Alternative Schemes for Dynamic Secure VPN Deployment in UMTS

Three alternative schemes for secure Virtual Private Network (VPN) deployment over the Universal Mobile Telecommunication System (UMTS) are proposed and analyzed. The proposed schemes enable a mobile node to voluntarily establish an IPsec-based secure channel to a private network. The alternative schemes differ in the location where the IPsec functionality is placed within the UMTS network architecture (mobile node, access network, and UMTS network border), depending on the employed security model, and whether data in transit are ever in clear-text, or available to be tapped by outsiders. The provided levels of privacy in the deployed VPN schemes, as well as the employed authentication models are examined. An analysis in terms of cost, complexity, and performance overhead that each method imposes to the underlying network architecture, as well as to the mobile devices is presented. The level of system reliability and scalability in granting security services is presented. The VPN management, usability, and trusted relations, as well as their behavior when a mobile user moves are analyzed. The use of special applications that require access to encapsulated data traffic is explored. Finally, an overall comparison of the proposed schemes from the security and operation point of view summarizes their relative performance. Christos Xenakis received his B.Sc. degree in computer science in 1993 and his M.Sc. degree in telecommunication and computer networks in 1996, both from the Department of Informatics and Telecommunications, University of Athens, Greece. In 2004 he received his Ph.D. from the University of Athens (Department of Informatics and Telecommunications). From 1998–2000 was with the Greek telecoms system development firm Teletel S.A., where was involved in the design and development of advanced telecommunications subsystems for ISDN, ATM, GSM, and GPRS. Since 1996 he has been a member of the Communication Networks Laboratory of the University of Athens. He has participated in numerous projects realized in the context of EU Programs (ACTS, ESPRIT, IST). His research interests are in the field of mobile/wireless networks, security and distributed network management. He is the author of over 15 papers in the above areas. Lazaros Merakos received the Diploma in electrical and mechanical engineering from the National Technical University of Athens, Greece, in 1978, and the M.S. and Ph.D. degrees in electrical engineering from the State University of New York, Buffalo, in 1981 and 1984, respectively. From 1983 to 1986, he was on the faculty of Electrical Engineering and Computer Science at the University of Connecticut, Storrs. From 1986 to 1994 he was on the faculty of the Electrical and Computer Engineering Department at Northeastern University, Boston, MA. During the period 1993–1994 he served as Director of the Communications and Digital Processing Research Center at Northeastern University. During the summers of 1990 and 1991, he was a Visiting Scientist at the IBM T. J. Watson Research Center, Yorktown Heights, NY. In 1994, he joined the faculty of the University of Athens, Athens, Greece, where he is presently a Professor in the Department of Informatics and Telecommunications, and Director of the Communication Networks Laboratory (UoA-CNL) and the Networks Operations and Management Center. His research interests are in the design and performance analysis of broadband networks, and wireless/mobile communication systems and services. He has authored more than 150 papers in the above areas. Since 1995, he is leading the research activities of UoA-CNL in the area of mobile communications, in the framework of the Advanced Communication Technologies & Services (ACTS) and Information Society Technologies (IST) programmes funded by the European Union (projects RAINBOW, Magic WAND, WINE, MOBIVAS, POLOS, ANWIRE). He is chairman of the board of the Greek Universities Network, the Greek Schools Network, and member of the board of the Greek Research Network. In 1994, he received the Guanella Award for the Best Paper presented at the International Zurich Seminar on Mobile Communications.     

Specification and Dynamic Introduction of 3rd Party,Service-Specific Adaptation Policies for Mobile Applications

The development, delivery and management of mobile services are the subject of many research activities in both the academia and industry. The ultimate goal of these efforts is a dynamic environment that enables the delivery of situation-aware, personalised multimedia services over heterogeneous, ubiquitous infrastructures, commonly termed as systems beyond 3rd generation (3G). Reconfigurability and adaptability are key aspects of the mobile systems beyond 3G. Reconfigurable mobile systems and networks introduce additional requirements and complexity in service adaptation. Moreover, it is widely recognised that services will be increasingly developed by independent third parties, besides mobile operators and equipment vendors. The present contribution complements previous work by the authors, related to mediating service provision platforms and advanced adaptability and profile management frameworks. It introduces mechanisms and middleware that undertake the service adaptation overhead, imposed by the complexity of reconfigurable mobile networks, from application developers and third party service providers. In particular, it enables the introduction of third party policies for adaptation decision. Finally, it facilitates the adaptable application development and service deployment independently from the underlying dynamically reconfigurable communication environment. Nikos Houssos holds a B.Sc. and a Ph.D. degree from the Department of Informatics Telecommunications at the University of Athens, Greece, and an M.Sc. degree (with distinction) in Telematics from the department of Electronic and Electrical Engineering, University of Surrey, UK. Since 1999, he is working at the Communication Networks Laboratory of the University of Athens. He has participated in various research projects of the European Union IST framework (MOBIVAS, ANWIRE, POLOS, E2R). His research interests include middleware platforms and business models for mobile service provision in 3G/4G environments, service adaptability, network reconfigurability and context-aware pervasive systems. Nancy Alonistioti has a B.Sc. degree and a PhD degree in Informatics and Telecommunications (University of Athens). She has been working for several years at the Dept. of Informatics and Telecommunications in University of Athens as a senior researcher and project manager. She has been involved in many European and national projects (CTS, SS#7, ACTS RAINBOW, EURESCOM) in the areas of protocol and service design of mobile systems. She has been the Technical manager of the IST-MOBIVAS and IST-ANWIRE projects. She had been working as expert at the Greek Regulatory Agency. She is member of the core management team of the Greek Universities Network (GUNET). Her current research includes: mobile communications, re-configurable mobile systems and networks, adaptability, service provision, protocol design and mobile computing. Lazaros Merakos received a Diploma in electrical and mechanical engineering form the National Technical University of Athens, Greece, in 1978 and M.S. and Ph.D. degrees in electrical engineering from the State University of New York, Buffalo, in 1981 and 1984, respectively. From 1983 to 1986 he was on the faculty of Electrical Engineering and Computer Science at the University of Connectitut, Storrs. From 1986 to 1994 he was on the faculty of the Electrical and Computer Engineering Department at Northeastern University, Boston, Massachusetts. During the period 1993–1994 he served as a director of the Communications and Digital Processing Research Center at Northeastern University. During the summers of 1990 and 1991, he was a visiting scientist at the IBM T. J. Watson Research Center, Yorktown Heights, New York. In 1994 he joined the faculty of the University of Athens, Greece, where he is presently a professor in the Department of Informatics and Telecommunications, and director of the Communication Networks Laboratory (UoA-CNL) and the Networks Operations and Management Center. His research interests are in the design and performance analysis of broadband networks, and wireless/mobile communication systems and services. He has authored more than 150 papers in the above areas. Since 1995, he is leading the research activities of UoA-CNL in the area of mobile communications, in the framework of the Advanced Communication Technologies and Services (ACTS) and Information Society Technologies (IST) programs funded by the European Union (projects RAINBOW, Magic WAND, WINE, MOBIVAS, POLOS). He is chairman of board of the Greek Universities Network, the Greek Schools Network, and a member of the board of the Greek Research Network. In 1994 he received the Guanella Award for the Best Paper presented at the International Zurich Seminar on Mobile Communications.This revised version was published online in August 2005 with a corrected cover date.     

