka and Alexandros Panagopoulos and Maria Nani}
}
@conference {2879,
	title = {Investigating Bandwidth Broker{\textquoteright}s inter-domain operation for dynamic and automatic end to end provisioning},
	booktitle = {Sixth International Network Conference, Plymouth, UK},
	year = {2006},
	month = {11 - 14 July},
	pages = {61-69},
	abstract = {This paper deals with a distributed bandwidth broker that we try to extend in order to perform inter-domain
operation. The basic issues for inter-domain operation are discussed and we try to approach the most demanding
issues as the selection of the best inter domain routing path. Generally, we discuss three models for inter domain
routing through bandwidth broker, analyzing their advantages. Also, a very important point that affects the inter-
domain operation is the SLAs between adjacent domains and the capability that a bandwidth broker should have
to ask and perform dynamic negotiation. Finally, we analyze the best model and present how it should be
incorporated in the existing distributed implementation.
},
	author = {Christos Bouras and Dimitris Primpas}
}
@article {3024,
	title = {IPv6 Deployment: Real Time Applications and QoS Aspects},
	journal = {Computer Communications Journal, Elsevier Science},
	year = {2006},
	pages = {Vol. 29, No. 9,  1393 - 1401},
	abstract = {This paper gives an overview of the issues related to the QoS mechanisms under IPv6 and the transition of applications to the new Internet protocol. We describe the implementation and testing of a QoS service on IPv6 networks, which is based on the DiffServ architecture (expedited forwarding) and provides strict priorities to packets that are produced from real time applications. The service was implemented and tested at the 6NET large-scale IPv6 network, and additional advanced testing was performed in a local testbed. We present and analyze the results from our tests under a number of different scenarios. In addition, we focus on issues regarding application transition to IPv6 and we briefly discuss as a case study the transition of OpenH323 protocol stack to support IPv6. We also discuss the usage and the expected impact of the new Flow Label field in the IPv6 header.},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos and Dimitris Primpas}
}
@conference {2890,
	title = {IPv6 QoS Testing on Dual Stack Networks},
	booktitle = {The Second International Workshop on Advanced Architectures and Algorithms for Internet Delivery and Applications (AAA-IDEA 2006), Pisa, Italy},
	year = {2006},
	month = {10 October},
	abstract = {This paper presents our work regarding the testing
and evaluation of DiffServ QoS mechanisms over IPv6
and IPv4 in dual stack software based platforms. IPv6
introduces some additional features (like flow label)
and the current support for QoS mechanisms in IPv6
implementations approaches the corresponding QoS
support in IPv4. Therefore, a number of tests with
DiffServ QoS mechanisms applied on IPv6 traffic have
been carried out on a testbed created specifically for
this purpose, in order to validate the mechanisms and
evaluate the router?s overall performance. Our
evaluations cover the load incurred to the routing
devices from the implementation of the mechanisms,
the level of support for QoS IPv6 features and the
comparison of performance over IPv4 and IPv6.},
	author = {Christos Bouras and Kostas Stamos and Dimitris Primpas}
}
@book {3154,
	title = {IPv6: The protocol, transition and porting mechanisms},
	series = {Ellinika Grammata},
	year = {2006},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos and Dimitris Primpas and A Karaliotas and Petros Ganos}
}
@conference {2877,
	title = {A Multicast Approach for UMTS: A Performance Study},
	booktitle = {2006 IFIP Networking Conference, Coimbra, Portugal},
	year = {2006},
	month = {15 - 19 May},
	pages = { 1086-1091},
	abstract = {In this paper, a multicast scheme for UMTS which only requires in-
significant modifications in the current UMTS network infrastructure is ana-
lyzed. We analytically present the multicast routing mechanism behind our
scheme as well as the multicast group management functionality of it. Further-
more, we present an evaluation of our scheme in terms of its performance. The
critical parameters for the evaluation of the scheme are the number of multicast
users within the multicast group, the amount of data sent to the multicast users,
the density of the multicast users within the cells and the type of transport
channel used for the transmission of the multicast data over the air.},
	keywords = {MBMS, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Dimitrios Antonellis}
}
@conference {2888,
	title = {A Multicast Packet Forwarding Mechanism for WCDMA Networks using Routing Lists},
	booktitle = {2nd  ACM Workshop on Wireless Multimedia Networking and Performance Modeling, (ACM WMuNeP 2006), MSWiM 2006 Workshops, Torremolinos, Malaga, Spain},
	year = {2006},
	month = {6 October},
	pages = { 27 - 34},
	abstract = {This paper proposes a multicast scheme for the packet forwarding mechanism in the Universal Mobile Telecommunications System (UMTS). This scheme relies on the introduction of the Permanent Multicast Routing List (PMRL) and Temporary Multicast Routing List (TMRL) in each node of the network except UEs. In the PMRL we record the nodes of the next level that the messages for every multicast group should be forwarded. The TMRL is useful for the temporary record of information from the path from the mobile users to the GGSN. Additionally, a Multicast Group List (MGL) is kept in the GGSN which records the members of each multicast group. These lists lead to the decrement of the transmitted packets and the more efficient use of the network resources in the multicast routing in UMTS. We analyze the exact steps that the multicast packets are transmitted to the members of each multicast group. Furthermore, special issues such as joining/leaving a multicast service are described. Our simulation results show that the proposed mechanism for the multicast packet forwarding in UMTS performs efficiently.},
	keywords = {MBMS, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Dimitrios Antonellis}
}
@conference {2886,
	title = {Pathfinding architectures for interdomain Bandwidth Broker operation},
	booktitle = {14th IEEE International Conference on Networks, Singapore},
	year = {2006},
	month = {13 - 15 September},
	pages = { 21 - 26},
	abstract = {This paper deals with bandwidth brokers and their
inter-domain operation. The basic issues for inter-domain operation are discussed and we try to approach the most demanding issues as the selection of the best inter domain routing path (pathfinding). Generally, we discuss two models for inter domain routing through bandwidth broker, analyzing their advantages and comparing them. Also, we simulated the second one (generalized distributed pathfinding) trying to evaluate its performance. Finally, we discuss the simulation?s results and present how this model should be incorporated in normal operation routing of commercial ISPs or academic networks that works on a federated way.},
	author = {Christos Bouras and Dimitris Primpas}
}
@conference {2871,
	title = {Personalized News Categorization through Scalable Text Classification},
	booktitle = {The Eight Asia Pacific Web Conference (APWeb {\textendash} 06), Harbin, China},
	year = {2006},
	month = {16 - 18 January},
	pages = { 391 - 401},
	abstract = {Existing news portals on the WWW aim to provide users with numerous articles that are categorized into specific topics. Such a categorization procedure improves presentation of the information to the end-user. We further improve usability of these systems by presenting the architecture of a personalized news classification system that exploits user?s awareness of a topic in order to classify the articles in a ?per-user? manner. The system?s classification procedure bases upon a new text analysis and classification technique that represents documents using the vector space representation of their sentences. Traditional ?term-to-documents? matrix is replaced by a ?term-to-sentences? matrix that permits capturing more topic concepts of every document.},
	author = {Christos Bouras and Vassilis Poulopoulos and Ioannis Antonellis}
}
@article {3023,
	title = {A Platform for Virtual Collaboration Spaces and Educational Communities: The case of EVE},
	journal = {Multimedia Systems Journal, Special Issue on Multimedia System Technologies for Educational Tools, Springer Verlang},
	year = {2006},
	pages = {Vol. 11, No. 3,  290 - 303},
	abstract = {<p>This paper presents the design, implementation and evaluation of EVE Community Prototype, which is an educational virtual community aiming to meet the requirements of a Virtual Collaboration Space and to support e-learning services. Furthermore, this paper describes the design and implementation of an integrated platform for Networked Virtual Environments, called EVE Platform, which supports the afore-mentioned educational community. This platform supports stable event sharing and creation of multi-user three dimensional (3D) places, H.323-based voice over IP services integrated in 3D spaces as well as multiple concurrent virtual worlds.</p>
},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka and Alexandros Panagopoulos}
}
@conference {2872,
	title = {Resubmissions and Partly Defined Requests in an Adaptive Admission Control Algorithm for Bandwidth Brokers},
	booktitle = {5th International Conference on Networking ICN06, Mauritius},
	year = {2006},
	month = {23 - 27 April},
	abstract = {The purpose of this paper is to examine the issues
related to the efficiency and adaptability of the
admission control module of a Bandwidth Broker. The
proposed architecture is able to handle situations such
as the resubmission of previously rejected requests and
offer a fair treatment for requests in an environment
where a subset of these requests do not specify their
ending time. We describe the proposed mechanisms for
such cases which aim at solving the additional
problems of fairly prioritizing resubmitted requests
and efficiently handle requests which do not specify
ending times. We also provide experimental
evaluations of the proposed algorithms and the
conclusions they lead us to.},
	author = {Christos Bouras and Kostas Stamos}
}
@conference {2875,
	title = {Scalability of text classification},
	booktitle = {2nd International Conference on Web Information
Systems and Technologies (WEBIST 2006), Setubal, Portugal},
	year = {2006},
	month = {19 - 22 April},
	pages = { 408 - 413},
	abstract = {We explore scalability issues of the text classification problem where using (multi)labeled training
documents we try to build classifiers that assign documents into classes permitting classification in multiple
classes. A new class of classification problems, called ?scalable? is introduced that models many problems
from the area of Web mining. The property of scalability is defined as the ability of a classifier to adjust
classification results on a ?per-user? basis. Furthermore, we investigate on different ways to interpret
personalization of classification results by analyzing well known text datasets and exploring existent
classifiers. We present solutions for the scalable classification problem based on standard classification
techniques and present an algorithm that relies on the semantic analysis using document decomposition into
its sentences. Experimental results concerning the scalability property and the performance of these
algorithms are provided using the 20newsgroup dataset and a dataset consisting of web news.
},
	author = {Christos Bouras and Vassilis Poulopoulos and Ioannis Antonellis and Anastasios Zouzias}
}
@conference {2884,
	title = {Supporting Group Communication in WCDMA Networks},
	booktitle = {11th IFIP International Conference on Personal Wireless Communications (PWC {\textquoteright}06), Albacete, Spain},
	year = {2006},
	month = {20 - 22 September},
	pages = { 13 - 24},
	abstract = {It is known that multicast is an efficient method of supporting group communication as it allows the transmission of the packets to multiple destinations using fewer network resources. Along with the widespread deployment of the third generation cellular networks and the fast-improving capabilities of the mobile devices, content and service providers are increasingly interested in supporting multicast communications over wireless networks and in particular over Universal Mobile Telecommunications System (UMTS). In this paper, a multicast scheme for UMTS is analyzed. We analytically present the multicast routing mechanism behind our scheme as well as the multicast group management functionality of the scheme. Furthermore, we present an evaluation of our scheme in terms of its performance. The critical parameters for the evaluation of the scheme are the number of users within the multicast group, the amount of data sent to the multicast users, the density of the multicast users within the cells and finally the type of transport channel used for the transmission of the multicast data over the air.},
	keywords = {MBMS, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Dimitrios Antonellis}
}
@conference {2876,
	title = {Using the ns-2 simulation environment to implement and evaluate Bandwidth Broker models},
	booktitle = { 2nd Conference on Next Generation Internet Design and Engineering (NGI 2006), Valencia},
	year = {2006},
	month = {3 - 5 April},
	pages = { 285 - 291},
	abstract = {In this paper we present and compare four different
models of implementing a Bandwidth Broker in a DiffServ
network. We describe the relevant implementation aspects in the
well-known ns-2 simulator and present a number of experiments
that were conducted in order to verify our implementation,
analyze the performance characteristics of the various
alternatives and evaluate the usefulness of the ns-2 simulation
environment for similar purposes. We present our experiments
that aim at investigating a number of issues related to the
operation of Bandwidth Broker modules, and in particular how
the acceptance rate, the network overhead and the response time
for each Bandwidth Broker model are affected by the network
topology, the available buffers for incoming requests and the
advance time from the moment a request is submitted to the
moment the reservation should take place.
},
	author = {Christos Bouras and Kostas Stamos and Dimitris Primpas and Ioannis Pappas}
}
@conference {2711,
	title = {An admission control and deployment optimization algorithm for an implemented distributed Bandwidth Broker in a simulation environment},
	booktitle = {4th International Conference on Networking {\textendash} ICN 2005, Reunion Island, France},
	year = {2005},
	month = {17 - 21 April},
	pages = { 766 - 773},
	abstract = {This paper describes and tests a distributed bandwidth broker that has
been implemented in NS simulator. It focuses on the admission control
algorithm, its advantages and drawbacks. Also, the bandwidth broker is tested,
managing the IP Premium service and we compare 2 different implementations
of the service. Finally it approaches the problem of the optimal location of a
bandwidth broker in a backbone network. For this purpose, a new model is
proposed that evaluates each node and finally selects the most capable node
where the base bandwidth broker should be located.},
	author = {Christos Bouras and Dimitris Primpas}
}
@conference {2863,
	title = {Advances in X3D multi - user virtual environments},
	booktitle = {IEEE International Symposium on Multimedia (ISM 2005), Irvine, California, USA},
	year = {2005},
	month = {12 - 14 December},
	pages = { 136 - 142},
	abstract = {This paper presents the current state of the art in web3d multi-user technologies and more specifically networked virtual environment platforms that support the X3D standard, which are currently limited in number, and also the existing X3D browsers that enable these applications. Furthermore, this paper presents the architecture of a platform, called EVE, which was developed to support multi-user virtual environments and was initially based on VRML, as well as the implementation regarding the process of upgrading this platform in order to fully support the X3D standard, using the open-source Xj3D library. Finally, the benefits of shifting to the X3D standard are presented, and some of the problems that currently exist are discussed.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Alexandros Panagopoulos}
}
@article {3030,
	title = {Application on Demand System over the Internet},
	journal = {Journal of Network and Computer Applications, Academic Press, Vol. 28, No. 3},
	year = {2005},
	month = {August},
	pages = { 209 - 232},
	abstract = {This paper describes the design and implementation of the ASP-NG system. The main modules of
the ASP-NG system are the AoD service and the Web Portal. The ASP-NG Portal is a portal for
providing the user with the necessary interface in order to access an Application on Demand (AoD)
service. The ASP-NG portal is responsible for the interaction with the user of the AoD service. Using
the AoD service the user rents an application for a limited time period at a fraction of the actual cost of
the application. The AoD service is responsible for downloading the appropriate parts of the
application according to the user{\textquoteright}s actions, while enforcing the mutually agreed frame between the
user and the Application Service Provider (ASP). The implementation of the ASP-NG portal is based
on the Web Services of the Java 2, Enterprise Edition platform and the implementation of the AoD
module is based onCCCprogramming language. The ASP-NG portal offers to its users the capability
to select and customize the language of the user interface in order to present information in their
preferred language. Moreover the ASP-NG portal offers to the portal administrator the capability to
customise the look and feel of the ASP-NG portal.},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos and Dimitris Primpas and I Nave and A Shani and O Sheory and Y Tzruya}
}
@article {3027,
	title = {Architecture and Performance Evaluation for Redundant Multicast Transmission Supporting Adaptive QoS},
	journal = {Tools and Applications, Kluwer Academic Publishers, Vol. 25, No. 1},
	year = {2005},
	month = {January},
	pages = { 85 - 110},
	abstract = {<p>In this paper we describe the architecture of an application that was developed for the transmission of multimedia data, using the multicast mechanism, over the Internet. There are two major issues that have to be considered when designing and implementing such a service, the fairness and the adaptation schemes. The fairness problem results from the fact that Clients with different capabilities have to be served. In our application we use a mechanism that categorizes the Clients into a number of groups according to each Client{\textquoteright}s capabilities and (the mechanism) serves each group of Clients with a different multicast stream. With the term {\textquotedblleft}capabilities{\textquotedblright} we do not only mean the processing power of the Client, but also the capacity and the condition of the network path towards that Client. Because of today{\textquoteright}s Internet heterogeneity and the lack of Quality of Service (QoS) support, the Server cannot assume that the Clients will permanently be able to handle a specific bit rate.We have therefore implemented an additional mechanism for the intra-stream bit rate adaptation. The proposed mechanism uses a {\textquotedblleft}friendly{\textquotedblright} to the network users congestion control policy to control the transmission of the data. We evaluate the adaptive multicast transmission mechanism through a number of experiments and a number of simulations in order to examine its behaviour to a heterogeneous group of Clients and its behaviour against TCP and UDP data streams.</p>
},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos and A Karaliotas}
}
@conference {2870,
	title = {The Broadband Status in the Region of Western Greece: Overview and Recommendations},
	booktitle = {Broadband Europe 2005, Bordeaux, France},
	year = {2005},
	month = {12 - 14 December},
	abstract = {This paper presents a study conducted in the Region of Western Greece, in order to propose an overall planning for the development of broadband infrastructure in the Region of Western Greece. The current broadband status in the region is being described, while the results of a survey on broadband usage and demand are being presented.
The paper proposes some Recommendations that should be adopted in the region of Western Greece in order for the appropriate broadband infrastructures to be developed and adopted so as to contribute to economic growth and to tackle any possible cases of {\textquotedblleft}digital gap{\textquotedblright} between the citizens of our country.},
	author = {Christos Bouras and Vaggelis Kapoulas and Thrasivoulos Tsiatsos and Antonios Alexiou and Vaggelis Igglesis and Mixalis Paraskevas and J Papagiannopoulos}
}
@conference {2865,
	title = {Creating a Polite Adaptive and Selective Incremental Crawler},
	booktitle = {IADIS International Conference WWW/INTERNET 2005, Lisbon, Portugal, Volume I},
	year = {2005},
	month = {19 - 22 October},
	pages = { 307 - 314},
	abstract = {The expansion of the World Wide Web has led to a chaotic state where the users of the internet have to face and overcome the major problem of discovering information. For the solution of this problem, many mechanisms were created based on crawlers who are browsing the www and downloading pages. In this paper we will describe a crawling mechanism which is created in order to support data mining and processing systems and to obtain a history of the web{\textquoteright}s content. A crawler has to be efficient and polite, trying not to harm or overload the pages it is visiting. Therefore, it is extremely important to follow specific rules when crawling. In addition to these rules, the mechanism we created includes a selective incremental algorithm, which is used to make the crawler more efficient and more polite in parallel. The structure and design of the mechanism is simple, but the experimental results showed us that this simplicity makes our crawler a very strong and stable mechanism.},
	author = {Christos Bouras and Vassilis Poulopoulos and A Thanou}
}
@conference {2707,
	title = {A Decision Feedback Scheme for Multimedia Transmission Over 3G Mobile Networks},
	booktitle = {The Second IEEE and IFIP International Conference on Wireless and Optical Communications Networks (WOCN 2005), Dubai, United Arab Emirates - UAE},
	year = {2005},
	month = {6 - 9 March},
	pages = { 357 - 361},
	abstract = {UMTS, the successor of GSM, is evolving toward a
future wireless all-IP network. In this paper we present how it
supports real-time IP multimedia services, as these services are
expected to drive the adoption of wireless all-IP networks. The
scheme of real time streaming video is one of the newcomers in
wireless data communication and in particular in UMTS, raising
a number of novel requirements in both telecommunication and
data communication systems. This scheme applies when the
mobile user is experiencing real time multimedia content. In this
paper, we describe the design and the implementation of a
decision feedback scheme, which is based on real time protocols
and it is used for streaming video over UMTS transport
channels. The decision feedback scheme uses a friendly, to the
mobile users, congestion control mechanism to control the
transmission rate of the real time video sequence. Furthermore,
we evaluate this mechanism through a number of experiments.
During these experiments we demonstrate the friendly behavior
of the decision feedback scheme to TCP and UDP data streams
that coexist in the same channel with the video sequence.},
	keywords = {MBMS, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Vaggelis Igglesis}
}
@conference {2864,
	title = {Deployment of Broadband Infrastructure in the Region of Western Greece},
	booktitle = {2nd IEEE/Create - net International Workshop on Deployment Models and First/Last Mile Networking, Boston, MA, USA},
	year = {2005},
	month = {7 October},
	pages = { 588 - 593},
	abstract = {This paper presents the work that is taking place in the Region of Western Greece in order to develop state-of-the-art broadband infrastructure. The current status of broadband infrastructure in the region is being analyzed and the main principles on which the deployment of the networks will be based on is being described, by presenting the Metropolitan Area Networks and the Wireless access networks that will be developed. Two case studies of such municipal networks are also presented in this paper.},
	author = {Christos Bouras and Vaggelis Kapoulas and Antonios Alexiou and Vaggelis Igglesis and Mixalis Paraskevas and I Scopoulis and J Papagiannopoulos}
}
@conference {2710,
	title = {Design and Implementation of a Game Based Learning Related Community},
	booktitle = {IADIS International Conference, Web Based Communities 2005, Algarve, Portugal},
	year = {2005},
	month = {23 - 25 February},
	pages = { 215 - 222},
	abstract = {A web-based community aims at providing communication and collaboration tools to a special interest group. This paper describes the functionality and architecture issues of a community which aims to bring together users who are interested in the field of game based learning and lifelong learning. The architecture and implementation issues of the platform developed are analyzed and their exact use is explained. More specifically the members of the community are provided with tools in order to share their knowledge and experience in game based learning through enhanced forums and chats, to read news or receive a newsletter concerning the aforementioned issue, arrange meetings, and make use of shared spaces. All these services are enhanced in order to meet the needs of this special interest group which is unique as it includes the collaboration of game developers, pedagogues and simple users. Furthermore, we describe a methodology to build a fully functional community with tools for communication and collaboration starting from a simple template and using core content management techniques.},
	author = {Christos Bouras and Vaggelis Kapoulas and Vassilis Poulopoulos and Ioannis Antonellis}
}
@conference {2705,
	title = {Designing Virtual Spaces to Support Learning Communities and e - Collaboration},
	booktitle = {5th IEEE International Conference on Advanced Learning Technologies, Koahsiung, Taiwan},
	year = {2005},
	month = {5 - 8 July},
	pages = { 328 - 332},
	abstract = {In this paper, we present the design principles for
virtual spaces and two different tools as solutions for
supporting e-collaboration and multi-user
communication in web-based learning communities.
