Performance of energy-aware and link-adaptive routing metrics for ultra wideband sensor networks

Wireless sensor networks are energy constrained since sensors operate with limited battery capacity. Thus, energy consumption is one of the most critical issues in the design of routing protocols. In addition, the link quality needs to be taken into account in the route decision for a wireless multihop network in order to efficiently exploit the inherent spatial diversity. In this paper we consider energy-aware and link-adaptive routing strategies for UWB (Ultra Wide Band) sensor networks. We utilize the ranging capabilities offered by UWB and employ adaptive modulation to take advantage of favorable link conditions. Different routing metrics are proposed based on the availability of sensor node’s location, link quality and next hop battery capacity information. These routing metrics integrate the measure of next hop remaining battery capacity with the throughput performance measures, Maximum Forward Progress (MFP) or Maximum Information Progress (MIP). The effectiveness of these metrics is evaluated in different simulation scenarios in terms of network throughput and lifetime for both random and grid sensor network topologies. Jinghao Xuis a D.Sc. candidate of the Department of Electrical and Computer Engineering at the George Washington University. He received his B.Sc. and M.S. degrees in telecommunication and electrical engineering from the Tianjin University, China, in 1993 and 1996, respectively. From 1996 to 2001, he was with Research Institute of Telecommunication Transmission of Ministry of Information Industry, Beijing, China, and China Wireless Telecommunication Standards group, where he was involved in the standardization of IMT-2000 communication systems for China. His research interests include performance evaluation and modeling of wireless ad hoc networks, Ultra Wide Band systems and multiuser detection techniques. Bojan M. Peric received the B.S. degree in electrical engineering from the University of Belgrade, Belgrade, Serbia and Montenegro in 2001. He is currently working toward the D.Sc. degree in electrical engineering at the George Washington University, Washington, DC. His research interests include wireless communications, with an emphasis on ad hoc networks. Branimir R. Vojcic is a professor in, and a past Chairman of, the Department of Electrical and Computer Engineering at the George Washington University. He has received his Dipl. Ing., M.Sc. and D.Sc. degrees from the University of Belgrade in Serbia and Montenegro in 1980, 1986 and 1989, respectively. His current research interests are in the areas of communication theory, performance evaluation and modeling mobile and wireless networks, mobile internet, code division multiple access, multiuser detection, adaptive antenna arrays, space-time coding and ad-hoc networks. He has also been an industry consultant and has published and lectured extensively in these areas. He co-authored the book: The cdma2000 System for Mobile Communications. Dr Vojcic received NSF CAREER Award in 1995. He is a Senior Member of IEEE, was an Associate Editor for IEEE Communications Letters and is presently an Associate Editor for Journal on Communications and Networks.     

Throughput Scalability of Wireless Hybrid Networks over a Random Geometric Graph

In this paper, we consider the transport capacity of ad hoc networks with a random flat topology under the present support of an infinite capacity infrastructure network. Such a network architecture allows ad hoc nodes to communicate with each other by purely using the remaining ad hoc nodes as their relays. In addition, ad hoc nodes can also utilize the existing infrastructure fully or partially by reaching any access point (or gateway) of the infrastructure network in a single or multi-hop fashion. Using the same tools as in [9], we show that the per source node capacity of Θ(W/log(N)) can be achieved in a random network scenario with the following assumptions: (i) The number of ad hoc nodes per access point is bounded above, (ii) each wireless node, including the access points, is able to transmit at W bits/sec using a fixed transmission range, and (iii) N ad hoc nodes, excluding the access points, constitute a connected topology graph. This is a significant improvement over the capacity of random ad hoc networks with no infrastructure support which is found as in [9]. We also show that even when less stringent requirements are imposed on topology connectivity, a per source node capacity figure that is arbitrarily close to Θ(1) cannot be obtained. Nevertheless, under these weak conditions, we can further improve per node throughput significantly. We also provide a limited extension on our results when the number of ad hoc nodes per access point is not bounded.Ulaş C. Kozat was born in 1975, in Adana, Turkey. He received his B.Sc. degree in Electrical and Electronics Engineering from Bilkent University, Ankara, Turkey and his M.Sc. in Electrical Engineering from The George Washington University, Washington D.C. in 1997 and 1999 respectively. He has received his Ph.D. degree in May 2004 from the Department of Electrical and Computer Engineering at University of Maryland, College Park. He has conducted research under the Institute for Systems Research (ISR) and Center for Hybrid and Satellite Networks (CSHCN) at the same university. He worked at HRL Laboratories and Telcordia Technologies Applied Research as a research intern. His current research interests primarily focus on wireless and hybrid networks that span multiple communication layers and networking technologies. Mathematical modelling, resource discovery and allocation, vertical integration of wireless systems and communication layers, performance analysis, architecture and protocol development are the main emphasis of his work. E-mail: kozat@isr.umd.eduLeandros Tassiulas (S′89, M′91) was born in 1965, in Katerini, Greece. He obtained the Diploma in Electrical Engineering from the Aristotelian University of Thessaloniki, Thessaloniki, Greece in 1987, and the M.S. and Ph.D. degrees in Electrical Engineering from the University of Maryland, College Park in 1989 and 1991 respectively.He is Professor in the Dept. of Computer and Telecommunications Engineering, University of Thessaly, Greece and Research Professor in the Dept. of Electrical and Computer Eng and the Institute for Systems Research, University of Maryland College Park since 2001. He has held positions as Assistant Professor at Polytechnic University New York (1991–95), Assistant and Associate Professor University of Maryland College Park (1995–2001) and Professor University of Ioannina Greece (1999–2001).His research interests are in the field of computer and communication networks with emphasis on fundamental mathematical models, architectures and protocols of wireless systems, sensor networks, high-speed internet and satellite communications.Dr. Tassiulas received a National Science Foundation (NSF) Research Initiation Award in 1992, an NSF CAREER Award in 1995 an Office of Naval Research, Young Investigator Award in 1997 and a Bodosaki Foundation award in 1999 and the INFOCOM′94 best paper award. E-mail: leandros@isr.umd.edu     

A rendezvous reservation protocol for energy constrained wireless infrastructure networks

