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.     

A Routing Protocol for Hierarchical LEO/MEO Satellite IP Networks

The rapid growth of Internet-based applications pushes broadband satellite networks to carry on IP traffic. In previously proposed connectionless routing schemes in satellite networks, the metrics used to calculate the paths do not reflect the total delay a packet may experience. In this paper, a new Satellite Grouping and Routing Protocol (SGRP) is developed. In each snapshot period, SGRP divides Low Earth Orbit (LEO) satellites into groups according to the footprint area of the Medium Earth Orbit (MEO) satellites. Based on the delay reports sent by LEO satellites, MEO satellite managers compute the minimum-delay paths for their LEO members. Since the signaling traffic is physically separated from the data traffic, link congestion does not affect the responsiveness of delay reporting and routing table calculation. The snapshot and group formation methods as well as fast reacting mechanisms to address link congestion and satellite failures are described in detail. The performance of SGRP is evaluated through simulations and analysis.Eylem Ekici was with the Broadband & Wireless Networking Laboratory, School of Electrical & Computer Engineering, Georgia Institute of Technology when this work was performed. This work is supported by the National Science Foundation under Grant ANI-0087762.Chao Chen received the BE and ME degrees from Deparment of Electronic Engineering, Shanghai Jiao Tong University, Shanghai, China in 1998 and 2001, respectively. She is currently working toward her Ph.D. degree in the School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA. She is a graduate research assistant in the Broadband and Wireless Networking Laboratory at Georgia Institute of Technology. Her current research interests include satellite and space networks, as well as wireless ad hoc and sensor networks. E-mail: cchen@ece.gatech.eduEylem Ekici has received his BS and MS degrees in Computer Engineering from Bogazici University, Istanbul, Turkey, in 1997 and 1998, respectively. He received his PhD degree in Electrical and Computer Engineering from the Georgia Institute of Technology, Atlanta, GA, in 2002. Currently, he is an assistant professor in the Department of Electrical and Computer Engineering of the Ohio State University, Columbus, OH. Dr. Ekici’s research interests include wireless sensor networks, space-based networks, and next generation wireless networks, with a focus on modeling, multiaccess control, routing and multicasting protocols, and resource management. E-mail: ekici@ece.osu.edu     

Medium Access Control for Integrated Multimedia Wireless Access with the Use of a Video Packet Discard Scheme

A well designed Medium Access Control (MAC) protocol for wireless networks should provide an efficient mechanism to share the limited bandwidth resources, and satisfy the diverse and usually contradictory Quality of Service (QoS) requirements of each traffic class. In this paper a new MAC protocol for next generation wireless communications is presented and investigated. The protocol uses a combined Packet Discard/Forward Error Correction scheme in order to efficiently integrate MPEG-4 videoconference packet traffic with voice, SMS data and web packet traffic over a noisy wireless channel of high capacity. Our scheme achieves high aggregate channel throughput in all cases of traffic load, while preserving the Quality of Service (QoS) requirements of each traffic type, and is shown to clearly outperform DPRMA, another efficient MAC protocol proposed in the literature for multimedia traffic integration over wireless networks. Dr. Polychronis Koutsakis was born in Hania, Greece, in 1974. He received his 5-year Diploma in Electrical Engineering in 1997 from the University of Patras, Greece and his MSc and Ph.D. degrees in Electronic and Computer Engineering in 1999 and 2002, respectively, from the Technical University of Crete, Greece. He was a Visiting Lecturer at the Electronic and Computer Engineering Department of the same University for three years (2003–2006). He is currently an Assistant Professor at the Electrical and Computer Engineering Department of McMaster University, Canada. His research interests focus on the design, modeling and performance evaluation of computer communication networks, and especially on the design and evaluation of multiple access schemes for multimedia integration over wireless networks, on call admission control and traffic policing schemes for both wireless and wired networks, on multiple access control protocols for mobile satellite networks, wireless sensor networks and powerline networks, and on traffic modeling. Dr. Koutsakis has authored more than 45 peer-reviewed papers in the above mentioned areas, has served as a Guest Editor for an issue of the ACM Mobile Computing and Communications Review, as a TPC member for conferences such as IEEE GLOBECOM, IEEE LCN and IEEE PerCom, will serve as Session Chair for the IEEE GLOBECOM 2006 Symposium on Satellite & Space Communications and serves as a reviewer for most of the major journal publications focused on his research field. Moisis Vafiadis was born in Elefsina, Greece, in 1980. He has recently completed his studies towards the Diploma in Electronic Engineering at the Technological Educational Institute of Crete, Greece. His research interests focus on wireless personal communication networks, and especially on the MAC layer and on the development and testing of wireless multimedia applications.     