The first solution, called Virtual Conference, is
designed and implemented in the framework of the
VirRAD European project. It is a two-dimensional
space where participants represented by their photos
can use various e-collaboration tools. The second
solution, called EVE Training Area, is a threedimensional
space where participants, represented by
3D humanoid avatars, can use a variety of ecollaboration
tools. This paper describes the
functionality provided by both tools, compares them,
and proposes cases for exploiting each solution.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka}
}
@article {3029,
	title = {Estimating and Eliminating Redundant Data Transfers Over the Web: A Fragment Based Approach},
	journal = {International Journal of Communication Systems, Wiley InterScience, Vol. 18, Issue 2},
	year = {2005},
	month = {March},
	pages = { 119- 142},
	abstract = {<p>Redundant data transfers over the Web, can be mainly attributed to the repeated transfers of unchanged data. Web caches and Web proxies are some of the solutions that have been proposed, to deal with the issue of redundant data transfers. In this paper we focus on the efficient estimation and reduction of redundant data transfers over the Web. We first prove that a vast amount of redundant data is transferred in Web pages that are considered to carry fresh data. We show this by following an approach based on Web page fragmentation and manipulation. Web pages are broken down to fragments, based on specific criteria. We then deal with these fragments as independent constructors of the Web page and study their change patterns independently and in the context of the whole Web page. After the fragmentation process, we propose solutions for dealing with redundant data transfers. This paper has been based on our previous work on {\textquoteleft}Web Components{\textquoteright} but also on related work by other researchers. It utilises a proxy based, client/ server architecture, and imposes changes to the algorithms executed on the Proxy server and on clients. We show that our proposed solution can considerably reduce the amount of redundant data transferred on the Web.</p>
},
	author = {Christos Bouras and Agis Konidaris}
}
@conference {2714,
	title = {Examining the Benefits of a Hybrid Distributed Architecture for Bandwidth Brokers},
	booktitle = {1st IEEE International Workshop on Multimedia Systems and Networking (WMSN 2005), Phoenix, Arizona, USA},
	year = {2005},
	month = {7 - 9 April},
	pages = { 491 - 498},
	abstract = {In this paper the issue of the architectural organization of a Bandwidth Broker with respect to the distribution of functionalities among separate entities is examined. We discuss the benefits of a distributed versus a centralized architecture and study some of the most important implementations. We also present a novel design proposal that builds on our earlier work on the admission control module of a Bandwidth Broker and introduces it in the framework of a distributed Bandwidth Broker architecture. Our conclusions are supported by a series of simulated experiments that we analyze.},
	author = {Christos Bouras and Kostas Stamos}
}
@conference {2712,
	title = {Fast IP handoff support for VoIP and multimedia applications in 802.11 WLANs},
	booktitle = {IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks - WoWMoM 2005, Taormina, Italy},
	year = {2005},
	month = {13 - 16 June},
	pages = { 332 - 337},
	abstract = {Wireless LANs (WLANs) have edged into numerous mobile and wireless users{\textquoteright} daily experience worldwide as a mainstream connectivity solution for a broad range of applications. Even though WLANs offer very high channel bandwidth, they show long network-layer handoff latency. This is a restraining factor for mobile clients using interactive multimedia applications such as voice over IP (VoIP) or video streaming. This paper presents an 802.11-dependent fast IP handoff method which quickly restores IP connectivity for mobile clients running next generation WLAN applications such as Voice over WLANs (VoWLAN). This method outperforms other existing proposed IP mobility solutions in 802.11 WLANs as verified from real performance testing, while introduces insignificant compulsory additions to the existing 802.11 wireless LAN framework.},
	author = {Christos Bouras and Ioanna Sampraku and T Karoubalis}
}
@conference {2701,
	title = {Game Based learning for Mobile Users},
	booktitle = {The 6th International GAME - ON Conference on the theme: Computer Games: AI and Mobile Users, Louisville, Kentucky, USA},
	year = {2005},
	month = {27 - 30 July},
	abstract = {Game based learning has been studied as an important alternative or supplement to traditional teaching. Existing web based platforms that utilize the power of the Internet in order to provide efficient access to information regarding computer learning games aim to create online communities. However, such attempts target only on traditional Internet users, excluding an ongoing population of people that access World Wide Web using mobile devices. In this paper, the restrictions of web browsing using personal digital assistants (PDAs) or smart mobile phones are considered and a methodology for the expansion of a preexisting community for game based learning in universities and lifelong is described in order to also attract mobile users. New, device-specific services are deployed so as to take advantage of game based learning opportunities that mobile phones offer and structural as well as design changes are described in order to fulfill requirements of web browsing using small screen devices.},
	author = {Christos Bouras and Vassilis Poulopoulos and Ioannis Antonellis}
}
@conference {2704,
	title = {The Grid Framework as a Suitable Infrastructure for Supporting Large - Scale Desktop Networked Virtual Environments},
	booktitle = {The 2005 International Conference on Grid Computing and Applications (GCA 05), Las Vegas, Nevada, USA},
	year = {2005},
	month = {20 - 23 June},
	pages = { 76 - 82},
	abstract = {The maturation of the Internet, the familiarization of the users with this powerful means of communication and mainly the increment of the available bandwidth, which is presented the last few years, led to the idea of extending small scale virtual environments to larger applications that could support a tremendous number of concurrent users. However, the introduction of Large Scale Virtual Environments brings along a series of problems that are mainly related to the serious increment of the transmitted information. Neither the traditional architectures, algorithms originally designed for the NVEs, nor the improvement of the network seem sufficient to support this new kind of applications. A solution to this problem seems to be the adoption of the GRID. In this paper we present an approach, which describes the way that a Desktop Networked Virtual Environment could be efficiently supported and maintained under a GRID infrastructure.},
	author = {Christos Bouras and Eleftheria Giannaka}
}
@conference {2700,
	title = {A host selection model for a distributed bandwidth broker},
	booktitle = {Third International Working Conference on Performance Modelling and Evaluation of Heterogeneous Networks, Ilkley, West Yorkshire, UK},
	year = {2005},
	month = {18 - 20 July},
	abstract = {This paper deals with a distributed bandwidth broker that we try to evaluate and therefore propose a model that will improve its operation in a backbone network. Such a distributed bandwidth broker has been implemented and tested in NS simulator. Its operation is affected very much by the network condition and the responding time is proportional to the delay of packets in the network. Therefore, the paper presents a model (heuristic) that evaluates each node and finally selects the most important node where the base bandwidth broker should be located. This model is also associated with the general model that describes the operation of the bandwidth broker, and we propose an adaptation module of the Bandwidth broker that optimizes its operation. Finally, the model is simulated in order to evaluate its performance and indicate points that can be improved.},
	author = {Christos Bouras and Dimitris Primpas}
}
@conference {2697,
	title = {Implementation issues of Managed Bandwidth Service: The case of GRNET},
	booktitle = {International Conference on High Speed Networks(ICHSN 2005), Montreal, Canada},
	year = {2005},
	month = {14 - 17 August},
	pages = { 293 - 298},
	abstract = {This paper describes the design and the implementation of the Managed Bandwidth Service (MBS) in a high speed backbone network as well as a management tool for the service. The service was designed taking advantage of features provided by the MPLS technology and also using the DiffServ architecture. So, it uses L2 MPLS VPNs to provide point to point connection and also marks the traffic in order to pass from certain priority queues (to provide guaranteed bandwidth). It also enables traffic engineering characteristics in order to provide load balancing on the network as well as fast rerouting in case of link failure. In addition we implemented a management tool for the service. The scope of this tool is to allow the users to manage their MBS requests (make a new one, edit, delete or view a request). Also the tool performs admission control and produces the necessary configuration that must be applied on the network in order to implement every service{\textquoteright}s request. This service was designed and implemented on GRNET{\textquoteright}s network.},
	author = {Christos Bouras and Dimitris Primpas}
}
@conference {2715,
	title = {Integration of 3D Mesh Streaming and Compression Techniques for Adaptive progressive Virtual World Transmission in NVEs},
	booktitle = {7th Virtual Reality Unternational Conference (VRIC), Laval, France},
	year = {2005},
	month = {20 - 22 April},
	pages = { 235 - 244},
	abstract = {In this paper, we present a framework for exploiting three-dimensional (3D) mesh streaming and compression techniques and algorithms in order to improve the performance of our EVE-II Networked Virtual Environments platform. These improvements are related to the progressive transmission of 3D worlds or separate meshes. We also present a 3D mesh compression method focused on network communication, which is designed to support progressive mesh transmission, offering a fast and effective means of reducing the storage and transmission needs for geometrical data.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Alexandros Panagopoulos}
}
@conference {2696,
	title = {Multimedia Transmission over Third Generation Cellurar Networks},
	booktitle = {10th IFIP International Conference on Personal Wireless Communications - PWC{\textquoteright}05, Colmar, France},
	year = {2005},
	month = {25 - 27 August},
	pages = { 317 324},
	abstract = {<p>The scheme of real time streaming video is one of the newcomers in wireless data communication, raising a number of new requirements in both telecommunication and data communication systems. This scheme applies when the user is experiencing real time multimedia content. This paper has as main target to study the performance of video transmission over the third generation cellular networks. In particular, we examine the performance of UMTS Dedicated Channels (DCHs) for real time MPEG-4 video transmission in Downlink direction. Finally, we examine if real time video transmission in conjunction with Internet traffic is applicable in UMTS radio interface.</p>
},
	keywords = {MBMS, UMTS},
	author = {Christos Bouras and Antonios Alexiou and Vaggelis Igglesis}
}
@book {3147,
	title = {Networked Virtual Environments},
	series = {Ellinika Grammata},
	year = {2005},
	author = {Christos Bouras and Vaggelis Kapoulas and Thrasivoulos Tsiatsos and Eleftheria Giannaka}
}
@conference {2713,
	title = {Performance enhancement of an AF service using TCP {\textendash} aware marking and dynamic WRED},
	booktitle = {10th IEEE Symposium on Computers and Communications, LaManga del Mar Menor, Cartagena, Spain},
	year = {2005},
	month = {27 - 30 June},
	pages = { 642 - 647},
	abstract = {The implementation of successful Assured
Forwarding (AF) services according to the DiffServ
framework remains a challenging problem today,
despite the numerous proposals for AF PHB
mechanisms and AF-based service implementations. In this work, we propose two modules, the TCP-Window
Aware Marker (TWAM) and the Dynamic WRED
(DWRED) mechanism for implementing the DiffServ
AF PHB. We provide analytical models and an
experimental evaluation in order to demonstrate how
they succeed in enhancing the quality, increasing
fairness, improving the performance and easing the
deployment of a production- level AF-based service.},
	author = {Christos Bouras and Afroditi Sevasti}
}
@conference {2703,
	title = {Performance of Adaptive Multimedia Transmission: The case of Unicast Technique},
	booktitle = {5th International Network Conference - INC 2005, Samos Island, Greece},
	year = {2005},
	month = {5 - 7 July},
	pages = { 121 - 128},
	abstract = {Unicast mechanisms for the adaptive transmission of multimedia data can be used for the transmission of multimedia data over heterogeneous networks, like the Internet with the use of one unicast stream for each receiver. Those mechanisms have the capability to adapt the transmission of the multimedia data to network changes. In this paper, we describe a unicast mechanism for adaptive transmission of multimedia data, which is based on real time protocols. The proposed mechanism can be used for unicast transmission of multimedia data over heterogeneous networks, like the Internet, and has the capability to adapt the transmission of the multimedia data to network changes. Moreover, the proposed mechanism uses a {\textquotedblleft}friendly{\textquotedblright} to the network users congestion control policy to control the transmission of the multimedia data. We evaluate the adaptive multicast transmission mechanism and we compare it with a number of similar mechanisms available to the literature (LBA, RAP, and TFRCP).},
	author = {Christos Bouras and Apostolos Gkamas}
}
@article {3031,
	title = {Porting and performance aspects from IPv4 to IPv6: The case of OpenH323},
	journal = {International Journal of Communication Systems, Wiley InterScience, Vol. 18, Issue 9},
	year = {2005},
	pages = { 847 - 866},
	abstract = {This paper is a summary of our experiences on a case study for porting applications to IPv6. We present the
results of the effort to port OpenH323, an open-source H.323 platform to IPv6, which we believe can serve
as guidelines for other projects with similar goals. We briefly present the structure of the OpenH323
platform. We also discuss a number of issues arising during the porting of a platform to IPv6, like which
would be the easiest approach to the porting procedure, how compatibility with earlier, IPv4-only versions
of the platform could be retained, if there are any useful tools for assisting this task, how and when one
could be positive that the necessary modifications had been made, and which testing procedures should be
followed. We then present a variety of experiments that we conducted in order to comparatively evaluate
the IPv4 and IPv6 protocol stacks. We also present the results of some initial experiments comparing IPv4
and IPv6 performance under congested network links and the conclusions that they lead us to.},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos and Dimitris Primpas}
}
@conference {2709,
	title = {QoS experiences in native IPv6 GRNET and 6NET networks},
	booktitle = {The 2005 International Conference on Telecommunication Systems {\textendash} Modeling and Analysis, Dallas, TX, USA},
	year = {2005},
	month = {17 - 20 November},
	pages = { 284 - 292},
	abstract = {Adoption of IPv6 technology has been accelerated in the last few years but there is limited experience in the deployment of Quality of Service (QoS) for IPv6 traffic in backbone networks. As available software and hardware is designed to handle IPv4 packets, there is a need to accurately measure the performance of QoS mechanisms in an IPv6 environment. This paper discusses tests in the deployment of IPv6 QoS in core networks, namely the production dual stack GRNET and the IPv6-only 6NET networks, using both hardware and software platforms. In either case, we succeeded in delivering advanced transport services to IPv6 traffic and provided different performance guarantees to portions of traffic. The deployed QoS schema was common for IPv6 and IPv4; in most cases both v4 and v6 traffic exhibited comparable performance per class while imposing no significantly different overhead on network elements. A major conclusion of our tests is that the IPv6 QoS mechanisms are efficiently supported with state-of-the-art router cards at gigabit speeds.},
	author = {Christos Bouras and Dimitris Primpas and A Liakopoulos and B Maglaris and D Kalogeras}
}
@conference {2698,
	title = {QoS issues in a large - scale IPv6 network},
	booktitle = {2005 International Symposium on Performance Evaluation of Computer and Telecommunication Systems (SPECTS{\textquoteright} 05), Philadelpia, Pennsylvania, USA,},
	year = {2005},
	month = {23 - 28 July},
	pages = { 406 - 415},
	abstract = {<p>This paper presents our work in the framework of the 6NET project, regarding the design, implementation and testing of a QoS service in a large-scale IPv6 network. The DiffServ mechanism for providing QoS guarantees, is generally preferred over IntServ. However, the current support for QoS mechanisms in IPv6 implementations still lags behind QoS support in IPv4. Furthermore, the new Internet Protocol introduces a different network environment in many aspects and therefore the QoS services should be specifically designed and evaluated for IPv6. In order to evaluate this different behaviour, large-scale experiments have been carried out within the scope of the 6NET project. This paper describes the results from the experimentation with the DiffServ mechanism on a large-scale native IPv6 network that aims to service aggregates of real time traffic with minimum delay, jitter and packet loss.</p>
},
	author = {Christos Bouras and Kostas Stamos and Dimitris Primpas}
}
@conference {2695,
	title = {QoS issues in the Research and Academic Networks: The case of GRnet},
	booktitle = {Industrial Conference on Multi-Provider QoS/SLA Internetworking (MPQSI 2005), Tahiti, French Polynesia},
	year = {2005},
	month = {23 - 28 October},
	abstract = {<p>This paper describes the design and the implementation of QoS services in a high speed backbone network as well as a management tool for the service. The services were designed taking advantage of features provided by the MPLS technology and also by using the DiffServ architecture. The supported QoS services include the IP Premium that tries to provide zero packet loss as well as minimum delay and jitter and the Less Than Best Effort service. In addition we implemented a management tool for the service. The scope of this tool is to allow the users to manage their QoS requests (make a new one, edit, delete or view a request). Also the tool performs admission control and produces the necessary configuration that must be applied on the network in order to implement every service{\textquoteright}s request.</p>
},
	author = {Christos Bouras and Dimitris Primpas and A Karaliotas and Mixalis Paraskevas and M Oikonomakos and C Sintoris}
}
@conference {2702,
	title = {Rate and Loss Control for Video transmission over UMTS using Real -Time Protocols},
	booktitle = {13th Annual Meeting of the IEEE/ACM International Symposium on Modeling, Analysis and Simulation of Computer and Telecommunication Systems (MASCOTS 2005), Atlanta, Georgia, USA},
	year = {2005},
	month = {27 - 29 September},
	pages = { 333 - 336},
	abstract = {UMTS is evolving toward a future wireless all-IP network. In this paper we present how it supports real-time IP multimedia services, as these services are expected to drive the adoption of wireless all-IP networks. The scheme of real time streaming video is one of the newcomers in wireless data communication and in particular in UMTS, raising a number of novel requirements in both telecommunication and data communication systems. This scheme applies when the mobile user is experiencing real time video content. In this work we focus on the design and implementation of a rate and loss control mechanism for monitoring the UMTS network state and estimating the appropriate rate of the streaming video data.},
	keywords = {Congestion Control, MBMS, UMTS},
	author = {Christos Bouras and Antonios Alexiou}
}
@conference {2706,
	title = {Securing a Bandwidth Broker Architecture},
	booktitle = {The 2005 International Conference on Internet Computing (ICOMP 05), Las Vegas, Nevada, USA},
	year = {2005},
	month = {27 - 30 June},
	pages = { 474 - 480},
	abstract = {In this paper we discuss the topic of the security in the context of a Bandwidth Broker?s operation based on the existing literature on this issue and new techniques and methods. We propose mechanisms to enhance the security of the communications during the Bandwidth Broker operation both within a single domain and across different domains. The message exchanges for the operation of a distributed Bandwidth Broker architecture are enumerated. The purpose is to examine the main security risks for a distributed Bandwidth Broker architecture operating in a real-world environment and address them using the PKI architecture mechanisms. We also present a proposal for identifying misbehaving flows that intends to be both simple and effective. We finally evaluate the performance impact that our solution incurs to the operation of the Bandwidth Broker and show that it offers an advantageous trade-off in most cases where security considerations exist.},
	author = {Christos Bouras and Kostas Stamos}
}
@article {3032,
	title = {Service Level Agreement for DiffServ - based services provisioning},
	journal = {Journal of Network and Computer Applications, Academic Press, Vol. 28, No. 4},
	year = {2005},
	month = {November},
	pages = { 285 - 302},
	abstract = {The evolution of mechanisms for providing Quality-of-Service (QoS) over the contemporary
network infrastructures has introduced the need for regulation and management of the emerging QoS
services with the use of Service Level Agreements (SLAs). SLAs define the qualitative and
quantitative characteristics of the services provided from a network provider to peering networks or
customers. In this work, we define a template for the SLA structure to support the provision of a QoS
service between two peering domains and then we proceed with the definition of an end-to-end SLA
across consecutive domains, based on the bilateral ones. We also propose a model for the service
provisioning procedures.},
	author = {Christos Bouras and Afroditi Sevasti}
}
@article {3028,
	title = {SRAMT: A hybrid sender and receiver-based adaptation scheme for TCP friendly multicast transmission},
	journal = {Computer Networks Journal, Elsevier Science, Vol. 47, No. 4},
	year = {2005},
	month = {March},
	pages = { 551 - 575},
	abstract = {In this paper,we describe a hybrid sender and receiver-based adaptation scheme for multicast transmission of multimedia
data,which we call SRAMT (Sender{\textendash}Receiver based Adaptation scheme for Multicast Transmission). The most
prominent features of SRAMT are its distributed (to sender and receivers) transmission rate estimation algorithm and
its innovative RTT (Round Trip Time) estimation algorithm based on one-way delay measurements. With the use of
SRAMT,we ensure that sender will transmit TCP friendly traffic and receivers with different capabilities (in terms of
available bandwidth) are able to receive the multimedia information. We evaluate SRAMT through a number of simulations
and compare it with other schemes available to the literature. Main target of the simulations was the examination
of SRAMT behavior to a heterogeneous group of receivers and its behavior against TCP connections.},
	author = {Christos Bouras and Apostolos Gkamas}
}
@article {3156,
	title = {Survey of IPv4 Dependencies in Global Grid Forum Specifications},
	year = {2005},
	author = {Christos Bouras and Kostas Stamos and Dimitris Primpas and Rute Sofia and Sheng Jiang}
}
@conference {2708,
	title = {Techniques for DiffServ - based QoS in Hierarchically Federated MAN Networks - the GRNET Case},
	booktitle = {The 14th IEEE Workshop on Local and Metropolitan Area Networks (LANMAN 2005), Chania. Island of Crete, Greece},
	year = {2005},
	month = {18 - 21 September},
	abstract = {DiffServ is the basis of contemporary QoS-enabled networks. Setting up DiffServ QoS requires extensive engineering effort in dimensioning and provisioning, especially for adjacent networks under different administrations linked in a {\textquotedblleft}federated{\textquotedblright} hierarchy. In this paper we present a case study for QoS techniques employed in the GRNET MAN networks of Athens and Crete. After introducing the supported QoS mechanisms and service types, we discuss our dimensioning methodology and present two algorithms for worst-case dimensioning. We explain the provisioning mechanisms of GRNET and we present in brief our new automated provisioning ANS tool. Finally, we deal with the extension of our mechanisms and tools in hierarchically federated networks and give some future directions of our work.},
	author = {Christos Bouras and Dimitris Primpas and A Liakopoulos and A Varvitsiotis and V Siris and G Fotiadis}
}
@conference {2869,
	title = {A Unified Framework for Political Support e - Democracy Practices},
	booktitle = {IADIS International Conference WWW/Internet 2005, Lisbon, Portugal, Volume II},
	year = {2005},
	month = {19 - 22 October},
	pages = { 119 - 123},
	abstract = {e-Government and e-Democracy constitute a central theme in information society policy at all levels: local, regional, national, European and even globally. To this direction, a variety of efforts have been made and many systems have been developed. This paper proposes a methodology for designing and implementing web-based services that can support e-Democracy practices. Furthermore, the paper presents and describes the effort made by a Greek political party to this direction, for the design and development of a unified framework for providing, supporting and managing e-Democracy services. The paper describes the actions taken and the work done according to the proposed methodology.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka and Vassilis Poulopoulos and T Karounos and A Priftis}
}
@article {3026,
	title = {A web - based virtual community},
	journal = {International Journal of Web Based Communities (IJWBC), Inderscience Publishers, Vol. 1, No 3},
	year = {2005},
	pages = { 127 - 139},
	abstract = {This paper describes functionality and architectural issues in the design of a web-based virtual community. This virtual community aims to meet the requirements of a virtual collaboration system with both autonomous and collaborative e-learning services, by supporting communities whose members interact and form groups based on their common interests.},
	author = {Christos Bouras and Vaggelis Kapoulas and Thrasivoulos Tsiatsos and Vaggelis Igglesis}
}
@conference {2699,
	title = {A Web Clipping Service{\textquoteright}s Information Extraction Mechanism},
	booktitle = {3rd International Conference on Universal Access in Human - Computer Interaction, Las Vegas, Nevada, USA},
	year = {2005},
	month = {22 - 27 July},
	abstract = {Information overload is one of the most important problems of today{\textquoteright}s WWW. Users are often lost in a wealth of information when searching about a topic. Although they have specific information needs, using a search engine or regularly browsing in popular news sites for updates can lead them to search in tens or hundreds of possibly relevant pages or loose some updates that were interesting for them. One promising solution for this problem is {\textquoteleft}web-clipping{\textquoteright} services. A service like this continuously searches the Web and whenever it finds a web page that might interest some users, it informs these users that they should visit this specific page. This paper describes the information extraction mechanism of a web-clipping service that is being designed as part of a larger project for information search and manipulation. This mechanism is used to extract information from web pages and find out which links should be followed.},
	author = {Christos Bouras and Vassilis Poulopoulos and Ioannis Misedakis and G Kounenis}
}
@conference {2729,
	title = {An Adaptive Admission Control Algorithm for Bandwidth Brokers},
	booktitle = {3rd IEEE International Symposium on Network Computing and Applications (NCA04), Cambridge, MA, USA},
	year = {2004},
	month = {30 August - 1 September},
	pages = { 243 - 250},
	abstract = {This paper focuses on the operation of the Bandwidth Broker, an entity that is responsible for managing the bandwidth within a network domain and for the communication with Bandwidth Brokers of neighboring domains. A very important aspect of the Bandwidth Broker is its admission control module that determines whether the bandwidth reservation requests are going to be accepted or not. We summarize the status of the current research in this field and propose a novel architecture for the admission control module that aims at achieving a satisfactory balance between maximizing the resource utilization for the network provider and minimizing the overhead of the module. This is achieved by gathering and examining sets of book-ahead requests and by adapting the size of the set to be examined so that the network utilization and the computation overhead are appropriately balanced.},
	author = {Christos Bouras and Kostas Stamos}
}
@book {3148,
	title = {Advanced Issues on Computer Networks and Services},
	series = {Ellinika Grammata},
	year = {2004},
	author = {Christos Bouras and Vaggelis Kapoulas and Apostolos Gkamas and Kostas Stamos and Dimitris Primpas}
}
@conference {2720,
	title = {Application on Demand Portal using J2EE technologies},
	booktitle = {IADIS International Conference - Applied Computing 2004, Lisbon, Portugal},
	year = {2004},
	month = {23 - 26 March},
	pages = { I.551 - I.558},
	abstract = {A Web Based Virtual Community is an example of a Collaborative Virtual Environment, which focalizes in providing collaborative functionalities and both synchronous and asynchronous interaction services. This paper describes a virtual community, which aims to meet the requirements of a virtual collaboration space and support autonomous and collaborative e-learning services. In particular, a web-based platform is described, which is able to support communities whose members are able to interact and form groups based on their common interests. The community provides its members with the ability to communicate through enhanced forums and chats, but also, to interact in the social interaction spaces. The users can arrange events, which occur in virtual meeting centers, where 3D avatars represent the users. In these multi-user spaces, extended functionalities are offered, while system agents assist and consult the users.},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos and Dimitris Primpas}
}
@conference {2717,
	title = {Design and implementation of a Bandwidth Broker in a simulation environment},
	booktitle = {7th International Symposium on Communications Interworking - INTERWORKING 2004, Ottawa, Canada},
	year = {2004},
	month = {29 November - 1 December},
	abstract = {A Bandwidth Broker is an entity that has been proposed in order to provide end-to-end
QoS. For this purpose it manages the bandwidth (the QoS services) within a network
domain and it is also responsible for the communication with Bandwidth Brokers of
adjacent domains. In this paper, we present a Bandwidth Broker implementation in the
widely used NS-2 simulation environment. We describe the Bandwidth Broker architecture
that was our model for the simulation implementation. Furthermore, we illustrate the
experiments that we conducted that examined the Bandwidth Broker functionality as well
as its performance. All the experiments demonstrated that with this implementation we can
achieve end-to-end QoS and that our implementation can be used in order to model the
behavior of a Bandwidth Broker in the widely popular NS-2 network simulator.},
	author = {Christos Bouras and Kostas Stamos and Dimitris Primpas and N Stathis}
}
@article {3041,
	title = {Distributed Virtual Reality:Building a Multi - User Layer in EVE Platform},
	journal = {Journal of Network and Computer Applications, Academic Press, Vol. 27, No. 2},
	year = {2004},
	month = {April},
	pages = { 91 - 111},
	abstract = {In this paper, we present the design and implementation of a VRML97 multi-user layer, which is
introduced in the EVE distributed virtual reality platform. Though other approaches use a VRML
node insertion mechanism, such as VSPLUS, or a substitution mechanism, such as SPIN-3D, our
approach uses a removal mechanism. Main consideration of our multi-user extension is the ease of
transforming single-user virtual worlds into multi-user virtual worlds, as well as the conformity with
any standard VRML97 browser. Furthermore, we present the EVE{\textquoteright} s communication platform,
which can be used in order to support Collaborative Virtual Environments. Main issues regarding the
effective network communication as well as the initialization of the 3D scene are discussed in this
paper.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos}
}
@conference {2724,
	title = {EVE - II: An Integrated Platform for Networked Virtual Environments},
	booktitle = {The Tenth International Conference on Distributed Multimedia Systems {\textendash} DMS{\textquoteright}2004, San Francisco, USA},
	year = {2004},
	month = {8 - 10 September},
	pages = { 81 - 85},
	abstract = {In this paper, we present the design and implementation of an integrated platform for Networked Virtual Environments. This platform called EVE-II is an enhancement of the EVE distributed virtual reality platform, supporting stable event sharing for multi-user 3D places, easy creation of 3D multi-user3D places, H.323-based Voice over IP services integrated in a 3D spaces well as many concurrent 3D multi-user spaces.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Alexandros Panagopoulos and Nikos Theoxaris}
}
@conference {2731,
	title = {Fast and Efficient IP Handover in IEEE 802.11 Wireless LANs},
	booktitle = {The 2004 International Conference on Wireless Networks (ICWN 04), Las Vegas, Nevada, USA},
	year = {2004},
	month = {21 - 24 June},
	pages = { 249 - 255},
	abstract = {This paper presents an effective and simple solution to the problem of Layer 3 (L3) handover in IEEE 802.11 wireless LANs (WLANs), so as to extend the IP mobility area of 802.11 wireless Stations (STAs). The IEEE 802.11f Inter-Access Point Protocol (IAPP), handles the Layer 2 (L2) mobility of STAs during L2 (intra-network) handovers, and offers IP connectivity via L2 specific methods. Instead of using a different protocol for the L3 mobility management of STAs, such as Mobile IP (MIP) [4] or a MIP-variant, the IAPP protocol is extended so as to also support the inter-network (L3) movements of 802.11 STAs. The proposed IAPP-based mechanism supports host mobility and offers substantial uninterrupted wireless IP-connectivity, even after L3 movements. The cornerstones of this mechanism are the zero-delay IP movement detection and the zero over-the-air IP signaling during IP handover establishment, which lead to seamless (very fast) and smooth IP handoffs. This fast IP-handoff method is especially suitable to 802.11 systems, as it has better performance than traditional MIP-based methods (shorter handover delays, near zero packet loss), while makes IP roaming transparent to the mobile STAs.},
	author = {Christos Bouras and Ioanna Sampraku and T Karoubalis}
}
@article {3036,
	title = {Game Based Learning Using Web Technologies},
	journal = {Journal of Intelligent Games and Simulation, Volume 3, Number 2},
	year = {2004},
	pages = { 67 - 84},
	abstract = {Game-based learning has been recognized as an
important alternative or supplement to traditional
in-class, face-to-face teaching. It can help both
adults and children in learning new concepts,
acquiring expertise and practicing knowledge.
Although game-based learning has been applied
mainly for teaching children, it can be quite
helpful for adult vocational or university learning.
In this paper, a web-based game is presented,
which has been developed for enhancing the
learning experience of university students. Its goal
is to serve as a complement to classes, although it
can be used independently. It provides the students
with many ways of synchronous or asynchronous
communication and knowledge acquisition.
Through the game, students have to search for
information, understand it and use it in discussions
with the members of other teams. Many users are
able to play the game simultaneously, while many
teachers may run different game themes.
Microsoft{\textquoteright}s ASP.NET scripting environment was
used for creating the game{\textquoteright}s website and its
rationale. The website utilizes also Macromedia{\textquoteright}s
communication technology (Flash Communication
Server MX) for enabling real-time communication
by several means (voice, text, etc). Flash was used
in the website for building the real-time
communication modules as well as for creating a
more elegant user interface.},
	author = {Christos Bouras and Vaggelis Kapoulas and Vaggelis Igglesis and Ioannis Misedakis and O Dziabenko and A Koubek and M Pivec and A Sfiri}
}
@conference {2730,
	title = {Monitoring and Analyzing Performance of Networked Virtual Environments: the case of EVE},
	booktitle = {8th IEEE International Symposium on Distributed Simulation and Real Time Applications, Budapest, Hungary},
	year = {2004},
	month = {21 - 23 October},
	pages = { 218 - 221},
	abstract = {This paper focuses on the performance monitoring of a networked virtual environment, called EVE, in order to identify the elements that degrade its network performance. In particular, based both on the architectural and communication model that EVE adopts in order to cope with the dynamic behavior of the network, we performed a series of experiments, taking into account the number of the connected users, the network load as well as the connection type of the users.},
	author = {Christos Bouras and Eleftheria Giannaka}
}
@conference {2722,
	title = {A new pricing mechanism for a high - priority DiffServ - based service},
	booktitle = {The 6th International Conference on Advanced Communication Technology, Phoenix Park, Republic of Korea},
	year = {2004},
	month = {9 - 11 February},
	pages = {585-590},
	abstract = {QoS provisioning according to the DiffServ framework has raised the requirements for pricing mechanisms that preserve the potential and flexibility of DiffServ. At the same time, such mechanisms should reflect resource usage, allocate resources efficiently, reimburse costs or maximize service provision profits and lead customers to requesting services that will maximize their revenue. This work proposes a policy for pricing based on resource allocation by a particular category of DiffServ-based services for aggregated traffic in the case of transport networks. Our research takes into account the particularities that apply to the case of DiffServ services{\textquoteright} provision over transport networks while imposing minimal overload and a-priori estimation of costs. The detailed pricing methodology is presented and experimentally evaluated.},
	author = {Christos Bouras and Afroditi Sevasti}
}
@conference {2727,
	title = {An optimized handoff scheme for IP mobility support in IEEE 802.11 WLANs},
	booktitle = {7th ACM International Symposium on Modeling, Analysis and Simulation of Wireless and Mobile Systems (MSWiM 2004), Venice, Italy},
	year = {2004},
	month = {4 - 6 October},
	pages = { 99 - 108},
	abstract = {This paper presents an 802.11-dependent IP mobility solution which ac-
celerates the network reconfiguration phase after subnet handoffs and
significantly reduces the IP handoff latency. The proposed fast IP hand-
off method offers the next generation WLAN applications such as Voice
over WLANs (VoWLAN) complete freedom of movement without expe-
riencing any connectivity problems. The performance results verify that
this method outperforms other existing proposed IP mobility solutions
inWLANs, in a way which introduces the lesser imperative amendments
to the existing 802.11 wireless LAN framework.},
	author = {Christos Bouras and Ioanna Sampraku and T Karoubalis}
}
@conference {2733,
	title = {Performance Evaluation of an IPv6 - capable H323 Application},
	booktitle = {The 18th International Conference on Advanced Information Networking and Applications (AINA 2004), Fukuoka, Japan},
	year = {2004},
	month = {29 - 31 March},
	pages = { 470 - 475},
	abstract = {OpenH323 is an open source H.323 implementation that has been ported to IPv6. In this paper we briefly introduce the library architecture and the performance citeria with which the ported version should be evaluated. We then present a variety of experiments that we conducted in order to comparatively evaluate the IPv4 and IPv6 protocol stacks. We also present the results of some initial experiments comparing IPv4 and IPv6 performance under congested network links and the conclusions that they lead us to.},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos and Dimitris Primpas}
}
@conference {2716,
	title = {Performance Evaluation of TCP over UMTS Transport Channels},
	booktitle = {7th International Symposium on Communications Interworking - INTERWORKING 2004, Ottawa, Canada},
	year = {2004},
	month = {29 November - 1 December},
	abstract = {Universal Mobile Telecommunications System
(UMTS) is a third-generation cellular network that
enables high-speed wireless Internet access. It can
provide maximum data-rates ranging from 64kb/s to
2Mb/s in different environmental types. UMTS is
designed to provide access to the existing Internet
services as well as to UMTS specific services. It will
augment the existing capabilities of 2G mobile
networks and GPRS, and one often envisaged strategy
is to offer a richer set of multimedia services. It is
widely known that TCP does not perform efficiently in
wireless links where the bit error rate is high enough.