This paper considers a low power wireless infrastructure network that uses multi-hop communications to provide end user connectivity. A generalized Rendezvous Reservation Protocol (RRP) is proposed which permits multi-hop infrastructure nodes to adapt their power consumption in a dynamic fashion. When nodes have a long-term association, power consumption can be reduced by having them periodically rendezvous for the purpose of exchanging data packets. In order to support certain applications, the system invokes a connection set up process to establish the end-to-end path and selects node rendezvous rates along the intermediate nodes to meet the application’s quality of service (QoS) needs. Thus, the design challenge is to dynamically determine rendezvous intervals based on incoming applications’ QoS needs, while conserving battery power. In this paper, we present the basic RRP mechanism and an enhanced mechanism called Rendezvous Reservation Protocol with Battery Management (RRP-BM) that incorporates node battery level information. The performance of the system is studied using discrete-event simulation based experiments for different network topologies. The chief metrics considered are average power consumption and system lifetime (that is to be maximized). The QoS metrics specified are packet latency and end-to-end setup latency. It is shown that the use of the RRP-BM can increase the lifetime up to 48% as compared to basic RRP by efficiently reducing the energy consumption. This work was supported by a grant from the Natural Sciences and Engineering Research Council of Canada and Communications and Information Technology Ontario (CITO). Part of the research was supported by Air Force Office of Scientific Research grants F-49620-97-1-0471 and F-49620-99-1-0125; Laboratory for Telecommunications Sciences, Adelphi, Maryland; and Intel Corporation. The authors may be reached via e-mail at todd@mcmaster. ca, krishna@umbc. edu. The basic RRP mechanism was presented at the IASTED International Conference on Wireless and Optical Communications, Banff, Canada, July 2002. Subalakshmi Venugopal received her Bachelors in Computer Science from R.V. College of Engineering, Bangalore, India and her M.S. degree in Computer Science from Washington State University. She interned as a student researcher at the Indian Institute of Science, Bangalore, India. Ms. Venugopal is currently employed with Microsoft Corporation in Redmond, WA and is part of the “Kids and Education Group”. Her research interests include low power wireless ad hoc networks. Zhengwei (Wesley) Chen received the M.E. in Electrical & Computer Engineering Dept from McMaster University in Canada in 2002. He joined Motorola Inc. as a CDMA2000 system engineer in 2000. In 2002, he joined UTStarcom as a manager of the Global Service Solution Department. He is currently in charge of R&D for Advanced Services related to the TVoIP and Softswitch products. Terry Todd received the B.A.Sc, M.A.Sc and Ph.D degrees in Electrical Engineering from the University of Waterloo in Waterloo, Ontario, Canada. While at Waterloo he also spent 3 years as a Research Associate with the Computer Communications Networks Group (CCNG). During that time he worked on the Waterloo Experimental Local Area Network, which was an early local area network testbed. In 1991 Dr. Todd was on research leave in the Distributed Systems Research Department at AT&T Bell Laboratories in Murray Hill, NJ. He also spent 1998 as a visiting researcher at The Olivetti and Oracle Research Laboratory (ORL) in Cambridge, England. While at ORL he worked on the piconet project, which was an embedded low power wireless network testbed. Dr. Todd is currently a Professor of Electrical and Computer Engineering at McMaster University in Hamilton, Ontario, Canada. At McMaster he has been the Principal Investigator on a number of major research projects in the optical and wireless networking areas. He currently directs a large group working on wireless mesh networks and wireless VoIP. Professor Todd holds the NSERC/RIM/CITO Chair on Pico-Cellular Wireless Internet Access Networks. Dr. Todd’s research interests include metropolitan/local area networks, wireless communications and the performance analysis of computer communication networks and systems. Professor Todd is a Professional Engineer in the province of Ontario. Krishna M. Sivalingam is an Associate Professor in the Dept. of CSEE at University of Maryland, Baltimore County. Previously, he was with the School of EECS at Washington State University, Pullman from 1997 until 2002; and with the University of North Carolina Greensboro from 1994 until 1997. He has also conducted research at Lucent Technologies’ Bell Labs in Murray Hill, NJ, and at AT&T Labs in Whippany, NJ. He received his Ph.D. and M.S. degrees in Computer Science from State University of New York at Buffalo in 1994 and 1990 respectively; and his B.E. degree in Computer Science and Engineering in 1988 from Anna University, Chennai (Madras), India. While at SUNY Buffalo, he was a Presidential Fellow from 1988 to 1991. His research interests include wireless networks, optical wavelength division multiplexed networks, and performance evaluation. He holds three patents in wireless networks and has published several research articles including more than thirty journal publications. He has published an edited book on Wireless Sensor Networks in 2004 and edited books on optical WDM networks in 2000 and 2004. He served as a Guest Co-Editor for special issues of the ACM MONET journal on “Wireless Sensor Networks” in 2003 and 2004; and an issue of the IEEE Journal on Selected Areas in Communications on optical WDM networks (2000). He is co-recipient of the Best Paper Award at the IEEE International Conference on Networks 2000 held in Singapore. His work has been supported by several sources including AFOSR, NSF, Cisco, Intel and Laboratory for Telecommunication Sciences. He is a member of the Editorial Board for ACM Wireless Networks Journal, IEEE Transactions on Mobile Computing, Ad Hoc and Sensor Wireless Networks Journal, and KICS Journal of Computer Networks. He serves as Steering Committee Co-Chair for IEEE/CreateNet International Conference on Broadband Networks (BroadNets) that was created in 2004. He is currently serving as General Co-Vice-Chair for the Second Annual International Mobiquitous conference to be held in San Diego in 2005 and as General Co-Chair for the First IEEE/CreateNet International Conference on Security and Privacy for Emerging Areas in Communication Networks (SecureComm) to be held in Athens, Greece in Sep. 2005. He served as Technical Program Co-Chair for the First IEEE Conference on Sensor and Ad Hoc Communications and Networks (SECON) held at Santa Clara, CA in 2004; as General Co-Chair for SPIE Opticomm 2003 (Dallas, TX) and for ACM Intl. Workshop on Wireless Sensor Networks and Applications (WSNA) 2003 held in conjunction with ACM MobiCom 2003 at San Diego, CA; as Technical Program Co-Chair of SPIE/IEEE/ACM OptiComm conference at Boston, MA in July 2002; and as Workshop Co-Chair for WSNA 2002 held in conjunction with ACM MobiCom 2002 at Atlanta, GA in Sep 2002. He is a Senior Member of IEEE and a member of ACM.     

A secure incentive protocol for mobile ad hoc networks

The proper functioning of mobile ad hoc networks depends on the hypothesis that each individual node is ready to forward packets for others. This common assumption, however, might be undermined by the existence of selfish users who are reluctant to act as packet relays in order to save their own resources. Such non-cooperative behavior would cause the sharp degradation of network throughput. To address this problem, we propose a credit-based Secure Incentive Protocol (SIP) to stimulate cooperation among mobile nodes with individual interests. SIP can be implemented in a fully distributed way and does not require any pre-deployed infrastructure. In addition, SIP is immune to a wide range of attacks and is of low communication overhead by using a Bloom filter. Detailed simulation studies have confirmed the efficacy and efficiency of SIP. This work was supported in part by the U.S. Office of Naval Research under Young Investigator Award N000140210464 and under grant N000140210554. Yanchao Zhang received the B.E. degree in Computer Communications from Nanjing University of Posts and Telecommunications, Nanjing, China, in July 1999, and the M.E. degree in Computer Applications from Beijing University of Posts and Telecommunications, Beijing, China, in April 2002. Since September 2002, he has been working towards the Ph.D. degree in the Department of Electrical and Computer Engineering at the University of Florida, Gainesville, Florida, USA. His research interests are network and distributed system security, wireless networking, and mobile computing, with emphasis on mobile ad hoc networks, wireless sensor networks, wireless mesh networks, and heterogeneous wired/wireless networks. Wenjing Lou is an assistant professor in the Electrical and Computer Engineering department at Worcester Polytechnic Institute. She obtained her Ph.D degree in Electrical and Computer Engineering from University of Florida in 2003. She received the M.A.Sc degree from Nanyang Technological University, Singapore, in 1998, the M.E degree and the B.E degree in Computer Science and Engineering from Xi'an Jiaotong University, China, in 1996 and 1993 respectively. From Dec 1997 to Jul 1999, she worked as a Research Engineer in Network Technology Research Center, Nanyang Technological University. Her current research interests are in the areas of ad hoc and sensor networks, with emphases on network security and routing issues. Wei Liu received his B.E. and M.E. in Electrical and Information Engineering from Huazhong University of Science and Technology, Wuhan, China, in 1998 and 2001. In August 2005, he received his PhD in Electrical and Computer Engineering from University of Florida. Currently, he is a senior technical member with Scalable Network Technologies. His research interest includes cross-layer design, and communication protocols for mobile ad hoc networks, wireless sensor networks and cellular networks. Yuguang Fang received a Ph.D. degree in Systems Engineering from Case Western Reserve University in January 1994 and a Ph.D degree in Electrical Engineering from Boston University in May 1997. He was an assistant professor in the Department of Electrical and Computer Engineering at New Jersey Institute of Technology from July 1998 to May 2000. He then joined the Department of Electrical and Computer Engineering at University of Florida in May 2000 as an assistant professor, got an early promotion to an associate professor with tenure in August 2003 and a professor in August 2005. He has published over 150 papers in refereed professional journals and conferences. He received the National Science Foundation Faculty Early Career Award in 2001 and the Office of Naval Research Young Investigator Award in 2002. He has served on many editorial boards of technical journals including IEEE Transactions on Communications, IEEE Transactions on Wireless Communications, IEEE Transactions on Mobile Computing and ACM Wireless Networks. He is a senior member of the IEEE.     