Metadata Design for Reconfigurable Protocol Stacks in Systems Beyond 3G

Global consensus on the next generation of wireless mobile communications, broadly termed “beyond 3G”, sketches a heterogeneous infrastructure comprising different wireless systems in a complementary manner and vested with reconfiguration capabilities, which support a flexible and dynamic adaptation of the wireless network and its spectrum resources to meet the ever-changing service requirements. For ubiquitous reconfiguration to become a practical capability of mobile communication systems, it is necessary to establish a global architecture for modeling, expressing, and circulating essential metadata related to reconfiguration, including reconfigurable device capabilities and semantic properties of protocol stacks. We outline the relevant standardization initiatives in the mobile domain, summarize existing work in reconfiguration-supporting architectures, and identify key shortcomings that may hinder the advent of ubiquitously reconfigurable systems. Further on, we point out some major limitations of current metadata standards in the mobile domain for the representation of capability information pertaining to reconfigurable protocol stacks. Next, we identify essential metadata classes in support of reconfigurable communication systems, introducing an associated object-oriented UML model. We elaborate on the design rationale of the UML model, presenting and discussing the alternative metadata representation standards and suitable encoding formats. Finally, we demonstrate the suitability of our UML model by applying our reconfiguration-supporting vocabulary in the cases of a standardized protocol stack of 3G mobile devices and stationary 3G cellular network elements. Vangelis Gazis received his B.Sc. and M.Sc. (Communication Networking) degrees from the Department of Informatics & Telecommunications of the University of Athens, Greece, in 1995, and 1998, respectively. He also received an M.B.A. degree from the Athens University of Economics and Business in 2001. Since 1996 until, he has been with the research staff of the Communication Networks Laboratory (CNL) of the University of Athens. He has participated in national and European research projects (MOBIVAS, ANWIRE) of the IST framework programme. He specializes in reconfigurable mobile systems and networks for beyond 3G, metadata and ontology languages, reflective and component middleware, adaptable services and open API frameworks for telecommunications. He is currently a Ph.D. candidate in the Department of Informatics & Telecommunications of the University of Athens. Nancy Alonistioti holds a B.Sc. degree and a Ph.D. degree in informatics and telecommunications from the University of Athens. Presently, she is a senior researcher in the Department of Informatics and Telecommunications of the University of Athens. In the past, she has held a research position with the Institute of Informatics and Telecommunications of NCSR “Demokritos” in the areas of protocol and service design and testing, mobile systems (UMTS), open architectures, and software defined radio systems and networks. Her current research interests are in reconfigurable mobile systems and networks beyond 3G, and adaptable services, pervasive computing and context awareness. She has participated in several national and European R&D projects, and has been the technical manager of the IST-MOBIVAS and IST-ANWIRE projects, which have had a focus on reconfigurable mobile systems, networks an respective service provision. She is currently a member of the management team and workpackage leader in the FP6 IST-E2R project on reconfigurability; she also serves as technical manager for the University of Athens in the FP6 IST-LIAISON project, which focuses on location based services in working environments. Dr Alonistioti is co-editor and co-author of the book entitled “Software defined radio, Architectures, Systems and Functions”, published by John Wiley in May 2003. She has authored over 55 publications in the area of mobile communications and reconfigurable systems and networks. Lazaros Merakos received the Diploma in electrical and mechanical engineering from the National Technical University of Athens, Athens, Greece, in 1978, and the M.S. and Ph.D. degrees in electrical engineering from the State University of New York, Buffalo, in 1981 and 1984, respectively. From 1983 to 1986, he was on the faculty of the Electrical Engineering and Computer Science Department, University of Connecticut, Storrs. From 1986 to 1994, he was on the faculty of the Electrical and Computer Engineering Department, Northeastern University, Boston, MA. During the period 1993D1994, he served as Director of the Communications and Digital Processing Research Center, Northeastern University. During the summers of 1990 and 1991, he was a Visiting Scientist at the IBM T. J. Watson Research Center, Yorktown Heights, NY. In 1994, he joined the faculty of the University of Athens, Athens, Greece, where he is presently a Professor in the Department of Informatics and Telecommunications, and Director of the Communication Networks Laboratory (UoA-CNL) and the Networks Operations and Management Center. Since 1995, he is leading the research activities of UoA-CNL in the area of mobile communications, in the framework of the Advanced Communication Technologies and Services (ACTS) and Information Society Technologies (IST) programs funded by the European Union (projects RAINBOW, Magic WAND, WINE, MOBIVAS, POLOS, ANWIRE, E2R, LIAISON). His research interests are in the design and performance analysis of communication networks, and wireless/mobile communication systems and services. He has authored more than 190 papers in the above areas. Dr. Merakos is Chairman of the Board of the Greek Universities Network, the Greek Schools Network, and Member of the Board of the Greek Research Network. In 1994, he received the Guanella Award for the Best Paper presented at the International Zurich Seminar on Mobile Communications.     

A Radio Resource Allocation Scheme for Fixed Broadband Wireless Access Systems with Avoidance of Major Interferers

An improved radio resource allocation scheme with avoidance of major interferers is proposed and analyzed for the downlink of Fixed Broadband Wireless Access (FBWA) systems with full frequency reuse. The scheme is based on Enhanced Staggered Resource Allocation (ESRA) and permits the enhancement of the throughput per sector. Simulation results show a maximum downlink throughput per sector in excess of 44% and an increase of 10% with respect to ESRA is achieved, with Base Station (BS) selection procedure, while meeting a 15 dB signal-to-interference ratio (SIR). Nicholas Vaiopoulos was bornin Lamia in 1977. He received his Physics degree and his M.Sc.degree in electronics and radio-communications from the University of Athens, Greecein 2000and 2003, respectively. Currently, he is working towards his Ph.D. degree on the resource allocation techniques with reference to wireless systems at the Department of informatics and Telecommunications at the same University. His research interests include broadband communications systems, scheduling algorithms and power control techniques for wireless systems. Alexander Vavoulaswas born in Athens in 1976. He received his B.Sc. degree in physics and the M.Sc. degree in electronics and radio-communications in 2000 and 2002 respectively,both from the University of Athens, Greece. Currently he is working toward the Ph.D. degree on the radio resource allocation techniques with the same University. His research interest is focused on broadband wireless access and interference management. He is a student nmember of the IEEE. Dimitris Varoutas holds BSc. degree in Physics, M.Sc. in electronics and radio-communi cations and Ph.D. in telecommunications systems and technoeconomics, all from the University of Athens. He is a lecturer in the Department of Informatics and Telecommunications of University of Athens and an adjunct assistant professor in the Department of Telecommunications of the newly founded University of Peloponnese. He has participating in numerous European R&D projects in the RACE I &II, ACTS, Telematics, RISI and IST framework in the areas of telecommunications and Technoeconomics. He is an adviser in several organisations including OTE and EETT (Greek NRA for telecommunications) in the fields of telecommunications, broadband and mobile services, licensing, spectrum management, pricing and legislation. His research interests are optical, microwave communications and technoeconomic evaluation of network architectures and services. He has more than 30 publications in refereed journal and conferences in the area of telecommunications, optoelectronics and technoeconomics. He is a member of IEEE and serves as reviewer in several journals and conferences. Thomas Sphicopoulos received the Physics degree from Athens University in 1976, the D.E.A. degree and Doctorate in Electronics both from the University of Paris VI in 1977 and 1980 respectively, the Doctorat Es Science from the Ecole Polytechnique Federale de Lausanne in 1986. From 1976 to 1977 he worked in Thomson CSF Central Research Laboratories on Microwave Oscillators. From 1977 to 1980 he was an Associate Researcher in Thomson CSF Aeronautics Infrastructure Division. In 1980 he joined the Electromagnetism Laboratory of the Ecole Polytechnique Federal de Lausanne where he carried out research on Applied Electromagnetism. Since 1987 he is with the Athens University engaged in research on Broadband Communications Systems. In 1990 he was elected as an Assistant Professor of Communications in the Department of Informatics & Telecommunications, in 1993 as Associate Professor and since 1998 he is a Professor in the same Department. His main scientific interests are Microwave and Optical Communication Systems and Networks and Techno-economics. He has lead about 40 National and European R&D projects. He has more than 100 publications in scientific journals and conference proceedings. From 1999 he is advisor in several organisations including EETT (Greek NRA for telecommunications) in the fields of market liberalisation, spectrum management techniques and technology convergence.     