On-demand diversity wireless relay networks

There has been much recent attention on using wireless relay networks to forward data from mobile nodes to a base station. This network architecture is motivated by performance improvements obtained by leveraging the highest quality links to a base station for data transfer. With the advent of agile radios it is possible to improve the performance of relay networks through intelligent frequency assignments. First, it is beneficial if the links of the relay network are orthogonal with respect to each other so that simultaneous transmission on all links is possible. Second, diversity can be added to hops in the relay network to reduce error rates. In this paper we present algorithms for forming such relay networks dynamically. The formation algorithms support intelligent frequency assignments and diversity setup. Our results show that algorithms that order the sequence in which nodes join a relay network carefully, achieve the highest amount of diversity and hence best performance. This research is supported in part by NSF grant CNS-0508114. JaeSheung Shin received the B.S. and M.S. degree in Computer Science and Engineering from DongGuk University, Korea, in 1991 and 1993, respectively. He is currently working toward the Ph.D. degree in Computer Science and Engineering at the Pennsylvania State University, University Park. He is a research assistant at the Networking and Security Research Center (NSRC). Prior to joining Pennsylvania State University, he was with Electronics and Telecommunications Research Institute (ETRI), Korea, since 1993. He worked on development of 2G and 3G wireless cellular core network elements. His research interests include mobility management and signaling for wireless cellular and routing and resource allocation for multi-radio multi-hop wireless cellular networks. Kyounghwan Lee received the B.S. degree in Electrical and Electronics Engineering from University of Seoul, Seoul, Korea, in 2000, and the M.S. degree in Information and Communication Engineering from Gwangju Institute of Science and Technology, Gwangju, Korea, in 2002. He is currently a Ph.D candidate at the Electrical Engineering department at the Pennsylvania State University and a research assistant at the Wireless Communications and Networking Laboratory (WCAN@PSU). His research interests include wireless communication theory and relay networks. E-mail: kxl251@psu.edu Aylin Yener received the B.S. degrees in Electrical and Electronics Engineering, and in Physics, from Bogazici University, Istanbul, Turkey, in 1991, and the M.S. and Ph.D. degrees in Electrical and Computer Engineering from Rutgers University, NJ, in 1994 and 2000, respectively. During her Ph.D. studies, she was with Wireless Information Network Laboratory (WINLAB) in the Department of Electrical and Computer Engineering at Rutgers University, NJ. Between fall 2000 and fall 2001, she was with the Electrical Engineering and Computer Science Department at Lehigh University, PA, where she was a P.C. Rossin assistant professor. Currently, she is with the Electrical Engineering department at the Pennsylvania State University, University Park, PA, as an assistant professor. Dr. Yener is a recipient of the NSF CAREER award in 2003. She is an associate editor of the IEEE Transactions on Wireless Communications. Dr. Yener’s research interests include performance enhancement of multiuser systems, wireless communication theory and wireless networking. Thomas F. La Porta received his B.S.E.E. and M.S.E.E. degrees from The Cooper Union, New York, NY, and his Ph.D. degree in Electrical Engineering from Columbia University, New York, NY. He joined the Computer Science and Engineering Department at Penn State in 2002 as a Full Professor. He is the Director of the Networking Research Center at Penn State. Prior to joining Penn State, Dr. La Porta was with Bell Laboratories since 1986. He was the Director of the Mobile Networking Research Department in Bell Laboratories, Lucent Technologies. He is an IEEE Fellow and Bell Labs Fellow. Dr. La Porta was the founding Editor-in-Chief of the IEEE Transactions on Mobile Computing. He has published over 50 technical papers and holds 25 patents.     

MANTIS OS: An Embedded Multithreaded Operating System for Wireless Micro Sensor Platforms