A game-theoretic look at simple relay channel

In this paper, we address the crosslayer problem of joint medium access control (MAC) and routing in ad hoc wireless networks from the novel perspective of stochastic dynamic games. As a starting point to understand the efficient modes of wireless network operation, we look at the basic problem of multi-hop communication over the simple topology of a single relay channel. A stochastic game is formulated for transmitter and relay nodes competing over collision channels to deliver packets to a common destination node using alternative paths. We rely on a reward mechanism to stimulate cooperation for packet forwarding and evaluate the conflicting multiple access and routing strategies of direct communication and relaying through a detailed foray into the questions of cooperation incentives, throughput, delay and energy-efficiency. Under the separate models of selfish and cooperative network operation, we study the interactions among the equilibrium strategies and present a detailed performance analysis based on multiple system parameters that involve the packet arrival rates, throughput rewards, delay and energy costs. The material in this paper was partially presented at WIOPT’04: Modeling and Optimization in Mobile, Ad Hoc and Wireless Networks, Cambridge, UK, March 2004. Prepared through collaborative participation in the Communications and Networks Consortium sponsored by the U. S. Army Research Laboratory under the Collaborative Technology Alliance Program, Cooperative Agreement DAAD19-01-2-0011. The U. S. Government is authorized to reproduce and distribute reprints for Government purposes notwithstanding any copyright notation thereon. Anthony Ephremides received his B.S. degree from the National Technical University of Athens (1967), and M.S. (1969) and Ph.D. (1971) degrees from Princeton University, all in electrical engineering. He has been at the University of Maryland since 1971, and currently holds a joint appointment as professor in the Electrical Engineering Department and the Institute of Systems Research (ISR). He is co-founder of the NASA Center for Commercial Development of Space on Hybrid and Satellite Communications Networks established in 1991 at Maryland as an offshoot of the ISR. He was a visiting professor in 1978 at the National Technical University of Athens, Greece, and in 1979 at the Electrical Engineering and Computer Science Department of the University of California at Berkeley and INRIA, France. During 1985–1986 he was on leave at Massachusetts Institute of Technology and the Swiss Federal Institute of Technology, Zurich. He has also been director of the Fairchild Scholars and Doctoral Fellows Program, an academic and research partnership program in satellite communications between Fairchild Industries and the University of Maryland. He has been President of the Information Theory Society of the IEEE (1987), and served on the Board of the IEEE (1989 and 1990). His interests are in the areas of communication theory, communication systems and networks, queuing systems, signal processing, and satellite communications. Yalin Evren Sagduyu received his B.S. degree from Bogazici University, Turkey, and M.S. degree from the University of Maryland at College Park in 2000 and 2002, respectively, all in electrical engineering. He is currently working toward his Ph.D. degree at the University of Maryland, where he has been a graduate research assistant with ISR since 2000. His research interests include wireless communication, ad hoc and sensor network design and optimization, stochastic game theory and network coding.     

Location-aware resource management in mobile ad hoc networks

We propose an innovative resource management scheme for TDMA based mobile ad hoc networks. Since communications between some important nodes in the network are more critical, they should be accepted by the network with high priority in terms of network resource usage and quality of service (QoS) support. In this scheme, we design a location-aware bandwidth pre-reservation mechanism, which takes advantage of each mobile node’s geographic location information to pre-reserve bandwidth for such high priority connections and thus greatly reduces potential scheduling conflicts for transmissions. In addition, an end-to-end bandwidth calculation and reservation algorithm is proposed to make use of the pre-reserved bandwidth. In this way, time slot collisions among different connections and in adjacent wireless links along a connection can be reduced so that more high priority connections can be accepted into the network without seriously hurting admissions of other connections. The salient feature of our scheme is the collaboration between the routing and MAC layer that results in the more efficient spatial reuse of limited resources, which demonstrates how cross-layer design leads to better performance in QoS support. Extensive simulations show that our scheme can successfully provide better communication quality to important nodes at a relatively low price. Finally, several design issues and future work are discussed. Xiang Chen received the B.E. and M.E. degrees in electrical engineering from Shanghai Jiao Tong University, Shanghai, China, in 1997 and 2000, respectively. Afterwards, he worked as a MTS (member of technical staff) in Bell Laboratories, Beijing, China. He is currently working toward the Ph.D. degree in the department of Electrical and Computer Engineering at the University of Florida. His research is focused on protocol design and performance evaluation in wireless networks, including cellular networks, wireless LANs, and mobile ad hoc networks. He is a member of Tau Beta Pi and a student member of IEEE. Wei Liu received the BE and ME degrees in electrical engineering from Huazhong University of Science and Technology, Wuhan, China, in 1998 and 2001, respectively. He is currently pursuing the P.hD. degree in the Department of Electrical and Computer Engineering, University of Florida, Gainesville, where he is a research assistant in the Wireless Networks Laboratory (WINET). His research interest includes QoS, secure and power efficient routing, and MAC protocols in mobile ad hoc networks and sensor networks. He is a student member of the IEEE. Hongqiang Zhai received the B.E. and M.E. degrees in electrical engineering from Tsinghua University, Beijing, China, in July 1999 and January 2002 respectively. He worked as a research intern in Bell Labs Research China from June 2001 to December 2001, and in Microsoft Research Asia from January 2002 to July 2002. Currently he is pursuing the Ph.D. degree in the Department of Electrical and Computer Engineering, University of Florida. He is a student member of IEEE. Yuguang Fang received a Ph.D. degree in Systems and Control Engineering from Case Western Reserve University in January 1994, and a Ph.D. degree in Electrical Engineering from Boston University in May 1997. From June 1997 to July 1998, he was a Visiting Assistant Professor in Department of Electrical Engineering at the University of Texas at Dallas. From July 1998 to May 2000, he was an Assistant Professor in the Department of Electrical and Computer Engineering at New Jersey Institute of Technology. In May 2000, he joined the Department of Electrical and Computer Engineering at University of Florida where he got the early promotion to Associate Professor with tenure in August 2003 and to Full Professor in August 2005. He has published over 180 papers in refereed professional journals and conferences. He received the National Science Foundation Faculty Early Career Award in 2001 and the Office of Naval Research Young Investigator Award in 2002. He is currently serving as an Editor for many journals including IEEE Transactions on Communications, IEEE Transactions on Wireless Communications, IEEETransactions on Mobile Computing, and ACM Wireless Networks. He is also actively participating in conference organization such as the Program Vice-Chair for IEEE INFOCOM’2005, Program Co-Chair for the Global Internet and Next Generation Networks Symposium in IEEE Globecom’2004 and the Program Vice Chair for 2000 IEEE Wireless Communications and Networking Conference (WCNC’2000).     

Energy aware efficient geographic routing in lossy wireless sensor networks with environmental energy supply

Wireless sensor networks are characterized by multihop wireless lossy links and resource constrained nodes. Energy efficiency is a major concern in such networks. In this paper, we study Geographic Routing with Environmental Energy Supply (GREES) and propose two protocols, GREES-L and GREES-M, which combine geographic routing and energy efficient routing techniques and take into account the realistic lossy wireless channel condition and the renewal capability of environmental energy supply when making routing decisions. Simulation results show that GREESs are more energy efficient than the corresponding residual energy based protocols and geographic routing protocols without energy awareness. GREESs can maintain higher mean residual energy on nodes, and achieve better load balancing in terms of having smaller standard deviation of residual energy on nodes. Both GREES-L and GREES-M exhibit graceful degradation on end-to-end delay, but do not compromise the end-to-end throughput performance. Kai Zeng received his B.E. degree in Communication Engineering and M.E. degree in Communication and Information System both from Huazhong University of Science and Technology, China, in 2001 and 2004, respectively. He is currently a Ph.D. student in the Electrical and Computer Engineering department at Worcester Polytechnic Institute. His research interests are in the areas of wireless ad hoc and sensor networks with emphases on energy-efficient protocol, cross-layer design, routing, and network security. Kui Ren received his B. Eng. and M. Eng. both from Zhejiang University, China, in 1998 and 2001, respectively. He worked as a research assistant at Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences from March 2001 to January 2003, at Institute for Infocomm Research, Singapore from January 2003 to August 2003, and at Information and Communications University, South Korea from September 2003 to June 2004. Currently he is a PhD candidate in the ECE department at Worcester Polytechnic Institute. His research interests include ad hoc/sensor network security, wireless mesh network security, Internet security, and security and privacy in ubiquitous computing environments. Wenjing Lou is an assistant professor in the Electrical and Computer Engineering department at Worcester Polytechnic Institute. She obtained her Ph.D. degree in Electrical and Computer Engineering from University of Florida in 2003. She received the M.A.Sc. degree from Nanyang Technological University, Singapore, in 1998, the M.E. degree and the B.E. degree in Computer Science and Engineering from Xi’an Jiaotong University, China, in 1996 and 1993 respectively. From December 1997 to July 1999, she worked as a Research Engineer in Network Technology Research Center, Nanyang Technological University. Her current research interests are in the areas of ad hoc and sensor networks, with emphases on network and system security and routing. Patrick J. Moran received his MSEE from Carnegie Mellon University, 1993. He is currently the CTO and Founder of AirSprite Technologies Inc, and is driving the company to utilize advanced networking protocols for low-power wireless network systems. His interests include architecture, protocols and high performance implementation of emerging communication technologies. Patrick has been involved in deployment of communication and signal processing technologies since graduating from the University of Minn. in 1986. He holds several patents and publications relating to storage, medical and data processing information systems. He is a member of the IEEE.     