Vehicle Velocity Estimation Based on RSS Measurements

This paper presents a technique which is based on pattern recognition techniques, in order to estimate Mobile Terminal (MT) velocity. The proposed technique applies on received signal strength (RSS) measurements and more precisely on information extracted from Iub air interface, in wIDeband code-division multiple access (WCDMA) systems for transmission control purposes. Pattern recognition is performed by HIDden Markov Model (HMM), which is trained with downlink signal strength measurements for specific areas, employing Clustering LARge Applications (CLARA) like a clustering method. Accurate results from a single probe vehicle show the potential of the method, when applied to large scale of MTs. Theodore S. Stamoulakatos is a Senior Research Associate with the Department of Electrical and Computer Engineering at National Technical University of Athens (NTUA). He received his B.Sc. in Mathematics from University of the Aegean, Greece, in 1997, and the M.Sc. in Computer Applications from Dublin City University, Ireland, in 1999 with scholarship from the Irish Ministry of Education. On April ’05 he received his Ph.D. degree from the Department of Electrical Engineering and Computer Science of the National Technical University of Athens. He has been lecturing in DCU various courses including Algorithms & Data Structures, Computer Systems, and Advanced Network Management to both undergraduate and postgraduate students. During his research in NTUA, he has been actively involved in many European and National projects that match his research interests. Both his academic as well as his industrial experience (four years in OTEnet S.A.) allow him to publish several papers in journals and international conferences, which are in the fields of Mobile and Personal Communication Networks, Active Networks, Location Based Services as well as Network and Service Management. Dr. Stamoulakatos is a member of the IEEE. Antonis E. Markopoulos obtained his degree in Informatics and Telecommunications Engineering from University of Athens, Greece in 2000. During his studies he participated in various research projects dealing with the management of fixed and wireless networks. He has also industrial experience for 2 years in INTRASOFT International S.A participating in several projects, national and European. He received his PhD in the field of Cellular and Wireless Communication from the National Technical University of Athens in 2005, where he is working as a Senior Research Engineer in the Telecommunication Laboratory. He has published several papers in journals, international conferences and book chapters. His research interests are in the fields of cellular and wireless networks of present and future generation (4G, WLAN/WPAN, WiMAX) and more specific in the areas of radio resource management and security. He has been mainly involved in many European (IST-CELLO, IST-PACWOMAN, IST-MAGNET, a.o) and National (Greek IST, GGRT) projects. Dr Markopoulos is a member of the IEEE and of the Greek Association of Mechanical and Electrical Engineers. Miltiades E. Anagnostou was born in Athens, Greece, in 1958. He received the Electrical Engineer’s Diploma from the National Technical University of Athens (NTUA) in 1981. In 1987 he received his PhD in the area of computer networks. Since 1989 he has been teaching at the Electrical and Computer Engineering School of NTUA, where he is currently a Full Professor. He teaches courses on modern telecommunications, computer networks, formal specification, stochastic processes, and network algorithms. His research spans several fields, including broadband networks, mobile and personal communications, service engineering, mobile agents, pervasive computing, network algorithms and queuing systems. He is a member of the IEEE and the ACM. Michael E. Theologou received the degree in Electrical Engineering from Patras University and his Ph.D. degree from the Department of Electrical Engineering and Computer Science of the National Technical University of Athens. Currently he is a Professor at National Technical University of Athens, Department of Electrical and Computer Engineering conducting teaching and research in the wider area of Telecommunication Networks and Systems. His research interests are in the fields of Mobile and Personal Communication Networks, Computer Networks, Quality of Service. He has many publications in the above areas.     

Optimizing the QoS of Ultra High and High Speed Moving Terminals in Satellite-Aided Cellular Networks

This paper presents a new channel assignment technique based on a three-layer cellular architecture which optimizes the QoS of Ultra High-Speed (UHSMT) and High-Speed Moving Terminals (HSMT) in a congested urban area. The lower layer of the proposed architecture is based on a microcellular solution, for absorbing the traffic loads of Low Speed Moving Terminals (LSMT). The second layer is based on a macro-cell umbrella solution, for absorbing the traffic load of the HSMT. The higher layer is based on satellite cell and absorbs the traffic load of UHSMT. The results show that assigning the optimum number of channels in every layer, the QoS of UHSMT and HSMT are optimized, having a small bad effect on the QoS of LSMT. Konstantinos Ioannou was born in Patras, Greece, in 1975. He received the Diploma and the PhD in Electrical and Computer Engineering in 1998 and 2004, respectively, from the Polytechnic School of the University of Patras. His dissertation, elaborated at the Wireless Telecommunications Laboratory of the Department of Electrical and Computer Engineers, dealt with Channel Assignment Techniques, Handover Procedures, Traffic Modeling and Call Admission Policies in 2G, 3G Mobile Systems and Security Mobile Systems. During his Postgraduate Studies, he participated in many European and National Research Projects. Since the October of 1999, he is working as an Assistant Professor (under contract) at the Technological Educational Institute of Messolongi – Departments of Applied Informatics in Management & Economy Electronics and Informatics. During the last 2 years, he belongs also to the Technical Consultants Team of the Ministry of Public Order, regarding the C4I Olympic Security System, involved, among others, with TETRA and AVL subsystems. His scientific interests include Mobile and Satellite Communications, Wired and Wireless Networks, Handover and Channel Assignment Techniques and Communication Services. A lot of publications in scientific journals and conference proceedings – 27 and 40, respectively – document his research activity. Konstantinos Ioannou is a member of the Technical Chamber of Greece (TEE). Ioannis Panoutsopoulos was born in Patras, Greece, in 1974. He received the Diploma and the PhD in Electrical and Computer Engineering in 1997 and 2003, respectively, from the Polytechnic School of the University of Patras. His dissertation, elaborated at the Wireless Telecommunications Laboratory of the Department of Electrical and Computer Engineers, dealt with Handover Procedures, Traffic modeling and Call Admission Policies in 2G and 3G Mobile Systems. During his Postgraduate Studies, he participated in many European and National Research Projects. Since the October of 2003, he is working as an Assistant Professor (under contract) at the Technological Educational Institute of Athens - Departments of Electronics and Informatics – teaching Antenna Theory, Electromagnetic Waves Propagation – Transmission Lines and Mobile Telecommunications Systems. During the last 2 years, he belongs also to the Technical Consultants Team of the Ministry of Public Order, regarding the C4I Olympic Security System, involved, among others, with TETRA and AVL subsystems. His scientific interests include Mobile and Satellite Communications, Wired and Wireless Networks, Handover and Channel Assignment Techniques and Communication Services. A lot of publications in scientific journals and conference proceedings – 12 and 18, respectively – document his research activity. Ioannis Panoutsopoulos is a member of the Technical Chamber of Greece (TEE). S. Kotsopoulos was born in Argos-Argolidos (Greece) in the year 1952. He received his B.Sc. in Physics in the year 1975 from the University of Thessaloniki, and in the year 1984 got his Diploma in Electrical and Computer Engineering from the University of Patras. He is an M.Phil and Ph.D. holder since 1978 and 1985 correspondingly. He did his postgraduate studies in the University of Bradford in United Kingdom. Currently he is member of the academic staff of the Department of Electrical and Computer Engineering of the University of Patras and holds the position of Professor. He develops his professional life teaching and doing research at the Laboratory of Wireless Telecommunications (Univ. Of Patras), with interest in mobile communications, interference, satellite communications, telematics, communication services and antennae design. Moreover he is the (co)author of the book titled “mobile telephony”. The research activity is documented by more than 160 publications in scientific journals and proceedings of conferences. Ast. Professor Kotsopoulos has been the leader of several international and many national research projects. Finally, he is member of the Greek Physicists Society and member of the Technical Chamber of Greece.     