The MANTIS MultimodAl system for NeTworks of In-situ wireless Sensors provides a new multithreaded cross-platform embedded operating system for wireless sensor networks. As sensor networks accommodate increasingly complex tasks such as compression/aggregation and signal processing, preemptive multithreading in the MANTIS sensor OS (MOS) enables micro sensor nodes to natively interleave complex tasks with time-sensitive tasks, thereby mitigating the bounded buffer producer-consumer problem. To achieve memory efficiency, MOS is implemented in a lightweight RAM footprint that fits in less than 500 bytes of memory, including kernel, scheduler, and network stack. To achieve energy efficiency, the MOS power-efficient scheduler sleeps the microcontroller after all active threads have called the MOS sleep() function, reducing current consumption to the μA range. A key MOS design feature is flexibility in the form of cross-platform support and testing across PCs, PDAs, and different micro sensor platforms. Another key MOS design feature is support for remote management of in-situ sensors via dynamic reprogramming and remote login. Shah Bhatti is a Ph.D. student in Computer Science at the University of Colorado at Boulder. He also works as a Senior Program Manager in the R&D Lab for Imaging and Printing Group (IPG) at Hewlett Packard in Boise, Idaho. He has participated as a panelist in workshops on Integrated Architecture for Manufacturing and Component-Based Software Engineering, at IJCAI ‘89 and ICSE ‘98, respectively. Hewlett Packard has filed several patents on his behalf. He received an MSCS and an MBA from the University of Colorado, an MSCE from NTU and a BSCS from Wichita State University. His research interests include power management, operating system design and efficient models for wireless sensor networks. James Carlson is a Ph.D. student in Computer Science at the University of Colorado at Boulder. He received his Bachelor’s degree from Hampshire College in 1997. His research is supported by the BP Visualization Center at CU-Boulder. His research interests include computer graphics, 3D visualization, and sensor-enabled computer-human user interfaces. Hui Dai is a Ph.D. student in Computer Science at the University of Colorado at Boulder. He received his B.E. from the University of Science and Technology, China in 2000, and received has M.S. in Computer Science from the University of Colorado at Boulder in 2002. He has been co-leading the development of the MANTIS OS. His research interests include system design for wireless sensor networks, time synchronization, distributed systems and mobile computing. Jing Deng is a Ph.D. student in Computer Science at the University of Colorado at Boulder. He received his B.E. from Univeristy of Electronic Science and Technology of China in 1993, and his M.E from Institute of Computing Technology, Chinese Academy of Science in 1996. He has published four papers on security wireless sensor networks and is preparing a book chapter on security, privacy, and fault tolerance in sensor networks. His research interests include wireless security, secure network routing, and security for sensor networks. Jeff Rose is an M.S. student in Computer Science at the University of Colorado at Boulder. He received his B.S. in Computer Science from the University of Colorado at Boulder in 2003. He has been co-leading the development of the MANTIS operating system. His research interests include data-driven routing in sensor networks. Anmol Sheth is a Ph.D. student in Computer Science at the University of Colorado at Boulder. He received his B.S. in Computer Science from the University of Pune, India in 2001. His research interests include MAC layer protocol design, energy-efficient wireless communication, and adapting communications to mobility. Brian Shucker is a Ph.D. student in Computer Science at the University of Colorado at Boulder. He received his B.S. in Computer Science from the University of Arizona in 2001, and his M.S. in Computer Science from the University of Colorado at Boulder in December 2003. He has been co-leading the development of the MANTIS operating system. His research interests in wireless sensor networks include operating systems design, communication networking, and robotic sensor networks. Charles Gruenwald is an undergraduate student in Computer Science at the University of Colorado at Boulder. He joined the MANTIS research group in Fall 2003 as an undergraduate researcher. Adam Torgerson is an undergraduate student in Computer Science at the University of Colorado at Boulder. He joined the MANTIS research group in Fall 2003 as an undergraduate researcher. Richard Han joined the Department of Computer Science at the University of Colorado at Boulder in August 2001 as an Assistant Professor, Prof. Han leads the MANTIS wireless sensor networking research project, http://mantis.cs.colorado.edu. He has served on numerous technical program committees for conferences and workshops in the field of wireless sensor networks. He received a National Science Foundation CAREER Award in 2002 and IBM Faculty Awards in 2002 and 2003. He was a Research Staff Member at IBM’s Thomas J. Watson Research Center in Hawthorne, New York from 1997-2001. He received his Ph.D. in Electrical Engineering from the University of California at Berkeley in 1997, and his B.S. in Electrical Engineering with distinction from Stanford University in 1989. His research interests include systems design for sensor networks, secure wireless sensor networks, wireless networking, and sensor-enabled user interfaces.This revised version was published online in August 2005 with a corrected cover date.     