This paper has as main target to evaluate the
performance of TCP data transfer over the UMTS air
interface, by means of a rather detailed simulation
model. We examine the performance of TCP over
UMTS Dedicated Channels (DCHs) with different bit
rates and Transmission Time Intervals (TTIs) and we
represent some simulation experiments for UMTS
High Speed Downlink Packet Access (HSDPA)
transmissions.},
	keywords = {UMTS},
	author = {Christos Bouras and Antonios Alexiou and Vaggelis Igglesis}
}
@article {3034,
	title = {Performance Evaluation of the Impact of Quality of Service mechanisms in an IPv6 network for IPv6 - capable real time applications},
	journal = {Journal of Network and Systems Management, Kluwer Academic Publishers, Volume 12, Issue 4},
	year = {2004},
	month = {December},
	pages = { 463 - 483},
	abstract = {This paper describes a Quality of Service (QoS) service on an IPv6 domain that aims
to service aggregates of real-time traffic with minimum delay, jitter, and packet loss. It
contains results from the tests that were performed in order to configure and evaluate the
QoSmechanisms.As an actual example of real-time traffic, we have used theOpenH323
project, an open source H.323 implementation that has been ported to IPv6. The QoS
mechanisms in IPv6 networks is still a field that has not been researched adequately,
and we therefore present the results from the experiments in our IPv6 network that
took advantage of the QoS mechanisms. This QoS service uses the Modular QoS CLI
(MQC) mechanism and especially the Low Latency Queue feature (LLQ) in order to
treat packets from real-time applications.},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos and Dimitris Primpas}
}
@conference {2726,
	title = {Performance Evaluation of UMTS for Mobile Internet Access},
	booktitle = {12th Annual Meeting of the IEEE/ACM International Symposium on Modeling, Analysis and Simulation of Computer and Telecommunication Systems (MASCOTS 2004), Volendam, The Netherlands},
	year = {2004},
	month = {5 - 7 October},
	pages = { 1 - 4},
	abstract = {UMTS constitutes the third generation of cellular wireless
networks which aims to provide high-speed data access
along with real time voice calls (Holma \& Toskala, 2001).
Wireless data is one of the major boosters of wireless
communications and one of the main challenges of next
generation standards (Chaudhury \& Mohr, 1999).
It can provide maximum data-rates ranging from 64kb/s
to 2Mb/s in different environmental types. UMTS is
designed to provide access to the existing Internet services
as well as to UMTS specific services. It will augment the
existing capabilities of 2G mobile networks and GPRS, and
one often envisaged strategy is to offer a richer set of
multimedia services.},
	keywords = {UMTS},
	author = {Christos Bouras and Antonios Alexiou and Vaggelis Igglesis}
}
@conference {2732,
	title = {Performance Monitoring on Networked Virtual Environments},
	booktitle = {5th International Conference on Internet Computing (IC 04) Las Vegas, Nevada, USA},
	year = {2004},
	month = {21 - 24 June},
	pages = { 302 - 308},
	abstract = {As networked virtual environments gain increasing interest and acceptance in the field of Internet applications, a lot of effort is drawn in the optimization of their performance, which will result in the wide adaptation of this evolving mean of communication. This paper focuses on the performance monitoring of such a networked virtual environment, called EVE, in order to identify the elements that degrade its network performance.},
	author = {Christos Bouras and Eleftheria Giannaka}
}
@conference {2723,
	title = {Performance of Adaptive Multimedia Transmission: The case of One Multicast Stream techniques},
	booktitle = {The International Conference on Information Networking (ICOIN), Busan, Korea},
	year = {2004},
	month = {18 - 20 February},
	abstract = {A {\textquotedblleft}one multicast stream{\textquotedblright} mechanism is a mechanism, which
can be used for multicast multimedia data with the use of one multicast
stream over heterogeneous networks, like the Internet, and has the
capability to adapt the transmission oft he multimedia data to network
changes. In this paper, we describe a {\textquotedblleft}one multicast stream{\textquotedblright} mechanism
for adaptive transmission of multimedia data, which is based on real time
protocols. In addition, the proposed mechanism uses an inter-receiver
fairness function in order to treat the group of receivers with fairness in
a heterogeneous environment. We evaluate the adaptive multicast transmission
mechanism through a number ofsim ulations and compare it with
a number ofsimilar schemes available to the literature (LBA+, TFMCC,
PGM, TBRCA).},
	author = {Christos Bouras and Apostolos Gkamas}
}
@article {3037,
	title = {Predictive Prefetching on the Web and its Potential Impact in the Wide Area},
	journal = {World Wide Web Journal: Internet and Web Information Systems, Kluwer Academic Publishers, Vol. 7, Issue 2},
	year = {2004},
	month = {June},
	pages = { 143 - 179},
	abstract = {The rapid increase of World Wide Web users and the development of services with high bandwidth requirements
have caused the substantial increase of response times for users on the Internet. Web latency would be significantly
reduced, if browser, proxy or Web server software could make predictions about the pages that a user is
most likely to request next, while the user is viewing the current page, and prefetch their content.
In this paper we study Predictive Prefetching on a totally new Web system architecture. This is a system
that provides two levels of caching before information reaches the clients. This work analyses prefetching on a
Wide Area Network with the above mentioned characteristics. We first provide a structured overview of predictive
prefetching and show its wide applicability to various computer systems. TheWAN that we refer to is the GRNET
academic network in Greece. We rely on log files collected at the network{\textquoteright}s Transparent cache (primary caching
point), located at GRNET{\textquoteright}s edge connection to the Internet. We present the parameters that are most important for
prefetching on GRNET{\textquoteright}s architecture and provide preliminary results of an experimental study, quantifying the
benefits of prefetching on theWAN. Our experimental study includes the evaluation of two prediction algorithms:
an {\textquotedblleft}n most popular document{\textquotedblright} algorithm and a variation of the PPM (Prediction by Partial Matching) prediction
algorithm. Our analysis clearly shows that Predictive prefetching can improve Web response times inside the
GRNET WAN without substantial increase in network traffic due to prefetching.},
	author = {Christos Bouras and Agis Konidaris and Dionisis Kostoulas}
}
@article {3039,
	title = {Pricing QoS over transport networks},
	journal = {Internet Research: Electronic Networking, Applications and Policy, Emerald, Volume 14, Number 2},
	year = {2004},
	pages = { 167 - 174},
	abstract = {In recent years, a number of alternatives for service
differentiation and QoS provision have been proposed and
standardized in communication networks. In the case of backbone
networks the DiffServ architecture has prevailed, due to its
scalability and deployment feasibility. The provisioning of
differentiated services has raised the requirements for
interdependent controlled resource allocation and service
pricing, with particular needs for pricing mechanisms that
preserve the potential and flexibility of the DiffServ framework.
At the same time, such mechanisms should reflect resource
usage, allocate resources efficiently, reimburse costs or maximize
service provision profits and lead customers to requesting
services that will maximize their revenue. Presents the key issues
involved in the area of pricing DiffServ-based services and the
research work carried out in this field, while at the same time
outlining the basic principles that such a pricing infrastructure
should obey with respect to the particularities that apply to the
case of DiffServ services provision.},
	author = {Christos Bouras and Afroditi Sevasti}
}
@article {3038,
	title = {Providing and verifying advanced IP services in hierarchical DiffServ networks - the case of GEANT},
	journal = {Journal of Communication Systems, Wiley InterScience},
	year = {2004},
	pages = { 321 - 336},
	abstract = {The differentiated services (DiffServ) framework is widely proposed as an efficient method for providing
advanced IP services to large-scale networks, with QoS requirements. However, the provisioning of such
services in production networks has proved to be more difficult than initially expected, in defining, setting
and verifying appropriate Service Level Agreements (SLAs). GEANT, the Gigabit core pan-European
research network, on a pilot basis introduced {\textquoteleft}Premium IP{\textquoteright} service, offering bounded delay and negligible
packet loss to the European National Research \& Education Networks (NRENs) that it interconnects.
However, large scale provisioning of this new service requires the definition of efficient interaction
procedures between administrative domains involved and methods for SLA monitoring. This paper focuses
on these issues and presents the experience acquired from the early experiments in GEANT, as an example
of hierarchical Gigabit multi-domain environment, enabled with QoS provisioning to its constituent
NRENs. This model scales more efficiently than the common peering Internet Service provider (ISP)
commercial paradigm. Finally, we outline other options that promise QoS, such as Layer 2 VPNs in MPLS
backbones, with non-standard (yet) mechanisms.},
	author = {Christos Bouras and Afroditi Sevasti and A Liakopoulos and B Maglaris}
}
@conference {2734,
	title = {Quality of Service aspects in an IPv6 domain},
	booktitle = {2004 International Symposium on Performance Evaluation of Computer and Telecommunication Systems (SPECTS{\textquoteright} 04), San Jose, California, USA},
	year = {2004},
	month = {25 - 29 July},
	pages = { 238 - 245},
	abstract = {During the last years 2 Quality of Service architectures (IntServ and DiffServ) have been proposed and evaluated. The DiffServ architecture has proved its ascendancy and some services have already been proposed and deployed on IPv4 domains. But the usage of IPv6 protocol creates new challenges, as the QoS mechanisms that are currently supported for IPv6 in most implementations are fewer (or different) compared to IPv4 and in addition the whole network{\textquoteright}s behaviour is different. So, as a result the QoS services should be designed and evaluated again. This paper describes a QoS service on an IPv6 domain that aims to service aggregates of real time traffic with minimum delay, jitter and packet loss. In addition, it contains results from the experiments in our IPv6 network that took advantage of the QoS mechanisms. This QoS service uses the Modular QoS CLI (MQC) mechanism and especially the Low Latency Queue feature (LLQ) in order to treat packets from real time applications.},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos and Dimitris Primpas}
}
@article {3035,
	title = {SLA - based QoS pricing in DiffServ networks},
	journal = {Computer Communications Journal, Special Issue, Performance and Control of Next Generation Communications Networks, Edited by F. Huebner and R. D. van der Mei, Elsevier Science, Volume 27, Issue 18},
	year = {2004},
	month = {December},
	pages = { 1868 - 1880},
	abstract = {The availability of high-speed transmission media and networking equipment in contemporary networks, as well as the evolution of
quality-demanding applications has focused research interest on the provision of advanced qualitative services in addition to the traditional
best-effort model of the Internet. A number of alternatives for service differentiation and QoS provisioning have been proposed and
standardized, but in the case of backbone, transport networks the DiffServ architecture has prevailed, due to its scalability and deployment
feasibility. The provisioning of services according to the DiffServ framework has in turn raised the requirements for interdependent,
controlled resource allocation and service pricing, with particular needs for pricing mechanisms that preserve the potential and flexibility of
DiffServ. At the same time, such mechanisms should reflect resource usage, allocate resources efficiently, reimburse costs or maximize
service provision profits and lead customers to requesting services that will maximize their revenue. In this work, after reviewing related
research, the principles that a pricing scheme for DiffServ-based services should follow are presented, stressing the differences form
traditional Internet pricing. Based on these principles, an analytical approach to pricing a particular class of DiffServ-based services and a
methodology for applying this approach in a real network are proposed and evaluated.},
	author = {Christos Bouras and Afroditi Sevasti}
}
@conference {2718,
	title = {Using VR technology to Support e - Learning: The 3D Virtual Radiopharmacy Laboratory},
	booktitle = {6th International Workshop on Multimedia Network Systems and Applications (MNSA 2004), Tokyo, Japan},
	year = {2004},
	month = {23 - 26 March},
	pages = { 268 - 273},
	abstract = {In this paper, we present a virtual laboratory, which is designed and implemented in the framework of the VirRAD European project. This laboratory represents a 3D simulation of a radio-pharmacy laboratory, where learners, represented by 3D avatars, can experiment on radio-pharmacy equipment by carrying out specific learning scenarios. This paper describes the functionality provided by this laboratory, the motivation factors which led to its formation, the technological decisions that were made for the optimization of the system as well as the envisioned steps to be carried out.},
	author = {Christos Bouras and Vaggelis Kapoulas and Thrasivoulos Tsiatsos and Eleftheria Giannaka and Antonios Alexiou and Maria Nani}
}
@conference {2728,
	title = {Virtual Laboratories in Education: A cheap way for schools to obtain laboratories for all courses by using the Computer Laboratory},
	booktitle = {18th IFIP WCC - Workshop Tel {\textquoteright}04, Technology Enhanced Learning, Toulouse, France},
	year = {2004},
	month = {22 - 27 August},
	pages = { 19 - 28},
	abstract = {Practical experience is an important component of the educational process. However, the time and economical resources often required for the setting up and construction of scientific laboratories is outside the scope of many institutions. A solution to this problem could be found in the adaptation of the Virtual Reality technology, which could allow the creation of Virtual Laboratories, which will simulate the processes and actions that could take place in real laboratories. In particular, this paper, based on the expertise and motivation gained by the VirRAD-IST project, proposes and describes such an educational virtual laboratory, which aims to meet the requirements of a real laboratory and furthermore to support communication and collaboration services. We propose a web-based system, which allows users to perform experiments on educational fields, such as Physics or Chemistry in 3D multi-user worlds where users are represented by avatars and they are offered a wide range of communication and collaboration services in order to simulate efficiently a real learning experimental process.},
	author = {Christos Bouras and Eleftheria Giannaka and Antonios Alexiou}
}
@article {3040,
	title = {The Virtual Radiopharmacy Laboratory: A 3D Simulation for Distance Learning},
	journal = {Journal of Educational Multimedia and Hypermedia {\textendash} JEMH, AACE },
	year = {2004},
	pages = { 307 - 322},
	abstract = {This article presents Virtual Radiopharmacy Laboratory (VR
LAB), a virtual laboratory accessible through the Internet.
VR LAB is designed and implemented in the framework of
the VirRAD European project. This laboratory represents a
3D simulation of a radio-pharmacy laboratory, where learners,
represented by 3D avatars, can experiment on radiopharmacy
equipment by carrying out specific learning scenarios.
This article describes the functionality provided by
this laboratory, the motivation factors which led to its formation,
the technological decisions that were made for the optimization
of the system, as well as the envisioned steps to be
carried out.},
	author = {Christos Bouras and Vaggelis Kapoulas and Thrasivoulos Tsiatsos and Eleftheria Giannaka and Antonios Alexiou and Maria Nani}
}
@conference {2725,
	title = {A Web - based Tool for Building and Accessing Learning Objects and Online Courses},
	booktitle = {4th IEEE International Conference on Advanced Learning Technologies, Joensuu, Finland},
	year = {2004},
	month = {30 August - 1 September},
	pages = { 645 - 647},
	abstract = {In this paper we present a web-based tool that facilitates instructors and trainers to easily develop learning objects and online courses so as to serve their distant learners? needs. Additionally, we present the way content created using that tool can be delivered to the learners during a learning process. We therefore present a sample content management and delivery system that exploits the potential of the above-mentioned web-based tool. The resultant e-learning content can be easily searched and retrieved, tracked in terms of the learners? interactions with it and reused within different learning objects and courses.},
	author = {Christos Bouras and Maria Nani}
}
@conference {2719,
	title = {A Web Based Virtual Community: Funcionality and Architecture Issues},
	booktitle = {IADIS International Conference - Web Based Communities 2004, Lisbon, Portugal},
	year = {2004},
	month = {23 - 26 March},
	pages = { 59 - 66},
	abstract = {A Web Based Virtual Community is an example of a Collaborative Virtual Environment, which focalizes in providing collaborative functionalities and both synchronous and asynchronous interaction services. This paper describes a virtual community, which aims to meet the requirements of a virtual collaboration space and support autonomous and collaborative e-learning services. In particular, a web-based platform is described, which is able to support communities whose members are able to interact and form groups based on their common interests. The community provides its members with the ability to communicate through enhanced forums and chats, but also, to interact in the social interaction spaces. The users can arrange events, which occur in virtual meeting centers, where 3D avatars represent the users. In these multi-user spaces, extended functionalities are offered, while system agents assist and consult the users.},
	author = {Christos Bouras and Vaggelis Kapoulas and Thrasivoulos Tsiatsos and Vaggelis Igglesis}
}
@conference {2735,
	title = {Web page fragmentation and content manipulation for constructing personalized portals},
	booktitle = {The Sixth Asia Pasific Web Conference (APWeb {\textquoteright}04), Hangshou, China},
	year = {2004},
	month = {14 - 17 April},
	pages = { 744 - 754},
	abstract = {This paper presents a web page fragmentation technique, which is
utilized for extracting specific parts of web pages and building personalized
portals using these fragments. It is based on an algorithm, which fragments a
web page in discrete fragments using the page{\textquoteright}s internal structure. A training
and update procedure is used for identifying the specific fragments of a web
page in different time points. Using this technique a service provider can offer
Web users a system for building personalized pages based on the content of
their favorite sites. This technique, besides providing a convenient way for
browsing, saves time and reduces the cost of browsing in different sites.},
	author = {Christos Bouras and Vaggelis Kapoulas and Ioannis Misedakis}
}
@conference {2736,
	title = {Web Page Fragmentation for Personalized Portal Construction},
	booktitle = {IEEE International Conference on Information Technology: Coding and Computing - ITCC 2004 (Web/IR Track), The Orleans, Las Vegas, Nevada, USA},
	year = {2004},
	month = {5 - 7 April},
	pages = { 332 - 336},
	abstract = {Web portals offer many services and wealth of content
to Web users. However, most users do not find interest in
all the content present in these sites. Most of them visit
some specific sites and browse in specific thematic areas of
them. In this paper, a software technique is presented that
allows the viewers of web sites to build their own
personalized portals, using specific thematic areas of their
preferred sites. This transcoding technique is based on an
algorithm, which fragments a web page in discrete
fragments using the page{\textquoteright}s internal structure. A training
and update procedure is used for identifying the different
instances of thematic areas in different time points.},
	author = {Christos Bouras and Vaggelis Kapoulas and Ioannis Misedakis}
}
@conference {2721,
	title = {A Web - page fragmentation technique for personalized browsing},
	booktitle = {19th ACM Symposium on Applied Computing - Track on Internet Data Management, Nicosia, Cyprus},
	year = {2004},
	month = {14 - 17 March},
	pages = { 1146 - 1147},
	abstract = {In this paper, a technique is presented that allows web sites
viewers to build personalized web pages, using specific thematic
areas of their preferred sites. This technique, besides saving from
the trouble of having to browse in different sites in order to find
the desired content, saves users time and reduces the cost of
browsing the web by minimizing the data that have to be
downloaded. It is based on an algorithm, which fragments a web
page in discrete fragments using the page{\textquoteright}s internal structure. A
training and update procedure is utilized for recognizing the
instances of the web page components in different time points.},
	author = {Christos Bouras and Vaggelis Kapoulas and Ioannis Misedakis}
}
@conference {2747,
	title = {Adding IPv6 support to H323 Gnomemeeting/openH323 port},
	booktitle = {11th International Conference on Software, Telecommunications and Computer Networks (SoftCOM 2003), Croatia, Italy},
	year = {2003},
	month = {7 - 10 October},
	pages = { 458 - 462},
	abstract = {This article deals with the port towards the new IPv6
Internet network of voice and multi-media over IP applications.
We explain in detail our experience in porting Gnomemeeting,
the well-known Linux based videoconference software, and
more particularly the H323 library which implements the
signaling protocols (call establishment, transfer, codec
negotiation,{\textellipsis}).},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos and S Josset}
}
@conference {2754,
	title = {Analytical approach and verification of a DiffServ {\textendash} based priority service},
	booktitle = {6th IEEE International Conference on High Speed Networks and Multimedia Communications (HSNMC 03), Estoril, Portugal},
	year = {2003},
	month = {23 - 25 July},
	pages = { 11 - 20},
	abstract = {The provision of Quality of Service (QoS) in a seamless way over the
dominating internetworking protocol of our times (IP), has been a challenge for
many researchers in the past years. Strict qualitative guarantees have proven
difficult to provide in a way that has discouraged efforts in the area. The lack of
a coherent provisioning methodology has been identified as the main reason for
this. In this work, we are attempting an analytical yet straightforward approach
to the provisioning methodology proposed for premium service of high-quality
demanding traffic in the wide-area. Our approach is based on a series of wellknown
results of queuing theory but is proven to provide good approximations
to experimental results as well as worthwhile qualitative guarantees.},
	author = {Christos Bouras and Afroditi Sevasti}
}
@conference {2753,
	title = {An approach to methodology and implementation of a Network Monitoring Analysis Tool},
	booktitle = {EUROMEDIA 2003 {\textendash} COMTEC, Plymouth, UK},
	year = {2003},
	month = {14 - 16 April},
	pages = { 125 - 129},
	abstract = {In this paper we describe the design and implementation of a
network monitoring analysis tool. The network resources
were configured to support SNMP under various operating
systems, thresholds definitions and events. The data were
collected by a network monitoring system and handled
according to the values of the variables or the event type. A
real- time report to a database was established via adaptive
scripts. A Network Node Manager (NNM) will inform an
external, remote database about the network status by
sending real time data containing alerts and events. The
whole tool is called Network Management Analysis Tool
(NMAT).},
	author = {Christos Bouras and Petros Ganos and E Aravantinos and A Ilias}
}
@conference {2740,
	title = {Building e {\textendash} learning communities: The case of VirRAD},
	booktitle = {3rd IEEE International Conference on Advanced Learning Technologies, Athens, Greece},
	year = {2003},
	month = {9-11 July},
	pages = { 452},
	abstract = {This paper discusses the development of virtual
communities and especially e-learning communities. In
particular, this paper is inspired by VirRAD European
project, and presents the intermediate results that have
raised from the definition of this virtual radiopharmacy
community.},
	author = {Christos Bouras and Vaggelis Kapoulas and Thrasivoulos Tsiatsos and Eleftheria Giannaka and Maria Nani}
}
@conference {2744,
	title = {Building reusable and interactive e-learning content using Web},
	booktitle = {2nd International Conference on Web - based Learning, Melbourne, Australia},
	year = {2003},
	month = {18 - 20 August},
	pages = { 497 - 508},
	abstract = {This paper presents the design of a web-based learning content
authoring tool as well as the way learners can access courseware material,
within the scope of a personalized, yet social, learning environment for
vocational training. The authoring tool is intended to be part of the instructional
component of the VirRAD European project, where the learning process is
inspired by the principles of the Mindful Learning theory and supported by an
intelligent learner modelling system. It will enable the creation of
Radiopharmacy-related learning content that can be easily accessed and reused.
In addition, it will facilitate the monitorship of the users{\textquoteright} learning activities.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Maria Nani}
}
@conference {2755,
	title = {Comparing performance of SRAMT {\textendash} LE vs other Layerd encoding schemes regarding TCP friendliness},
	booktitle = {6th IEEE International Conference on High Speed Networks and Multimedia Communications (HSNMC{\textquoteright}03), Estoril, Portugal},
	year = {2003},
	month = {23 - 25 July},
	pages = { 493 - 502},
	abstract = {In this paper we describe a hybrid sender and receiver-based
adaptation scheme for multicast transmission of multimedia data using layered
encoding, which we call SRAMT-LE (Sender-Receiver based Adaptation
scheme for Multicast Transmission using Layered Encoding). The most
prominent features of SRAMT-LE are its distributed (to sender and receivers)
transmission rate estimation algorithm and its innovative RTT (Round Trip
Time) estimation algorithm based on one-way delay measurements. SRAMTLE
is using both a TCP model and an AIMD (Additive Increase Multiplicative
Decrease) algorithm in order to estimate a TCP friendly bandwidth share. We
evaluate SRAMT-LE and compare it with a number of similar layered encoding
schemes available to the literature (PLM, RLC, MLDA). Main conclusion of
this evaluation was that SRAMT-LE has friendly behavior against the dominant
traffic types of today{\textquoteright}s Internet and has a relative good behavior comparing
with the other layered encoding schemes available to the literature.},
	author = {Christos Bouras and Apostolos Gkamas}
}
@article {3048,
	title = {Competitive Video on Demand Schedulers for Popular Movies},
	journal = {Discrete Applied Mathematics, Special Issue Algorithmic Aspects of Communication, Elsevier Science, Vol. 129, Issue 1},
	year = {2003},
	pages = {PP. 49 - 61},
	abstract = {<p>In this paper we investigate the online video on demand problem, namely having to accept or reject a request for a movie without knowing the future requests. We present online movie-scheduling schemes that implement the principles of refusal by choice and delayed noti- 4cation. A novel way to schedule movies that exploits the knowledge of the distribution of the preference of requests for movies, is shown to have a competitive ratio that outperforms all the previously knownschemes inpractical situations. Infact, our scheduler has a competitive ratio bounded above by a constant, independent of the number of the users, channels, or movies, in the case that a large fraction of the requests tends to concentrate in a small number of movies. We extend our approach by presenting an {\textquotedblleft}adaptive{\textquotedblright} randomized scheduler which initially is not aware of the movie popularities but it adapts to it, and achieves the same asymptotic competitive ratio.</p>
},
	author = {Christos Bouras and Vaggelis Kapoulas and Paul Spirakis and G Pantziou}
}
@conference {2743,
	title = {Delivering Interactive Enhanced Sports Content to Thin {\textendash} Client DTV STBs},
	booktitle = {International Conference on Cross {\textendash} Media Service Delivery (CMSD {\textendash} 2003), Santorini, Greece},
	year = {2003},
	month = {30 - 31 May},
	pages = { 193 - 204},
	abstract = {Digital Television (DTV) was the first major advance in the television industry
since the establishment of color TV sets in the 50{\textquoteright}s. However, despite the
ambitious anticipations, most DTV operators offering subscriber TV services
are facing serious economic problems. Many believe that significantly
increasing the DTV operator revenues is closely linked to the provision of
advanced interactive TV applications which, on one-hand, based on content
enhancements will attract more subscribers, and on the other hand will also
generate indirect revenues through services like TV-commerce or on-line
betting. In this paper an end-to-end interactive TV application is presented.