On the Economics of 3G Mobile Virtual Network Operators (MVNOs)

The paper assesses the market conditions and dynamics, the architectures and the different approaches for deployment of 3G Mobile Virtual Network Operators (MVNOs), in an attempt to address specific advantages and pitfalls. Following the definition of appropriate service sets and tariff structures, and taking into account demand scenarios, a techno-economic model has been developed, in order to compute key economic indicators. The paper presents techno-economic results of specific business cases and deployment alternatives for an average “large” European country and a smaller, Nordic-type country. Fixed and variable costs have been identified and the business case shows how different service sets lead to different costs. Different MVNO business profiles have been investigated. Profitability for all scenarios and business profiles has been calculated, presented and discussed. Major opportunities and threats, as well as critical parameters and uncertainties have been identified through sensitivity analysis. Dimitris Varoutas holds Physics degree and M.Sc. and Ph.D degrees in electronics and radio-communications from the University of Athens. He is a research fellow and adjunct lecturer in the Department of Informatics and Telecommunications of University of Athens. He is also an adjunct lecturer in the Department of Telecommunications of the newly founded University of Peloponnese. He has participating in numerous European R&D projects in the RACE I &II, ACTS, Telematics, RISI and IST framework in the areas of telecommunications and Technoeconomics. He is an adviser in several organisations including OTE and EETT (Greek NRA for telecommunications) in the fields of telecommunications, broadband and mobile services, licensing, spectrum management, pricing and legislation. His research interests are optical, microwave communications and technoeconomic evaluation of network architectures and services. He has more than 30 publications in refereed journal and conferences in the area of telecommunications, optoelectronics and technoeconomics. He is a member of IEEE and serves as reviewer in several journals and conferences. Dimitris Katsianis received the Informatics degree and the M.Sc in Signal Processing and Computational Systems from the University of Athens. He is a research fellow in the Informatics Department of University of Athens. He was technical consultant scientific co-operator for Hellenic Telecommunication Organisation (OTE) in networking aspects concerning simulation of ATM networks and Management in an all Optical network, participating in several Eurescom (European Institute for Research and Strategic Studies in Telecommunication) projects. He was consultant in investment analysis projects for OTE Consulting S.A. He was also technical consultant in Telecommunication and signal processing for Space Hellas and technical consultant in Networking Applications for ICL-Hellas. He was participating in several ACTS and IST projects (AC364 OPTIMUM, AC364TERA, IST 25172-TONIC, etc.) as the case study leader for 3G and 4G business cases. He has more than 25 publications in journal and conferences in the field of techno-economics and 3G-network design. Thomas Sphicopoulos received the Physics degree from Athens University in 1976, the D.E.A. degree and Doctorate in Electronics both from the University of Paris VI in 1977 and 1980 respectively, the Doctorat Es Science from the Ecole Polytechnique Federale de Lausanne in 1986. From 1976 to 1977 he worked in Thomson CSF Central Research Laboratories on Microwave Oscillators. From 1977 to 1980 he was an Associate Researcher in Thomson CSF Aeronautics Infrastructure Division. In 1980 he joined the Electromagnetism Laboratory of the Ecole Polytechnique Federal de Lausanne where he carried out research on Applied Electromagnetism. Since 1987 he is with the Athens University engaged in research on Broadband Communications Systems. In 1990 he was elected as an Assistant Professor of Communications in the Department of Informatics, in 1993 as Associate Professor and since 1998 he is a Professor in the same Department. His main scientific interests are Microwave and Optical Communication Systems and Networks and Techno-economics. He is leading about 30 National and European R&D projects (RACE I and II, ACTS, RISI, HCM, COST, Eurescom, etc.) including Synthesis and TITAN. He has more than 80 publications in scientific journals and conference proceedings. He is also a reviewer in journals of IEEE and IEE and auditor and evaluator of RACE and ACTS projects. He is the Chairman of the IEEE LEOS Chapter (Bulgaria, Greece, Romania and Yugoslavia). From 1999 he is advisor in several organisations including EETT (Greek NRA for telecommunications) in the fields of market liberalisation, spectrum management techniques and technology convergence. Kjell Stordahl received his M.Sc. from Oslo University in 1972. He has been at the Research Department Telenor for 15 years; 7 years as a manager of the Teletraffic field. He joined Telenor Networks in 1989 as Chief Planning Manager until 1996. He has been manager of Market analysis in Telenor Networks 1997–2002. Kjell Stordahl was appointed associated reporter and special reporter 1981–1988 in CCITT SGII for “Forecasting International Traffic”. From 1985 to 1988 he participated in CCITT GAS 10 and developed a forecasting handbook. He has also worked for ITU's headquarter as a specialist on forecasting. From 1994 to 1997 he was on the Board of Telenor Consult AS. He was referee for Project Imagine 21 in the ESPRIT Programme 1999–2001. Kjell Stordahl was on the Technical Advisory Board of Virtual Photonics 2000–2002. Since 1992 he has participated in various projects funded by the European Commission: RACE/TITAN, ACTS/OPTIMUM and TERA, IST/TONIC and CELTIC/ECOSYS. Kjell Stordahl has published over 150 papers in International Journals and Conferences.     

Mean Waiting Time Analysis in Finite Storage Queues for Wireless Cellular Networks