Self-management in chaotic wireless deployments

Over the past few years, wireless networking technologies have made vast forays into our daily lives. Today, one can find 802.11 hardware and other personal wireless technology employed at homes, shopping malls, coffee shops and airports. Present-day wireless network deployments bear two important properties: they are unplanned, with most access points (APs) deployed by users in a spontaneous manner, resulting in highly variable AP densities; and they are unmanaged, since manually configuring and managing a wireless network is very complicated. We refer to such wireless deployments as being chaotic. In this paper, we present a study of the impact of interference in chaotic 802.11 deployments on end-client performance. First, using large-scale measurement data from several cities, we show that it is not uncommon to have tens of APs deployed in close proximity of each other. Moreover, most APs are not configured to minimize interference with their neighbors. We then perform trace-driven simulations to show that the performance of end-clients could suffer significantly in chaotic deployments. We argue that end-client experience could be significantly improved by making chaotic wireless networks self-managing. We design and evaluate automated power control and rate adaptation algorithms to minimize interference among neighboring APs, while ensuring robust end-client performance. This work was supported by the Army Research Office under grant number DAAD19-02-1-0389, and by the NSF under grant numbers ANI-0092678, CCR-0205266, and CNS-0434824, as well as by IBM and Intel. Aditya Akella obtained his Ph.D. in Computer Science from Carnegie Mellon University in September 2005. He obtained a B.Tech in Computer Science and Engineering from IIT Madras in May 2000. Currently, Dr. Akella is a post-doctoral associate at Stanford University. He will join the Computer Sciences faculty at the University of Wisconsin-Madison in Fall 2006. Dr. Akella's research interests include Internet Routing, Network Protocol Design, Internet Security, and Wireless Networking. His web page is at . Glenn Judd, is a Computer Science Ph.D. candidate at Carnegie Mellon University. His research interests include wireless networking and pervasive computing. He has an M.S. and B.S. in Computer Science from Brigham Young University. Srinivasan Seshan is currently an Associate Professor and holds the Finmeccanica chair at Carnegie Mellon University’s Computer Science Department. Dr. Seshan received his Ph.D. in 1995 from the Computer Science Department at University of California, Berkeley. From 1995 to 2000, Dr. Seshan was a research staff member at IBM’s T.J. Watson Research Center. Dr. Seshan’s primary interests are in the broad areas of network protocols and distributed network applications. In the past, he has worked on topics such as transport/routing protocols for wireless networks, fast protocol stack implementations, RAID system design, performance prediction for Internet transfers, Web server benchmarking, new approaches to congestion control, firewall design and improvements to the TCP protocol. His current work explores new approaches in overlay networking, sensor networking, online multiplayer games and wide-area Internet routing. His web page is at . Peter Steenkiste is a Professor of Computer Science and of Electrical and Computer Engineering at Carnegie Mellon University. His research interests include networking, distributed systems, and pervasive computing. He received an M.S. and Ph.D. in Electrical Engineering from Stanford University and an Engineering degree from the University of Gent, Belgium. You can learn more about his research from his home page .     

Exploiting Mobility for Energy Efficient Data Collection in Wireless Sensor Networks

We analyze an architecture based on mobility to address the problem of energy efficient data collection in a sensor network. Our approach exploits mobile nodes present in the sensor field as forwarding agents. As a mobile node moves in close proximity to sensors, data is transferred to the mobile node for later depositing at the destination. We present an analytical model to understand the key performance metrics such as data transfer, latency to the destination, and power. Parameters for our model include: sensor buffer size, data generation rate, radio characteristics, and mobility patterns of mobile nodes. Through simulation we verify our model and show that our approach can provide substantial savings in energy as compared to the traditional ad-hoc network approach. Sushant Jain is a Ph.D. candidate in the Department of Computer Science and Engineering at the University of Washington. His research interests are in design and analysis of routing algorithms for networking systems. He received a MS in Computer Science from the University of Washington in 2001 and a B.Tech degree in Computer Science from IIT Delhi in 1999. Rahul C. Shah completed the B. Tech (Hons) degree from the Indian Institute of Technology, Kharagpur in 1999 majoring in Electronics and Electrical Communication Engineering. He is currently pursuing his Ph.D. in Electrical Engineering at the University of California, Berkeley. His research interests are in energy-efficient protocol design for wireless sensor/ad hoc networks, design methodology for protocols and next generation cellular networks. Waylon Brunette is a Research Engineer in the Department of Computer Science and Engineering at the University of Washington. His research interests include mobile and ubiquitous computing, wireless sensor networks, and personal area networks. Currently, he is engaged in collaborative work with Intel Research Seattle to develop new uses for embedded devices and RFID technologies in ubiquitous computing. He received a BS in Computer Engineering from the University of Washington in 2002. Gaetano Borriello is a Professor in the Department of Computer Science and Engineering at the University of Washington. His research interests are in embedded and ubiquitous computing, principally new hardware devices that integrate seamlessly into the user’s environment with particular focus on location and identification systems. His principal projects are in creating manageable RFID systems that are sensitive to user privacy concerns and in context-awareness through sensors distributed in the environment as well as carried by users. Sumit Roy received the B. Tech. degree from the Indian Institute of Technology (Kanpur) in 1983, and the M. S. and Ph. D. degrees from the University of California (Santa Barbara), all in Electrical Engineering in 1985 and 1988 respectively, as well as an M. A. in Statistics and Applied Probability in 1988. His previous academic appointments were at the Moore School of Electrical Engineering, University of Pennsylvania, and at the University of Texas, San Antonio. He is presently Prof, of Electrical Engineering, Univ. of Washington where his research interests center around analysis/design of communication systems/networks, with a topical emphasis on next generation mobile/wireless networks. He is currently on academic leave at Intel Wireless Technology Lab working on high speed UWB radios and next generation Wireless LANs. His activities for the IEEE Communications Society includes membership of several technical committees and TPC for conferences, and he serves as an Editor for the IEEE Transactions on Wireless Communications.     