Power proximity based key management for secure multicast in ad hoc networks

As group-oriented services become the focal point of ad hoc network applications, securing the group communications becomes a default requirement. In this paper, we address the problem of group access in secure multicast communications for wireless ad hoc networks. We argue that energy expenditure is a scarce resource for the energy-limited ad hoc network devices and introduce a cross-layer approach for designing energy-efficient, balanced key distribution trees to perform key management. To conserve energy, we incorporate the network topology (node location), the “power proximity” between network nodes and the path loss characteristics of the medium in the key distribution tree design. We develop new algorithms for homogeneous as well as heterogeneous environments and derive their computational complexity. We present simulation studies showing the improvements achieved for three different but common environments of interest, thus illustrating the need for cross-layer design approaches for security in wireless networks. Loukas Lazos received the B.S. and M.S. degrees from the Electrical Engineering Department, National Technical University of Athens, Athens, Greece, in 2000 and 2002, respectively. He is currently working towards the Ph.D. degree in the Electrical Engineering Department, University of Washington, Seattle. His current research interests focus on cross-layer designs for energy-efficient key management protocols for wireless ad-hoc networks, as well as secure localization systems for sensor networks. Radha Poovendran received the Ph.D. degree in electrical engineering from the University of Maryland, College Park, in 1999. He has been an Assistant Professor in the Electrical Engineering Department, University of Washington, Seattle, since September 2000. His research interests are in the areas of applied cryptography for multiuser environment, wireless networking, and applications of information theory to security. Dr. Poovendran is a recipient of the Faculty Early Career Award from the National Science Foundation (2001), Young Investigator Award from the Army Research Office (2002), Young Investigator Award from the Office of Naval Research (2004), and the 2005 Presidential Early Career Award for Scientists and Engineers, for his research contributions in the areas of wired and wireless multiuser security.     

Energy-aware on-demand routing protocols for wireless ad hoc networks

Energy use is a crucial design concern in wireless ad hoc networks since wireless terminals are typically battery-operated. The design objectives of energy-aware routing are two folds: Selecting energy-efficient paths and minimizing the protocol overhead incurred for acquiring such paths. To achieve these goals simultaneously, we present the design of several on-demand energy-aware routing protocols. The key idea behind our design is to adaptively select the subset of nodes that are required to involve in a route-searching process in order to acquire a high residual-energy path and/or the degree to which nodes are required to participate in the process of searching for a low-power path in networks wherein nodes have transmission power adjusting capability. Analytical and simulation results are given to demonstrate the high performance of the designed protocols in energy-efficient utilization as well as in reducing the protocol overhead incurred in acquiring energy-efficient routes. Baoxian Zhang received his B.S., M.S., and Ph.D. degrees in Electrical Engineering from Northern Jiaotong University, Beijing, China in 1994, 1997, and 2000, respectively. From January 2001 to August 2002, he was working with Department of Electrical and Computer Engineering at Queen’s University in Kingston as a postdoctoral fellow. He is currently a research scientist with the School of Information Technology and Engineering (SITE) of University of Ottawa in Ottawa, Ontario, Canada. He has published over 40 refereed technical papers in international journals and conference proceedings. His research interests include routing algorithm and protocol design, QoS management, wireless ad hoc and sensor networks, survivable optical networks, multicast communications, and performance evaluation. He is a member of the IEEE. Hussein Mouftah joined the School of Information Technology and Engineering (SITE) of the University of Ottawa in September 2002 as a Canada Research Chair (Tier 1) Professor in Optical Networks. He has been with the Department of Electrical and Computer Engineering at Queen’s University (1979-2002), where he was prior to his departure a Full Professor and the Department Associate Head. He has three years of industrial experience mainly at Bell Northern Research of Ottawa, now Nortel Networks (1977-79). He has spent three sabbatical years also at Nortel Networks (1986-87, 1993-94, and 2000-01), always conducting research in the area of broadband packet switching networks, mobile wireless networks and quality of service over the optical Internet. He served as Editor-in-Chief of the IEEE Communications Magazine (1995-97) and IEEE Communications Society Director of Magazines (1998-99) and Chair of the Awards Committee (2002-2003). He is a Distinguished Speaker of the IEEE Communications Society since 2000. Dr. Mouftah is the author or coauthor of five books, 22 book chapters and more than 700 technical papers and 8 patents in this area. He is the recipient of the 1989 Engineering Medal for Research and Development of the Association of Professional Engineers of Ontario (PEO), and the Ontario Distinguished Researcher Award of the Ontario Innovation Trust. He is the joint holder of the Best Paper Award for a paper presented at SPECTS’2002, and the Outstanding Paper Award for papers presented at the IEEE HPSR’2002 and the IEEE ISMVL’1985. Also he is the joint holder of a Honorable Mention for the Frederick W. Ellersick Price Paper Award for Best Paper in the IEEE Communications Magazine in 1993. He is the recipient of the IEEE Canada (Region 7) Outstanding Service Award (1995). Also he is the recipient of the 2004 IEEE Communications Society Edwin Howard Armstrong Achievement Award, and the 2004 George S. Glinski Award for Excellence in Research of the Faculty of Engineering, University of Ottawa. Dr. Mouftah is a Fellow of the IEEE (1990) and Fellow of the Canadian Academy of Engineering (2003).     

Virtual Private Ad Hoc Networking

The fact that a lot of applications require secure communication to take place only between a dynamic subset of distributed devices sharing a common context, is, from a network point of view, very challenging and demanding. Existing technologies such as VPN, P2P overlays or VLANs can only partially respond to these requirements. This observation is the key factor that has driven the proposal of the virtual private ad hoc network concept. Virtual private ad hoc networks (VPAN) are secure and self-organizing overlay networks on top of existing IP infrastructure that use ad hoc networking techniques to enable network connectivity. The underlying IP infrastructure can be the Internet, cellular networks, ad hoc networks, mesh networks … or combinations thereof. A virtual private ad hoc overlay network creates a transparent, shielded and trusted environment for the applications and services running on the participants' devices. The overlay uses internal addressing and ad hoc routing, thereby forming a virtual network on top of the physical infrastructure. In addition, the overlay must be self-organizing and self-maintaining upon member mobility or membership changes. This paper gives an overview of the potential applications, a high-level network architecture and the network challenges emerging from the novel concept of virtual private ad hoc networking. Jeroen Hoebeke was born in Ghent, Belgium in 1979. In 2002 he received the Masters degree in engineering (Computer Science) from the University of Ghent. In August 2002, he joined the Broadband Communications Networks Group. His PhD research includes the development of adaptive routing protocol techniques for mobile ad hoc networks. His main research interests are in ad hoc wireless communications and, more generally, in broadband wireless communications. Within the European MAGNET project, he is actively involved in the development of a network architecture and demonstrator for Personal Networks, with a prime focus on routing and connectivity. Gerry Holderbeke was born in Zottegem, Belgium in 1982. He graduated in Informatics at the University of Ghent in 2004. In August 2004 he joined the Broadband Communications Networks Group where he is currently working as a project developer. His research currently includes the development of an emulator for mobile ad hoc networks. His main research interests are in ad hoc networks and broadband wireless communications and involve routing, addressing and more generally, communication within mobile ad hoc networks and infrastructured networks. Within the European MAGNET project, he is actively involved in the development of a network architecture for Personal Networks, with a prime focus on the implementation of the routing architecture. Ingrid Moerman was born in Gent, Belgium in 1965. She received the degree in Electro-technical Engineering and the Ph.D degree from the Ghent University, Gent, Belgium in 1987 and 1992, respectively. Since 1987, she has been with the Interuniversity Micro-Electronics Centre (IMEC) at the Department of Information Technology (INTEC) of the Ghent University, where she conducted research in the field of optoelectronics. In 1997, she became a permanent member of the Research Staff at IMEC. Since 2000 she is part-time professor at the Ghent University. Since 2001 she has switched her research domain to broadband communication networks. She is currently involved in the research and education on broadband mobile & wireless communication networks and on multimedia over IP. The main research topics related to mobile & wireless communication networks are: wireless access to vehicles (high bandwidth & driving speed), adaptive QoS routing in wireless ad hoc networks, body area networks, protocol boosting on wireless links, design of fixed access/metro part, traffic engineering and QoS support in the wireless access network. Ingrid Moerman is author or co-author of more than 300 publications in the field of optoelectronics and communication networks. Bart Dhoedt received a degree in Engineering from the Ghent University in 1990. In September 1990, he joined the Department of Information Technology of the Faculty of Applied Sciences, University of Ghent. His research, addressing the use of micro-optics to realize parallel free space optical interconnects, resulted in a PhD degree in 1995. After a 2 year post-doc in opto-electronics, he became professor at the Faculty of Applied Sciences, Department of Information Technology. Since then, he is responsible for several courses on algorithms, programming and software development. His research interests are software engineering and mobile & wireless communications. Bart Dhoedt is author or co-author of approximately 70 papers published in international journals or in the proceedings of international conferences. His current research addresses software technologies for communication networks, peer-to-peer networks, mobile networks and active networks. Piet Demeester received the Masters degree in Electro-technical engineering and the Ph.D degree from the Ghent University, Gent, Belgium in 1984 and 1988, respectively. In 1992 he started a new research activity on broadband communication networks resulting in the IBCN-group (INTEC Broadband communications network research group). Since 1993 he became professor at the Ghent University where he is responsible for the research and education on communication networks. The research activities cover various communication networks (IP, ATM, SDH, WDM, access, active, mobile), including network planning, network and service management, telecom software, internetworking, network protocols for QoS support, etc. Piet Demeester is author of more than 300 publications in the area of network design, optimization and management. He is member of the editorial board of several international journals and has been member of several technical program committees (ECOC, OFC, DRCN, ICCCN, IZS, &).     