In this paper priority is assigned to the handover calls over new call attempts and blocked handover calls are placed in a finite storage queue. Total handover forced termination probability is evaluated and a suitable function for the mean service time at each position in the queue is theoretically estimated. Quality of service is obtained by introducing a threshold in the maximum waiting time of a handover call in the queue. In case the handover call mean service time at each queue position is found to be greater than this threshold, this call will be blocked. Simulation results show that this scheme provides satisfactory results for both types of calls. Spiros Louvros was born in Corfu Island, Hellas in 1971. He received his Bachelor in Physics from the University of Crete, Hellas and his Master of Science in telecommunications from the University of Cranfield, U.K. with a graduate scholarship from the Alexandros Onassis Institution. In 2004 he received his PhD from the University of Patras, Hellas, in mobile communications. He has worked for Siemens as a microwave engineer, for Vodafon-Hellas as a switching engineer and for Cosmote S.A. as section manager in the Operations, Maintenance & Optimization Department. His current occupation is in the Telecommunication Systems & Networks Department, Technical University of Messologi, Hellas, as an Assistant Professor. He holds several papers in international journals and conferences and he has participated in several research projects regarding mobile communications. His area of interest is in mobile networks, telecommunication traffic engineering, wireless ATM and optical communications and is documented by over 30 papers in international literature and conference proceedings. He is member of FITCE and Hellenic Physics Union. Gerasimos Pylarinos – Stamatelatos was born in Kefalonia, Greece in 1966. He receieved the B.E. in Electrical and Computer Systems Engineering from Monash University, Melbourne, Australia in 1992 and the B.E. in Electrical and Computer Systems Engineering from the University of Patras, Greece in 1994. He received the M.Sc. in Data Communications Systems from Brunel University, United Kingdom. He is currently pursuing the PhD degree at the University of Patras Greece. He has worked at Philips Radio Communication Systems, Melbourne, Australia developing hardware for mobile radio communication systems for 2 years. He subsequently worked as project manager in the Research and Development department at Intracom Radio Communication Systems, Greece for 7 years. He is now manager of the Biomedical Engineering department of Kefalonia Hospital, Greece. His research interests lie in the areas of 3G and 4G wireless communications. S. Kotsopoulos was born in Argos-Argolidos (Greece) in the year 1952. He received his B.Sc. in Physics in the year 1975 from the University of Thessaloniki, and in the year 1984 got his Diploma in Electrical and Computer Engineering from the University of Patras. He did his postgraduate studies in the University of Bradford in United Kingdom. And he is an M.Phil and Ph.D. holder since 1978 and 1985 correspondingly. Currently he is member of the academic staff of the Department of Electrical and Computer Engineering of the University of Patras and holds the position of Associate Professor. Since 2004, is the Director of the Wireless Telecommunications Laboratory and develops his professional life teaching and doing research in the scientific area of Telecommunications, with interest in mobile communications, interference, satellite communications, telematics applications, communication services and antennae design. Moreover he is the (co)author of the book titled “mobile telephony”. The research activity is documented by more than 160 publications in scientific journals and proceedings of International Conferences. Associate Professor Kotsopoulos has been the leader of several international and many national research projects. Finally, he is member of the Greek Physicists Society and member of the Technical Chamber of Greece.     

Delay Performance Analysis and Evaluation of IEEE 802.11e EDCA in Finite Load Conditions

The paper presents an analytical model for the performance evaluation of IEEE 802.11e EDCA scheme under finite load conditions on the basis of various instances of delay metric (i.e., media access delay, queuing delay and total delay). The simulation results show that the analytical estimated instances of the delay metric are almost accurate. The paper exhibits that concerning the delay of serving classes, EDCA compared to the conventional DCF, favors high priority classes against low priority ones, while almost does not affect the behavior of medium ones. Dimitris Vassis was born in Ioannina, Greece, in 1978. He received the Diploma in Electrical and Computing Engineering and the MBA in Techno-economic Systems both from the National Technical University of Athens (NTUA), Greece, in 2001 and 2004 respectively. Currently, he is a Ph.D. student in the University of the Aegean, Department of Information and Communication Systems Engineering. His research interests are in the fields of performance evaluation and performance analysis of wireless access networks. George Kormentzas is currently lecturer in the University of the Aegean, Department of Information and Communication Systems Engineering. He was born in Athens, Greece on 1973. He received the Diploma in Electrical and Computer Engineering and the Ph.D. in Computer Science both from the National Technical University of Athens (NTUA), Greece, in 1995 and 2000, respectively. From 2000 to 2002, he was a research associate with the Institute of Informatics & Telecommunications of the Greek National Center for Scientific Research “Demokritos”. His research interests are in the fields of traffic analysis, network control, resource management and quality of service in broadband networks. He has published extensively in the fields above, in international scientific journals, edited books and conference proceedings. He is a member of pronounced professional societies, an active reviewer and guest editor for several journals and conferences and EU-evaluator for Marie Curie Actions. George Kormentzas has participated in a number of national and international research projects, serving in some instances as the project's technical representative for University of Aegean and/or as WP leader and/or as the project's Technical Manager.     

An Integrated Model to Design PCS Networks

An integrated model is proposed that comprises essentially, an Enhanced Profile-Based Strategy (EPBS) for small-scale roaming and a Caching Two-Level Forwarding Pointer (C2LFP) strategy for large-scale roaming. The idea behind the integrated model is how those two location management solutions are applied, and what is the suitable approach to specify the physical parameters of PCS networks from mobility management’s point of view so that our solutions can be more cost effective for location management. An evolutionary method, using a constrained Genetic Algorithm (GA) has been used to achieve network parameters optimization. For convenience, we selected the underlying planning problem with an appropriate set of parameters so that it can be treated, in what follows, both genetically and analytically. Thus one can easily verify the accuracy and efficiency of the evolutionary solution that would be obtained from the genetic algorithm. For more realistic environments, GA could be used reliably to build up sophisticated models that integrate the small-scale and large-scale roaming parameters of PCS networks. The results that have been obtained from a case study are presented in order to provide a deep explanation for the proposed integration approach. Salah M. Ramadan (samohra@yahoo.com) received the BS and MS degrees from Computers Engineering Department, Al-Azhar University, Cairo, Egypt, in 1995 and 2002, respectively. From 2002, he was a PhD student in Computers Engineering Department at Al-Azhar University and is currently pursuing the PhD degree, where he is a research assistant in the Wireless Networks Branch. His research interests include traffic management in ATM networks, routing protocols, mobility management in PCS networks, and mobile computing. He is currently an instructor in Cisco Academy, Egypt. Ahmed M. El-Sherbini (Sherbini@mcit.gov.eg) received the Ph.D. in Electrical and Communication Engineering, Case Western University, U.S.A. March 1983 and M.Sc. in Communication Engineering, Cairo University, Giza, Egypt, June 1980. (M.Sc. Research Studies at the Ecole Nationale Superieure des Telecommunications (ENST), Paris, France) He is the Director, National Telecommunication Institute – Ministry of Communications and Information Technology, Egypt and Professor of Electrical and Communication Engineering Dept. Faculty of Engineering, Cairo University, Egypt. M. I. Marie(azhar@mailer.scu.eun.eg) received his B.Sc, M.Sc and PhD in electronic and communication engineering from Cairo University on 1972, 1981, 1985, respectively. Now he is a professor of communications at Computer and System Engineering Department Al-Azhar University, Cairo, Egypt. His fields of interest includes digital communication, computer networks and protocols development. M. Zaki is the professor of software engineering, Computer and System Engineering Department, Faculty of Engineering, Al-Azhar University at Cairo. He received his B.Sc. and M.Sc. degrees in electrical engineering from Cairo University in 1968 and 1973 respectively. He received his Ph.D. degrees in computer engineering from Warsaw Technical University, Poland in 1977. His fields of interest include artificial intelligence, soft computing, and distributed system.     