Admission control with load balancing in IEEE 802.11-based ESS mesh networks

In this paper we study connection admission control (CAC) in IEEE 802.11-based ESS mesh networks. An analytical model is developed for studying the effects of CAC on mesh network capacity. A distributed CAC scheme is proposed, which incorporates load balancing when selecting a mesh path for new connections. Our results show that connection level performance, including both average number of connections and connection blocking probability, can be greatly improved using the proposed mechanism compared to other admission control schemes. 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 networks. Dr. Zhao is a member of the IEEE. Jun Zou received his B. Eng. and M. Eng. Degrees from Tianjin University, China in 1999 and 2002, respectively. He worked at Siemens Communication Networks Ltd., Beijing from 2002 to 2004. Currently, he is a PhD. student at McMaster University, Canada. His research interests include wireless networking, routing protocols, architecture of next generation networks and network security. 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 Dr. Todd 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. At McMaster he has been the Principal Investigator on a number of projects in the optical networks and wireless networking areas. 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 January-December 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. Dr. Todd is a past Editor of the IEEE/ACM Transactions on Networking and currently holds the NSERC/RIM/CITO 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.     

Finding Minimum Energy Disjoint Paths in Wireless Ad-Hoc Networks

We develop algorithms for finding minimum energy disjoint paths in an all-wireless network, for both the node and link-disjoint cases. Our major results include a novel polynomial time algorithm that optimally solves the minimum energy 2 link-disjoint paths problem, as well as a polynomial time algorithm for the minimum energy k node-disjoint paths problem. In addition, we present efficient heuristic algorithms for both problems. Our results show that link-disjoint paths consume substantially less energy than node-disjoint paths. We also found that the incremental energy of additional link-disjoint paths is decreasing. This finding is somewhat surprising due to the fact that in general networks additional paths are typically longer than the shortest path. However, in a wireless network, additional paths can be obtained at lower energy due to the broadcast nature of the wireless medium. Finally, we discuss issues regarding distributed implementation and present distributed versions of the optimal centralized algorithms presented in the paper.Anand Srinivas is currently a PhD candidate in the Laboratory for Information and Decision Systems (LIDS) at MIT. He recieved his Masters of Science in EECS from MIT in 2004, and his Bachelors of Applied Science in Computer Engineering from the University of Toronto in 2001. In 2004 he also received a Masters of Science in Aerospace Engineering from MIT. His current research interests include reliability and energy-efficiency in wireless ad-hoc networks, routing and network optimization, graph theory, and the design of efficient algorithms. E-mail: anand3@mit.eduEytan Modiano received his B.S. degree in Electrical Engineering and Computer Science from the University of Connecticut at Storrs in 1986 and his M.S. and Ph.D. degrees, both in Electrical Engineering, from the University of Maryland, College Park, MD, in 1989 and 1992 respectively. He was a Naval Research Laboratory Fellow between 1987 and 1992 and a National Research Council Post Doctoral Fellow during 1992–1993 while he was conducting research on security and performance issues in distributed network protocols.Between 1993 and 1999 he was with the Communications Division at MIT Lincoln Laboratory where he designed communication protocols for satellite, wireless, and optical networks and was the project leader for MIT Lincoln Laboratory’s Next Generation Internet (NGI) project. He joined the MIT faculty in 1999, where he is presently an Associate Professor in the Department of Aeronautics and Astronautics and the Laboratory for Information and Decision Systems (LIDS). His research is on communication networks and protocols with emphasis on satellite, wireless, and optical networks.He is currently an Associate Editor for Communication Networks for IEEE Transactions on Information Theory and for The International Journal of Satellite Communications. He had served as a guest editor for IEEE JSAC special issue on WDM network architectures; the Computer Networks Journal special issue on Broadband Internet Access; the Journal of Communications and Networks special issue on Wireless Ad-Hoc Networks; and for IEEE Journal of Lightwave Technology special issue on Optical Networks. He is the Technical Program co-chair for Wiopt 2006 and vice- chair for Infocom 2007. E-mail: modiano@mit.edu     

How is the capacity of ad hoc networks improved with directional antennas?