The application has been developed for accompanying sport broadcasts, given
that sports content is very attractive for the majority of subscribers. This
application enhances sport broadcasts with relevant content (statistics, news,
information) appearing on user-demand, as well as with an innovative
interactive entertaining game of predictions challenging users to make
predictions and to prove their anticipatory skills and sport knowledge. The
application supports multiple types of forward and return channels and STB
middleware systems. Furthermore, its components can be used in content
distribution networks targeting multiple network-enabled information
appliances},
	author = {Christos Bouras and Vaggelis Kapoulas and Ioannis Misedakis and H Karathanasis and V Tzovla and G Vrahliotis and M Makris}
}
@conference {2758,
	title = {Deployment of a DiffServ - based priority service in a MAN/WAN environment},
	booktitle = {The International Conference on Advanced Information Networking and Applications (AINA), Xi an, China},
	year = {2003},
	month = {27 - 29 March},
	pages = { 27 - 32},
	abstract = {The increased need for Quality of Service (QoS) in
today?s networks has concentrated a lot of research and
implementation efforts. Particular interest exists for the
exploitation of the DiffServ framework towards the
provision of qualitative services in MANs and WANs
worldwide. Although individual mechanisms have been
widely investigated, not many references to studies
combining all levels of priority and QoS provisioning
exist. This work aims at presenting a thorough and
unified approach to the dimensioning and provisioning of
a high priority service for high-quality demanding traffic
over a MAN/WAN environment. Our approach anticipates
for bounds in specific quality metrics and is demonstrated
by the experimental case-study of a high-priority service
over a MAN topology.},
	author = {Christos Bouras and Afroditi Sevasti}
}
@article {3047,
	title = {The deployment of IPv6 in an IPv4 world and Transition Mechanisms},
	journal = {Internet Research: Electronic Networking, Applications and Policy, Emerald, Volume 13, Number 2},
	year = {2003},
	pages = { 86 - 93},
	abstract = {It is stated that the new version of the IP protocol, IPv6, is
the answer to the majority of the problems that were raised
during the enormous expansion of the Internet and its
transformation to a global communication platform with
commercial scope. At the same time it is also stated that
IPv6 dominance will not be easy and there will be a period
when the two versions of the protocol will co-exist. In this
paper we describe some of the main transition mechanisms
that can be deployed in order to facilitate the transition
process to the new version of the IP protocol. Furthermore,
the presented mechanisms are discussed regarding their
usability, usefulness and manageability. Describes the way
some of these mechanisms were applied to the Greek
Research \& Technology Network (GRNET).},
	author = {Christos Bouras and A Karaliotas and Petros Ganos}
}
@conference {2750,
	title = {Educational Information Society in Greece: The Greek School Network},
	booktitle = {IADIS International Conference e {\textendash} SOCIETY, Lisbon, Portugal},
	year = {2003},
	month = {3 - 6 June},
	pages = { 179 - 186},
	abstract = {In this paper, we present the Greek School Network. This project is financed by the Second and Third Community Support
Framework of the European Union. Research and Academic Computer Technology Institute (CTI) has the responsibility for
the design, coordination and the implementation of the project. The main object of the project is the implementation of a
network infrastructure for the interconnection of school laboratories and educational administration offices and the provision
of network services in a wide range. It forms a closed educational network, which is based on the Greek educational and
research backbone network (GRNET). The Greek School Network statistics show that teachers and students have adopted the
services of GSN in their school life and learning activities.},
	author = {Christos Bouras and Mixalis Paraskevas}
}
@conference {2748,
	title = {Efficient Reduction of Web Latency through Predictive Prefetching on a WAN},
	booktitle = {The Fourth International Conference on Web - Age Information Management (WAIM03) Chengdu, China},
	year = {2003},
	month = {17 - 19 August},
	pages = { 25 - 36},
	abstract = {This paper studies Predictive Prefetching on a Web system that provides
two levels of caching before information reaches the clients. We analyze
prefetching on a Wide Area Network with the above mentioned characteristics.
First, we provide a structured overview of predictive prefetching and show its
wide applicability to various computer systems. The WAN that we refer to is
the GRNET academic network in Greece. We rely on log files collected at the
network{\textquoteright}s Transparent cache (primary caching point), located at GRNET{\textquoteright}s edge
connection to the Internet. We present the parameters that are most important
for prefetching on GRNET{\textquoteright}s architecture and provide preliminary results of an
experimental study, quantifying the benefits of prefetching on the WAN.},
	author = {Christos Bouras and Agis Konidaris and Dionisis Kostoulas}
}
@article {3051,
	title = {An electronic voting service to support decision making in Local Government},
	journal = {Journal of Telematics and Informatics-Special Issue, The Internet and Local Governance: Issues for Democracy, Elsevier Science, Vol. 20, Issue 3},
	year = {2003},
	pages = { 255 - 274},
	abstract = {This paper presents details of a web-based, database-oriented {\textquoteleft}{\textquoteleft}electronic voting service{\textquoteright}{\textquoteright}.
Rapid world-wide growth in Internet and Web use has stimulated many initiatives aimed at
applying information and communication innovations to create what has been called a
{\textquoteleft}{\textquoteleft}digital{\textquoteright}{\textquoteright} or {\textquoteleft}{\textquoteleft}electronic democracy{\textquoteright}{\textquoteright}. Internet voting is already widespread in a variety of
forms, some serious, most not. A new set of opportunities is offered to facilitate closer links
among citizens, between citizens and politicians and direct democratic participation through
online voting and interactive polling. Local government decision-making procedures can be
enhanced by the application of a electronic voting service to evaluate citizens responses to
certain issues and to canvass the possible solutions they have in mind.
The main characteristics of this electronic voting service were developed on the basis of
strong lengthy experience of and a good deal of consultation with local authorities. This interaction
revealed a demand for an easy to use (for novice users) and administer tool, low cost
with a minimum set of security mechanisms, but still able to provide valid results. The systems
services were planned and implemented to be easily expandable. The application is based on
state-of-the-art software platform, integrating WWW and database. The system aims to become
a pilot for implementing efforts to support on line voting procedures. The service provides
the capability to create a questionnaire/poll, view the subject and participate in the
voting procedure. Only authorised users can use the system to vote or create a questionnaire.
All users can view results from previous voting procedures.},
	author = {Christos Bouras and Vasilis Triantafillou and N Katris}
}
@article {3043,
	title = {Evaluation of Teleteaching Services over ATM and IP Networks},
	journal = {Journal of Telematics and Informatics, Elsevier Science, Vol. 20, Issue 1},
	year = {2003},
	pages = { 1 - 18},
	abstract = {This paper presents the components of a synchronous teleteaching application, their underlying
technology and their interaction with network services. In addition, it presents the
architecture and design of a synchronous teleteaching application used over the public ATM
network in Greece. This paper presents various teleteaching scenarios over an ATM network
infrastructure with the use of native ATM and IP over ATM. In each scenario we present the
standards used, the logical components, the resource demands (network and equipment) and
its special characteristics. For each scenario we give detailed information about the transmission
and frame rates and the video delay. The main result of our experiments is that
broadband networks offer many capabilities for high quality teleteaching, and generally
speaking, high quality telematic services.},
	author = {Christos Bouras and Vaggelis Kapoulas and Apostolos Gkamas and Thrasivoulos Tsiatsos}
}
@conference {2761,
	title = {From IPv4 to IPv6: The Case of OpenH323 Library},
	booktitle = {SAINT-2003, The 2003 International Symposium on Applications and the Internet, Workshop in IPv6 and Applications, Orlando, Florida, USA},
	year = {2003},
	month = {27 - 31 January},
	pages = { 196 - 199},
	abstract = {In this paper, we discuss our experience form porting
the OpenH323 platform to IPv6. We briefly discuss the
structure of the platform, and we present the various
problems we faced and choices we made, regarding the
easiest approach to the porting procedure, the
compatibility with earlier, IPv4-only versions of the
platform, the existence of tools that could aid us with the
porting task and the verification of result. We believe
that the results of our effort can serve as guidelines for
other similar projects and we present a general
methodology which might be applicable to similar
porting projects.},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos}
}
@conference {2752,
	title = {Issues for the Performance Monitoring of an Open Source H.323 Implementation Ported to IPv6 {\textendash} Enabled Networks with QoS Characteristics},
	booktitle = {The 2003 International Conference in Internet Computing (IC 2003), Las Vegas, Nevada, USA},
	year = {2003},
	month = {23 - 26 June},
	pages = { 765 - 771},
	abstract = {OpenH323 is an open source H.323 implementation
that has been ported to IPv6. It therefore presents an
opportunity to perform experiments and compare the
performance of an H.323 application when using the
IPv4 stack and when using the IPv6 stack. In this
paper we initially introduce briefly the porting
procedure and the methodology we used in order to
achieve it. We then present the appropriate
experiments that have to be performed in order to
comparatively evaluate the IPv4 and IPv6 protocol
stacks. We also present the results of some initial
experiments comparing IPv4 and IPv6 performance
and the conclusions that they can lead us to.},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos and Dimitris Primpas and A Karaliotas}
}
@conference {2751,
	title = {Issues for the Performance Monitoring on Networked Virtual Environments},
	booktitle = {7th ConTEL {\textendash} International Conference on Telecommunications, Zagreb, Croatia},
	year = {2003},
	month = {11 - 13 June},
	pages = { 725 - 728},
	abstract = {The wide expansion and increasing demand for
Networked Virtual Environments resulted in efforts for the
optimization of these environments with the enhancement of
advanced features, which offered extended functionality and
created an improved sense of realism. However, the added
functionality often creates resource overhead both in the system
as well as in the network host, which results in performance
reduction. This paper presents such a networked virtual
environment and based on the system?s architecture tries to trace
down with the time and recourse consuming parameters and
proposes models on which a networked virtual environment, like
the one presented, could achieve optimization of its performance.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka}
}
@conference {2759,
	title = {Management Bandwidth Sevice on MPLS domain},
	booktitle = {17th IEEE International Workshop on Communications Quality \& Reliability {\textendash} CQR 2003, Kiawah Island, South Karolina, USA},
	year = {2003},
	month = {7 - 10 April},
	abstract = {This paper describes an efficient way to implement managed bandwidth services. The
proposed solution is based on MPLS technology and especially with the creation of
virtual private networks. The virtual private networks will be layer 3 VPNs (IP VPNs)
and are described all the mechanisms and the MPLS features that are necessary for the
MBS service implementation. The paper also describes how the service will interact
with the users and finally presents a schema for the interconnection with the MBS
service of Geant.},
	author = {Christos Bouras and Vaggelis Kapoulas and Dimitris Primpas}
}
@conference {2741,
	title = {Managing users and services using an LDAP based web - application},
	booktitle = {APPLIED INFORMATICS 2003 - Parallel and Distributed Computing and Networks, Innsbruck, Austria},
	year = {2003},
	month = {10 - 13 February},
	pages = { 773 - 778},
	author = {Christos Bouras and C Sintoris and A Limperis}
}
@inbook {3123,
	title = {Modeling Data Intensive Web Sites for Personalisation, Integrity and Performance},
	booktitle = {Information Modeling for Internet Applications},
	year = {2003},
	pages = { 259 - 276},
	publisher = {IDEA Group Publishing},
	organization = {IDEA Group Publishing},
	chapter = {XII},
	abstract = {<p>This chapter presents a step-by-step approach to the design, implementation and management of a Data-Intensive Web Site (DIWS). The approach introduces five data formulation and manipulation graphs that are presented analytically. The core concept behind the modeling approach is that of {\textquotedblleft}Web fragments,{\textquotedblright} that is an information decomposition technique that aids design, implementation and management of DIWS. We then present the steps that must be followed in order to {\textquotedblleft}build{\textquotedblright} a DIWS based on Web fragments. Finally, we show how our approach can be used to ensure the basic DIWS user requirements of personalization, integrity and performance.</p>
},
	author = {Christos Bouras and Agis Konidaris}
}
@conference {2737,
	title = {A Most Popular Approach of Predictive Prefetching on a WAN to Efficiently Improve WWW Response Times},
	booktitle = {The Second International Workshop on Grid and Cooperative Computing, Shangai, China},
	year = {2003},
	month = {7 - 10 Devember},
	pages = { 344 - 351},
	abstract = {This paper studies Predictive Prefetching on a Wide Area Network
with two levels of caching. The WAN that we refer to is the GRNET academic
network in Greece. We rely on log files collected at the network{\textquoteright}s Transparent
cache (primary caching point), located at GRNET{\textquoteright}s edge connection to the
Internet. Our prefetching model bases its predictions on popularity ranking of
passed requests. We present a {\textquotedblleft}n-next most popular{\textquotedblright} approach used for prefetching
on GRNET{\textquoteright}s architecture and provide preliminary results of our experimental
study, quantifying the benefits of prefetching on the WAN.},
	author = {Christos Bouras and Agis Konidaris and Dionisis Kostoulas}
}
@conference {2756,
	title = {Multi {\textendash} User Layer in the EVE Distributed Virtual Reality Platform},
	booktitle = {5th International Workshop on Multimedia Networks Systems and Applications (MNSA2003), Providence, Rhode Island, USA},
	year = {2003},
	month = {19 - 22 May},
	pages = { 602 - 607},
	abstract = {In this paper, we present the design and
implementation of a VRML97 multi-user layer, which is
introduced in the EVE distributed virtual reality platform.
Main consideration of our multi-user extension is the ease
of transforming single-user virtual worlds to multi-user
virtual worlds, as well as the conformity with any standard
VRML97 browser. Furthermore, we present the EVE{\textquoteright} s
communication platform, which can be used in order to
support Collaborative Virtual Environments (CVEs). Main
issues regarding the effective network communication as
well as the initialization of the 3D scene are discussed in
this paper.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and D Psaltoulis and C Psaroudis}
}
@article {3046,
	title = {Multimedia Transmission with Adaptive QoS based on Real Time Protocols},
	journal = {International Journal of Communications Systems, Wiley InterScience, Volume 16, Issue 2},
	year = {2003},
	pages = { 225 - 248},
	abstract = {In this paper, we describe a mechanism for adaptive transmission of multimedia data, which is based on
real-time protocols. The proposed mechanism can be used for unicast or multicast transmission of
multimedia data over heterogeneous networks, like the Internet, and has the capability to adapt the
transmission of the multimedia data to network changes. In addition, the implemented mechanism uses an
inter-receiver fairness function in order to treat the group of clients with fairness during the multicast
transmission in a heterogeneous environment. The proposed mechanism uses a {\textquoteleft}friendly{\textquoteright} to the network
users congestion control policy to control the transmission of the multimedia data. We implement a
prototype application based on the proposed mechanism and we evaluate the proposed mechanism both in
unicast and multicast transmission through a number of experiment and a number of simulations in order
to examine its fairness to a group of clients and its behaviour against transport protocols (TCP) and UDP
data streams.},
	author = {Christos Bouras and Apostolos Gkamas}
}
@conference {2757,
	title = {Performance Analysis for a DiffServ - enabled network : the case of Relative Service},
	booktitle = {2nd IEEE International Symposium on Network Computing and Applications (NCA-03), Cambridge, Massachusetts, USA},
	year = {2003},
	month = {16 - 18 April},
	pages = { 381 - 387},
	abstract = {A lot of research work has recently focused on the exploitation of the DiffServ framework towards building reliable networking services that provide deterministic quality guarantees. In this work we are attempting to devise a DiffServ-based service model for relative differentiation of traffic in a network serving aggregated traffic. The service model proposed aims at providing a minimum capacity during congestion and a bounded average end-to-end delay to profile-conforming traffic, obtaining thus a relatively better performance when compared to the best-effort service. We provide the framework on which the proposed service model is based and we present results from its deployment in a simulation environment.},
	author = {Christos Bouras and Afroditi Sevasti}
}
@article {3050,
	title = {Performance Evaluation of a Hybrid Run-time Management Policy for Data intensive Web Sites},
	journal = {World Wide Web Journal: Internet and Web Information Systems, Kluwer Academic Publishers, Vol 6, Issue 1},
	year = {2003},
	month = {March},
	pages = { 23 - 47},
	abstract = {The issues of performance, response efficiency and data consistency are among the most important for data
intensive Web sites. In order to deal with these issues we analyze and evaluate a hybrid run-time management
policy that may be applied to data intensive Web sites. Our research relies on the performance evaluation of
experimental client/server configurations. We propose a hybrid Web site run-time management policy that may
apply to differentWeb site request patterns and data update frequencies. A run-time management policy is viewed
as a Web page materialization policy that can adapt to different conditions at run-time. We define a concept
that we have named the Compromise Factor (CF), to achieve the relationship between current server conditions
and the materialization policy. The issue of Web and database data consistency is the driving force behind our
approach. In some cases though, we prove that certain compromises to consistency can be beneficial to Web
server performance and at the same time be unnoticeable to users. We first present a general a comparative cost
model for the hybrid management policy and three other related and popular Web management policies. We then
evaluate the performance of all the approaches. The results of our evaluation show that the concept of the CF may
be beneficial to Web servers in terms of performance.},
	author = {Christos Bouras and Agis Konidaris}
}
@conference {2746,
	title = {Performance Evaluation of the Managed Bandwidth Service with QoS guarantees},
	booktitle = {7th IEEE International Symposium on Distributed Simulation and Real Time Applications, Delft, The Netherlands},
	year = {2003},
	month = {23 - 25 October},
	pages = { 93 - 100},
	abstract = {This paper describes a solution to extend the Managed Bandwidth Service (MBS), which is provided on a backbone network using MPLS VPNs, to non-MPLS domains and also evaluates it. It is based on the Class Based Weighted Fair Queueing mechanism (CBWFQ) [4] and describes the way it should be implemented to provide guaranteed bandwidth connections. In particular, CBWFQ can provide assured bandwidth connections when simultaneously leads to efficient bandwidth utilization. In addition, the proposed solution is being tested on simulation environment (using the Network Simulator) in order to evaluate its performance characteristics. On the simulation tests had been reserved specific amount of bandwidth for specific flows and their throughput was measured in order to understand if the proposed solution works well. Finally, the results are very well and prove that this method can guarantee bandwidth for every flow in all network conditions (congested or un-congested). At last, the paper presents a technical example of router configuration for implementing the MBS service according to the basic proposed solution.},
	author = {Christos Bouras and Vaggelis Kapoulas and Dimitris Primpas}
}
@article {3042,
	title = {Performance issues of bandwidth management in ATM networks},
	journal = {International Journal of Communication Systems, Wiley InterScience, Volume 16, Issue 2},
	year = {2003},
	pages = { 151 - 169},
	abstract = {In our days, efficient management of the available network resources becomes a critical issue, both from a
functional point of view (so that users can be provided with the bandwidth they need), and an economical
point of view (so that carriers can satisfactorily and efficiently serve as many customers as possible and at
the same time increase their revenue). In this paper we consider a bandwidth control scheme (i.e. managed
bandwidth service) for an ATM network infrastructure which is applied to the Greek research and
technology network (GRNET). We present some methods that we have tested (in a simulation setting) in
order to increase the efficiency of the system and the utilization of the available bandwidth. More
specifically, we consider a bandwidth-resizing algorithm for virtual paths, in order to keep the allocated
bandwidth very close to the bandwidth actually used. This leads to an increased number of accepted
requests and better network utilization. We, also, use the simulation results in order to get an estimation of
the effective bandwidth for VBR paths that can be used in call admission. Finally, we consider a semioffline
scheme where requests are gathered and considered for acceptance in regular intervals. Simulation
results show an increase in the utilization of resources. As a further improvement, we allow connections to
be allocated a little before or after the time initially requested. This leads to further improvement in
network utilization. All the improvement schemes were tested with the ATM-TN simulator and the results
look promising.},
	author = {Christos Bouras and Vaggelis Kapoulas and Alexandros Panagopoulos and Afroditi Sevasti and Chrysa Chantzi and Ioanna Sampraku}
}
@article {3044,
	title = {Policies for Content Filtering in Educational Networks: The case of Greece},
	journal = {Journal of Telematics and Informatics, Elsevier Science, Vol. 20, Issue 1},
	year = {2003},
	pages = { 71-95},
	abstract = {The Internet removes all barriers to sending and receiving information. An increasing
number of nations connect their schools on the Internet as an acknowledgment of its importance
in education. Despite its undeniable usefulness, it also has certain perils. This study
specifies and evaluates these, finding the technologies that are currently available to address
filtering issues and comparing them. We present our proposed solution for the Greek School
Network, and illustrate to what extent our solution successfully addresses the issues discussed.},
	author = {Christos Bouras and Maria Avgoulea and Mixalis Paraskevas and G Stathakopoulos}
}
@article {3045,
	title = {QoS and SLA aspects across multiple management domains: The SEQUIN approach},
	journal = {Future Generation Computer Systems (FGCS) Journal, Special Issue from the TERENA 2002 Networking Conference, Elsevier Science, Volume 19, Issue 2},
	year = {2003},
	month = {February},
	pages = { 313-326},
	abstract = {The aim of this work is to define and implement an end-to-end approach to quality of service (QoS), operating across
multiple management domains and exploiting a combination of link layer technologies. The architecture for the Premium IP
service is presented, which aims at offering the equivalent of an end-to-end virtual leased line service at the IP layer across
multiple domains. Also, the results of the initial testing performed for the validation of the service and the provisioning
model for Premium IP are described. The work presented has been carried out in the framework of SEQUIN, a European
Commission-funded research project.},
	author = {Christos Bouras and Afroditi Sevasti and M Campanella and M Przybylski}
}
@conference {2745,
	title = {A SCORM {\textendash} conformant LMS},
	booktitle = {ED {\textendash} MEDIA 2003, Honolulu, Hawaii, USA},
	year = {2003},
	month = {23 - 28 June},
	pages = { 10 - 13},
	abstract = {In this paper we propose a sample Learning Management System (LMS) that
will be conformant with the SCORM v1.3 Specification. In particular, the sample LMS
we propose will make use of both, the SCORM Run Time Environment, in order to
communicate with the learning content, and a sequencing engine so as to sequence
discrete learning activities in a consistent way, based on the learners{\textquoteright} interactions with
the content. Even if the SCORM v1.3 Specification is not yet finalized, the proposed
LMS intends to be an attempt to test and evaluate the specification in its present form.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Maria Nani}
}
@conference {2742,
	title = {SRAMT-LE: A Hybrid Sender And Receiver-Based Adaptation Scheme For TCP friendly multicast transmission using layered encoding},
	booktitle = {Communication Networks and Distributed Systems Modeling and Simulation Conference (CNDS-03 Part of the 2003 Western MultiConference), Orlando, Florida},
	year = {2003},
	month = {19 - 23 January},
	pages = { 71 - 76},
	abstract = {In this paper we describe a hybrid sender and receiver-based adaptation
scheme for multicast transmission of multimedia data using layered
encoding, which we call SRAMT-LE (Sender-Receiver based Adaptation
scheme for Multicast Transmission using Layered Encoding). The most
prominent features of SRAMT-LE are its distributed (to sender and
receivers) transmission rate estimation algorithm and its innovative RTT
(Round Trip Time) estimation algorithm based on one-way delay
measurements. In addition, SRAMT-LE adjusts the transmission rates of the
layers in order to service better the group of the receivers. SRAMT-LE is
using both a TCP model and an AIMD (Additive Increase Multiplicative
Decrease) algorithm in order to estimate a TCP friendly bandwidth share.
With the use of SRAMT-LE, we ensure that sender will transmit TCP
friendly traffic and receivers with different capabilities (in terms of
available bandwidth) are able to receive the multimedia information. We
evaluate SRAMT-LE through a number of simulations in order to examine
its behaviour to a heterogeneous group of receivers and its behaviour against
TCP connections. Main conclusion of the simulations was that SRAMT-LE
has friendly behaviour against the dominant traffic types of today{\textquoteright}s Internet
and treats a heterogeneous group of receivers with fairness.},
	author = {Christos Bouras and Apostolos Gkamas}
}
@conference {2739,
	title = {Using J2EE Web Services for the Implementation of an Application on Demand Portal},
	booktitle = {The Second Workshop on e {\textendash} Business (WeB 2003), Seattle, USA},
	year = {2003},
	month = {13 - 14 December},
	pages = { 72 - 83},
	abstract = {This paper describes the design of the ASP-NG portal, which is a portal for providing the user with the
necessary interface in order to access an Application on Demand (AoD) service. The ASP-NG portal is
responsible for the interaction with the user of the Application on Demand service. The implementation of
the ASP-NG portal is going to be based on the Web Services of the Java 2, Enterprise Edition (J2EE)
platform. The ASP-NG portal will offer to its users the capability to select and customize the language of
the user interface in order to present information in their preferred language. Moreover the ASP-NG
portal will offer to the portal administrator the capability to customise the look and feel of the ASP-NG
portal.},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos and Dimitris Primpas}
}
@conference {2760,
	title = {Virtual Collaboration Spaces: The EVE Community},
	booktitle = {The 2003 Symposium on Applications \& the Internet- SAINT-2003, Orland, Florida},
	year = {2003},
	month = {27 - 31 January},
	pages = { 48 - 55},
	abstract = {An Educational Virtual Environment (EVE) is an
instance of a Collaborative Virtual Environment (CVE),
which focalises in providing collaborative, as well as
educational, functionalities, such as synchronous and
asynchronous e-learning services. This paper describes
such an educational virtual community, which aims to
meet the requirements of a virtual collaboration space
and furthermore to support e-learning services. In
particular, we are developing a web-based system, which
allows users to communicate with the other members of
the community through forums, chat, e-mail, to schedule
events which take place in the learning environment and
to join, and even create, courses, which are held in 3D
multi-user worlds where users are represented by avatars.
These characteristics offer extended functionalities such
as support of application sharing and voice chat,
transmission of the educational material as well as
transmission of the users{\textquoteright} profiles to the other community
members. We describe the model of this community and
the functionalities that it provides.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Eleftheria Giannaka}
}
@conference {2738,
	title = {Virtual Learning Communities - Theory and Practice: The case of VirRAD},
	booktitle = {E-Learn 2003, Phoenix, Arizona, USA},
	year = {2003},
	month = {7 - 11 November},
	pages = { 495 - 498},
	abstract = {In this paper we discuss the development of virtual communities and especially virtual learning communities, taking into account basic community requirements as well as social factors of e-learning. This paper has been inspired by the VirRAD European project and presents the intermediate results that have raised form the definition of a virtual community for the vocational training of radiopharmacists. We therefore present the user requirements that form the functional specification of such an environment along with the role model that provides a mindful but solid distribution of the access level in the system.},
	author = {Christos Bouras and Vaggelis Kapoulas and Thrasivoulos Tsiatsos and Eleftheria Giannaka and Maria Nani}
}
@conference {2749,
	title = {A web-based game for supporting game-based learning},
	booktitle = {GAME-ON 2003, London, UK},
	year = {2003},
	month = {19 - 21 November},
	pages = { 111 - 118},
	abstract = {Game-based learning has been recognized as an important
alternative or supplement to traditional in-class, face-to-face
teaching. It can help both adults and children in learning new
concepts, acquiring expertise and practicing knowledge.
Although game-based learning has been applied mainly for
teaching children, it can be quite helpful for adult vocational
or university learning. In this paper, a web-based game is
presented, which has been developed for enhancing the
learning experience of university students. Its goal is to
serve as a complement to classes, although it can be used
independently. It provides the students with many ways for
communicating (synchronously or asynchronously) and
acquiring information. Through the use of the game, the
students gain easily new knowledge, since they have to
search for it, understand it and use it in discussions with
other students, who are members of other teams. The game
is played by many users simultaneously. Microsoft{\textquoteright}s
ASP.NET scripting environment was used for creating the
game{\textquoteright}s website. The website utilizes also Macromedia{\textquoteright}s
communication technology (Flash Communication Server
MX) for enabling real-time communication by several means
(voice, text, etc). Flash was used in the website for building
the real-time communication modules as well as for creating
a more elegant user interface. The game platform can be
used by many teachers simultaneously for running different
game themes. It also gives the opportunity to visitors to
watch games as spectators.},
	author = {Christos Bouras and Vaggelis Kapoulas and Vaggelis Igglesis and Ioannis Misedakis and O Dziabenko and M Pivec}
}
@article {3049,
	title = {Wireless School Network},
	journal = {Learning Technology Newsletter {\textendash} IEEE Learning Technology Task Force(on line), Vol. 5, Issue 2},
	year = {2003},
	month = {April},
	abstract = {The architecture of the wireless network consists of 3 main parts. The wireless infrastructure, the connection of the
wireless island to the rest network and the interconnection between the neighboring schools a near one participating in
the wireless network. The wireless connection supports Point-to-Multipoint technology [3] and uses the frequency band
2,4 Ghz to 2,4835 Ghz. The reserved bandwidth of this wireless LAN is order of magnitude 11 Mbps. In each school the
bridge device is connected to a newly equipped Fast Ethernet switch interconnecting the internal schools network to the
wireless network. Between the schools a fast Ethernet network is built using copper and Fiber optic cabling. The
interconnection of the wireless network upstream to the backbone is achieved with the use of the link between the E.A.O
and the local main distribution node of the EDUNET network. This link had to be upgrade because it will carry the
traffic from the wireless network too. The selected solution was the VDSL technology by engaging the appropriate
modems over a two-wire leased line between the E.A.O and the main node. We have a selected point in each school unit
that wireless bridge and antenna will be installed. The wireless bridge must stand near to antenna because long cabling
distances will produce noise in the transmission signal. The wireless bridge will be housed at waterproof cabinet, which
offers all the necessary specifications for protection and electric feeding. The waterproof cabinet is installed at the
antenna pylon.},
	author = {Christos Bouras and A Karaliotas and Mixalis Paraskevas and V Papoutsis and Christos Ntokos and N Drosopoulos}
}
@article {3053,
	title = {An Architecture for Interactive Distributed Multimedia Information Services},
	journal = {Telecommunication Information Management Journal, Volume 2, Issue 4},
	year = {2002},
	pages = { 3 - 10},
	abstract = {In this work, we present an architecture for interactive distributed multimedia information services. The service
consists of three basic parts, the clients, the access servers, and the content servers. Clients manage the
presentation of the requested multimedia documents, while also ensure the synchronization among various
involved media. Special policies for the synchronized presentation of multimedia documents and user
interactions management are discussed. Access servers authorize the users for legitimate use of the service,
while also provide various searching capabilities Content servers manage the transportation of multimedia
documents over a broadband network and the user interactions. The proposed architecture preserves
scalability, flexibility and modularity due to the distributed nature of the architecture, while also results in good
performance due to the dynamic allocation of resources.},
	author = {Christos Bouras and Vaggelis Kapoulas and Paul Spirakis and D Moiras and V Ouzounis}
}
@conference {2767,
	title = {Behaviour Investigation using Simulation for Redundant Multicast Transmission Supporting Adaptive QoS},
	booktitle = {10th IEEE International Conference on Networks (ICON 2002), Singapore},
	year = {2002},
	month = {27 - 30 August},
	pages = { 112 - 117},
	abstract = {In this paper we describe a mechanism for redundant multicast
transmission of multimedia data supporting adaptive QoS over
the Internet and we investigate its behaviour using simulation.