Location Management in PCS Networks by Caching Two-Level Forwarding-Pointers

One of the challenging tasks in Personal Communication Services (PCS) is to efficiently maintain the location of PCS subscribers who move from one region to another (hereafter called mobile users). When a mobile user receives a call, the network has to quickly determine its current location. The existing location management scheme suffers from high signaling traffic in locating the mobile users. Two-level forwarding pointer scheme has been proposed from per-user forwarding pointer scheme to reduce the cost of signaling traffic. In this paper, we enhance the two-level forwarding pointer scheme. When a mobile user moves from its current Registered Area (RA), which is served by Mobile Switching Center (MSC), to another RA the local switch that acts as a parent of those two MSCs maintains this movement in its memory (hereafter called cache entry). A cache entry is used to locate rapidly the mobile user instead of querying the Home Location Register (HLR) and waiting for its reply. HLR is centralized in the network and far away from the mobile users so that the signaling traffic crossing it is expensive. Sometimes the cache entry may be failed to reach the mobile user then a two-level forwarding pointers will be created from the corresponding Visitor Location Register (VLR), attached to its MSC, through a correct path to locate the mobile user. Thus, there is a saving in cost of querying the underlying HLR. The analytical results indicate that such proposal efficiently reduces the signaling traffic cost for all values of Call to Mobility Ratio (CMR), this is especially considerable when CMR ≥1, without any increase in the call setup delay. Salah M. Ramadan (samohra@yahoo.com) received the BS and MS degrees from Computers Engineering Department, Al-Azhar University, Cairo, Egypt, in 1995 and 2002, respectively. From 2002, he was a Ph.D. student in Computers Engineering Department at Al-Azhar University and is currently pursuing the Ph.D. degree, where he is a research assistant in the Wireless Networks Branch. His research interests include traffic management in ATM networks, routing protocols, mobility management in PCS networks, and mobile computing. He is currently an instructor in Cisco Academy, Egypt. Ahmed M. El-Sherbini (Sherbini@mcit.gov.eg) received the Ph.D. in Electrical and Communication Engineering, Case Western University, U.S.A. March 1983 and M.Sc. in Communication Engineering, Cairo University, Giza, Egypt, June 1980. (M. Sc. Research Studies at the Ecole Nationale Superieure des Telecommunications (ENST), Paris, France). He is the Director, National Telecommunication Institute – Ministry of Communications and Information Technology, Egypt and Professor of Electrical and Communication Engineering Dept. Faculty of Engineering, Cairo University, Egypt. M. I. Marie received his B.Sc., M.Sc. and Ph.D. in electronic and communication engineering from Cairo University on 1972, 1981, 1985, respectively. Now he is a professor of communications at Computer and System Engineering department Al-Azhar University, Cairo, Egypt. His fields of interest includes digital communication, computer networks and protocols development. M. Zaki (azhar@mailer.scu.eun.eg) is the professor of software engineering, Computer and System Engineering Department, Faculty of Engineering, Al-Azhar University at Cairo. He received his B.Sc. and M.Sc. degrees in electrical engineering from Cairo University in 1968 and 1973 respectively. He received his Ph.D. degrees in computer engineering from Warsaw Technical University, Poland in 1977. His fields of interest include artificial intelligence, soft computing, and distributed system.     

MIMO Channel Characterization for Short Range Fixed Wireless Propagation Environments

This paper reports results from wideband MIMO measurements performed in short range fixed wireless environments at 5.2 GHz. The objective is to provide MIMO channel characterization results for the measured environments and contribute to the limited available similar studies. Two kinds of propagation scenarios are investigated, rooftop to rooftop and street to rooftop, at three different sites always under LOS propagation conditions. The analysis of measurement data is performed in the context of non physical modeling, providing insight into the statistics of the measured channels. In particular, the slow time varying nature of the channel is studied and the narrow Doppler spectrum shape is approximated. Furthermore, frequency correlation results are obtained and the typical delay dispersion measures are extracted. Then, the antenna correlation is studied and the error of the Kronecker product approximation is evaluated. Finally, capacity results are provided and the channel measurements are characterized in terms of spatial multiplexing quality and multipath richness through condition number analysis. Nikolaos D. Skentos received his Diploma in Electrical and Computer Engineering from the National Technical University of Athens (NTUA), Greece in October 2000. Since January 2001 he has been a research associate at the Mobile Radio Communications Laboratory at the NTUA, and he is currently working towards the Ph.D. degree. His research interests include channel measurements, MIMO channel characterization, MIMO algorithms and space time processing. He has been active in the IST STINGRAY project, the COST 273 Action and the ACE Network of Excellence. He is also a member of the National Technical Chamber of Greece since 2001. Athanasios G. Kanatas received the Diploma in Electrical Engineering from the National Technical University of Athens, Greece, in 1991, the M.Sc. degree in Satellite Communication Engineering from the University of Surrey, Surrey, UK in 1992, and the Ph.D. degree in Mobile Satellite Communications from the National Technical University of Athens, Greece in February 1997. From 1993 to 1994 he was with National Documentation Center of National Research Institute. In 1995 he joined SPACETEC Ltd. where he was Technical Project Manager for VISA/EMEA VSAT Project in Greece. In 1996 he joined the Mobile Radio Communications Laboratory as a research associate. From 1999 to 2002 he was with the Institute of Communication & Computer Systems. In 2000 he became a member of the Board of Directors of OTESAT S.A. He is an Assistant Professor in the Department of Technology Education and Digital Systems at University of Piraeus. His current research interests include channel characterization and estimation, simulation and modeling for mobile, mobile satellite, and future wireless communication systems. He has been a Senior Member of IEEE since 2002, and is also a member of the Technical Chamber of Greece. In 1999 he was elected Chairman of the Communications Society of the Greek IEEE Section. Panagiotis I. Dallas was born 1967 in Thessaloniki, Greece. He obtained his diploma and Ph.D. degree from the Electrical and Computer Engineering Department of Aristotle University of Thessaloniki, Greece, in 1990 and 1997, respectively. Since 1998 he joined with INTRACOM where he currently is Section Manager of Advanced Communications Technologies branch of Emerging Technologies & Markets department, leading the next generation of broadband wireless access systems for internal and EU projects. He runs the relevant standardization activities (IEEE 802.16 and ETSI/BRAN HIPERMAN) in INTRACOM and he represents the company in WiMAX forum. Finally, he has over 30 publications in international journals and conferences. Philip Constantinou received the Diploma in Physics from the National University of Athens in 1972, the Master of Applied Science in Electrical Engineering from the University of Ottawa, Ontario, Canada in 1976, and the Ph.D. degree in Electrical Engineering in 1983 from Carleton University, Ottawa, Ontario, Canada. From 1976 to 1979 he was with Telesat Canada as a Communications System Engineer. In 1980 he joined the Ministry of Communications in Ottawa, Canada where he was engaged in the area of Mobile Communication. From 1984 to 1989 he was with the National Research Center Demokritos in Athens, Greece where he was involved in several research projects in the area of Mobile Communications. In 1989 he joined the National Technical University of Athens where he is currently a Professor and Director of the Mobile Radio Communications Laboratory. His current research interests include Personal Communications, Mobile Satellite Communications, and Interference Problems on Digital Communications Systems.     

Packet concatenation at the IP level for performance enhancement in wireless local area networks