The capacity of wireless ad hoc networks is constrained by the interference caused by the neighboring nodes. Gupta and Kumar have shown that the throughput for such networks is only Θ bits per second per node in a unit area domain when omnidirectional antennas are used [1]. In this paper we investigate the capacity of ad hoc wireless networks using directional antennas. Using directional antennas reduces the interference area caused by each node, thus increases the capacity of the network. We will give an expression for the capacity gain and we argue that in the limit, when the beam-width goes to zero the wireless network behaves like the wired network. In our analysis we consider both arbitrary networks and random networks where nodes are assumed to be static. We have also analyzed hybrid beamform patterns that are a mix of omnidirectional/directional and a better model of real directional antennas. Simulations are conducted for validation of our analytical results. Su Yi received the B.S. and M.S degrees in automation from Tsinghua University, China, in 1998 and 2001, respectively. She received her Ph.D. degree in electrical engineering from Rensselaer Polytechnic Institute, in December 2005. Her research interests include various topics in wireless ad hoc networks, including capacity of wireless networks, error control coding, and multimedia communications over wireless. Yong Pei is currently a tenure-track assistant professor in the Computer Science and Engineering Department, Wright State University, Dayton, OH. Previously he was a visiting assistant professor in the Electrical and Computer Engineering Department, University of Miami, Coral Gables, FL. He received his B.S. degree in electrical power engineering from Tsinghua University, Beijing, in 1996, and M.S. and Ph.D. degrees in electrical engineering from Rensselaer Polytechnic Institute, Troy, NY, in 1999 and 2002, respectively. His research interests include information theory, wireless communication systems and networks, and image/video compression and communications. He is a member of IEEE and ACM. Shivkumar Kalyanaraman is an Associate Professor at the Department of Electrical, Computer and Systems Engineering at Rensselaer Polytechnic Institute in Troy, NY. He received a B.Tech degree from the Indian institute of Technology, Madras, India in July 1993, followed by M.S. and Ph.D. degrees in computer and Information Sciences at the Ohio State University in 1994 and 1997 respectively. His research interests are in network traffic management topics such as congestion control, reliability, connectionless traffic engineering, quality of service (QoS), last-mile community wireless networks, low-cost free-space-optical networks, automated network management using online simulation, multicast, multimedia networking, and performance analysis. His special interest lies in developing the interdisciplinary connections between network architecture and fields like control theory, economics, scalable simulation technologies, video compression and optoelectronics. He is a member of ACM and IEEE. Babak Azimi-Sadjadi received his B.Sc. from Sharif University of Technology in 1989, his M.Sc. from Tehran University in 1992, and his Ph.D. from the University of Maryland at College Park in 2001 all in Electrical Engineering. He is currently with Intelligent Automation Inc. where he is a Senior Research Scientist He also has a joint appointment with the department of Electrical, Systems, and Computer Engineering of Rensselaer Polytechnic Institute where he is a research assistant professor. His research interests include, nonlinear filtering, networked control systems, and wireless networks.     

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.     

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.     