There are two major issues that have to be considered when
designing and implementing such a mechanism, the fairness,
which is the ability to cope with receiver heterogeneity, and the
adaptation schemes. The proposed mechanism uses a friendly to
the network users congestion control policy to control the
transmission of the data. We evaluate the adaptive multicast
transmission mechanism through a number of simulations in
order to examine its behaviour to a heterogeneous group of
receivers and its behaviour against TCP and UDP data streams.
Main conclusion of the simulation was that the proposed
mechanism has friendly behaviour against the dominant traffic
types of today{\textquoteright}s Internet and treats a heterogeneous group of
receivers with fairness.},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos and A Karaliotas}
}
@conference {2772,
	title = {Building Educational Virtual Environments},
	booktitle = {2nd IEEE International Conference on Advanced Learning Technologies, Kazan, Russia},
	year = {2002},
	month = {9 - 12 September},
	pages = { 547 - 548},
	abstract = {The collaborative virtual environments have become a
good media for supporting collaborative e-learning
services. In this paper we present the Educational Virtual
Environments (EVE) platform, which integrates a variety
of communication a collaboration tools to support
collaborative virtual environments focused on
collaborative e-learning.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos}
}
@conference {2779,
	title = {Desktop Synchronous Distance Learning Application Enhanced with Efficient Chair Control Capabilities},
	booktitle = {The 2002 International Conference on Parallel and Distributed Processing Techniques and Applications (PDPTA 02), Monte Carlo Resort, Las Vegas, Nevada, USA },
	year = {2002},
	month = {24 - 27 June},
	pages = { 1158 - 1164},
	abstract = {The use of multimedia in Telematics
and new services has been greatly improved by the
introduction of new systems and techniques. These
new systems and techniques made the implementation
of many telematic applications like Synchronous
Distance Learning possible. In this paper, we present
design, functionality and implementation issues, which
concern a Synchronous Distance Learning
application. The described application is a networkbased
application, which can be used over IP and
ISDN networks. In addition the implemented
Synchronous Distance Learning application uses an
innovative chair control module, which does not
require any support from the MCU (Multipoint
Control Unit).},
	author = {Christos Bouras and Vaggelis Kapoulas and Apostolos Gkamas and Kostas Stamos}
}
@conference {2762,
	title = {An Educational Community Using Collaborative Virtual Environments},
	booktitle = {1st International Conference on Web-based Learning, Hong Kong, China},
	year = {2002},
	month = {17 - 19 August},
	pages = { 180 - 191},
	abstract = {The use of Collaborative Virtual Environments in e-learning is one of
the most promising uses of the virtual reality technology. While a lot of
research has been done in the area of collaborative virtual environments
corresponding to the sharing of events, very little research has been done on
specific services and functionality. However both the requirements and the kind
of the offered services affect significantly the design of a system. In this paper
we present an Educational Community to support e-learning services using
Collaborative Virtual Environments from both the technical and functional
point of view.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and D Psaltoulis and C Psaroudis}
}
@conference {2766,
	title = {Efficient Materialization of Dynamic Web Data to Improve Web Performance},
	booktitle = {15th International Conference on Computer Communication, Mumbai, India},
	year = {2002},
	month = {11 - 14 August},
	pages = { 866 - 879},
	abstract = {The issues of performance, response efficiency and data consistency
are among the most important ones for data intensive Web sites on the Internet
today. In order to deal with these issues we analyze and evaluate a
materialization policy that may be applied to data intensive Web sites. Our
research relies on the performance evaluation of experimental client/server
configurations. We propose a materialization policy that applies to different
Web site request patterns and data update frequencies. The issue of Web and
database data consistency is the driving force behind our approach. In some
cases though, we prove that certain compromises to consistency can be
beneficial to Web server performance and at the same time be unnoticeable to
users. We evaluate the performance of our approach and compare it with other
popular materialization approaches. The results of our evaluation show that the
concept of {\textquotedblleft}acceptable inconsistencies{\textquotedblright} between Web and Database data may
be beneficial to Web servers in terms of performance.},
	author = {Christos Bouras and Agis Konidaris}
}
@conference {2771,
	title = {Enhancing the DiffServ Architecture of a Simulation Environment},
	booktitle = {Sixth IEEE International Workshop on Distributed Simulation and Real Time Applications, Fort Worth, USA},
	year = {2002},
	month = {11 - 13 October},
	pages = { 108 - 118},
	abstract = {Simulation has always been a valuable tool for
experimentation and validation of models, architectures
and mechanisms in the field of networking. In the case of
the DiffServ framework, simulation is even more valuable,
due to the fact that an analytical approach of mechanisms
and services is infeasible because of the aggregation and
multiplexing of flows. In this work, we have extended the
functionality of a widely used simulation environment
towards the direction of realistic traffic generation and a
series of mechanisms defined by the DiffServ architecture.
The modules created are being presented and a case
study of a simulation scenario that exploits the
functionality provided by them is described.},
	author = {Christos Bouras and Dimitris Primpas and Afroditi Sevasti}
}
@article {3055,
	title = {An environment for the annotation of multimedia material by younger children},
	journal = {Journal of Educational Multimedia and Hypermedia, (JEMH), AACE, Vol. 11, Issue 4},
	year = {2002},
	pages = { 363 - 385},
	abstract = {The exceptional advent of interactive multimedia applications
has led to the need for their exploitation for educational
purposes. In this article, the design and implementation of a
multimedia annotation environment for young children is
presented. This environment was developed to provide children
aged 4 - 8 with the opportunity to reflect upon and annotate
episodes from their everyday life. The aim was to exploit
the latest technological developments in the field of
multimedia, to build an annotation environment where children
would be able to add multimedia annotations to videos.
Apart from the environment itself, design choices, interface
realization, as well as media handling methods and performance
issues are also presented.},
	author = {Christos Bouras and Apostolos Gkamas and Afroditi Sevasti}
}
@article {2777,
	title = {Estimating and Eliminating Redundant Data Transfers Over the Web: A Fragment Based Approach},
	journal = {3rd International Conference on Internet Computing (IC 2002), Las Vegas, Nevada, USA},
	year = {2002},
	month = {24 - 27 June},
	pages = { 95 - 102},
	abstract = {Redundant data transfers over the Web, can mainly be attributed to repeated transfers of unchanged data. Web caches and Web proxies are some of the solutions that have been proposed, to deal with the issue of redundant data transfers. In this paper we focus on the efficient estimation and reduction of redundant data transfers over the Web. We first prove that a vast amount of redundant data is transferred in Web pages that are considered to carry fresh data. We show this by following an approach based on Web page fragmentation and manipulation. Web pages are broken-down into fragments, based on specific criteria. We then deal with these fragments as independent constructors of the Web page and study their change patterns independently and in the context of the whole Web page. After the fragmentation process we propose solutions for dealing with redundant data transfers.},
	author = {Christos Bouras and Agis Konidaris}
}
@conference {2769,
	title = {Extending the Limits of CVEs to Support Collaborative e-Learning Scenarios},
	booktitle = {2nd IEEE International Conference on Advanced Learning Technologies, Kazan, Russia},
	year = {2002},
	month = {9 - 12 September},
	pages = { 420 - 424},
	abstract = {This paper proposes the use of collaborative virtual
environments in order to provide collaborative e-learning
services in an efficient and cost effective way. On the one
hand, we present the transformation of well known
collaborative learning techniques to collaborative elearning
scenarios. The collaborative learning
techniques, which are discussed in this paper, are
brainstorming/roundtable, think pair share, jigsaw,
quickwrites/microthemes, and structured academic
controversies. On the other hand, we describe the
necessary modifications of the collaborative virtual
environments in order to support collaborative e-learning
services and scenarios. Main proposals are the
integration of more media to offer more awareness, the
support of more people with different roles, and the
definition of an integrated system architecture.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos}
}
@article {3052,
	title = {A Framework for Intelligent Virtual Training Environment: The steps from specification to design},
	journal = {Journal of International Forum of Educational Technology \& Society (IFETS) Special Issue on Innovations in Learning Technology, Learning Technology Task Force {\textendash} IEEE (on {\textendash} line), Vol. 5, Issue 4},
	year = {2002},
	pages = { 11 - 26},
	abstract = {The growing need for communication, visualization and organization technologies in the field of e-learning
environments has led to the application of virtual reality and the use of collaborative virtual environments.
This paper presents a system architecture to support such environments, defined by user needs and using
state of the art technologies.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Vasilis Triantafillou}
}
@conference {2775,
	title = {HTTP Traffic Simulation and Evaluation for multiple Users in Intranet Network },
	booktitle = {EUROMEDIA-WEBTEC 2002, Modena, Italy},
	year = {2002},
	month = {14 - 17 April},
	pages = { 63 - 67},
	abstract = {In this paper we describe the architecture and design of a network-stressing tool developed to simulate and evaluate the HTTP requests and responses of hundreds of users. There are two major issues that have to be considered when designing and implementing such a simulation tool, the reliability evaluation and the user {\textquotedblleft}friendly{\textquotedblright} environment. In our application we use a mechanism exploiting Intranet technology to stress the tested network and confirm the performance, proper operation and delay issues. We have also implemented an easy interaction with the user considering the creation of the scenarios and the presentation of the simulation results, pointing out the problems and the network{\textquoteright}s status. Finally, we examined through a number of experiments using different simulation scenarios the behavior of the Intranet by load balancing the simulated users.},
	author = {Christos Bouras and Petros Ganos and E Aravantinos and P Kokkinos}
}
@conference {2764,
	title = {A Managed Bandwidth Service for IP Networks},
	booktitle = {9th IEEE International Conference on Telecommunications(ICT 2002), Beijing, China},
	volume = {1},
	year = {2002},
	month = {23 - 26 June},
	pages = {644-648},
	abstract = {The work presented here attempts to face the problem of bandwidth management in IP networks, especially in cases where the available resources have to be shared among many users with demanding and conflicting needs. We have designed a Managed Bandwidth Service (MBS) that allows users to make bandwidth reservations throughout the topology of the network infrastructure to which they have access based on the establishment of Virtual Private Networks (VPNs) using the Multiprotocol Label Switching (MPLS) technology. In this paper we present the MBS developed along with our on-going and future work on the subject.},
	author = {Christos Bouras and Vaggelis Kapoulas and Afroditi Sevasti and Chrysa Chantzi}
}
@conference {2780,
	title = {Performance Analysis of a Managed Bandwidth Service for ATM Networks},
	booktitle = {Communication Networks and Distributed Systems Modeling and Simulation Conference (CNDS 2002), Riverwalk North, San Antonio, Texas, USA},
	year = {2002},
	month = {27 - 31 January},
	pages = { 220 - 225},
	abstract = {In this paper we are considering methods to improve the performance
of a bandwidth control scheme (i.e. Managed Bandwidth
Service) for an ATM network infrastructure (with application to the
Greek Research and Technology Network - GRNET). These methods
try to increase the efficiency of the system and the utilisation of
the available bandwidth. More specifically, we consider: a) a
bandwidth-resizing algorithm for virtual paths in order to (constantly)
keep the allocated bandwidth very close to the bandwidth
actually used, b) a simple method to estimate the effective bandwidth
for VBR paths that can be used in call admission, and c) a
semi-offline call admission scheme where requests are gathered and
considered for acceptance in regular intervals (with a further improvement,
of allowing connections to be allocated a little before or
after the time initially requested). All these methods were tested in
a simulation setting (with the ATM-TN simulator), and results indicate
that they lead to an increased number of accepted requests and
better network utilisation.},
	author = {Christos Bouras and Vaggelis Kapoulas and Alexandros Panagopoulos and Afroditi Sevasti and Chrysa Chantzi and Ioanna Sampraku}
}
@conference {2765,
	title = {A platform for gaming in Digital Interactive TV},
	booktitle = {10th International Conference on Software, Telecommunications and Computer Networks(SoftCOM 2002), Croatia, Italy},
	year = {2002},
	month = {9 - 11 October},
	pages = { 105 - 109},
	abstract = {Digital Television has increased its popularity the last
years. Its{\textquoteright} main advantage over traditional analogue TV is that
it offers the viewers the ability to use their TV system in order to
view or search for information in a way that is impossible with
analogue TV. The next important step is the offer of
interactivity with Service Providers, exchanging information,
with the use of a return channel. Modern Set-Top-Boxes are not
just decoders of the transmitted digital signals, but can be
programmed to execute complex applications that can interact
with the user through the use of the remote control and with
Service Providers using a built-in modem and the PSTN
network. Applications can be downloaded from satellite, loaded
and executed dynamically, multiplexed with video and audio
streams, along with the data needed, while a viewer changes the
channel he/she watches. Using these types of applications the
viewer becomes a user, using the provided services, despite of
passively watching TV channels.
In this paper, we describe an Interactive Digital TV platform
being developed for delivering statistical and interactive services
to the public. In particular, we use it for offering statistical data
and an interactive game in which the users of the platform can
compete by answering questions and making predictions.},
	author = {Christos Bouras and Vaggelis Kapoulas and Ioannis Misedakis}
}
@conference {2778,
	title = {Policies for Content Filtering in Educational Networks : the Case of Greece},
	booktitle = {ED {\textendash} MEDIA 2002, Denver, Colorado, USA},
	year = {2002},
	month = {24 - 29 June},
	pages = { 57 - 62},
	abstract = {An increasing number of nations connect their schools on the Internet as an
acknowledgment to its extreme importance in the education area. Our study specifies the
perils that arise from its use when the users are minors and evaluates the technologies that are
currently available to address the filtering issues. The thoughts presented in this paper outline
our proposed solution for the Greek School Network. By no means the thoughts that are
presented here, apply for adults or people who pay to establish access to the Internet.},
	author = {Christos Bouras and Maria Avgoulea and Mixalis Paraskevas and G Stathakopoulos}
}
@conference {2770,
	title = {Pricing priority services over DiffServ {\textendash} enabled transport networks},
	booktitle = {6th International Symposium on Communication Interworking(Interworking 2002), Perth, Australia},
	year = {2002},
	month = {13 - 16 October},
	pages = { 25 - 37},
	abstract = {The rapid evolution of the DiffServ framework in our days has provided the means for efficient QoS provisioning over contemporary IP networks. The provisioning of services according to the DiffServ framework has in turn raised the requirements for pricing mechanisms that preserve the potential and flexibility of the DiffServ framework. At the same time, such mechanisms should reflect resource usage, allocate resources efficiently, reimburse costs or maximize service provision profits and lead customers to requesting services that will maximize their revenue. This work proposes a policy for pricing based on resource allocation of a particular category of DiffServ-based services for aggregated traffic in the case of transport networks. Our research takes into account the particularities that apply to the case of DiffServ services{\textquoteright} provision over transport networks while imposing minimal overload and a-priori estimation of costs.},
	author = {Christos Bouras and Afroditi Sevasti}
}
@conference {2774,
	title = {SEQUIN: Results on QoS},
	booktitle = {TERENA Networking Conference 2002, Limerick, Ireland},
	year = {2002},
	month = {3 - 6 June},
	abstract = {SEQUIN has defined and implemented an end-to-end
approach to Quality of Service (QoS), operating across
multiple management domains based on IP protocol and
independent of link layer technology
\&$\#$149; The project has specified the implementation architecture
for the Premium IP service, which aims at offering the
equivalent of an end-to-end virtual leased line service at
the IP layer across multiple domains.},
	author = {Afroditi Sevasti}
}
@conference {2773,
	title = {SLA definition for the provision of an EF-based service},
	booktitle = {16th International Workshop on Communications Quality \& Reliability (CQR 2002), Okinawa, Japan},
	year = {2002},
	month = {14 - 16 May},
	pages = { 17 - 21},
	abstract = {The evolution of mechanisms for providing
Quality-of-Service (QoS) over the contemporary network
infrastructures has introduced the need for regulation and
management of the emerging QoS services with the use of
Service Level Agreements (SLAs). SLAs for QoS-enabled
networks move one step forward in the direction of
traditional ones, in the sense that they do not only have to
specify availability, security, quantity of allocated resources
and a number of other quantitative values but also have to
specify the values of appropriate quality parameters. This
paper deals with the particular cases of introduction of QoS
mechanisms to large transport networks according to the
DiffServ architecture. In these cases, the extensive level of
aggregation of flows and the connectionless nature of QoS
services{\textquoteright} provisioning makes the definition of QoS
parameters and the engineering of QoS metrics in the
traditional SLA specification a demanding task. Due to the
fact that strictly bounded deterministic guarantees are not
realistic, usually only upper bounds for the relevant
parameters can be defined and the corresponding SLAs have
to be defined accordingly.},
	author = {Christos Bouras and Afroditi Sevasti and M Campanella}
}
@conference {2763,
	title = {Speeding-up, filtering and manipulating the web to meet specific user needs},
	booktitle = {2nd IEEE International Symposium on Signal Processing and Information Technology, Marrakech, Marocco},
	year = {2002},
	month = {18 - 21 December},
	abstract = {In our days the Web has become a large
repository of information. This information is constantly
updated and altered. In this work we describe a software
architecture that has been used to implement a tool that
may potentially aid individual Web users but also
groups of users, to upgrade their browsing sessions and
make these sessions more productive. The software that
is presented here, uses documented and widely accepted
techniques to improve users{\textquoteright} browsing sessions. It also
utilizes new experimental and emerging techniques. The
software can be used in various client/server
configurations. We present the software modules and
their configuration, as well as the interaction that is
carried out between them.},
	author = {Christos Bouras and Agis Konidaris}
}
@conference {2768,
	title = {SRAMT-S: A hybrid sender and receiver-based adaptation scheme for TCP friendly multicast transmission using simulcast approach},
	booktitle = {1st IFIP Workshop on Internet Technologies, Applications and Social Impact (WITASI-02), Wroclaw, Poland},
	year = {2002},
	month = {10 - 11 October},
	pages = { 105 - 122},
	abstract = {In this paper, we describe a hybrid sender and receiver-based adaptation
scheme for multicast transmission of multimedia data using the simulcast
approach, which we call SRAMT-S (Sender-Receiver based Adaptation
scheme for Multicast Transmission using Simulcast). The most prominent
features of SRAMT-S are its distributed (to sender and receivers) transmission
rate estimation algorithm and its innovative RTT (Round Trip Time)
estimation algorithm based on one-way delay measurements. SRAMT-S is
using both an AIMD algorithm and a TCP model in order to estimate a TCP
friendly bandwidth share. We evaluate SRAMT-S through a number of
simulations in order to examine its behaviour to a heterogeneous group of
receivers and its behaviour against TCP connections. Main conclusion of the
simulation was that SRAMT-S has friendly behaviour against the dominant
traffic types of today{\textquoteright}s Internet and treats a heterogeneous group of receivers
with fairness.},
	author = {Christos Bouras and Apostolos Gkamas}
}
@article {3054,
	title = {STEPS: Supporting Traditional Education ProcedureS-A TCP/IP Multimedia Networks-Based Model},
	journal = {Multimedia Tools And Applications, Kluwer Academic Publishers,  Vol. 16, No 3},
	year = {2002},
	month = {March},
	pages = { 251 - 276},
	abstract = {This paper describes an integrated model for the realization of an Open and Distance Learning (ODL)
environment supporting traditional learning procedures, through collaborative learning and active participation
of the involved group of students. Internet technologies are used as a vehicle for distribution of interactive multimedia
at the user{\textquoteright}s desktop. We also present off-the-shelf solutions for the architecture and implementation of
an Educational Network necessary to support the ODL environment. An Educational Entity (specially shaped
part of a legal educational authority) is also prescribed as the central point for the Educational Network, being
the content provider and the learning procedure evaluator. It is mainly intended to be used in a higher education
setting, aspiring to be an efficient solution for the common educational needs of a group of students and teachers or
researchers.},
	author = {Christos Bouras and Paul Spirakis and P Lampsas}
}
@conference {2776,
	title = {Transition Strategies from IPv4 to IPv6: The case of GRNET},
	booktitle = {3rd International Network Conference-INC 2002, Plymouth, UK},
	year = {2002},
	month = {16 - 18 July},
	pages = { 89 - 96},
	abstract = {In this paper we describe the results that came out from the project of employing the IPv6 protocol over the Greek Research \& Technology Network (GRNET). In the way of this process one of the big issues that had to be considered was the transition strategy that would be deployed. The main goals of a transition strategy are to be smooth enough and therefore to put the less of configuration overhead to the end users and the network administrators.},
	author = {Christos Bouras and A Karaliotas and Petros Ganos}
}
@conference {2789,
	title = {Architecture and Performance Evaluation for Redundant Multicast Transmission Supporting Adaptive QoS},
	booktitle = {9th International Conference on Software, Telecommunications and Computer Networks (SoftCom 2001) Split, Dubrovnik(Croatia), Ancona, Bari (Italy), vol II},
	year = {2001},
	month = {9 - 12 October},
	pages = { 585 - 592},
	abstract = {<p>In this paper we describe the architecture of an application that was developed for the transmission of multimedia data, using the multicast mechanism, over the Internet. There are two major issues that have to be considered when designing and implementing such a service, the fairness and the adaptation schemes. In our application we use a mechanism that categorizes the receivers into a number of groups according to each receiver{\textquoteright}s capabilities and (the mechanism) serves each group of users with a different multicast stream. We have also implemented an additional mechanism for the intra-stream bit rate adaptation. The proposed mechanism uses a {\textquotedblleft}friendly{\textquotedblright} to the network users congestion control policy to control the transmission of the data. We evaluate the adaptive multicast transmission mechanism through a number of experiments in order to examine its behaviour to a heterogeneous group of receivers and its behaviour against TCP and UDP data streams.</p>
},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos and A Karaliotas}
}
@conference {2788,
	title = {An Architecture for Redundant Multicast Transmission Supporting Adaptive QoS},
	booktitle = {7th International WORKSHOP ON MULTIMEDIA SYSTEMS, Capri, Italy},
	year = {2001},
	month = {7 - 9 November},
	pages = { 133 - 142},
	abstract = {In this paper we describe the architecture and the implementation of an application that was
developed for the transmission of multimedia data, using the multicast mechanism, over the
Internet. There are two major issues that have to be considered when designing and implementing
such a service, the fairness and the adaptation schemes. The fairness problem results from the fact
that receivers with different capabilities have to be served. In our application we use a mechanism
that categorizes the receivers into a number of groups according to each receiver{\textquoteright}s capabilities and
(the mechanism) serves each group of users with a different multicast stream. With the term
{\textquotedblleft}capabilities{\textquotedblright} we do not only mean the processing power of the client, but also the capacity and the
condition of the network path towards that client. Because of today{\textquoteright}s Internet heterogeneity and the
lack of Quality of Service (QoS) support, the sender cannot assume that the receivers will
permanently be able to handle a specific bit rate. We have therefore implemented an additional
mechanism for the intra-stream bit rate adaptation.},
	author = {Christos Bouras and Apostolos Gkamas and Kostas Stamos and A Karaliotas}
}
@conference {2781,
	title = {Architectures and Protocols for Educational Virtual Environments},
	booktitle = {IEEE International Conference on Multimedia and Expo (ICME2001),Tokyo, Japan},
	year = {2001},
	month = {22 - 25 August},
	pages = { 1107 - 1110},
	abstract = {Shared or networked virtual environments are one of the most
promising uses of the virtual reality technology. While a lot of
research has been done in the area of multi-user virtual
environments corresponding to the sharing of events very few
research has been done on specific services and functionality.
However both the requirements and the kind of the offered
services affect significantly the design of a system. In this paper
we present the main issues in the design of a platform to support
the distant education process using networked virtual
environments. We also introduce the term Educational Virtual
Environments and their basic requirements. According to these
requirements of the educational virtual environments we propose
both a suitable architecture and a protocol for the interaction
between the components of this architecture.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos}
}
@conference {2791,
	title = {Architectures Supporting e-Learning Through Collaborative Virtual Environments: The Case of INVITE},
	booktitle = {IEEE International Conference on Advanced Learning Technologies-ICALT 2001, Madison, Wisconsin, USA},
	year = {2001},
	month = {6 - 8 August},
	pages = { 13 - 16},
	abstract = {The growing need for communication, visualization and
organization technologies in the field of e-learning
environments has led to the application of virtual reality
and the use of collaborative virtual environments. This
paper presents a system architecture to support such
environments, defined by user needs and using state of the
art technologies.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Vasilis Triantafillou and G Hornig}
}
@conference {2785,
	title = {Aspects of collaborative learning environment using distributed virtual environments},
	booktitle = {ED-MEDIA 2001, Tampere, Finland},
	year = {2001},
	month = {25 - 30 June},
	pages = { 173 - 178},
	abstract = {A decisive factor for new technologies is always the added value with respect to
the efficiency and capacity of traditional technologies. This also is true when considering the
impact of new technologies in training applications. New types of applications have been
developed along the last few years to incorporate information technology in the learning
environment. The growing need for communication, visualisation and organisation features in
the field of learning and training environments, the e-learning approach, has led to the
application of virtual reality and the use of multi-user real-time communication platforms to
support these needs. This paper presents the first approach of such a system as well as useful
technologies and standards for its implementation.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and Vasilis Triantafillou}
}
@article {3058,
	title = {Basic Internet Services Environment for the Education Society},
	journal = {International Journal of Computers and Applications, Acta Press, Vol. 23 , No. 1},
	year = {2001},
	pages = { 35 - 44},
	abstract = {Computer-based, networking learning environments play a signif-
icant role in the improvement of the learning procedure. Elec-
tronic communication and collaboration services provide tutors and
trainees with continual, close, and e{\'a}cient cooperation. An increase
in the use of the Internet as a repository of resources for learning,
and also as a means for delivery of specially prepared teaching
materials, is a particularly signi{\ss}cant innovation in the {\ss}eld of
education. Educational applications are increasingly based on the
World Wide Web, combining simpli{\ss}ed access to the application
and integration into a Web-based learning environment. This work
presents a {\`a}exible communication and collaboration environment,
developed within the framework of the ODYSSEAS project, that
may be used by educators. The basic services environment presented
in this paper is built upon the well-known and popular standards
HTTP, SMTP, and POP3 and is accessible to the potential user
through a web browser and connection to a user authentication
server that will handle the user{\textquoteright}s private information, with minimal
installation cost.},
	author = {Christos Bouras and Vaggelis Kapoulas}
}
@article {3057,
	title = {Cost of implementing Banyan networks for use in ATM switching fabrics},
	journal = {Networking and Information Systems Journal, Hermes Science Publishing, Volume 3, No 5-6},
	year = {2001},
	pages = { 771 - 791},
	abstract = {In this paper, we present a model for computing the cost of implementing Banyan
networks. We limit our interest in Banyan networks which are used in ATM switching fabrics
and are build in VLSI. The cost is given as a function of the characteristics of the network (i.e.
length of buffers, speed of links, etc.). It is well-known that the implementation cost must be
related to the performance of the network. The choices, that the designer may have, impact both
the performance and the cost. We demonstrate the case where a slight increase in performance
implies a great increase in cost (in that case it is not cost effective to build a better switching
network), and of course the reverse, i.e., the case where a decrease in cost implies a degradation
of the performance of the switch.},
	author = {Christos Bouras and C Gkantsidis}
}
@article {3059,
	title = {e-Learning through Distributed Virtual Environments},
	journal = {Journal of Network and Computer Applications, Academic Press, No.3, Vol 24},
	year = {2001},
	month = {July},
	pages = { 175 - 199},
	abstract = {e-learning is one of the emerging needs of the information age. Access to education
is going to become crucial for the success of our information society, and therefore
a lot of potential is seen in distance learning and distributed virtual environments. The
communicative character of the distributed virtual environments would allow students and
staff to meet in social shared spaces and engage in on-line real-time seminars and tutorials.