Tree Based Broadcast in Ad Hoc Networks

Although broadcasting using tree structure established in a network is a well known and widely used technique, it is typically claimed to be inappropriate for ad hoc networks, being the maintained tree very sensitive to network changes. On the contrary this paper presents an efficient tree based broadcasting scheme, which is reliable and stable even in case of the ever changing network structure of the ad hoc networks.To achieve this, first, a novel method is presented to maintain a spanning tree in an ad hoc network in a fully distributed, on-line and asynchronous way. Once the tree is established the broadcast itself is performed based on this tree. Some further improvements on the basic algorithm are also presented that reduce the resource requirements even more, increase the stability of the tree, enable the mobility of the nodes to be taken into account and make the method more configurable.As it is shown by simulation, the obtained broadcast scheme is stable, reliable and it uses small amount of resources: the acyclic structure of the broadcast tree ensures that the nodes get the broadcast messages only once, so the broadcast needs little bandwidth and the nodes need not store the recent broadcast messages, reducing the computational and memory requirements.As a byproduct a technique is proposed to measure the mobility of the nodes. This technique needs no additional GPS device or any geographical information but it is based on the stability of the links of the node.Alpár Jüttner received his M. Sc. degree in 1998 at the Eötvös Loránd University of Budapest, where he is currently working on his Ph. D. at Operational Research Departement. He also works as a research fellow at Ericsson Traffic Analysis and Network Performance Laboratory in Budapest, Hungary. His main interests are combinatorial optimization and its applications.Ádám Magi received his M. Sc. degree in 1996 at the Technical University of Budapest in Electrical Engineering. He is currently working on his Ph. D. there. He also works as a research fellow at Ericsson Traffic Analysis and Network Performance Laboratory in Budapest, Hungary. His main interests are mobile ad hoc networks and routing in telecommunication networks.     

A novel learning based solution for efficient data transport in heterogeneous wireless networks

There has been a spectacular growth in the use of wireless networks in recent times and consequently, adapting TCP to the wireless networks is a hot topic of current research. However, most of the existing works proposed for this problem have been designed for specific wireless networks, or they necessitate changes at either the receiver or the intermediate nodes, or at both, because of which their deployment becomes difficult. In this work, we propose a TCP variant which works over both multi-hop ad hoc wireless networks as well as single-hop (last-hop) wireless networks, like Wireless LANs, cellular, and satellite networks. We use a learning based method to dynamically change the congestion window size according to the network conditions. Our protocol does not rely on any explicit feedback from the network and requires only sender-side modifications. Through extensive simulations we show that our protocol achieves the desired goals of performance improvement in goodput, reduction in packet loss, and fairness to the competing flows. To the best of our knowledge, this is the first unified solution for both single-hop and multi-hop wireless networks.     

Analysis of bandwidth allocation algorithms for wireless personal area networks

A major issue in the design and operation of ad hoc networks is sharing the common spectrum among links in the same geographic area. Bandwidth allocation, to optimize the performance of networks in which each station can converse with at most a single neighbor at a time, has been recently studied in the context of Bluetooth Personal Area Networks. There, centralized and distributed, capacity assignment heuristics were developed, with applicability to a variety of ad hoc networks. Yet, no guarantees on the performance of these heuristics have been provided. In this paper, we extend these heuristics such that they can operate with general convex objective functions. Then, we present our analytic results regarding these heuristics. Specifically, we show that they are β-approximation (β<2) algorithms. Moreover, we show that even though the distributed and centralized algorithms allocate capacity in a different manner, both algorithms converge to the same results. Finally, we present numerical results that demonstrate the performance of the algorithms. Randeep Bhatia received the Ph.D. degree in Computer Science from University of Maryland, the M.S. degree in Mathematics and Computer Science from University of Illinois at Chicago and the B.Tech. degree in Computer Science and Engineering from Indian Institute of Technology, Delhi. He is currently with the High Speed Networks Research Department at Bell Labs, Lucent technologies, working on network design, traffic engineering and scheduling algorithms. His current research interests are in the area of QoS for multimedia services in wireless data networks. Adrian Segall received the B.Sc. and M.Sc. degrees in electrical engineering from the Technion, Israel Institute of Technology in 1965 and 1971, respectively, and the Ph.D. degree in electrical engineering with a minor in statistics from Stanford University in 1973. After serving active duty in the Israel Defense Forces, he joined in 1968 the Scientific Department of Israel’s Ministry of Defense. From 1973 to 1974 he was a Research Engineer at System Control Inc., Palo Alto, CA and a Lecturer at Stanford University. From 1974 to 1976 he was an Assistant Professor of Electrical Engineering and Computer Science at the Massachusetts Institute of Technology. From 1987 to 1998 he was on the faculty of the Department of Computer Science at the Technion. He is presently Benjamin Professor of Computer-Communication Networks in the Department of Electrical Engineering, Technion, Israel Institute of Technology. From 1982 to 1984 he was on leave with the IBM T.J.Watson Research Center, Yorktown Heights, NY. He held visiting positions with IBM, AT&T and Lucent Bell Labs. His current research interests are in the area of optical networks, wireless, sensor and ad-hoc networks. Dr. Segall is an IEEE Fellow and has served in the past as Editor for Computer Communication Theory of the IEEE Transactions on Communications, Editor for the IEEE Information Theory Society Newsletter and Senior Editor for the IEEE Journal on Selected Areas in Communications. He was selected as an IEEE delegate to the 1975 IEEE-USSR Information Theory Workshop, and is the recipient of the 1981 Miriam and Ray Klein Award for Outstanding Research and of the 1990 Taub Award in Computer Science. Gil Zussman received the B.Sc. degree in Industrial Engineering and Management and the B.A. degree in Economics (both summa cum laude) from the Technion—Israel Institute of Technology in 1995. He received the M.Sc. degree (summa cum laude) in Operations Research from Tel-Aviv University in 1999 and the Ph.D. degree in Electrical Engineering from the Technion—Israel Institute of Technology in 2004. Between 1995 and 1998, he served as an engineer in the Israel Defense Forces. He is currently a Postdoctoral Associate in the Laboratory for Information and Decision Systems in MIT. His current research interests are in the area of ad hoc and sensor networks. In particular, he is interested in energy efficient protocols, medium access control protocols, and personal area networks. Gil received the Knesset (Israeli Parliament) Award for distinguished students, the Best Student Paper Award at the IFIP-TC6 Networking 2002 Conference, and the IEEE Communications Magazine Best Paper Award at the OPNETWORK 2002 Conference. In 2004 he received the Marie Curie Outgoing International Fellowship and the Fulbright Fellowship.     