Scheduling Sleeping Nodes in High Density Cluster-based Sensor Networks

In order to conserve battery power in very dense sensor networks, some sensor nodes may be put into the sleep state while other sensor nodes remain active for the sensing and communication tasks. In this paper, we study the node sleep scheduling problem in the context of clustered sensor networks. We propose and analyze the Linear Distance-based Scheduling (LDS) technique for sleeping in each cluster. The LDS scheme selects a sensor node to sleep with higher probability when it is farther away from the cluster head. We analyze the energy consumption, the sensing coverage property, and the network lifetime of the proposed LDS scheme. The performance of the LDS scheme is compared with that of the conventional Randomized Scheduling (RS) scheme. It is shown that the LDS scheme yields more energy savings while maintaining a similar sensing coverage as the RS scheme for sensor clusters. Therefore, the LDS scheme results in a longer network lifetime than the RS scheme. Jing Deng received the B.E. and M.E. degrees in Electronic Engineering from Tsinghua University, Beijing, P. R. China, in 1994 and 1997, respectively, and the Ph.D. degree in Electrical and Computer Engineering from Cornell University, Ithaca, NY, in 2002. Dr. Deng is an assistant professor in the Department of Computer Science at the University of New Orleans. From 2002 to 2004, he visited the CASE center and the Department of Electrical Engineering and Computer Science at Syracuse University, Syracuse, NY as a research assistant professor, supported by the Syracuse University Prototypical Research in Information Assurance (SUPRIA) program. He was a teaching assistant from 1998 to 1999 and a research assistant from 1999 to 2002 in the School of Electrical and Computer Engineering at Cornell University. His interests include mobile ad hoc networks, wireless sensor networks, wireless network security, energy efficient wireless networks, and information assurance. Wendi B. Heinzelman is an assistant professor in the Department of Electrical and Computer Engineering at the University of Rochester. She received a B.S. degree in Electrical Engineering from Cornell University in 1995 and M.S. and Ph.D. degrees in Electrical Engineering and Computer Science from MIT in 1997 and 2000 respectively. Her current research interests lie in the areas of wireless communications and networking, mobile computing, and multimedia communication. Dr. Heinzelman received the NSF Career award in 2005 for her work on cross-layer optimizations for wireless sensor networks, and she received the ONR Young Investigator award in 2005 for her research on balancing resource utilization in wireless sensor networks. Dr. Heinzelman was co-chair of the 1st Workshop on Broadband Advanced Sensor Networks (BaseNets '04), and she is a member of Sigma Xi, the IEEE, and the ACM. Yunghsiang S. Han was born in Taipei, Taiwan, on April 24, 1962. He received the B.S. and M.S. degrees in electrical engineering from the National Tsing Hua University, Hsinchu, Taiwan, in 1984 and 1986, respectively, and the Ph.D. degree from the School of Computer and Information Science, Syracuse University, Syracuse, NY, in 1993. From 1986 to 1988 he was a lecturer at Ming-Hsin Engineering College, Hsinchu, Taiwan. He was a teaching assistant from 1989 to 1992 and from 1992 to 1993 a research associate in the School of Computer and Information Science, Syracuse University. From 1993 to 1997 he was an Associate Professor in the Department of Electronic Engineering at Hua Fan College of Humanities and Technology, Taipei Hsien, Taiwan. From 1997 to 2004 he was with the Department of Computer Science and Information Engineering at National Chi Nan University, Nantou, Taiwan. He was promoted to Full Professor in 1998. From June to October 2001 he was a visiting scholar in the Department of Electrical Engineering at University of Hawaii at Manoa, HI, and from September 2002 to January 2004 he was the SUPRIA visiting research scholar in the Department of Electrical Engineering and Computer Science and CASE center at Syracuse University, NY. He is now with the Graduate Institute of Communication Engineering at National Taipei University, Taipei, Taiwan. His research interests are in wireless networks, security, and error-control coding. Dr. Han is a winner of 1994 Syracuse University Doctoral Prize. Pramod K. Varshney was born in Allahabad, India on July 1, 1952. He received the B.S. degree in electrical engineering and computer science (with highest honors), and the M.S. and Ph.D. degrees in electrical engineering from the University of Illinois at Urbana-Champaign in 1972, 1974, and 1976 respectively. Since 1976 he has been with Syracuse University, Syracuse, NY where he is currently a Professor of Electrical Engineering and Computer Science and the Research Director of the New York State Center for Advanced Technology in Computer Applications and Software Engineering. His current research interests are in distributed sensor networks and data fusion, detection and estimation theory, wireless communications, intelligent systems, signal and image processing, and remote sensing he has published extensively. He is the author of Distributed Detection and Data Fusion, published by Springer-Verlag in 1997 and has co-edited two other books. Dr. Varshney is a member of Tau Beta Pi and is the recipient of the 1981 ASEE Dow Outstanding Young Faculty Award. He was elected to the grade of Fellow of the IEEE in 1997 for his contributions in the area of distributed detection and data fusion. In 2000, he received the Third Millennium Medal from the IEEE and Chancellor's Citation for exceptional academic achievement at Syracuse University. He serves as a distinguished lecturer for the AES society of the IEEE. He is on the editorial board Information Fusion. He was the President of International Society of Information Fusion during 2001.     

A Development Environment for OSA-Based Applications over the Interworked WLAN and Cellular Networks