Such technologies may mitigate some of the problems of isolation that distance learning
brings. This paper presents our work in multi-user distributed virtual environments which
are designed and implemented for educational uses in the bounds of the VES project.
Furthermore, it presents our proposal for the extensions and reconstruction of the current
system in order to create a more efficient system, which can be characterized as a learning
virtual environment.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and A Philopoulos}
}
@conference {2783,
	title = {An Electronic Polling Service to support Public Awareness using Web Technologies},
	booktitle = {Proceedings 9th European Conference on Information Systems-ECIS 2001, Bled, Slovenia , Vol. 2},
	year = {2001},
	month = {27 - 29 June},
	pages = { 935 - 946},
	abstract = {This paper presents a Web-based, database-oriented application called {\textquotedblleft}Electronic Polling{\textquotedblright}, a smart
way to support voting on common subjects in which all people of a Local Authority are interested. The
systems services were planned and implemented to be easily expandable. The application is based on
state-of-the-art software platform, integrating WWW and database. The system aims to become a pilot
in future efforts relative with {\textquotedblleft}on line Democracy{\textquotedblright}. The system provides the capability to create a
poll, view the subject and participate to the voting procedure. Only authorised users can participate to
use the system to vote or create a poll but all users can view results from previous voting procedures.},
	author = {Christos Bouras and Vasilis Triantafillou and N Katris}
}
@conference {2782,
	title = {Introducing Navigation Graphs as a Technique for Improving WWW User Browsing},
	booktitle = {The Second International Conference on Web-Age Information Management(WAIM 01), Xi an, China},
	year = {2001},
	month = {9 - 11 July},
	pages = { 249 - 256},
	abstract = {In this paper we show that users move from page to page, in the
WWW, by following similar browsing patterns when they have similar
browsing experience. Similar browsing patterns do not absolutely imply that the
same URL{\textquoteright}s are visited. They only mean that users react in similar ways to
similar web sites and follow almost foreseen routes. In order to prove this
conclusion we introduce the Navigation Graph technique to trace users{\textquoteright} web
browsing patterns. We also categorize sites according to their structure by using
a commercial tool. Having done these, we analyze the results of the navigation
graphs and present them, pointing out the problems that users may encounter.
Finally, in order to answer to these problems, we propose enhancements that
can improve the performance of web browsers and web servers.},
	author = {Christos Bouras and Agis Konidaris and Afroditi Sevasti and E Konidari}
}
@conference {2787,
	title = {A Mechanism for Multicast Multimedia Data With Adaptive QoS Characteristics},
	booktitle = {6th International Conference on Protocols for Multimedia Systems-PROMS 2001, Enschede, The Netherlands},
	year = {2001},
	month = {17 - 19 October},
	pages = { 74 - 88},
	abstract = {In this paper, we describe a mechanism for adaptive transmission of
multimedia data, which is based on real time protocols. The proposed
mechanism can be used for multicast multimedia data over heterogeneous
networks, like the Internet, and has the capability to adapt the transmission of
the multimedia data to network changes. In addition, the adaptive multicast
transmission mechanism uses an inter-receiver fairness function in order to treat
the group of receivers with fairness in a heterogeneous environment. The
proposed mechanism uses a {\textquotedblleft}friendly{\textquotedblright} to the network users congestion control
policy to control the transmission of the data. We evaluate the adaptive
multicast transmission mechanism through a number of simulations in order to
examine its fairness to the group of receivers and its behavior against TCP and
UDP data streams.},
	author = {Christos Bouras and Apostolos Gkamas}
}
@conference {2786,
	title = {An On-line Managed Bandwidth Service for ATM Networks},
	booktitle = {8th IEEE International Conference on Telecommunications (ICT 2001), Vol. 1, Bucharest, Romania},
	year = {2001},
	month = {4 - 7 June},
	pages = { 315 - 320},
	abstract = {In our days, the number of demanding, in terms of
network bandwidth, applications increases dramatically
as the number of users that obtain access to networking
facilities augments. As a result, efficient management of
the available network resources becomes a critical issue
both from a functional point of view, so that users can be
provided with the bandwidth they need, and an
economical point of view, so that carriers can
satisfactorily and efficiently serve as many customers as
possible. The work presented here attempts to face from
a practical point of view the problem of bandwidth
management in ATM networks, especially in cases
where the available resources have to be shared among
many users with conflicting needs. We have designed
and implemented a Managed Bandwidth Service (MBS)
that allows users to make multiple bandwidth
reservations throughout the topology of the network
infrastructure to which they have access. This MBS also
provides an administrative module for configuring and
monitoring the service{\textquoteright}s operation. In this paper we
present the MBS developed and all the implementation
issues related to it, as well as our on-going and future
work on the service.},
	author = {Christos Bouras and Vaggelis Kapoulas and Afroditi Sevasti and Chrysa Chantzi and Ioanna Sampraku}
}
@conference {2790,
	title = {A Platform for Sharing Educational Virtual Environments},
	booktitle = {9th International Conference on Software, Telecommunications and Computer Networks (SoftCOM 2001) Split, Dubrovnik (Croatia) Ancona, Bari (Italy), Vol II},
	year = {2001},
	month = {9 - 12 October},
	pages = { 659 - 666},
	abstract = {In recent years, a lot of work has been done on multi-user virtual environments. This
work led to platforms that aim to support 3D virtual communities. However, little research has
been done on specific services and functionality, which affect significantly the design of a system.
The growing need for communication, visualisation and organisation technologies in the field of
e-learning environments, has led to the application of virtual reality and the use of multi-user
real-time communication platforms to support these needs. In this paper we present the design
and implementation of a platform, suitable for educational virtual environments. Apart from the
platform itself, we present the technological choices, a new method for sharing virtual
environments and a new protocol for educational virtual environments.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and D Psaltoulis and C Psaroudis}
}
@conference {2792,
	title = {Run-time Management Policies for Data Intensive Web sites},
	booktitle = {International Workshop on Web Dynamics (In conjuction with the 8th International Conference on Database Theory), London, UK},
	volume = {701},
	year = {2001},
	month = {3 January},
	pages = {61-70},
	abstract = {Web developers have been concerned with the issues of Web latency and Web data consistency
for many years. These issues have become more important in our days since the accurate and
imminent dissemination of information is vital to businesses and individuals that rely on the
Web. In this paper, we evaluate different run-time management policies against real Web site
data. We first define the meaning of data intensive Web sites and categorize them according to
their hit patterns. Our research relies on real world Web data collected from various popular Web
sites and proxy log files. We propose a Web site run-time management policy that may apply to
various real Web site hit patterns and Web data update frequencies.},
	author = {Christos Bouras and Agis Konidaris}
}
@article {3056,
	title = {School Networks and Telematics Services:perspectives of international co-operation in the Mediterranean},
	journal = {Telecommunication Information Management Journal, Volume 2, Issue 6},
	year = {2001},
	month = {March},
	pages = { 17 - 18},
	abstract = {The forthcoming {\textquoteleft}Information Society{\textquoteright} is expected to transform radically the way of
communicating knowledge and expertise. The application of ICT for educational purposes
should be aimed to improve the education process in terms of pedagogical methodologies,
school infrastructure, human resources development and organisational restructuring, in order
to efficiently absorb and utilise the technological developments. New learning paradigms
have already emerged giving emphasis to the communication and collaborative aspects of the
learning process. Self-supported and collaborative learning is expected to transform the
traditional educational activities (teacher-centred model) and promote flexibility, reflection
and group interaction.},
	author = {Christos Bouras and G Tsakarissianos}
}
@conference {2784,
	title = {Web Components: A Concept for Improving Personalization and Reducing User Perceived Latency on the World Wide Web},
	booktitle = {The 2nd International Conference on Internet Computing (IC2001),Las Vegas,Nevada, USA, Vol 2},
	year = {2001},
	month = {25 - 28 June},
	pages = { 238 - 244},
	abstract = {In this paper we address one of the
performance problems of the World Wide Web, known
as User Perceived Latency (UPL). We begin by
presenting a new definition of UPL. Next we present a
concept that may benefit the WWW and reduce UPL.
This is the concept of Web Components. We show how
Web Components can work together with other
concepts for efficient Web Data manipulation and
delivery, in order to reduce UPL. We then show how
Web Components can also be used to support Web
personalization as a means for reducing latency. After
that we present the operation of the WWW model (Web
Servers, Web Proxies and Web Browsers) for
supporting the Web Component concept.},
	author = {Christos Bouras and Agis Konidaris}
}
@conference {2795,
	title = {Accounting management system enhancement supporting automated monitoring and storing facilities},
	booktitle = {2nd International Network Conference-INC 2000, Plymouth, UK},
	year = {2000},
	month = {3 - 6 July},
	pages = { 117 - 124},
	abstract = {In this work we present the design, development and implementation of a set of tools embedded
in a network management system used in the University of Patras Network (UPatrasnet),
providing advanced accounting management services. These tools help the critical network
parameters monitoring and storing procedure in order to provide the information needed for
efficient management. We defined which resources to be watched and what kind of information
to be collected by the management system in order to deploy the specifications of the
processing and analyzing tools. Finally, we used HP OpenView as a network manager.},
	author = {Christos Bouras and S Kastaniotis}
}
@conference {2802,
	title = {Citizen information services using Internet technologies},
	booktitle = {8th European Conference on Information Systems-ECIS 2000, Vienna, Austria, Vol. 1},
	year = {2000},
	month = {3 - 5 July},
	pages = { 1123 - 1130},
	abstract = {This paper presents a Web-based, database-oriented
set of applications, namely {\textquotedblleft}Public Information{\textquotedblright} and {\textquotedblleft}Electronic
Voting{\textquotedblright}, to support information services (exchange and
sharing) between Local Government authorities (Region, Prefecture
and Municipalities) and the citizens. The whole set of
services developed exploits Internet and Extranet technologies
enabling asynchronous cooperation, manipulation of information
from heterogeneous sources, security and easy administration,
providing in parallel advanced telecommunication facilities.
We propose an innovating approach for submitting questions,
remarks and comments from citizen to Local authorities
(prefecture) and receiving response/correspondence in a reasonable
period of time (Public Information) and, on the other hand,
a smart way to support voting on common subjects in which all
local community is interested in. The system included applications
and services were planned and implemented to be easily
expandable to any organizational chart of any Local Administration.
Both applications are based on state-of-the-art software
platforms, integrating WWW and database. The system
aims to become a pilot in future efforts relative with distribution
and management information between and within different
types of local authorities.},
	author = {Christos Bouras and Vasilis Triantafillou and S Kastaniotis}
}
@conference {2807,
	title = {Cost/Performance evaluation of Banyan networks which are used in ATM switching fabrics},
	booktitle = {14th International Conference on Information Networking(ICOIN-14), Hsin-Chu, Taiwan},
	year = {2000},
	month = {26 - 28 January},
	pages = { 1A-2.1/1.A-2.8},
	abstract = {In this paper, we present a model for computing the cost
of implementing Banyan networks. We limit our interest in
Banyan networks which are used in ATM switching fabrics
and are build in VLSI. The cost is given as a function of the
characteristics of the network (ie. length of buffers, speed
of links, etc). We are focusing in this area because such
networks have been used extensively in the design of large
ATM switches, which are the core elements of broadband
networks. It is well-known that the cost of implementing
must be related to the performance of the network. The
choices, that the designer may have, impact both the per-
formance and the cost. We will show when a slight increase
in performance implies a great increase in cost, in which case
it is not cost effective to build a better switching network,
and of course the reverse, when a decrease in cost implies a
degradation of the performance of the switch.},
	author = {Christos Bouras and C Gkantsidis}
}
@book {3149,
	title = {Data Communication and Computer Networks I \& II},
	series = {Book for Secondary Education School,Greek Ministry of Education and Religious Affairs},
	year = {2000},
	author = {Christos Bouras}
}
@conference {2810,
	title = {Distributed Virtual Learning Environment: A Web-Based Approach},
	booktitle = {EUROMICRO WORKSHOP on Multimedia and Telecommunications, Maastricht, Netherlands, Vol II},
	year = {2000},
	month = {4 - 7 September},
	pages = { 50 - 55},
	abstract = {In this paper, we present a web-based Distributed
Virtual Learning Environment (DVLE) that could be used
as a sophisticated tool for distance education and
collaboration between teachers and students. We design
and develop this application and the corresponding
Graphical User Interface (GUI) as a proposal that aims
at providing an integrated communicational environment
which supplies the communicative needs of an
educational community, using the latest
telecommunication and multimedia information
processing technology. The environment that we propose
can be used for virtual lectures, virtual conferences, and
exchange of useful material and experiences among
teachers and students. It is a web-based application that
is being developed as client/server architecture using
standard protocols and technologies such as HTTP,
HTML, Java and VRML.},
	author = {Christos Bouras and A Philopoulos}
}
@conference {2800,
	title = {A Dynamic Distributed Video on Demand Service},
	booktitle = {20th IEEE International Conference on Distributed Computing Systems-ICDCS 2000, Taipei, Taiwan},
	year = {2000},
	month = {10 - 13 April},
	pages = { 496 - 503},
	abstract = {In our days, the use of Internet services has become a part of every day life. The need
for more advanced applications is increasing and solutions have to be provided in
order to meet it. Multimedia information is constantly getting more popular. The
connections{\textquoteright} bandwidth though is not ready yet to cope with the rising expectations of
applications such as Video on Demand (VoD), which are very consuming in terms of
bandwidth. In this paper we propose a way to implement such a service over a limited
bandwidth/best effort Internet based network. Our proposal consists of the
implementation of algorithms and the attempt to introduce Quality of Service features
on a network such as the Internet that inherently does not support such features. In this
paper we propose two techniques that can serve in the implementation of an Internet
based Video on Demand service. The first deals with the distribution of video titles on
the several Video Servers and is called Disk Manipulation Algorithm (DMA). The
second gives a dynamic nature to the service, imposes a virtual routing procedure to
the system and is called Virtual Routing Algorithm (VRA).},
	author = {Christos Bouras and Vaggelis Kapoulas and Agis Konidaris and Afroditi Sevasti}
}
@conference {2798,
	title = {e-DEDALUS: A dynamic tool for data publishing on the web},
	booktitle = {2000 International Conference on Information Society in the 21st Century-Emerging Technologies and new Challenges(IS 2000), Aizu-Wakamatsu City, Fukushima, Japan},
	year = {2000},
	month = {5 - 8 November},
	pages = { 98 - 105},
	abstract = {TheWorld WideWeb (WWW) provides a great
opportunity for companies and individuals to publish their
ideas, products and everything they would like other peo-
ple to view. Since the Internet community and the Web
are expanding every day, the demand for user friendly Web
publishing applications is rising. The procedures that could
be followed by Internet users in order to publish content on
the web till now, were to either buy and read some books
on HTML and have some basic knowledge on Web Servers,
or pay an ISP a quite substantial amount of money to do
it for them. In this paper we rst justify the necessity of
the existence of an alternative method for online web pub-
lishing. We then describe the method and a tool, called
e-DEDALUS, which can be used by many diverse Internet
user groups. An Internet user that has no previous expe-
rience in programming, or desktop design, will be able to
create his/her own Web site, online. The e-DEDALUS tool
that will be described in this paper aims at oering simplic-
ity, customisability and multilingual support to a substantial
number of WWW users.},
	author = {Christos Bouras and Agis Konidaris and C Sintoris and A Apostolopoulos and V Khan}
}
@conference {2797,
	title = {An efficient algorithm to improve handoff in mobility for IP v6 protocol},
	booktitle = {8th International Conference on Software, Telecommunications and Computer Networks-SoftCOM 2000, Split, Rijeka, Dubrovnik(Croatia), Trieste, Venice(Italy), Vol I},
	year = {2000},
	month = {11 - 14 October},
	pages = { 505 - 511},
	abstract = {This paper describes an extension of the mobility support for the IPv6 protocol, which
is currently an Internet Draft. We argue that by processing geographical data information a
mobile node can efficiently switch between different LANs without disturbance to ongoing data
sessions. Furthermore the number of location update messages diminishes as the mobile node
transmits them only when switching to a new LAN. This extension requires that each router of
the foreign networks the mobile node visits, advertises the GPS coordinates of x points that
describe its region. It also requires that the mobile node is capable of receiving GPS signals.
Once having collected this information the mobile node can safely figure whether it will continue
to be served by the same LAN or it has to switch to a different one because soon it will be out of
the old LAN{\textquoteright}s range. Furthermore using this information the mobile node can also decide to
which LAN it is preferable to switch. Lower-layer information, when it is available, such as
signal strength or signal quality can be used as auxiliary indications for the switch decision.},
	author = {Christos Bouras and Paul Spirakis and Y Siahos}
}
@article {3061,
	title = {Efficient Web-Based Open and Distance Learning Services},
	journal = {Journal of Telematics and Informatics, Elsevier Science, Vol. 17, Issue 3},
	year = {2000},
	pages = { 213 - 237},
	abstract = {In this paper, we present data management issues faced during the design and development
of an open distance learning system for the University of Patras, Greece. In order to handle
data e\&$\#$129;ciently, as required in a web tele-training application, for each type of information
maintained, di\&$\#$128;erent strategies must be deployed according to their behaviour and structure.
The diversity and complexity of data, the network aspect of the application and web de{\textregistered}-
ciencies impose an architecture design incorporating a plethora of technologies and tools that
must be integrated in such a fashion that they e\&$\#$129;ciently organise these data preserving their
relationships. This presents a software engineering challenge requiring coherence of solutions
at all levels: structures, consistency, security, models, and protocols. The paper presents the
data components of an open and distance learning (ODL) system that access the information
stored in a database and the {\textregistered}le system, their underlying technology, their interaction with the
network services, and features regarding the ways they address issues faced in an open vendorindependent
distance learning environment and outlines the system{\textquoteright}s overall architecture. In
addition, this paper presents the architecture, the design and the services of a network-based
information system that supports open and distance learning activities. The open and distance
learning information system (ODLIS) o\&$\#$128;ers synchronous and asynchronous distance learning
and management of information system (MIS) services to support the educational procedure.
The ODLIS is a web-based application, which runs over the Internet using real time protocols.},
	author = {Christos Bouras and Apostolos Gkamas and Thrasivoulos Tsiatsos and P Destounis and J Garofalakis and G Sakalis and B Sakopoulos and J Tsaknakis}
}
@conference {2811,
	title = {Information services using Internet technologies in the Public Sector},
	booktitle = {Neties 2000, Oulu, Finland},
	year = {2000},
	month = {23 - 25 March},
	pages = { 112 - 119},
	abstract = {This work presents a Web-based, database-oriented set of applications,
which include an asynchronous Open Distance Learning tool (without the presence of
a tutor), an application for retrieving information about work safety issues and allows
information exchange between the public and different departments of Greek Power
Company (GPC). All applications offer secure and easy administration, providing in
parallel advanced telecommunication facilities.},
	author = {Christos Bouras and Vasilis Triantafillou and S Kastaniotis}
}
@conference {2801,
	title = {Internet Protocols for Synchronous Distance Learning},
	booktitle = {3rd International Workshop on Network-Based Information Systems-NBIS{\textquoteright}2000, Greenwich, UK},
	year = {2000},
	month = {4 - 8 September},
	pages = { 46 - 50},
	abstract = {The use of multimedia in telematics and new services
has been greatly improved by the introduction of new
systems and techniques. These new systems and techniques
made the implementation of many telematic applications
like tele-teaching, collaborative or tele-medicine
applications possible. In this paper, we present design,
protocols and implementation issues, which concern an
Internet based synchronous distant learning application.
We describe in detail the design and the implementation of
each application{\textquoteright}s module and we appose the protocols,
which control the communication among the application{\textquoteright}s
components. The described application is a network-based
application, which follows the client-server model. The
application runs over the Internet and more specifically
over the web. The users of the application access its
services through web pages.},
	author = {Christos Bouras and Apostolos Gkamas and Thrasivoulos Tsiatsos}
}
@book {3150,
	title = {Multimedia and Computer Networks},
	series = {Book for Secondary Education School,Greek Ministry of Education and Religious Affairs},
	year = {2000},
	author = {Christos Bouras}
}
@article {3060,
	title = {Network-Based Distributed Learning Environment},
	journal = {WebNet Journal: Internet, Technologies, Applications \& Issues, AACE, Vol.2},
	year = {2000},
	month = {July - September},
	pages = { 29 - 37},
	author = {Christos Bouras and Apostolos Gkamas and Thrasivoulos Tsiatsos}
}
@conference {2868,
	title = {A Networked Intelligent Distributed Virtual Training Environmnet:A First Approach},
	booktitle = {5th Joint Conference on Information Sciences-JCIS 2000-1st International Workshop on Intelligent Multimedia Computing and Networking, Taj Mahal, Atlantic City, New Jersey, USA, Vol. 2},
	year = {2000},
	month = {27 February - 3 March},
	pages = { 604 - 607},
	abstract = {Collaborative livelong learning is one of the emerging
needs of the information age. Access to education is going
to become crucial for the success of our information
society. Therefore a lot of potential is seen in distance
learning and online collaborative environments. This paper
proposes an intelligent distributed virtual training
environment for distance education through shared 3D
spaces},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and A Philopoulos}
}
@conference {2867,
	title = {The Performance of Simple Queueing Theoretic Video On Demand Algorithms},
	booktitle = {APPLIED INFORMATICS (AI 2000), Innsbruck, Austria},
	year = {2000},
	month = {14 - 17 February},
	abstract = {Video On Demand (VOD) Systems comprise an
emerging new technology, which is expected to
significantly affect everyday life. The implementation of
effective commercial VOD systems has to overcome some
technical limitations, such as the low bandwidth offered
by the existing communication channels. In our work we
present some simple queuing theoretic algorithms for the
optimal use of a limited number of communication
channels keeping a fair policy for the users requests. We
compare our algorithms with well-known algorithms, by
means of simulation.},
	author = {Christos Bouras and J Garofalakis and J Tzimas and P Petridis}
}
@conference {2796,
	title = {pLVE: Suitable Network Protocol Supporting Multi-User Virtual Environments in Education},
	booktitle = {International Confertence on Information and Communication Technologies for Education/ED-ICT 2000, Vienna, Austria},
	year = {2000},
	month = {6 - 9 December},
	pages = { 73 - 81},
	abstract = {Virtual Reality Modeling Language (VRML) and the broad use of communication networks provide
the users with realistic virtual environments. However these environments need and a pioneer
application such as distance learning. In order to realize suitable educational virtual environments
the desired functionality should be collected, a general architecture should be specified and a
suitable communication protocol between the components of the system should be designed. In this
paper we present the design rationale for such a communication protocol.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos}
}
@conference {2806,
	title = {Streaming multimedia data with adaptive QoS characteristics},
	booktitle = {5th International Conference on Protocols for Multimedia Systems-PROMS 2000, Cracow, Poland},
	year = {2000},
	month = {22 - 25 October},
	pages = { 129 - 139},
	abstract = {In this paper, we describe the design and the
implementation of an adaptive streaming architecture,
which is based on real time protocols. The adaptive
streaming application, which we have developed, can
be used for streaming multimedia data over
heterogeneous networks like the Internet and has the
capability to adapt the streaming of multimedia data to
network changes. The adaptive streaming application
uses a friendly to the network users congestion control
mechanism to control the transmission of the media.
We evaluate the adaptive streaming application
through a number of experiments. During these
experiments, we demonstrate the friendly behaviour of
the adaptive streaming application to TCP and UDP
data streams.},
	author = {Christos Bouras and Apostolos Gkamas}
}
@conference {2794,
	title = {Telematic Services over ATM Networks: The case of Teleteaching},
	booktitle = {2nd International ATM Technology Users Symposium-ATMTU 2000, Kosice, Slovakia},
	year = {2000},
	month = {13 - 15 September},
	pages = { 26 - 31},
	abstract = {In this paper we present various tele-teaching scenarios over ATM network infrastructure.
In each scenario we present the standards which we use, the logical components, the demand in
resources (network resources and equipment) and its special characteristics. Main result of our
experiments is that broadband networks offer many capabilities for high quality Teleteaching and
generally speaking high quality Telematic services.},
	author = {Christos Bouras and Vaggelis Kapoulas and Apostolos Gkamas and Thrasivoulos Tsiatsos}
}
@conference {2805,
	title = {Tele-teaching Scenarios over Broadband Networks},
	booktitle = {Web-based Learning Environments-WBLE 2000, Porto, Portugal},
	year = {2000},
	month = {5 - 6 June},
	pages = { 64 - 66},
	abstract = {In this paper we present various tele-teaching scenarios over ATM
network infrastructure. In each scenario we present the standards
which we use, the logical components, the demand in resources
(network resources and equipment) and its special characteristics.
Main result of our experiments is that broadband networks offer many
capabilities for high quality tele-teaching and generally speaking high
quality Telematic services.},
	author = {Christos Bouras and Vaggelis Kapoulas and Apostolos Gkamas and Thrasivoulos Tsiatsos}
}
@conference {2808,
	title = {Using Java to implement a multimedia annotation environment for young children},
	booktitle = {ACM MULTIMEDIA 2000, Los Angeles, California, USA},
	year = {2000},
	month = {30 October - 3 November},
	pages = { 187 - 194},
	author = {Christos Bouras and Afroditi Sevasti}
}
@conference {2799,
	title = {Using Multimedia to Support Reflection on Past Events for Young Children},
	booktitle = {ED-MEDIA 2000, Montreal, Canada},
	year = {2000},
	month = {26 June - 1 July},
	pages = { 105 - 110},
	abstract = {The work presented in this paper focuses on software tools that act as video explorers
and annotation platforms and more specifically as diary composers for younger children. Through
such tools, children can have as their raw material video recordings from everyday life and they are
given the opportunity to review this material, reflect upon it and annotate it, thus creating the
stories of everyday life from their own perspective. The specific tool proposed, focuses on multiperspective
capture of events by one or more children and their cooperation during the annotation
procedure.},
	author = {Christos Bouras and Vaggelis Kapoulas and Agis Konidaris and Afroditi Sevasti and M Ramalho and W Van de Velde}
}
@conference {2793,
	title = {Using Multi-user Distributed Virtual Environments in Education},
	booktitle = {World Conference of the WWW, Internet and Intranet- WebNet 2000, San Antonio, Texas, USA},
	year = {2000},
	month = {30 October - 4 November},
	pages = { 56 - 62},
	abstract = {On-line learning is one of the emerging needs of the information age. Access to
education is going to become crucial for the success of our information society. Therefore a lot of
potential is seen in distance learning and distributed virtual environments. The communicative
character of the distributed virtual environments would allow for students and stuff to meet in
social shared spaces and engage in on-line real-time seminars and tutorials. Such technologies may
mitigate some of the problems of isolation that distance learning brings. This paper presents multiuser
distributed virtual environments, which are designed and implemented for educational uses.},
	author = {Christos Bouras and Thrasivoulos Tsiatsos and A Philopoulos}
}
@inbook {3124,
	title = {Virtual Environments in Educational Networks},
	booktitle = {COMMUNICATIONS AND NETWORKING IN EDUCATION Learning in a Networked society, Edited by T. Downes and D. Watson},
	year = {2000},
	pages = { 195 - 203},
	publisher = {Kluwer Academic Publishers},
	organization = {Kluwer Academic Publishers},
	abstract = {<p>The field of Virtual Environments (VEs) is rapidly evolving into a new means of communication and accessing information, likely to overcome many existent technologies. However, being a new field makes the design and implementation of educational VEs an important aspect for scientific research in their educational potentials and the exploitation of existent technologies. New technologies in the field of VEs have appeared the establishment and combination of which, is yet to be investigated. This paper makes an effort to approach the issue of developing educational VEs introducing new aspects in the issues of interface, interaction with the user and functionality.</p>
},
	author = {Christos Bouras and Agis Konidaris and Afroditi Sevasti}
}
@conference {2803,
	title = {A Web Based open distance learning tool for tutors of special social groups},
	booktitle = {EUROMEDIA-APTEC 2000, Antwerp, Belgium},
	year = {2000},
	month = {8 - 10 May},
	pages = { 189 - 193},
	abstract = {This work presents an integrated information system to
support Open Distance Learning activities for tutors of
special social groups. All applications and services are
implemented based on Internet Technologies that allow
the asynchronous cooperation between users, flexible
and secure data management, offering advanced
communication facilities. We propose an ODL tool that
will be able to support tutors and professionals working
at different institutions and organizations, especially
those unable to attend long term training courses. The
system includes a Database where all relevant data
about organizations in Greece offering vocational and
lifelong training programs can be found and
individuals professionally involved in such activities as
trainers. The user can attend asynchronous lessons
(with video or sound), communicate with the
responsible tutor and at the same time consult a library,
the glossary or fill in a evaluation report.},
	author = {Christos Bouras and Vasilis Triantafillou and S Kastaniotis}
}
@conference {2809,
	title = {Winds of Aiolos: How connect the Greek Schools in Internet},
	booktitle = {Towards the e-learning Community, Bolton International Conference, Bolton, UK},
	year = {2000},
	month = {19 - 20 October},
	pages = { 27 - 37},
	abstract = {In this paper, we present the first Greek School Network, which is implemented by the project
"Winds of Aiolos{\textquotedblright}. This project is subsumed in the framework of the European Community
Action "Operational Program for the Education and Initial Vocational Training - Odysseia".