Energy-Aware Interoperability of Manet and 4g Ran Routing

The requirements for telecommunication at 2012 are estimated to be on such demanding level that the 3G technologies will not be sufficient. It is unlikely that the 3G Radio Access Network (RAN) would scale up i.e., Fourth Generation (4G) RAN will need to be developed. The requirements for 4G are demanding and the level of uncertainty is high. The novel ad hoc networking technologies could provide flexible solutions for the 4G RAN and extend the operator radio coverage. Combining these differing communication technologies provides insight for the 4G RAN design. This paper analyses the Mobile Ad hoc Networks (MANET) requirements against the 4G requirements in terms of energy conservation. We find that there is mismatch between these two sets of requirements. Nevertheless, we demonstrate how these two approaches could co-exist in a mutually beneficial way. Finally, we propose interoperability requirements for MANET and 4G routing from the perspective of energy conservation. Harri Paloheimo is a researcher in Networking Technologies Laboratory at Nokia Research Center, Helsinki. In addition, he is a post graduate student in Telecommunications Software and Multimedia Laboratory, Department of Computer Science and Engineering, Helsinki University of Technology. He received M.Sc. degree majoring in space technology from Department of Electrical and Communications Engineering, Helsinki University of Technology in 2000. He currently works on next generation wireless networks with special interest in hybrid and relay networking solutions. Sudhir Dixit is currently a Nokia Research Fellow and works on next generation wireless networks. From 1996 to 2003 he was a Senior Research Manager, focusing on IP/ATM, wireless, content networks, and optical networks. Prior to that he worked at NYNEX Science & Technology (now Verizon), GTE (now Verizon), Codex Motorola, Wang, Harris, and STL (now Nortel Europe Labs). He has published or presented over 150 papers, published three books, and holds 14 patents. He is on the Editorial Board of the IEEE Communications Magazine, Springer's Wireless Personal Communications Journal, and KIC's Journal of Communications and Networks. He received a B.E. degree from MANIT, Bhopal, India, an M.E. degree from BITS, Pilani, India, a Ph.D. degree from the University of Strathclyde, Glasgow, Scotland, and an M.B.A. degree from Florida Institute of Technology, Melbourne. He is a Fellow of IEE (UK) and IETE (India). He represents Nokia on the Steering Board of the Wireless World Research Forum, and is also Vice Chair of the SIG on Self-Organization of Wireless World Systems. Dr.Tech. Antti Ylä-Jääski is a Professor of Telecommunications Software, Telecommunications Software and Multimedia Laboratory, Department of Computer Science and Engineering, Helsinki University of Technology. He is also a Research Fellow in Network Technologies Laboratory, Nokia Research Center, Helsinki. Prof Dr.Tech. Antti Ylä-Jääski received his PhD in ETH Zuerich 1993. Antti has worked with Nokia 1994–2004 in several research management positions with focus on future Internet technologies, mobile networks, applications, services, service management and service architectures. He has published about 30 articles and he holds several approved patents. Antti's current research interests include mobile networking, heterogeneous network environments, services, service architectures, service management and security issues.     

Dropping Rate Reduction in Hybrid WLAN/Cellular Systems by Mobile Ad Hoc Relaying

Future mobile handsets will often be multi-mode, containing both wireless LAN (WLAN) and cellular air interfaces. When such a device is within a WLAN it can be served by the WLAN resources. As it moves out of the WLAN coverage area, it has to be served by the cellular system. Therefore, handoffs are necessary between the WLAN and the cellular system. In loosely coupled WLAN/Cellular systems the system administrator of the WLAN is different from the cellular one. Therefore, in these situations, reducing the dropping probability based on classical methods, such as using some reserved guard channels, is difficult. In this paper, we propose to use ad hoc relaying during the vertical handoff process in a hybrid WLAN/Cellular system. The method that we propose in this paper improves the dropping probability regardless of the number of reserved channels. Therefore, this method could be employed in loosely coupled hybrid systems. Both analytical reasoning and simulation results support the effectiveness of the proposed method. Pejman Khadivi received the BS and MS degrees in computer engineering (Hardware and Computer Systems Architecture) in 1998 and 2000, respectively from Isfahan University of Technology, where he is currently working toward his Ph.D. During the 2003/2004 academic year, he was a Visiting Researcher with the Electrical and Computer Engineering Department, McMaster University, ON, Canada. Different aspects of computer architecture and networking are Mr. Khadivi’s research interests specially, adhoc networks, QoS routing and seamless handoff in hybrid mobile networks. Shadrokh Samavi received the B.S. degrees in industrial technology and electrical engineering from the California State University, Fresno, in 1980 and 1982, respectively, the M.S. degree from the University of Memphis, Memphis, TN, in 1985, and the Ph.D. degree in electrical engineering from Mississippi State University, Mississippi State, in 1989. In 1995, he joined the Electrical and Computer Engineering Department, Isfahan University of Technology, Isfahan, Iran, where he was an Associative Professor. During the 2002/2003 academic year, he was a Visiting Professor with the Electrical and Computer Engineering Department, McMaster University, Hamilton, ON, Canada. His current research interests are implementation and optimization of image-processing algorithms and area-performance tradeoffs in computational circuits. Dr. Samavi is a Registered Professional Engineer (P.E.), USA, and is a member of Eta Kappa Nu, Tau Beta Pi, and the National Association of Industrial Technologists (NAIT). Hossein Saidi received the B.S. and M.S. degrees in electrical engineering (Electronics and communication Eng.) from Isfahan University of Technology (IUT), in 1986 and 1989, respectively, and the Ph.D. degree in electrical engineering from the Washington University in St. Louis, MO. in 1994.From 1994 to 1995, he was a research associates at Washington Univ. St. Louis, and in 1995 he joined the Electrical and Computer Engineering of IUT, where he is an Associate Professor. His Research interest includes ATM, high speed networking, QoS guarantees, routing, algorithms and information theory. Terence D. Todd received the B.A.Sc, M.A.Sc and Ph.D degrees in Electrical Engineering from the University of Waterloo, Waterloo, Ontario, Canada. While at Waterloo he spent 3 years as a Research Associate with the Computer Communications Networks Group (CCNG). He is currently a Professor of Electrical and Computer Engineering at McMaster University in Hamilton, Ontario, Canada.Professor Todd spent 1991 on research leave in the Distributed Systems Research Department at AT&T Bell Laboratories in Murray Hill, NJ. He also spent 1998 on research leave at The Olivetti and Oracle Research Laboratory in Cambridge, England. While at ORL he worked on the piconet project which was an early embedded wireless network testbed.Dr. Todd’s research interests include metropolitan/local area networks, wireless communications and the performance analysis of computer communication networks and systems. He currently holds the NSERC/RIM/CITO Industrial Research Chair on Pico-Cellular Wireless Internet Access Networks. Dr. Todd is a Professional Engineer in the province of Ontario and a member of the IEEE. Dongmei Zhao received the Ph.D degree in Electrical and Computer Engineering from the University of Waterloo, Waterloo, Ontario, Canada in June 2002. Since July 2002 she has been with the Department of Electrical and Computer Engineering, McMaster University, Hamilton, Ontario, Canada where she is an assistant professor. Dr. Zhao’s research interests include modeling and performance analysis, quality-of-service provisioning, access control and admission control in wireless cellular networks and integrated cellular and ad hoc networks. Dr. Zhao is a member of the IEEE.     

Energy-Efficient Operation through Interference Avoidance for Interconnected Bluetooth WPANs