Wireless local area networks experience performance degradation in presence of small packets. The main reason for that is the large overhead added at the physical and link layers. This paper proposes a concatenation algorithm which groups IP layer packets prior to transmission, called PAC-IP. As a result, the overhead added at the physical and the link layers is shared among the grouped packets. Along with performance improvement, PAC-IP enables packet-based fairness in medium access as well as includes QoS support module handling delay-sensitive traffic demands. The performance of the proposed algorithm is evaluated through both simulations and an experimental WLAN testbed environment covering the single-hop and the widespread infrastructure network scenarios. Obtained results underline significant performance enhancement in different operating scenarios and channel conditions. Dzmitry Kliazovich received his Masters degree in Telecommunication science from Belarusian State University of Informatics and Radioelectronics in 2002. He is currently working towards the Ph.D. degree in University of Trento, Italy. From September 2005 to February 2006 he was a visiting researcher at the Computer Science Department of the University of California at Los Angeles. He is an author of more than 20 research papers published in international books, journals and conference proceedings. His main research interest lies in field of wireless networking with a focus on performance optimization and cross-layer design. Fabrizio Granelli was born in Genoa in 1972. He received the “Laurea” (M.Sc.) degree in Electronic Engineering from the University of Genoa, Italy, in 1997, with a thesis on video coding, awarded with the TELECOM Italy prize, and the Ph.D. in Telecommunications from the same university, in 2001. Since 2000 he is carrying on his teaching activity as Assistant Professor in Telecommunications at the Dept. of Information and Communication Technology—University of Trento (Italy). In August 2004, he was visiting professor at the State University of Campinas (Brasil). He is author or co-author of more than 60 papers published in international journals, books and conferences, and he is member of the Technical Committee of the International Conference on Communications (from 2003 to 2007) and Global Telecommunications Conference (GLOBECOM2003 and GLOBECOM2004). Dr. Granelli is guest-editor of ACM Journal on Mobile Networks and Applications, special issues on “WLAN Optimization at the MAC and Network Levels” and “Ultra-Wide Band for Sensor Networks”, and Co-Chair of 10th IEEE Workshop on Computer-Aided Modeling, Analysis, and Design of Communication Links and Networks (CAMAD’04). Dr. Granelli is General Vice-Chair of the First International Conference on Wireless Internet (WICON’05) and General Chair of the 11th IEEE Workshop on Computer-Aided Modeling, Analysis, and Design of Communication Links and Networks (CAMAD’06). His main research activities are in the field of networking and signal processing, with particular reference to network performance modeling, medium access control, wireless networks, cognitive radio systems, and video transmission over packet networks. He is Senior Member of IEEE and Associate Editor of IEEE Communications Letters.     

New Paradigms in Wireless Communication Systems

This paper discusses what a new paradigm can be in wireless communication systems of the twenty-first century. First, it suggests two directions for the new paradigm; one is “micro- and nano-device communication system” which is the projected scenario considering that the entities in source and destination have been shrinking throughout the history of wireless communication systems. The second direction is “networked robot system”, which emerges as a natural extension of mobile ad hoc networking where the networking is closely related to motion control of robots. Secondly, it shows two interesting research topics, “the new communication protocol design” and “signal processing”, respectively, that arise in the wake of the fusion between the two directions in the novel communication paradigm. Finally, it considers a new science of wireless communications in the twenty-first century. Shinsuke Hara received the B.Eng., M.Eng. and Ph.D. degrees in communications engineering from Osaka University, Osaka, Japan, in 1985, 1987 and 1990, respectively. From April 1990 to March 1997, he was an assistant professor in the Department of Communication Engineering, School of Engineering, Osaka University, and from October 1997 to September 2005, he was an associate professor in the Department of Electronic, Information and Energy Engineering, Graduate School of Engineering, Osaka University. Since October 2005, he has been a professor in the Department of Physical Electronics and Informatics, Graduate School of Engineering, Osaka City University. In addition, from April 1995 to March 1996, he was a visiting scientist at Telecommunications and Traffic Control Systems Group, Delft University of Technology, Delft, The Netherlands. His research interests include wireless communications systems and digital signal processing. Hiroyuki Yomo received B.S. degree in communication engineering from Department of Communication Engineering, Osaka University, Osaka, Japan, in 1997, and M.S. and Ph.D. degrees in communication engineering from Department of Electronic, Information, and Energy Engineering, Graduate School of Engineering, Osaka University, Osaka Japan, in 1999 and 2002, respectively. From April 2002 to March 2004, he was a Post-doctoral Fellow in Department of Communication Technology, Aalborg University, Denmark. From April 2004 to September 2004, he was at Internet System Laboratory, NEC Corporation, Japan. Since October 2004, he has been an Assistant Research Professor in Center for TeleInfrastructure (CTIF), Aalborg University, Denmark. His main research interests are access technologies, radio resource management, and link-layer techniques in the area of short-range communication, cellular network, cognitive radio, and sensor network. Petar Popovski received the Dipl.-Ing. in electrical engineering and M.Sc. in communication engineering from the Faculty of Electrical Engineering, Sts. Cyril and Methodius University, Skopje, Republic of Macedonia, in 1997 and 2000, respectively. He received a Ph.D. degree from Aalborg University, Denmark, in 2004. From 1998 to 2001 he was a teaching and research assistant at the Institute of Telecommunications, Faculty of Electrical Engineering in Skopje. He is currently Assistant Professor at the Department of Communication Technology at the Aalborg University. His research interests are related to the PHY-MAC aspects of wireless protocols, wireless sensor networks, random access protocols, and network coding. Kazunori Hayashi received the B.E., M.E. and Ph.D. degrees in communication engineering from Osaka University, Osaka, Japan, in 1997, 1999 and 2002, respectively. He spent 3 months in 2000 at Aalborg University, Denmark, as a Visiting Scholar. Since 2002, he has been with the Department of Systems Science, Graduate School of Informatics, Kyoto University. He is currently an Assistant Professor there. His research interests include digital signal processing for communications systems.     

Improved Performance of Maximum Likelihood Decoding Algorithm with Efficient Use of Algebraic Decoder

A new soft decision maximum-likelihood decoding algorithm, which generates the minimum set of candidate codewords by efficiently applying the algebraic decoder is proposed. As a result, the decoding complexity is reduced without degradation of performance. The new algorithm is tested and verified by simulation results.Panagiotis G. Babalis was born in Athens, Greece, on January 3, 1974. He received his Diploma of electrical and computer engineering and the Ph.D. degree, both from National Technical University of Athens (NTUA), Athens, Greece, in 1996 and 2001, respectively. His main research interests include mobile satellite communications, modulation, and wireless communications systems coding. Dr. Babalis is a member of the technical Chamber of Greece.Panagiotis T. Trakadas was born in Athens, Greece, on January 14, 1972. He received his Diploma of Electrical and Computer Engineering and the Ph.D. degree from National Technical University of Athens (NTUA), Athens, Greece, in 1996, and 2001, respectively. From 1998 to 2001, he participated in many European projects as a researcher. His main research interests include mobile communications systems and electromagnetic compatibility topics. Dr. Trakadas is a member of the Technical Chamber of Greece and IEEE Society.Theodore B. Zahariadis received his Ph.D. degree in electrical and computer engineering from the National Technical University of Athens, Greece, and his Dipl.-Ing. Degree in computer engineering and information science from the University of Patras, Greece. Currently, he is the technical director of Ellemedia Technologies, where he leads R&D of end-to-end interactive multimedia services, embedded systems, and 3G/4G core network services. Since 1994 he has participated in many European co-funded projects. His research interests are in the fields of broadband wireline/wireless/mobile communications, interactive service deployment, management of IP/WDM networks, and embedded systems. He has published more than 30 papers. He has been a reviewer and principal guest editor in many journals and magazines. He is a member of the ACM and the Technical Chamber of Greece.Christos N. Capsalis was born in Greece, in 1956. He received the diploma in electrical and mechanical engineering from the National Technical University of Athens (NTUA), Athens, Greece, in 1979, the B.Sc. degree in economics from the University of Athens, Athens, Greece, in 1983, and the Ph.D. degree in electrical engineering from NTUA in 1985. He is currently a Professor at NTUA and Director of the wireless communications laboratory. His current research activities include wireless and satellite communications systems and EMC topics.     