Computer Technology Institute (CTI) has the responsibility for the design and the
implementation of the project. On the basis of the influence of the networking technologies to
the educational activities and according to the international experience, the usage of the
network to the educational procedure acts as knowledgeable object, information source,
learning tool and communication tool. The main object of the project is the implementation of
a network infrastructure for the interconnection of school laboratories and educational
administration offices and the provision of network services in a wide range. It forms a closed
educational network, which is based on the Greek educational and research backbone network
(GRNET). The Greek school network statistics show that the students prefer the Greek
Domain. The educational units of the Greek School Network still act more as consumers than
as creators in the information society.},
	author = {Christos Bouras and Mixalis Paraskevas and Petros Ganos and N Adamopoulos and D Karaiskakis}
}
@article {3063,
	title = {A Cooperative Environment for Local Government: An Internet {\textendash} Intranet Approach},
	journal = {Journal of Telematics and Informatics, Elsevier Science, Vol. 16, Issue 1-2},
	year = {1999},
	pages = { 75 - 89},
	abstract = {<p>In this paper we present a Web-based, database oriented CSCW system to support information dispersal between di{\texteuro}erent Local Government authorities (Region, Prefecture and Municipalities) and the citizens. The system is implemented around the {\textquoteleft}shared workspace{\textquoteright} notion, a group of directories and {\textregistered}les controlled by the users of the workspace. Intranet and Extranet technologies are exploited to enable asynchronous and synchronous co-operation, manipulation of information from heterogeneous sources, security and easy administration, providing in parallel advanced communication facilities. We propose an innovative approach for the development of shared workspaces over WWW, based on state-of-the-art software platforms, integrating WWW and database technologies. The whole system was developed under a project funded by the Greek General Secretariat of Research and Technology and aims in the ecient distribution and management of information between and within di{\texteuro}erent types of local authorities (Municipalities, Prefectures).</p>
},
	author = {Christos Bouras and Vasilis Triantafillou and P Destounis and J Garofalakis and J Tzimas and P Zarafidis}
}
@conference {2819,
	title = {Cooperative Information Systems over the Internet and the WWW},
	booktitle = {EUROMEDIA 99-APTEC, Munich, Germany},
	year = {1999},
	month = {25 - 28 April},
	pages = { 232 - 236},
	abstract = {In this paper we present a WWW-based approach for the
development of a system supporting information sharing
within an organizational environment. The system developed
is exploiting Intranet and Extranet technologies enabling
asynchronous and synchronous cooperation, manipulation of
information from heterogeneous sources, security and easy
administration, providing in parallel advanced communication
facilities. We propose an innovative approach for the
development of shared workspaces over WWW, based on
state-of-the-art software platforms, integrating WWW and
database technologies. The whole system was developed
under a project funded by the Greek General Secretariat of
Research and Technology and aims in the efficient
distribution and management of information between and
within different types of local authorities (Municipalities,
Prefectures).},
	author = {Christos Bouras and Vasilis Triantafillou and P Destounis and J Garofalakis and J Tzimas and P Zarafidis}
}
@conference {2814,
	title = {Deployment scenarios of Dves in Education},
	booktitle = {ED-MEDIA and ED-TELECOM 1999,Seattle, Washington, USA},
	year = {1999},
	month = {19 - 24 June},
	pages = { 317 - 322},
	abstract = {DVEs, along with the Internet in general, offer a number of attractive features for the
education sector. However deployment in traditional educational environments, such as
secondary schools, has not been achieved on a noticeable scale so far. In this contribution, we
discuss technical and pedagogical issues, and specifically define possible scenarios of how this
technology can be introduced to the school sector in a sustainable way.},
	author = {Christos Bouras and Vaggelis Kapoulas and A Koubek and H Mayer}
}
@conference {2821,
	title = {Distributed Learning Environment using Advanced Services over the Internet},
	booktitle = {3rd Internet and Multimedia Systems and Applications(IMSA), Nassau, Grand Bahamas},
	year = {1999},
	month = {18 - 21 October},
	pages = { 182 - 186},
	abstract = {Multimedia and hypermedia had and still have a
tremendous impact on the evolution of educational
software. In this paper we propose an Integrated
Distributed Learning Environment (IDLE) for the
implementation of the services of an educational network
over TCP/IP networks such as the Internet. Our proposal
aims at providing an integrated communicational
environment, which supplies the communicative needs of
an educational community, using the latest
telecommunication and multimedia information
processing technology. The environment that we
implemented can be used for virtual lectures, virtual
conferences, collaborative work on projects, which are
shared among institutions, exchange of useful material
and experiences among teachers, and creation of
educational material.},
	author = {Christos Bouras and Apostolos Gkamas and Thrasivoulos Tsiatsos}
}
@conference {2820,
	title = {Efficient Data Management to support Educational Activities},
	booktitle = {Interactive Computer aided Learning-Tools and Applications-ICL 99,Villach, Austria},
	year = {1999},
	month = {7 - 8 September},
	abstract = {In this paper we present data management issues faced during the design and
development of an Open Distance Learning system for the University of Patras,
Greece. In order to handle data efficiently, as required in a Web Tele-training
Application, for each type of information maintained different strategies must be
deployed according to their behaviourand structure.
The diversity and complexity of data, the network aspect of the application and web
deficiencies impose an architecture design incorporating a plethora of technologies
and tools that must be integrated in such a fashion that they efficiently organise these
data preserving their relationships. This presents a software engineering challenge
requiring coherence of solutions at all levels: structures, consistency, security, models,
and protocols.
The paper presents the data components of a open and distance learning system that
access the information stored in a database and the file system, their underlying
technology, their interaction with the network services, and features regarding the
ways they address issues faced in a open vendor-independent distance learning
environment and outlines the system{\textquoteright}s overall architecture.},
	author = {Christos Bouras and Apostolos Gkamas and Thrasivoulos Tsiatsos and P Destounis and J Garofalakis and G Sakalis and B Sakopoulos and J Tsaknakis}
}
@conference {2824,
	title = {Improving and Utilizating Web and Data Interaction},
	booktitle = {The 1999 International Symposium on Database, Web and Cooperative Systems-DWACOS 99, Baden-Baden, Germany},
	year = {1999},
	month = {3 - 4 August},
	pages = { 7 - 12},
	abstract = {Web and Database Interaction is one of the growing trends in Web-site creation. This
interaction can facilitate the needs of the online community in various ways. Until now
databases were only used to hold large amounts of information needed for certain
applications. Many of these applications are nowadays Web-based. The constant interaction
that is needed by them is very demanding in terms of computer resources. In this paper we
propose a technique that can reduce the amount of resources needed to run these demanding
applications. We also introduce an alternative model according to which databases can be
used for many other purposes in the process of Web and Database interaction.},
	author = {Christos Bouras and Vaggelis Kapoulas and Agis Konidaris and Afroditi Sevasti}
}
@conference {2816,
	title = {The Information and Communication Technologies in Education},
	booktitle = {3rd Open Classroom Conference, Balatonfured, Hungary},
	year = {1999},
	month = {25 - 26 March},
	pages = { 27 - 31},
	abstract = {In the majority of the advanced countries there are many educational school networks and even more and
more schools are getting equipped with multimedia computers and connected to the Internet. Through the
advancements of the personal computer and the Internet, the school of the future will find new strengths
in both personalised and community learning environments. The prevailing perspective for the
introduction of the Information and Communication Technologies can be characterised as the {\textquotedblleft}computer
as a tool{\textquotedblright}. However, as with all tools, effective use of the technology is embedded within practices and
activities that realise its functionality for specific purposes and situations. On the other hand, the
investigation of the relationship between practices, purposes, and situations and computer-based
learning technologies is a major topic on pedagogic research.},
	author = {Christos Bouras and A Philopoulos and D Fotakis}
}
@book {3151,
	title = {Introduction to graphs: Theory, problems and solutions},
	series = {Gutenberg},
	year = {1999},
	author = {Christos Bouras and Lefteris Kirousis and Paul Spirakis and G Stamatiou}
}
@conference {2812,
	title = {Network Based Information System to support ODL Activities},
	booktitle = {International Coference on Telecommunications for Education and Training 1999-TET99, Gjovik, Norway},
	year = {1999},
	month = {8 - 11 June},
	pages = { 117 - 125},
	abstract = {This paper presents the architecture, the design and the services of a network based
Information System that supports ODL (Open and Distance Learning) activities. The ODLIS
(Open and Distance Learning Information System) offers synchronous and asynchronous
distance learning and MIS (Management of Information System) services to support the
educational procedure. The ODLIS is a web-based application, which runs over the Internet
using real time protocols.},
	author = {Christos Bouras and Vaggelis Kapoulas and Apostolos Gkamas and Thrasivoulos Tsiatsos and S Kontogiannis}
}
@conference {2815,
	title = {ODL services and PTTs: The Greek PTT case},
	booktitle = {19th World Conference on Open Learning and distance Education, Vienna, Austria},
	year = {1999},
	month = {20 - 24 June},
	abstract = {During the last years Open and Distance Learning (ODL) methods that utilise network resources and
services are gaining wide acceptance. An increasingly number of enterprises uses ODL for training
their employees. Interestingly enough not all the enterprises that want to and can use ODL are doing
so. The role of PTTs is important in here. PTTs can provide not only the connections necessary for
the implementation of ODL services but the ODL services themselves, thus making the process of
adopting ODL easier for the enterprises. In Greece the main PTT organisation, as part of its strategy
to offer integrated telematics services in various areas, designed and currently operates a pilot
network offering ODL services. The services offered include among others Synchronous Distance
Education, Asynchronous Distance Education, Co-operative Learning etc.The network utilises ISDN
links to connect the users of the ODL services (either trainers or trainees) to a central site. This site is
used to interconnect the users among themselves, and to host the services and any educational
material needed. The ODL services can be offered either over ISDN services or over the Internet
(using TCP/IP services and applications). In the first case the central site utilises a Multipoint Control
Unit (MCU). In the second case the ISDN lines are used to the implement the connections to the
Internet, and the central site utilises a powerful server. Each user may access the ODL service using
an ISDN enabled personal computer. Small groups of users that wish to participate from the same
location can be accommodated using larger displays. The ODL services (and the network that
supports them) are currently being used and evaluated by a variety of organisations and enterprises
including schools, hospitals, vocational training centres, etc. The results of the evaluation will be
used to guide the deployment of the system in full scale.},
	author = {Christos Bouras and Vaggelis Kapoulas and Apostolos Gkamas and Thrasivoulos Tsiatsos}
}
@article {3062,
	title = {On-Demand Hypermedia/Mutimedia Service using Pre-Orcestrated Scenarios over the Internet},
	journal = {Networking and Information Systems Journal, Hermes Science Publishing, Volume 2, No. 5-6},
	year = {1999},
	pages = { 741 - 762},
	abstract = {In this paper we present a unified approach for delivering hypermedia/multimedia
objects over broadband networks. The described service consists of several multimedia servers
and a set of functions that intend to present to the end user interactive information in real-time.
The hypermedia documents are structured using a hypermedia markup language that keeps information
of the spatiotemporal relationships among document{\textquoteright}s media components. In order to
deal with the variant network behavior, buffering manipulation mechanisms and grading of the
transmitted media quality techniques are proposed to smooth presentation and synchronization
anomalies.},
	author = {Christos Bouras and Vaggelis Kapoulas and Paul Spirakis and D Moiras and V Ouzounis and A Tatakis}
}
@conference {2813,
	title = {Tele-working services from the Greek PTT},
	booktitle = {3rd International Conference on Networking Entities-The organisational impact of telematics, Neties{\textquoteright}99, Krems, Austria},
	year = {1999},
	month = {18 - 19 March},
	pages = { 17 - 22},
	abstract = {During the last years tele-working methods that utilise network resources and
services are gaining wide acceptance. Interestingly enough not all the enterprises
that want to and can use tele-working are doing so. The main obstacles in adopting
and implementing tele-working techniques are lack of technical knowledge, poor
infrastructure, and lack of support. In Greece the main PTT organisation, as part of
its strategy to offer integrated Telematic services in various areas, designed and is
currently testing under several tele-working scenarios various services that will be
offered in suitable packages. The services offered include telephony services, basic
and advanced network services etc. The packages to be offered cover a wide area of
tele-workers, including tele-workers from home, mobile tele-workers, telecommuters
etc. The packages also cover the need to establish suitable infrastructure
for the tele-workers in the enterprise{\textquoteright}s premises, and the establishment of
telecentres/telecottages or satellite centres.In order to effectively test all the
proposed services a pilot network has been established. The network is based on
ISDN links and it consists of a few central nodes (i.e. representing enterprises{\textquoteright}
premises) and several remote nodes (some of them mobile) representing for the teleworkers.
The central nodes are equipped with an ISDN PBX, an enterprise server,
and a router. These nodes are connected to the public ISDN network via a few
Primary Rate Interface (PRI) ISDN links. The tele-workers{\textquoteright} nodes are equipped
with communication devices, such as telephones and facsimiles, and with personal
computers. The nodes are connected to the public ISDN network via one or a few
Basic Rate Interface (BRI) ISDN links. The initial tests show very promising
results. The offered integrated services are easy to use and very reliable. As a
consequence the tele-workers exhibit improved performance.},
	author = {Christos Bouras and Vaggelis Kapoulas and B Mamalis}
}
@conference {2866,
	title = {Today{\textquoteright}s Stories },
	booktitle = {i3 Conference, Sienna, Italy},
	year = {1999},
	month = {22 - 24 October},
	pages = { 88 - 94},
	abstract = {Research frameworks are being developed that involve very
young children in the process of development of future technologies. Children,
their teachers and parents from schools in Israel and Denmark are coming together
with researchers, educationalists, psychologists, designers and technologists
to develop a wearable technology for educational use- the KidsCam.
This example of a hyper-camera will facilitate and support the development of
social, communicative and emotional skills in the context of the everyday activities
of children. It is envisioned that such digital technology will become
embedded in educational culture and create opportunities for shared reflection
on early life experiences. Integral to the work is the development of an ethically
theorized and ethically led practical framework to consider the issues that
surround the development and deployment of new technology by and for children.
These will include issues of appropriateness, need and value. A series of
interactive presentations will be used to illustrate both the work in progress
and the vision of the project.},
	author = {Christos Bouras and Vaggelis Kapoulas and Agis Konidaris and Afroditi Sevasti and M Panayi and D Roy and N Bernsen and W Velde and J Klaff and O Cakmakci and K Paepe and G Lassbo and I Hakvoort and D Beach and Y Barlev and A Aviram and G Neofotistos}
}
@conference {2823,
	title = {The transition from contemporary to virtual user interfaces for Web-based Services},
	booktitle = {World Conference of the WWW, Internet and Intranet-WebNet 99, Honolulu, Hawaii, USA},
	year = {1999},
	month = {25 - 30 October},
	pages = { 125 - 130},
	abstract = {Computer and Internet based services are increasingly provided to users in our
days. The users are also increasing exponentially and it is obvious that they are not
experienced in the use of computers. This paper examines the problem of user friendly web
based service interfaces and proposes a new kind of interface. This interface is called a
Virtual Interface and is thoroughly presented. The Virtual Interface is compared to
contemporary User Interfaces and the results of this comparison are also presented.},
	author = {Christos Bouras and Agis Konidaris and Afroditi Sevasti}
}
@conference {2817,
	title = {Virtual European School-VES},
	booktitle = {IEEE Multimedia Systems{\textquoteright}99, Special Session on European Projects, Florence, Italy},
	year = {1999},
	month = {7 - 11 June},
	pages = { 1055 - 1057},
	abstract = {The Virtual European School (VES) is an ongoing
European project - funded by the Educational Multimedia
Task Force Initiative of the European Union - with the
aim to develop a comprehensive on-line resource of
teaching material for secondary school education. The
system will be fed by a group of smaller publishing houses
from different European countries (Austria, Italy, Greece,
Great Britain) specialised in educational material. The
offer will contain multimedia material, CBT products, and
also additional background materials, such as passages
from schoolbooks, or Internet resources. The technical
structure of the VES system will be based on Internet
technologies, with interconnected VES servers in each
participating region. The multimedia material will be
stored in a database, with multi-lingual annotations for
each project. There exist three user groups within the
VES: publishers, teachers and pupils.},
	author = {Christos Bouras and Vaggelis Kapoulas and A Koubek and D Fotakis and H Mayer and H Rehatscheck}
}
@conference {2818,
	title = {A Web-based distributed environment to support teleteaching: Design and Implementations issues},
	booktitle = {3rd International Workshop on Query Processing and Multimedia Issues in Distributed Systems (QPMIDS 99), Florence, Italy},
	year = {1999},
	month = {1 - 2 September},
	pages = { 906 - 911},
	abstract = {Web based systems have been shown to be useful tools
for supporting educational communication for teachers
and students. In this paper we present such a system,
which is an Integrated Distributed Learning Environment
(IDLE). We present the technical description of this IDLE
and we discuss its main characteristics like the
transmission of multimedia data over the network, the
manipulation of the educational procedure and the
management of the users. In addition we list the
functionalities of the IDLE and also discuss some
implementation issues.},
	author = {Christos Bouras and Apostolos Gkamas and Thrasivoulos Tsiatsos}
}
@conference {2822,
	title = {A Web-enabled Communication Environment for the Education Community},
	booktitle = {World Conference of the WWW, Internet and Intranet-WebNet 99, Honolulu, Hawaii, USA},
	year = {1999},
	month = {25 - 30 October},
	pages = { 1198 - 1199},
	abstract = {The research and development of computer-based, networked learning
environments will be built around electronic communication and collaboration services that
will play a significant role in the improvement of the learning procedure. Applications of this
kind provide tutors and trainees with the ability of continual, close and efficient cooperation,
en masse as well as individually. The goal of this work is the presentation of a communication
environment that was developed in the framework of Odysseas project. The flexible design
and implementation of basic communication services, accompanied with a friendly user
interface, comprise an ergonomic environment and ensure the introduction of information
technology in education as a daily communication and collaboration tool.},
	author = {Christos Bouras and S Kontogiannis and A Bazaios and A Zoura}
}
@article {3064,
	title = {Analytical Performance Models for Multistage Interconnection Networks with finite, infinite and zero length buffers},
	journal = {PERFORMANCE EVALUATION JOURNAL, Elsevier Science, Vol. 34},
	year = {1998},
	pages = { 169 - 182},
	abstract = {Multistage Interconnection Networks (MINs) with crossbar switches have been used
to interconnect processors and memory modules in parallel multiprocessor systems.
They also play an increasingly important role in the development of ATM networks.
In this paper we analyze the general case of MINs, made of kxk switches with
finite, infinite or zero length buffers (unbuffered). The exact solution of the steady
state distribution of the first stage is derived for all cases. We use this to get an
approximation for the steady state distributions in the second stage and beyond. In
the case of unbuffered switches we reach the known exact solution for all the stages
of the MIN. Our results are validated by extensive simulations.},
	author = {Christos Bouras and Paul Spirakis and Vasilis Triantafillou and J Garofalakis}
}
@conference {2834,
	title = {On Demand Delivery of Multimedia Documents using Distributed Objects},
	booktitle = {2nd International Conference on Parallel and Distributed Computing Networks-PDCN 98, Brisbane, Australia},
	year = {1998},
	month = {14 - 16 December},
	pages = { 357 - 360},
	abstract = {In this paper, we propose an architecture for the ondemand
delivery of multimedia documents over
broadband networks using distributed objects. The basic
components of our model are the network agents and the
presentation agents. Our model preserves flexibility,
transparency and modularity and value added opportunity
due to the usage of distributed objects.},
	author = {Christos Bouras and Paul Spirakis and V Ouzounis}
}
@conference {2829,
	title = {A Distributed Virtual Learning Center in Cyberspace},
	booktitle = {4th International Conference on Virtual Systems and Multimedia, Gifu, Japan, Vol. 2},
	year = {1998},
	month = {18 - 20 November},
	pages = { 410 - 415},
	abstract = {In this paper, we present a user-friendly 3D Distributed Virtual
Environment (DVE) that would be used for on-line access to educational multimedia
material over the Internet. We design and develop this application and the
corresponding Graphical User Interface (GUI) in the framework of the European
project {\textquotedblleft}Virtual European School{\textquotedblright} (VES) whose aim is to develop a comprehensive
resource of teaching material for secondary school education and to provide access
to this material over Internet. It is a web-based application that is being developed as
a client/server architecture using standard protocols and technologies such as
TCP/IP, HTTP, HTML, Java and appropriate 3D formats.},
	author = {Christos Bouras and A Philopoulos and D Fotakis}
}
@conference {2826,
	title = {Distributed Virtual Reality Environments Over Web for Distance Education},
	booktitle = {EDEN Conference, Bologna, Italy},
	year = {1998},
	month = {24 - 26 June},
	pages = { 481 - 484},
	abstract = {Virtual Environments for education have been discussed in various ways. While advanced multi-user
educational VEs are still speculation, simpler VEs based on standard technologies have been in
existence for some time. On the other hand, there is a great enthusiasm for promoting Virtual Reality
as a major factor in future (and present) environments for training and education. In this paper, we
discuss the concept of the Distributed Virtual Environments and the use of them in distance education
applications. Next, we consider VRML technology as the key technology for building such
environments and we present the basic features and functionalities of it that make it suitable for
delivering VEs over the Web. In addition to this, we present some of the roles of VRML in education.
Finally, we conclude with some recommendations on the construction of Virtual Reality
Environments for educational purposes.},
	author = {Christos Bouras and A Philopoulos}
}
@conference {2835,
	title = {A Framework for a Distributed Information Service Using Hypermedia/Multimedia Pre-Orchestrated Scenarios},
	booktitle = {10th International Conference on Parallel and Distributed Computing and Systems-Special Session on Communication and Computing for Distributed Multimedia Systems, Las Vegas, Nevada, USA},
	year = {1998},
	month = {28 - 31 October},
	pages = { 226 - 229},
	abstract = {Real time delivery of multimedia objects based on preorchestrated
scenarios, seems to have several difficulties
due to presentation deadlines that should be satisfied, and
network{\textquoteright}s unpredictable behavior which may lead to synchronization
anomalies among related media streams. Beyond
these, a structural model that represents such scenarios
is required. In this paper, we present a general framework
that addresses the above mentioned issues, and we
attempt to describe a unified approach for delivering hypermedia/
multimedia objects over network connections
preserving their timing constraints. We mainly concentrate
on the study and development of a markup language that
models the presentational structure of a multimedia object
and provides primitives that assure playout synchronization
of the different media streams that compose these
hypermedia objects. Methods for keeping a constant quality
level of presentation in times of network load are discussed.},
	author = {Christos Bouras and Vaggelis Kapoulas and D Moiras and V Ouzounis}
}
@conference {2827,
	title = {Implementing spatio-temporal relations for hypermedia presentations using an HTML-like language},
	booktitle = {Workshop on Internet Programming Languages(in conjunction with 1998 IEEE International Conference on Programming Languages), Chicago, Illinois, USA},
	year = {1998},
	month = {13 May},
	abstract = {Hypermedia is currently the trend in delivering information composed of various
forms of media. Up to now most systems lack the ability to present the user with
hypermedia information containing various media that have specific spatio-temporal
relations. In this paper we propose and describe a model that can describe such kinds
of hypermedia presentations. The core of the model is an HTML-like language that
supports tags for the description of timing relations between the information objects
that compose a hypermedia presentation.},
	author = {Christos Bouras and Vaggelis Kapoulas and Paul Spirakis and D Moiras and V Ouzounis and A Tatakis}
}
@conference {2828,
	title = {An Intranet and Internet based Information System for Administration and Information purposes},
	booktitle = {4th European Digital Cities Conference: Changing patterns of urban life, Salzburg, Austria},
	year = {1998},
	month = {29 - 30 October},
	pages = { 211 - 215},
	abstract = {This work presents a system developed within a project funded by the Greek Government.
The system deals with the distribution of information and the exchange of documents within,
from and towards (region, municipalities, citizens, various groups etc.) the prefecture of
Corfu. It is exploiting Intranet and Extranet technologies in order to enable asynchronous
and synchronous cooperation, manipulation of information from heterogeneous sources,
security and easy administration, providing in parallel advanced communication facilities.},
	author = {Christos Bouras and Vasilis Triantafillou and P Destounis and J Garofalakis and J Tzimas and P Zarafidis}
}
@inbook {3125,
	title = {MRP II-based Production Management Using Intelligent Decision Making},
	booktitle = {Advanced Models and Methods for Production Planning, Editors. A. Drexl, A. Kimms},
	year = {1998},
	pages = { 379 - 412},
	publisher = {Springer Verlag},
	organization = {Springer Verlag},
	abstract = {<p>This paper presents an extended MRP II-based production management system (PMS), which improves the traditional MRP II paradigm by attaching an intelligent decision supporting system (IDSS) to it. The IDSS is attached to the lowest level of the PMS, namely the production activity control (PAC) subsystem, and includes a simulator, that imitates real system behaviour, a knowledge-based component, that imitates expert reasoning, and a real-time database manager, that acts as the data pool and the communication gate between them. The IDSS is capable of performing off-line and on-line rescheduling, thus resulting in more realistic short-term plans. Analysis of the related case problem and implementation of the system are also discussed.</p>
},
	author = {D Sofotassios and Paul Spirakis and Vasilis Triantafillou and Ioannis Hatzilygeroudis and N Dendris and A Tsakalidis}
}
@conference {2825,
	title = {Multimedia Architecture offering Open Distance Learning Services over Internet},
	booktitle = {5th IEEE International Conference on Telecommunications - ICT 98, Chalkidiki, Greece, Vol. 4},
	year = {1998},
	month = {22 - 25 June},
	pages = { 145 - 149},
	abstract = {The increase in the use of the Internet not only as a
repository of resources for learning but also as a
means for the delivery of courses and specially
prepared teaching material is a particularly
significant innovation in the range of education.