A Wireless Personal Area Network (WPAN) provides wireless networking among proximate devices, usually carried by an individual. Bluetooth is a first instance of the WPAN technology. The basic networking entity in Bluetooth is a piconet. Several piconets (WPANs) can be interconnected into a scatternet, which can be considered as an extendable multi-hop ad hoc networking structure. Since Bluetooth operates in the unlicensed ISM band, each piconet uses pseudorandom frequency hopping. If collocated piconets use the same channel simultaneously, the piconets interfere with each other and the transmitted packets are lost in collisions. This interference is termed self-interference. The piconets that are networked into scatternet exhibit spatial overlapping and naturally produce multi-piconet self-interference. The collisions cause retransmissions and increase the energy spent per data portion, which results in energy-inefficient operation. To tackle this problem, in our previous work we have proposed a self-interference avoidance (SIA) mechanism. However, this basic SIA mechanism is oblivious with respect to the physical topology and does not account for the mitigation of self-interference due to the propagation effects. Furthermore, the basic SIA mechanism relies on the assumption that all piconets are using packets of identical and fixed length. In this paper we will generalize the SIA mechanism to overcome the stated restrictions. We propose the adaptive SIA (A-SIA) algorithm, which adapts the SIA algorithm to the actual interference. The simulation results show that A-SIA largely retains the energy gain offered by the SIA algorithm, while significantly improving the goodput. We also design an instance of the SIA mechanism that operates with variable-length packets, referred as generalized SIA (G-SIA) algorithm. Our simulation results show that the G-SIA algorithm offers good performance in terms of goodput and energy efficiency, but the goodput is degraded if inappropriate segmentation/reassembly policy is used. 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, Macedonia, in 1997 and 2000, respectively and a Ph.D. degree from Aalborg University, Denmark, in 2004. He is currently Assistant Research Professor at the Department of Communication Technology at the Aalborg University. His research interests are focused on wireless ad hoc networks, wireless sensor networks, and high-speed wireless multi-carrier communications. 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 working at NEC Corporation, Japan. Since October 2004, he has been an Assistant Research Professor in Center for TeleInfrastructure (CTIF), Aalborg University, Denmark. His research interests include medium access protocols, link-layer techniques, routing protocols, and their interactions in wireless networks. Liljana Gavrilovska received her B.Sc., M.Sc. and Ph.D. from University of Skopje (76), University of Belgrade (85) and University of Skopje (95) respectively. She joined the Faculty of Electrical Engineering, University of Skopje, Republic of Macedonia, where she currently holds positions of Professor at the Institute for Telecommunications, chief of Telecommunications Laboratory and head of CWMC (Center for Wireless and Mobile Communications), working in the area of networking and mobile communications. During 2001–2002 she joined the Centre for PersonKommunikation, Aalborg University, Denmark, where she was holding a position as Associate Research Professor and was involved in several EU (ASAP, PACWOMAN, MAGNET) and national/international projects. She is still working part-time for CTiF, Aalborg University, Denmark. Her major research is concentrated on ad hoc networking, wireless and personal area networks, cross layer optimizations, future mobile systems, traffic analysis and admission techniques. She is a senior member of IEEE and serves as a Chair of the Macedonian Communications Chapter. Ramjee Prasad is a distinguished educator and researcher in the field of wireless information and multimedia communications. During February 1988–May 1999 he has been with the Telecommunications and Traffic-Control Systems Group of Delft University of Technology (DUT), The Netherlands, where he was actively involved in the area of wireless personal and multimedia communications (WPMC). He was head of the Transmission Research Section of International research Centre for Telecommunications Transmission and Radar (IRCTR) and also Founding Program Director of the Centre for Wireless Personal Communications (CWPC). As from June 1999 Ramjee Prasad joined as the Wireless Information Multimedia Communications chair and co-director of Centre for PersonKommunikation at Aalborg University, Denmark. From January 2004 he is Founding Director of the “Centre for Teleinfrastruktur (CTIF)”. He has published over 500 technical papers, and authored and co-edited 15 books about Wireless Multimedia Communications (Artech House). His research interest lies in wireless networks, packet communications, multiple access protocols, adaptive equalisers, spread-spectrum CDMA systems and multimedia communications. Prof. Prasad is the founding chairperson of the European centre of Excellence in Telecommunications known as HERMES Partnership. He is the General Chairman of International Wireless Summit (IWS 2005) to be held in Aalborg, Denmark in September 17–22, 2005. He is a fellow of the IEE, a fellow of IETE, a senior member of IEEE, a member of NERG, and a member of the Danish Engineering Society (IDA). He is advisor to several multinational companies.     

Cooperative-diversity slotted ALOHA

We propose a cooperative-diversity technique for ad hoc networks based on the decode-and-forward relaying strategy. We develop a MAC protocol based on slotted ALOHA that allows neighbors of a transmitter to act as relays and forward a packet toward its final destination when the transmission to the intended recipient fails. The proposed technique provides additional robustness against fading, packet collisions and radio mobility. Network simulations confirm that under heavy traffic conditions, in which every radio always has packets to send, the proposed cooperative-diversity slotted-ALOHA protocol can provide a higher one-hop and end-to-end throughput than the standard slotted-ALOHA protocol can. A similar advantage in end-to-end delay can be obtained when the traffic is light. As a result, the proposed cooperative-diversity ALOHA protocol can be used to improve these measures of Quality of Service (QoS) in ad hoc wireless networks. John M. Shea (S’92–M’99) received the B.S. (with highest honors) in Computer Engineering from Clemson University in 1993 and the M.S. and Ph.D. degrees in electrical engineering from Clemson University in 1995 and 1998, respectively. Dr. Shea is currently an Associate Professor of electrical and computer engineering at the University of Florida. Prior to that, he was an Assistant Professor at the University of Florida from July 1999 to August 2005 and a post-doctoral research fellow at Clemson University from January 1999 to August 1999. He was a research assistant in the Wireless Communications Program at Clemson University from 1993 to 1998. He is currently engaged in research on wireless communications with emphasis on error-control coding, cross-layer protocol design, cooperative diversity techniques, and hybrid ARQ. Dr. Shea was selected as a Finalist for the 2004 Eta Kappa Nu Outstanding Young Electrical Engineer Award. He received the Ellersick Award from the IEEE Communications Society in 1996. Dr. Shea was a National Science Foundation Fellow from 1994 to 1998. He is an Associate Editor for the IEEE Transactions on Vehicular Technology. Tan F. Wong received the B.Sc. degree (1st class honors) in electronic engineering from the Chinese University of Hong Kong in 1991, and the M.S.E.E. and Ph.D. degrees in electrical engineering from Purdue University in 1992 and 1997, respectively. He was a research engineer working on the high speed wireless networks project in the Department of Electronics at Macquarie University, Sydney, Australia. He also served as a post-doctoral research associate in the School of Electrical and Computer Engineering at Purdue University. Since August 1998 he has been with the University of Florida, where he is currently an associate professor of electrical and computer engineering. He serves as Editor for Wideband and Multiple Access Wireless Systems for the IEEE Transactions on Communications and as the Editor for the IEEE Transactions on Vehicular Technology.     

Controlled sink mobility for prolonging wireless sensor networks lifetime

This paper demonstrates the advantages of using controlled mobility in wireless sensor networks (WSNs) for increasing their lifetime, i.e., the period of time the network is able to provide its intended functionalities. More specifically, for WSNs that comprise a large number of statically placed sensor nodes transmitting data to a collection point (the sink), we show that by controlling the sink movements we can obtain remarkable lifetime improvements. In order to determine sink movements, we first define a Mixed Integer Linear Programming (MILP) analytical model whose solution determines those sink routes that maximize network lifetime. Our contribution expands further by defining the first heuristics for controlled sink movements that are fully distributed and localized. Our Greedy Maximum Residual Energy (GMRE) heuristic moves the sink from its current location to a new site as if drawn toward the area where nodes have the highest residual energy. We also introduce a simple distributed mobility scheme (Random Movement or RM) according to which the sink moves uncontrolled and randomly throughout the network. The different mobility schemes are compared through extensive ns2-based simulations in networks with different nodes deployment, data routing protocols, and constraints on the sink movements. In all considered scenarios, we observe that moving the sink always increases network lifetime. In particular, our experiments show that controlling the mobility of the sink leads to remarkable improvements, which are as high as sixfold compared to having the sink statically (and optimally) placed, and as high as twofold compared to uncontrolled mobility. Stefano Basagni holds a Ph.D. in electrical engineering from the University of Texas at Dallas (December 2001) and a Ph.D. in computer science from the University of Milano, Italy (May 1998). He received his B.Sc. degree in computer science from the University of Pisa, Italy, in 1991. Since Winter 2002 he is on faculty at the Department of Electrical and Computer Engineering at Northeastern University, in Boston, MA. From August 2000 to January 2002 he was professor of computer science at the Department of Computer Science of the Erik Jonsson School of Engineering and Computer Science, The University of Texas at Dallas. Dr. Basagni’s current research interests concern research and implementation aspects of mobile networks and wireless communications systems, Bluetooth and sensor networking, definition and performance evaluation of network protocols and theoretical and practical aspects of distributed algorithms. Dr. Basagni has published over four dozens of referred technical papers and book chapters. He is also co-editor of two books. Dr. Basagni served as a guest editor of the special issue of the Journal on Special Topics in Mobile Networking and Applications (MONET) on Multipoint Communication in Wireless Mobile Networks, of the special issue on mobile ad hoc networks of the Wiley’s Interscience’s Wireless Communications & Mobile Networks journal, and of the Elsevier’s journal Algorithmica on algorithmic aspects of mobile computing and communications. Dr. Basagni serves as a member of the editorial board and of the technical program committee of ACM and IEEE journals and international conferences. He is a senior member of the ACM (including the ACM SIGMOBILE), senior member of the IEEE (Computer and Communication societies), and member of ASEE (American Society for Engineering Education). Alessio Carosi received the M.S. degree “summa cum laude” in Computer Science in 2004 from Rome University “La Sapienza.” He is currently a Ph.D. candidate in Computer Science at Rome University “La Sapienza.” His research interests include protocols for ad hoc and sensor networks, underwater systems and delay tolerant networking. Emanuel Melachrinoudis received the Ph.D. degree in industrial engineering and operations research from the University of Massachusetts, Amherst, MA. He is currently the Director of Industrial Engineering and Associate Chairman of the Department of Mechanical and Industrial Engineering at Northeastern University, Boston, MA. His research interests are in the areas of network optimization and multiple criteria optimization with applications to telecommunication networks, distribution networks, location and routing. He is a member of the Editorial Board of the International Journal of Operational Research. He has published in journals such as Management Science, Transportation Science, Networks, European Journal of Operational Research, Naval Research Logistics and IIE Transactions. Chiara Petrioli received the Laurea degree “summa cum laude” in computer science in 1993, and the Ph.D. degree in computer engineering in 1998, both from Rome University “La Sapienza,” Italy. She is currently Associate Professor with the Computer Science Department at Rome University “La Sapienza.” Her current work focuses on ad hoc and sensor networks, Delay Tolerant Networks, Personal Area Networks, Energy-conserving protocols, QoS in IP networks and Content Delivery Networks where she contributed around sixty papers published in prominent international journals and conferences. Prior to Rome University she was research associate at Politecnico di Milano and was working with the Italian Space agency (ASI) and Alenia Spazio. Dr. Petrioli was guest editor of the special issue on “Energy-conserving protocols in wireless Networks” of the ACM/Kluwer Journal on Special Topics in Mobile Networking and Applications (ACM MONET) and is associate editor of IEEE Transactions on Vehicular Technology, the ACM/Kluwer Wireless Networks journal, the Wiley InterScience Wireless Communications & Mobile Computing journal and the Elsevier Ad Hoc Networks journal. She has served in the organizing committee and technical program committee of several leading conferences in the area of networking and mobile computing including ACM Mobicom, ACM Mobihoc, IEEE ICC,IEEE Globecom. She is member of the steering committee of ACM Sensys and of the international conference on Mobile and Ubiquitous Systems: Networking and Services (Mobiquitous) and serves as member of the ACM SIGMOBILE executive committee. Dr. Petrioli was a Fulbright scholar. She is a senior member of IEEE and a member of ACM. Z. Maria Wang received her Bachelor degree in Electrical Engineering with the highest honor from Beijing Institute of Light Industry in China, her M.S. degree in Industrial Engineering/Operations Research from Dalhousie University, Canada and her Ph.D. in Industrial Engineering/Operations Research from Northeastern University, Boston. She served as a R&D Analyst for General Dynamics. Currently MS. Wang serves as an Optimization Analyst with Nomis Solutions, Inc.     