Resource management of IP-enabled DVB-T networks in the context of wireless B3G systems

The wireless beyond 3G systems or the so called Composite Radio Environments (CRE) (or even 4G systems), consist of multiple type radio access technologies, collaborating with each other, providing both diverse access alternatives and QoS improvement, especially as far as concerns protection against traffic congestion and loss of radio coverage situations. The merits deriving from beyond 3G systems interest not only network and service providers but also the mobile users. Additionally, the need of broadband wireless access is directly associated with the intense demand for IP multimedia services (e.g. video streaming or high speed web browsing), mainly inside hot-spot areas. Taking into consideration the above described tendency in the area of wireless network systems, the IP-enabled DVB-T (the terrestrial specification of the Digital Video Broadcasting family) systems appear as an attractive alternative network access in the CRE context. Along this direction, this paper presents the most important aspects of a CRE network management system (NMS), focusing on the component responsible for the DVB-T resource management (RM). Finally, we implement and investigate through simulation a greedy algorithm suitable for DVB-T networks that performs fast resource management and configuration. We also provide some indicative results which prove that the algorithm demonstrates a close to optimal performance at the RM functionality. This work is partially funded by the Commission of the European Communities, under the Fifth Framework Program, within the IST project CREDO (Composite Radio for Enhanced Service Delivery during the Olympics). Dimitris Kouis is currently a research associate at the Electrical Engineers School of the National Technical University of Athens, in Greece. He received his diploma from the Computer Engineering and Informatics department of the Polytechnic School of the University of Patras and a Ph.D. degree in Telecommunications and Computing from the National Technical University of Athens, Greece, in 1999 and 2005 respectively. He has worked in research projects in the context of the IST framework. His research interests include mobile and wireless networking, wireless network resources optimization techniques and large-scale software platforms. He is a member of the Technical Chamber of Greece since 1999. Panagiotis Demestichas received the Diploma and the Ph.D. degrees in Electrical and Computer Engineering from the National Technical University of Athens (NTUA). From September 2002 he is an Assistant Professor at the University of Piraeus, in the department of Technology Education and Digital Systems. From 1993 until August 2002 he has been a senior research engineer with the Telecommunications Laboratory in NTUA. From February 2001 until August 2002 he was a lecturer at NTUA, in the department of Applied Mathematics and Physics, teaching courses on programming languages, data structures, data bases, telecommunications. From September 2000 until August 2002 he taught telecommunication courses, in the department of Electronics of the Technological Education Institute of Piraeus. Most of his current activities focus on the FP6/IST project E2R (End-to-End Reconfigurability). He is also the chairman of Working Group 6 (WG6), titled Reconfigurability, of the Wireless Word Research Forum (WWRF). At the international level he has actively participated in the projects IST MONASIDRE Management of Networks and Services in a Diversified Radio Environment), where he was the project manager, as well as other EU projects under the IST, ACTS, RACE II, EURET, BRITE/EURAM frameworks. His research interests include the design, management and performance evaluation of mobile and broadband networks, service and software engineering, algorithms and complexity theory, and queueing theory. He has authored over 100 publications in these areas in international journals and refereed conferences. He is a member of the IEEE, ACM and the Technical Chamber of Greece. George Koundourakis was born in Alex/polis, Greece, in 1979. He received the degree of Electrical and Computer Engineer from the National Technical University of Athens (NTUA), Greece, in July 2001. He is a Research Associate and PhD candidate at the Telecommunications Laboratory of the Division of Communication, Electronic and Information Engineering at NTUA. He has worked in research projects in the context of the IST framework. He is the author of several scientific papers in the areas of mobile communications. He is a member of the Technical Chamber of Greece. Michael E. Theologou received the degree in Electrical Engineering from Patras University and his Ph.D. degree from the School of Electrical Engineering and Computer Science of the National Technical University of Athens (NTUA). Currently he is a Professor in the School of Electrical Engineering and Computer Science of NTUA. His research interests are in the field of Mobile and Personal communications. He has many publications in the above areas. Dr Theologou is a member of IEEE and the Technical Chamber of Greece.     

A New Low Latency Parallel FIR Filter Scheme

A new array type parallel scheme for an FIR digital filter is presented in this paper. The proposed scheme is based on the structure of the carry-save array multiplier where each cell implements the computation of an FIR filter at the bit-level. This structure leads to latency independent of the number of the filter taps. The proposed scheme is pipelined at the bit-level, is systolic at the cell-level and requires less hardware than other schemes based on discrete multipliers.Paraskevas Kalivas received his Diploma and Ph.D. degree in electrical and computer engineering from the National Technical University of Athens, Greece, in 1990 and 2000 respectively.His research interests include computer arithmetic and efficient realization of arithmetic circuits and digital filters.Vassilis Vassilakis received his Diploma in electrical and computer engineering from NationalTechnical University of Athens, Greece, in 1997. He isworking toward the Ph.D. degree in electrical engineering at National Technical University of Athens.His research interests include efficient circuit implemenation of DSP algorithms and java processor architectures.Chris Meletis received his Diploma in electrical and computer engineering from National Technical University of Athens in 1997. Currently, he is working toward the Ph.D. degree in electrical engineering at National Technical University of Athens.His research interests include multirate filter banks, digital filter design and their efficient realization.Kiamal Z. Pekmestzi received his Diploma in electrical engineering from the National Technical University of Athens, Greece, in 1975. From 1975 to 1981, he was a research fellow in the Electronics Department of the Nuclear Research Center Demokritos. He received his Ph.D. in electrical engineering from the University of Patras, Greece, in 1981.From 1983 to 1985, he was a professor at the Higher School of Electronics in Athens. Since 1985, he has been with the National Technical University of Athens, where he is currently a professor. His research interests include computer arithmetic, VLSI digital filters and VLSI design automation.     

A MC-CDMA Mobile Communication System Employing Pre-Rake and Transmit Diversity

In this paper, a multi-carrier code division multiple access (MC-CDMA) downlink mobile communication system employing pre-rake and dual transmit diversity is proposed. It combines high spectral efficiency with an immunity to channel dispersion and fading. It also ensures small size, cost and power consumption of the terminal. Theoretical and simulation results for the system under consideration are obtained. Depicted results show appreciable improvements of the proposed system over those previously known.Emad K. Al-Hussaini received his B.Sc degree in Electrical Communication Engineering from Ain-Shams University, Cairo, Egypt, in 1964 and his M.Sc and Ph.D. degrees from Cairo University, Giza, Egypt, in 1974 and 1977, respectively. From 1964 to 1970, he was with the General Egyptian Aeroorganization. Since 1970, he has been with the Department of Electronics and Communications, Faculty of Engineering, Cairo University, and is currently professor there. He was a research fellow at Imperial College, London, UK, and at the Moore School of Electrical Engineering, University of Pennsylvania, Philadelphia, PA, USA, in the academic years 1976/1977 and 1981/1982, respectively. In 1990, he received the Egyptian national encouragement award for outstanding engineering research. He has written several papers for technical international journals and conferences. His research interests include signal processing, fading channel communication, modulation, and cellular mobile radio systems. Dr Al-Hussaini is a senior member of IEEE. He is listed in Marquis Whos Who in the World and in the IBC (International Biographical Center, Cambridge) for outstanding people of the 20th century.Hebat-Allah M.Mourad received her B.Sc, M.Sc and Ph.D degrees in Electrical Communication Engineering from Cairo University, Egypt, in 1983, 1987 and 1994 respectively. Since 1983 she has been with the Electronics and Communications Department, Faculty of Engineering Cairo University and is currently associate professor there. Her research interests include mobile communications, satellite communications and optical fiber communications.Fatma A. Newagy received her B.Sc and M.Sc degrees in electrical communication engineering from Cairo University, Egypt in 1998 and 2002 respectively. Since 1999, she has been a research assistant with the Department of Electronics and Communications, Faculty of Engineering, Cairo University. She is pursuing her Ph.D. there. Her research interests include mobile communications and modulation techniques for spread spectrum and wireless communications.