The main concept here is a Virtual class, which is
based on the principles of CSCL (Computer
Supported Collaborative Learning) systems. This
paper describes an integrated, WWW based
platform for the development of web enabled
environments over TCP/IP networks, such as
Internet. This platform is designated through a
Teletraining and Collaborative Learning
Application. The proposed platform aspires to be
an efficient solution for a group of students and
teachers that need a shared workspace, supporting
remote interactive lectures, flexible exchange of
teaching material and various communication
utilities, with focus on transparent and secure
interaction.},
	author = {Christos Bouras and Paul Spirakis and P Lampsas and P Zarafidis and A Bazaios and A Zoura}
}
@conference {2830,
	title = {A platform for the implementation of the services of an Educational Network},
	booktitle = {15th IFIP World Computer Congress-Teleteaching{\textquoteright} 98, Vienna, Austria,  Part I},
	year = {1998},
	month = {31 August - 4 September},
	pages = { 159 - 169},
	abstract = {Multimedia and hypermedia had and still have a tremendous impact on the evolution of educational
software. In this paper we propose a platform for the implementation of the services of an
educational network over TCP/IP networks such as the Internet. Our proposal aims at providing an
integrated communicational environment which supplies the communicative needs of one
educational community, using the latest telecommunication and multimedia information processing
technology. We propose various kinds of communication forms for the interaction between the
participants.},
	author = {Christos Bouras and Vaggelis Kapoulas and Apostolos Gkamas and Thrasivoulos Tsiatsos and P Lampsas}
}
@article {3065,
	title = {Results and experience from the application of a common methodology for Users Requirements Specification in Distance Education using Telematics},
	journal = {Journal of Technology and Teacher Education -JTATE, AACE, Vol. 6, Issue 1},
	year = {1998},
	pages = { 61 - 74},
	abstract = {The cooperation of the Information and Communications Technologies (ICT) and the Educational communities, is
recognised as a necessity that must result in the adaptation and tuning of the education processes in terms of
pedagogical methodologies, school infrastructure, human resources development and organisational restructuring, in
order to efficiently absorb and utilize technological developments. The ICT community has to realize the significance
of the users{\textquoteright} needs, the difficulties of the intervention to an old and traditional process. And the need to view their
technology applications not only as a technical exercise. The initial phases of the TRENDS project, which are
described in this paper, resulted in an agreed common methodology for carrying out the necessary investigation of
the user needs in secondary education. This methodology, which was followed more or less in all participating
countries, produced answers to questions concerning the role of the educators and their basic training, their
familiarity with technology, education policies from a trans-European perspective, the content, forms and aims of
further training, the distance training of teachers in the use of new technologies, the motives, incentives and
organisational schemes for enhancing re-education, the needs of the educational environment and technology-based
training, the needs of the educators in practical didactic methods, etc.},
	author = {Christos Bouras and Paul Spirakis and P Lampsas and G Tsakarissianos and J Garofalakis and K Antonis and N Kastis and S Kontogiannis}
}
@conference {2833,
	title = {Training Centres: An Architecture for the Realisation of Open and Distance Learning Environments using Telematics},
	booktitle = {9th International Conference Society for Information Technology and Teacher Education-SITE 98, Washington, DC, USA, Vol. 1},
	year = {1998},
	month = {10 - 14 March},
	pages = { 118 - 120},
	abstract = {In this paper, we are describing an architecture for the realisation of Open and Distance
Learning (ODL) Environments using Telematics. The approach of using Training Centres as
dedicated education services providers, located at the premises of an educational authority is
discussed. These Training Centres may be Points of Presence of an international educational network
(as is the case in the TRENDS Project in the context of which Training Centres were studied).
Crucial aspects of the feasibility study, aiming to investigate the operational and organisational
conditions of the Centres, that must precede the implementation of a Training Centre, are cited.},
	author = {Christos Bouras and Paul Spirakis and P Lampsas}
}
@conference {2831,
	title = {Web-Enabled Distance Education Environment},
	booktitle = {World Conference of the WWW, Internet and Intranet-WebNet 98, Orlando, Florida, USA},
	year = {1998},
	month = {7 - 12 November},
	pages = { 80 - 85},
	abstract = {As the new network computer technology forces into every aspect of daily life,
many things change in a rather rapid way, compared to what we were used to until recently.
One of the most important aspects in the social activity of people, Education, could not be an
exception. Advances in network infrastructures and telematics services, combined with
multimedia techniques and powerful personal computers provide the opportunity to make a
network-based multimedia system for distance learning (teletraining) a real fact.},
	author = {Christos Bouras and P Lampsas and A Bazaios and G Tsindilas}
}
@conference {2832,
	title = {Web-Enabled Distributed Collaborative Learning Environment},
	booktitle = {6th International Conference on Computers in Education-ICCE 98, Beijing, China},
	year = {1998},
	month = {14 - 17 October},
	pages = { 489 - 493},
	abstract = {This paper describes, in design, architecture and implementation
level, a web based environment for co-operative teleworking and
collaborative learning over TCP/IP networks, such as Internet. The
implemented tool claims to be an efficient solution for a group of
users/students that need a shared workspace containing various
communication utilities, including on-line and off-line communication,
with focus on transparent and secure interaction.},
	author = {Christos Bouras and P Lampsas and P Zarafidis and A Zoura}
}
@conference {2847,
	title = {Competitive Video on Demand Schedulers for Popular Movies},
	booktitle = {Workshop on Algorithmic Aspects of Communications (ICALP satellite workshop),  Bologna, Italy},
	year = {1997},
	month = {11 - 12 July},
	abstract = {<p>In this paper we investigate the online video on demand problem, namely having to accept or reject a request for a movie without knowing the future requests. We present online movie-scheduling schemes that implement the principles of refusal by choice and delayed notication. A novel way to schedule movies that exploits the knowledge of the distribution of the preference of requests for movies, is shown to have a competitive ratio that outperforms all the previously known schemes in practical situations. In fact, our scheduler has a competitive ratio bounded above by a constant, independent of the number of the users, channels, or movies, in the case that a large fraction of the requests tends to concentrate in a small number of movies. We extend our approach by presenting an \adaptive" randomized scheduler which initially is not aware of the movie popularities but it adapts to it, and achieves a similar asymptotic competitive ratio.</p>
},
	author = {Christos Bouras and Vaggelis Kapoulas and Paul Spirakis and G Pantziou}
}
@conference {2837,
	title = {Conclusions on the Analysis of User Requirements concerning the use of ICT in the Didactic Process},
	booktitle = {ED-MEDIA/ED-TELECOM 97, Calgary, Canada},
	year = {1997},
	month = {14 - 19 June},
	pages = { 13 - 18},
	abstract = {The co-operation of the Information and Communications Technologies (ICT)
and the Educational Society, is deemed necessary for the adaptation and tuning of the
didactic process in terms of pedagogical methodologies, school infrastructure, human
resources utilisation and organisational restructuring. The use of ICT in the classroom
should be viewed as a highly influencing tool that will support the educators{\textquoteright} effort for
interaction with their students, rather than as a technical exercise. The initial phases of the
TRENDS project, which are described in this paper, resulted in a widely accepted common
methodology, that complies with the international standards for determining the User
Requirements in the Secondary Education. The major results emerged from this survey are
presented here, as well as some common axes that deal with the application of ICT in the
didactic process.},
	author = {Christos Bouras and Paul Spirakis and P Lampsas and G Tsakarissianos and J Garofalakis and K Antonis and N Kastis and S Kontogiannis}
}
@conference {2841,
	title = {The Design and Development of Advanced Network Services over the Patras University Campus Network},
	booktitle = {5th International Conference on Computers in Education-ICCE 97, Sarawak, Malaysia},
	year = {1997},
	month = {2 - 6 December},
	pages = { 420 - 427},
	abstract = {This paper presents some results of the initial phases of a big internal
project running at the University of Patras. In this project - which is co-funded by the
European Union - our team is responsible for the development of the Advanced
Network Services over the Campus Network, which is being established during the
project. In the following chapters we first present the general perspective and the
architecture of the integrated system which offers the set of advanced services to the
University community. We then describe in detail the different services (WWW and
Intranet, On-line teletraining, Computer supported cooperative work, and Off-line
teletraining). A key characteristic of the system is the integration of existing
commercial tools, with tools that we are developing for the specific needs of the
foreseen users. It is evident that this system can be considered as a pilot project for
large and demanding user communities, as is the case with the University of Patras.},
	author = {Christos Bouras and Paul Spirakis and Vasilis Triantafillou and J Garofalakis and J Tsaknakis and J Tzimas and A Tsakalidis and I Antoniou and D Karageorgopoylos and B Basiliadis and P Kappos}
}
@conference {2842,
	title = {Enabling Distance Education over the World Wide Web},
	booktitle = {World Conference of the WWW, Internet and Intranet- WebNet 97,Torodo,Canada},
	year = {1997},
	month = {31 Octiber - 5 November},
	abstract = {The recent advancements in the field of the information and communication technology
resulted in a revolution comparable to the industrial revolution. The basis of this revolution
is the information and the value it has as the pure expression of human knowledge. The
technological advancements offer us the ability to process, store, retrieve and transmit
information in multiple formats (text, sound, image, video) independently of time, volume
and distance. In this paper we present the technology that is required and an architecture for
the realization of distance education over the World Wide Web. We also address some basic
aspects of the users{\textquoteright} needs that every software tool for distance education should meet.},
	author = {Christos Bouras and Paul Spirakis and P Lampsas and I Antoniou}
}
@conference {2845,
	title = {A General Performance Model for Multistage Interconnection Networks},
	booktitle = {Euro-Par {\textquoteright}97, Passau, Germany},
	year = {1997},
	month = {25 - 29 August},
	pages = { 993 - 1000},
	abstract = {Multistage Interconnection Networks (MINs) with crossbar
switches are used to interconnect processors and memory modules in
parallel multiprocessor systems. In this paper we analyze the general case
of MINs, made of kk switches with nite, innite or zero length buers
(unbuered). The exact solution of the steady state distribution of the
rst stage is derived for all cases. We use this to get an approximation
for the steady state distributions in the second stage and beyond. In the
case of unbuered switches we reach the known exact solution for all the
stages of the MIN. Our results are validated by extensive simulations.
Keywords: analytical models, queueing theory models, evaluation.},
	author = {Christos Bouras and Paul Spirakis and Vasilis Triantafillou and J Garofalakis}
}
@conference {2840,
	title = {Hermes Service: Distributed Hypermedia Educational Services on Demand},
	booktitle = {ED-MEDIA/ED-TELECOM 97, Calgary, Canada},
	year = {1997},
	month = {14 - 19 Jne},
	pages = { 19 - 24},
	abstract = {In this paper we present a distributed HypERMEdia SERVICE
(HERMES SERVICE) which supports integrated capabilities for distance
education and learning purposes. Hermes service consists of hermes servers
and hermes browsers. The users are connected with the service using hermes
browsers and retrieve hypermedia lessons organised in thematical units. The
lessons are stored in various distributed Hermes servers which retrieve the
requested lesson and transmit it to the corresponding browser on on-demand
basis. The requested lesson is presented to the user according to a well defined
presentation scenario. The media objects are rendered in a synchronized
manner according to the spatio-temporal relationships existing among them.
Finally, special monitoring mechanism controls the state of the network and
adjusts the presentation process so as to improve presentation quality.},
	author = {Christos Bouras and Vaggelis Kapoulas and Paul Spirakis and D Moiras and V Ouzounis and I Antoniou and D Karageorgopoylos}
}
@conference {2844,
	title = {An HTML like language supporting time-depended transmission of hypermedia},
	booktitle = {The Eighth International ACM Hypertext Conference-Hypertext 97, Southampton, UK},
	year = {1997},
	month = {6 - 11 April},
	author = {Christos Bouras and Vaggelis Kapoulas and Paul Spirakis and A Tatakis}
}
@conference {2846,
	title = {HY-MOST: HYpermedia MOdel for Synchronised presenTations},
	booktitle = {3rd Workshop on Open Hypermedia Systems, Southampton, UK},
	year = {1997},
	month = {6 - 11 April},
	pages = { 18 - 23},
	abstract = {A brief abstract. In this paper we present a new model for
hypermedia presentations. This model is based on an
HTML-like language which provides the necessary modules
for the intermedia synchronisation of the inline media that
comprise the hypermedia document. The model also enables
a distributed approach in the storage of the hypermedia
documents. Additionally, it is capable of incorporating the
necessary protocols needed for the real-time delivery of
continuous media such as audio and video.},
	author = {Christos Bouras and Paul Spirakis and D Moiras and V Ouzounis and I Antoniou}
}
@conference {2838,
	title = {In-Service Training through ODL Environments:From User Needs To Functional Specifications},
	booktitle = {8th International Conference Society for Information Technology and Teacher Education-SITE 97, Orlando, USA},
	year = {1997},
	month = {1 - 5 April},
	pages = { 519 - 522},
	author = {Christos Bouras and Paul Spirakis and P Lampsas}
}
@conference {2839,
	title = {Major Principles on the Design of an Educational Network},
	booktitle = {Open Classroom II Conference, Crete, Greece},
	year = {1997},
	month = {17 - 19 September},
	pages = { 359 - 366},
	abstract = {The modern communication networks, apart from the specialized applications that they
offer depending on the nature of their target groups, they support a set of general purpose elementary
network services, that provide some essential communication facilities to the end users.
Regarding an educational network, these facilities include collaboration, navigation into the
information resources, as well as interpersonal communication, to the members of the Education
Society. In the sequel the major principles on providing these elementary network services are
presented. On-lline/off-line contact over an alternative means of communication among the members
of the trans-European Education Society could be an adequate reason for the deployment of an
educational communication network. This category of services will offer the members of the
Education Society the ability of exchanging opinions on educational and social matters, as well as
interpersonal messages, and collaborating. These facilities should be provided by already existing
network services, enhanced where necessary by supporting multimedia information exchange (mostly
off-line). In the latter case external media players of attachment viewers may be used for the
presentation of the multiple media of information.},
	author = {Christos Bouras and Agis Konidaris and Afroditi Sevasti and S Kontogiannis and D Fotakis and A Katanou and E Stephanou}
}
@conference {2836,
	title = {ODYSSEAS: The Greek Educational Network for Secondary Education},
	booktitle = {EUROAMERITEL{\textquoteright}97 Conference, San Jose, Costa Rica},
	year = {1997},
	month = {5 - 7 November},
	abstract = {The purpose of this paper is the description of the project
ODYSSEAS. The aim of the project is the design, development, and
pilot operation of an integrated network of schools in secondary
education in the Greek areas of Achaia, Thrace and Aegean Islands. A
special network infrastructure will be created and network software and
services (containing a WWW server, network software for teaching the
Greek language, applications of administrative support and so on) will
be developed. Training of the teachers and pupils and evaluation of the
project results will be the final project actions.},
	author = {Christos Bouras and Paul Spirakis and A Hatzilakos and M Koutlis and N Panopoulos}
}
@article {3067,
	title = {Pure greedy Hot-Potato routing in the 2-d mesh with random destinations},
	journal = {Parallel Processing Letters Vol. 7 No. 3},
	year = {1997},
	pages = { 249 - 258},
	abstract = {We analyze here a pure greedy hot-potato routing strategy on a two-dimensional
mesh of n^2 nodes. We specifically study the case of n^
2 packets, originating one per
node, to be delivered at random uniform destinations. Each packet attempts to follow
the shortest path leading first to the destination row/column (whichever is closest) and
then to the actual destination node. A de
ection policy is adopted to solve con
icts. We prove that all packets are delivered to the destinations in average time O(nlogn). The
average is taken over all possible destination functions. No average case analysis of pure
greedy hot-potato routing was known up to now.},
	author = {Paul Spirakis and Vasilis Triantafillou}
}
@conference {2843,
	title = {Superhighways for Open and Distance Learning},
	booktitle = {1997 EDEN Conference, Budapest, Hungary},
	year = {1997},
	month = {23 - 25 June},
	pages = { 32 - 36},
	abstract = {An educational information network, is a multimedia network with a centralized architecture for the
provision of educational services. The educational services comprise basic network applications (such
as multimedia e-mail, fora for debates on educational subjects, access to already existing
information), video distribution of multimedia lessons and a custom developed teletraining tool for
the conduction of lessons over a broadband networking infrastructure.
The suitability of the widely available broadband networking technologies (ATM, ISDN), as opposed
to the alternative of using already existing networking infrastructure (Internet, CATV), for the
implementation of educational networks for the realization of an Open and Distance Learning
Environment will be examined. More specifically the types of educational services that can be best
hosted by each technology and the costs as opposed to the maturity for the deployment of each
networking technology will be cited.
Finally, a proposal for an implementation scheme of an educational information network, concerning
the appropriate (and cost effective) networking infrastructure that can best accommodate the
aforementioned educational services will be elaborated.},
	author = {Christos Bouras and Paul Spirakis and P Lampsas}
}
@article {3066,
	title = {Using Multimedia/Hypermedia Tools over Networks for Distance Education and Training},
	journal = {Journal of Educational Technology Review - ETR, AACE, No. 7},
	year = {1997},
	month = {Summer},
	pages = { 20 - 26},
	abstract = {The rapid developments in the Information Technology sector as well as the
deployment of faster networks brings us to the era of the New Information
Technology (NIT). The citizen of the near future must be able to use them else he will
be seriously handicapped in his everyday life. Thus NIT becomes part of the
educational process while on the other hand offers the tools and the infrastructure for
the establishment of the distance education process. The educators are one of the first
professions that must learn to use NIT and its tools. Multimedia/hypermedia tools
offer solutions to the problems posed by the distance education process. They can be
user-friendly and enticing and they can cover most, if not all, the needs of their users.
A lot of prototype systems (tools) for distance education have been developed, each
offering a number of functions that aid the process of distance education. The rapid
growth of World Wide Web is adding another factor that can lead to the wider
deployment of distance education systems. Although the value of distance education
is unquestionable there is still a lot of work to be done before a wide spread
implementation platform emerges.},
	author = {Christos Bouras and Vaggelis Kapoulas and Paul Spirakis and P Lampsas and A Tatakis and S Kontogiannis and D Fotakis}
}
@conference {2850,
	title = {FINE:Implementation of a Distributed Telematics Environment for Clinical Engineers},
	booktitle = {1996 Concurrent Engineering Europe, Cambridge, UK},
	year = {1996},
	month = {10 -12 April},
	pages = { 56 - 60},
	author = {Christos Bouras and Vaggelis Kapoulas and Paul Spirakis and A Tatakis and D Fotakis and P Balaouras and L Chadelis and N Palikarakis and R Sandalatzopoulos}
}
@conference {2852,
	title = {An Interactive Cooperative Teleworking Environment-Tηλε{\textmu}άθεια *},
	booktitle = {ED-TELECOM 96, Boston, USA},
	year = {1996},
	month = {17 - 22 June},
	pages = { 37 - 42},
	abstract = {<p>In this paper we present the design and the implementation of an interactive environment for cooperative teleworking. Telemathea offers tools that support the communication and the teleworking between tutor and trainee, who may reside in remote geographical regions. This environment offers audio communication over the network as well as support for joint editing of text documents and still images. It supports different audio coding techniques so as to adjust to the available bandwidth, and makes use of the RTP protocol in order to facilitate the exchange of audio and, in the future, video packets.</p>
},
	author = {Christos Bouras and Vaggelis Kapoulas and Paul Spirakis and P Lampsas and A Tatakis and S Kontogiannis and D Fotakis and K Kyriakou}
}
@conference {2848,
	title = {On-Demand Hypermedia/Multimedia Service over Broadband Networks},
	booktitle = {5th IEEE International Symposium On High Performance Distributed Computing-HPDC-5, Syracuse, New York, USA},
	year = {1996},
	month = {6 - 9  August},
	pages = { 224 - 231},
	abstract = {In this paper we present a unied approach for de-
livering hypermedia/multimedia objects over broadband
networks. Documents are stored in various multimedia
servers, while the inline data may reside in their own
media servers, attached to the multimedia servers. The
described service consists of several multimedia servers
and a set of functions that intend to present to the
end user interactive information in real-time. Users
interact with the service requesting multimedia docu-
ments on demand. Various media streams are trans-
mitted over dierent parallel connections according to
their transmission requirements. The hypermedia doc-
uments are structured using a hypermedia markup lan-
guage that keeps information of the spatiotemporal re-
lationships among document{\textquoteright}s media components.
In order to deal with the variant network behavior,
buering manipulation mechanisms and grading of the
transmitted media quality techniques are proposed to
smooth presentation and synchronization anomalies.},
	author = {Christos Bouras and Vaggelis Kapoulas and Paul Spirakis and D Moiras and V Ouzounis and A Tatakis}
}
@article {3068,
	title = {Performance Modeling of Distributed Timestamp Ordering: Perfect and Imperfect Clocks},
	journal = {PERFORMANCE EVALUATION JOURNAL, Elsevier Science, Vol. 25, No. 2},
	year = {1996},
	month = {April},
	pages = { 105 - 130},
	abstract = {This work presents a model of a distributed database system which provides the framework to study the performance of timestamp ordering concurrency control. Locking and timestamping are two popular approaches to concurrency control in database systems. Timestamp-based algorithms have been proposed to protect distributed databases from inconsistencies during concurrent access. In these algorithms, transactions may reach a particular site in different order than their timestamps, due to unexpected network delays. This causes conflicts which the distributed concurrency control mechanism has to cope with. We exhibit an analytical solution, which has been tested with extensive simulation. The accuracy seems to be very high. We assume perfect and also imperfect clocks for synchronization and quantify the way in which local clock inaccuracies affect the phenomenon of transaction conflicts. In particular, we derive a lot of interesting performance measures such as probability of abort, mean waiting time, throughput, mean queue length and others.},
	author = {Christos Bouras and Paul Spirakis}
}
@conference {2849,
	title = {Randomized adaptive video on demand},
	booktitle = {15th ACM-PODC, Philadelphia PA, USA},
	year = {1996},
	pages = {179},
	author = {Christos Bouras and Vaggelis Kapoulas and Paul Spirakis and G Pantziou}
}
@conference {2851,
	title = {TRENDS: Training Educators through Networks and Distributed Systems},
	booktitle = {EDEN Conference 1996, Futuroscope Poitiers, France},
	year = {1996},
	month = {8 - 10 July},
	pages = { 195 - 199},
	abstract = {The TRENDS project aims at the in-service, distance training of 2,400 school teachers in Secondary Education,
and the use of Information Technology and Telematics in the learning process, by six countries (Greece, Italy,
Spain, Portugal, France, and United Kingdom). The training process will be implemented by flexible and
distance learning methods, through the development and use of an in-service school-based training system,
which will be based on multimedia telematics and existing mature network technologies, and the establishment
and operation of a European Teacher{\textquoteright}s Training Network, consisted of six interconnected National Sites
(Training Centre, schools and teachers per country). Each Training Centre in the Network will act as service
provider to the schools and the teachers. The major aspect of the project is to provide the educator and their
trainers, with various services including : e-mail contact with other educators and trainers, access to multimedia
information, forums for the discussion and debate on educational projects, access to curriculum-related
information for the educators, and multimedia teletraining for the conduction of lessons over the network. Due
to the nature of the planned services and applications, the network infrastructure that will be used for the
realization of the TRENDS, must offer high speed, multicasting, trans-European interoperability and certified
quality of services.},
	author = {Christos Bouras and Vaggelis Kapoulas and Paul Spirakis and G Tsakarissianos and N Kastis}
}
@conference {2853,
	title = {HIPPOCRATES: A multimedia tool for distance education},
	booktitle = {ED-MEDIA 95, Gratz, Austria},
	year = {1995},
	month = {17 - 21 June},
	pages = { 103 - 108},
	abstract = {In this paper we present a software tool for the realisation of the distance education
service, that is the conduction of classes through the use of computers. The classes
are directed towards personnel in various areas and aim at the retraining and update
of the personnel in subjects of special interest in their line of work. The conduction of
classes takes place, from and towards, remote regions with the aid of a computer network.
Hippocrates is a flexible and easy-to-use application, which permits students, who sit in
front of remotely situated workstations, to attend classes or seminars given by a teacher
or expert, who can also be located in some remote geographical area. Hippocrates can be
thought of as a distributed transparency projector. The teacher can project transparencies
on the screens of the students{\textquoteright} workstations and can emphasize or indicate regions of
interest on them by using the graphical tools offered by Hippocrates. Immediate results
of the use of Hippocrates are the fast updating of the personnel in remote areas and the
upgrading of the quality of the services they offer.},
	author = {Christos Bouras and Vaggelis Kapoulas and Paul Spirakis and P Lampsas and A Tatakis and D Fotakis and G Papoutsopoulos}
}
@conference {2854,
	title = {Multilingual Implementations of OSI Applications},
	booktitle = {10th International Symposium on Computers and Information Sciences-ISCIS X, Izmir, Turkey},
	year = {1995},
	month = {30 October - 1 November},
	pages = { 367 - 374},
	abstract = {In this work the problem of supporting multilingual environments over
OSI applications is addressed. Initially a solution based on the idea of using
multilingual structures and transcription techniques is presented. Another
solution based on the major principles of the former follows, which exploits
the coding of all of character sets uniformally.},
	author = {Christos Bouras and Vaggelis Kapoulas and Paul Spirakis and P Lampsas and A Tatakis and S Kontogiannis and D Fotakis}
}
@conference {2855,
	title = {Randomized Competitive Algorithms for Admission Control in General Networks},
	booktitle = {14th ACM-PODC, Ottawa, Canada},
	year = {1995},
	author = {Vaggelis Kapoulas and Paul Spirakis}
}
@book {3152,
	title = {Discrete Mathematics: Problems and Solutions},
	series = {Gutenberg},
	year = {1994},
	author = {Christos Bouras and Lefteris Kirousis and Paul Spirakis and G Voutsadakis}
}
@conference {2857,
	title = {The perfect and imperfect clocks approach to performance analysis of basic timestamp ordering in distributed databases},
	booktitle = {ICCI{\textquoteright}93, Sudbury, Ontario, Canada},
	year = {1993},
	month = {27 - 29 May},
	pages = { 403 - 407},
	abstract = {Locking and timestamping are two popular approaches
to concurrency control in databases systems.
Although more than a dozen analytic performance
studies of locking techniques have recently appeared
in the literature, analytic performance study
of timestamp{\textendash}based concurrency algorithms largely remains
an unexplored area. This work presents a model
of a distributed database system which provides the
framework to study the performance of timestamp ordering
concurrency control. We exhibit an analytical
solution, which has been tested with extensive simulation.
The accuracy seems to be very high. We assume
perfect and also imperfect clocks for synchronization
and quantify the way in which local clock inaccuracies
affect the phenomenon of transaction conflicts. In
particular, we derive a lot of interesting performance
measures such as probability of abort, throughput and
others.},
	author = {Christos Bouras and Paul Spirakis}
}
@conference {2856,
	title = {Performance Models for Perfect and Imperfect Clocks on Timestamp Ordering in Distributed Databases},
	booktitle = {MASCOTS{\textquoteright}93, San Diego, California, USA},
	year = {1993},
	month = {17 - 20 January},
	pages = { 243 - 246},
	abstract = {This work presents a model of a distributed
database system which provides the framework to
study the performance of timestamp ordering concurrency
control. We exhibit an analytical solution, which
has been tested with extensive simulation. The accuracy
seems to be very high. We assume perfect and
also imperfect clocks for synchronization and quantify
the way in which local clock inaccuracies affect the
phenomenon of transaction conflicts.},
	author = {Christos Bouras and Paul Spirakis}
}
@book {3153,
	title = {Discrete Mathematics},
	series = {Gutenberg},
	year = {1992},
	author = {Christos Bouras and Lefteris Kirousis and Paul Spirakis}
}
@conference {2858,
	title = {MIPL:An Image Processing Library for Medical Applications},
	booktitle = {S/CAR{\textquoteright}92, Baltimore, Maryland, USA},
	year = {1992},
	month = {14 - 17 June},
	pages = { 519 - 525},
	author = {Christos Bouras and Vaggelis Kapoulas and Paul Spirakis and T Georgantas and K Goutis}
}
@conference {2860,
	title = {The effect of clock drifts on the performance of distributed timestamp ordering},
	booktitle = {3rd COMAD 91, Bombay, India},
	year = {1991},
	month = {12 - 14 December},
	pages = { 69 - 85},
	abstract = {Timestamp{\textendash}based algorithms have been proposed to protect distributed
database from inconsistencies during concurrent access. In such algorithms,
transactions may reach a paricular site out of the order of their timestamps,
due to unexpected network delays. This causes conflicts which the distributed
concurrency control mechanism has to cope with. In this paper we analyze
the essential features of the conflict phenomenon under the realistic assumption
of the local site clocks out of total synchrony. We quantify the way in
which local clock inaccuracies affect the phenomenon of transaction conflicts.
In particular, we express the probability of order{\textendash}reverse as a particular increasing
function of the maximum clock drift.},
	author = {Christos Bouras and Paul Spirakis}
}
@conference {2859,
	title = {RECPHONE: A new environment for medical remote expert consultation},
	booktitle = {EuroPACS{\textquoteright}91, 9th International Meeting, Berlin, Germany},
	year = {1991},
	month = {2 -3 July},
	pages = { 22 - 23},
	author = {Christos Bouras and Paul Spirakis and J Garofalakis and G Papoutsopoulos and P Basiroglou}
}
@conference {2861,
	title = {Simplified performance models of the reordering issue in timestamp ordering concurrency control in distributed databases},
	booktitle = {5th International Symposium on Computers and Information Sciences- ISCIS V, Volume II, Cappadocia, Nevsehir, Turkey},
	year = {1990},
	month = {30 October - 2 November},
	pages = { 719 - 727},
	author = {Christos Bouras and Paul Spirakis}
}
@conference {2862,
	title = {Queueing Delays in Buffered Multistage Interconnection Networks},
	booktitle = {ACM SIGMETRICS Conference 1987, Banff, Alberta, Canada},
	year = {1987},
	month = {11 - 14 May},
	pages = { 111 - 121},
	author = {Christos Bouras and Paul Spirakis and Vasilis Triantafillou and J Garofalakis}
}