Maximizing Network Lifetime of Broadcasting Over Wireless Stationary Ad Hoc Networks

We investigate the problem of extending the network lifetime of a single broadcast session over wireless stationary ad hoc networks where the hosts are not mobile. We define the network lifetime as the time from network initialization to the first node failure due to battery depletion. We provide through graph theoretic approaches a polynomial-time globally optimal solution, a variant of the minimum spanning tree (MST), to the problem of maximizing the static network lifetime. We make use of this solution to develop a periodic tree update strategy for effective load balancing and show that a significant gain in network lifetime over the optimal static network lifetime can be achieved. We provide extensive comparative simulation studies on parameters such as update interval and control overhead and investigate their impact on the network lifetime. The simulation results are also compared with an upper bound to the network lifetime. A preliminary version of this paper appeared in IEEE ICC 2003 [35]. This research was funded in part by NSF grant ANI-0093187, ONR award #: N00014-04-1-0479 and Collaborative Technology Alliance (CTA) from ARL under DAAD19-01-2-0011. All statements and opinions are that of the authors and do not represent any position of the U.S government Intae Kang received his B.S. degree in physics from Seoul National University, Seoul, Korea and M.S. degree in electrical engineering from the Johns Hopkins University, Baltimore, MD. He is currently working toward the Ph.D. degree in the Department of Electrical Engineering at the University of Washington, Seattle, WA. His current research interests are in the area of ad hoc and sensor networks. In particular, he is interested in energy efficient routing, topology control, medium access control, mobility management, and modeling and performance analysis of network protocols using directional/smart antennas. Radha Poovendran has been an assistant professor at the Electrical Engineering Department of the University of Washington at Seattle since September 2000. He received his Ph.D. in Electrical Engineering from the University of Maryland, College Park in 1999. His research interests are in the areas of applied cryptography for multiuser environment, wireless networking, and applications of Information Theory to security. He is a recipient of Faculty Early Career Award from the National Science Foundation (2001), Young Investigator Award from the Army Research Office (2002), Young Investigator Award from the Office of Naval Research (2004), and the 2004 Presidential Early Career Award for Scientists and Engineers, for his research contributions in the areas of wired and wireless multiuser security. He is also a co-recipient of the 2002 Outstanding Teaching as well as the Outstanding Advisor Awards from the Department of Electrical Engineering of the University of Washington.     

The Medium Time Metric: High Throughput Route Selection in Multi-rate Ad Hoc Wireless Networks

Modern wireless devices, such as those that implement the 802.11abg standards, utilize multiple transmission rates in order to accommodate a wide range of channel conditions. The use of multiple rates presents a significantly more complex challenge to ad hoc routing protocols than the traditional single rate model. The hop count routing metric, which is traditionally used in single rate networks, is sub-optimal in multi-rate networks as it tends to select short paths composed of maximum length links. In a multi-rate network, these long distance links operate at the slowest available rate, thus achieving low effective throughput and reduced reliability due to the low signal levels. In this work we explore the lower level medium access control and physical phenomena that affect routing decisions in multi-rate ad hoc networks. We provide simulation results which illustrate the impact of these phenomena on effective throughput and show how the traditional minimum hop routing strategy is inappropriate for multi-rate networks. As an alternative, we present the Medium Time Metric (MTM) which avoids using the long range links often selected by shortest path routing in favor of shorter, higher throughput, more reliable links. Our experimental results with 802.11 g radios show that the Medium Time Metric achieves significantly higher throughput then alternative metrics. We observed up to 17 times more end-to-end TCP throughput than when the Min Hop or ETX metrics were used. Baruch Awerbuch is currently a professor at the Computer Science Dept. at Johns Hopkins University. His current Research interests include: Security, Online Algorithms, Distributed and Peer-to-Peer Systems, Recommendation Systems, and Wireless Networks. Baruch Awerbuch has published more than 100 papers in journals and refereed conferences in the general area of design and analysis of online algorithms, combinatorial and network optimization, distributed algorithms, learning, fault tolerance, network architecture, and others. Baruch Awerbuch is a co-director of the JHU Center for Networks and distributed systems http://www.cnds.jhu.edu. He is supervising the Archipelago project http://www.cnds.jhu.edu/archipelago whose goal is developing WiFi (IEEE 802.11 based) multi-hop wireless network based on novel rerouting algorithms. Dr. Awerbuch served as a member of the Editorial Board for Journal of Algorithms, Wireless Networks and Interconnection Networks. He was a program chair of the 1995 ACM Conference on Wireless Computing & Communication and a member of the program committees of the 2004 ACM Mobihoc, as well as PC member ACM PODC Principles of Distributed Computing (PODC) Conference in 1989 and of the Annual ACM STOC (Symposium on Theory of Computing) Conference in 1990 and 1991. Web: http://www.cs.jhu.edu/~baruch David Holmer received his B.S. in electrical engineering and MSE in computer science from the Johns Hopkins University in 2001 and 2002. He is now a Ph.D. candidate in the Department of Computer Science at Johns Hopkins University, and a research assistant in the Wireless Communication Group. The theme of his research is the development of deployable high performance ad hoc networking technology. As a result, his interests span many aspects of wireless networking including: routing, medium access control, physical layer properties and simulation, security, and energy efficiency. Herbert Rubens is a Ph.D. candidate in the Computer Science Department at the Johns Hopkins University (JHU) in Baltimore, Maryland. He is a member of the Wireless Communication Group, and specializes in multi-hop ad hoc protocol design. He has designed innovative mechanisms allowing power efficiency, high scalability, and efficient resource allocation in wireless networks. He obtained his B.Sc. and Masters Degree in computer science from Johns Hopkins University in 2001 and 2002 respectively. His research interests include ad hoc routing, medium access control, network security, and distributed algorithms.