In this paper, we propose an OSA-based development environment for interworking WLAN and 3G cellular networks. The main goal of our work is to establish and create an environment that can serve as a demonstration of a working network for OSA-based application developers while featuring mobile services over the interworked LAN and 3G cellular networks. The proposed simulating environment has (i) a location update scheme that is used to obtain mobile users' locations and status information over the interworked WLAN and cellular networks, (ii) an instant message gateway (IMG) simulator that is developed to send and receive generic messages over the interworked WLAN and cellular networks, and (iii) a mapping of Parlay APIs onto SIP signaling messages for multiparty call applications over the interworked WLAN and cellular networks. An illustrated OSA-based application that utilizes the corresponding system functions and modules is developed and verified using the proposed simulating environment. Chung-Ming Huang received the B.S. degree in Electrical Engineering from National Taiwan University on 1984/6, and the M.S. and Ph.D. degrees in Computer and Information Science from The Ohio State University on 1987/12 and 1991/6 respectively. He is currently a professor in Department of Computer Science and Information Engineering, National Cheng Kung University, Taiwan, R.O.C. He is the director of The Promotion Center for Network Applications and Services, Innovative Communication Education Project, Ministry of Education, Taiwan, R.O.C. His research interests include broadband Internet and applications, wireless and mobile network protocols, ubiquitous computing and communications, and multimedia streaming. Tz-Heng Hsu received the B.S. degree from Department of Computer Science and Information Engineering, Feng Chia University on 1996/6, and the M.S. degree and Ph.D from Department of Computer Science and Information Engineering, National Cheng Kung University on 1998/7 and 2005/7, Taiwan, R.O.C. He is currently a assistant professor in Department of Computer Science and Information Engineering, Southern Taiwan University of Technology. His research interests are wireless and mobile network protocols, applications over interworked WLAN and cellular networks and communications, and multimedia streaming. Chih-Wen Chao received the B.S. degree from Department of Engineering Science, National Cheng Kung University on 2003/6, and the M.S. degree from Department of Computer Science and Information Engineering, National Cheng Kung University on 2005/7, Taiwan, R.O.C. His research interests are OSA-based applications and distributed multimedia systems.     

Signal threshold adaptation for vertical handoff in heterogeneous wireless networks

The convergence of heterogeneous wireless access technologies has been envisioned to characterize the next generation wireless networks. In such converged systems, the seamless and efficient handoff between different access technologies (vertical handoff) is essential and remains a challenging problem. The heterogeneous co-existence of access technologies with largely different characteristics results in handoff asymmetry that differs from the traditional intra-network handoff (horizontal handoff) problem. In the case where one network is preferred, the vertical handoff decision should be carefully executed, based on the wireless channel state, network layer characteristics, as well as application requirements. In this paper, we study the performance of vertical handoff using the integration of 3G cellular and wireless local area networks as an example. In particular, we investigate the effect of an application-based signal strength threshold on an adaptive preferred-network lifetime-based handoff strategy, in terms of the signalling load, available bandwidth, and packet delay for an inter-network roaming mobile. We present an analytical framework to evaluate the converged system performance, which is validated by computer simulation. We show how the proposed analytical model can be used to provide design guidelines for the optimization of vertical handoff in the next generation integrated wireless networks. This article is the extended version of a paper presented in IFIP Networking 2005 Ahmed H. Zahran is a Ph.D. candidate at the Department of Electrical and Computer Engineering, University of Toronto. He received both his M.Sc. and B.Sc. in Electrical Engineering from Electronics and Electrical Communication Department in the Faculty of Engineering, Cairo University in 2002 and 2000 respectively, where he was holding teaching and research positions. Since September 2003, he has been working as a research assistant in the Department of Electrical and Computer Engineering, University of Toronto under the supervision of Professor Ben Liang. His research interest is wireless communication and networking with an emphasis on the design and analysis of networking protocols and algorithms. Ben Liang received honors simultaneous B.Sc. (valedictorian) and M.Sc. degrees in Electrical Engineering from Polytechnic University in Brooklyn, New York, in 1997 and the PhD degree in Electrical Engineering with Computer Science minor from Cornell University in Ithaca, New York, in 2001. In the 2001–2002 academic year, he was a visiting lecturer and post-doctoral research associate at Cornell University. He joined the Department of Electrical and Computer Engineering at the University of Toronto as an Assistant Professor in 2002. His current research interests are in the areas of mobile networking and wireless multimedia systems. He is a member of Tau Beta Pi, IEEE, and ACM and serves on the organization and technical program committees of a number of major conferences each year. Aladdin Saleh earned his Ph.D. degree in Electrical Engineering from London University, England. Since March 1998, Dr. Saleh has been working in the Wireless Technology Department of Bell Canada, the largest service provider of wireless, wire-line, and Internet in Canada. He worked as a senior application architect in the wireless data group working on several projects among them the wireless application protocol (WAP) and the location-based services. Later, he led the work on several key projects in the broadband wireless network access planning group including planning of the IEEE 802.16/ Wimax, the IEEE 802.11/ WiFi, and the integration of these technologies with the 3G cellular network including Mobile IP (MIP) deployment. Dr. Saleh also holds the position of Adjunct Full Professor at the Department of Electrical and Computer Engineering of Waterloo University, Canada since January 2004. He is currently conducting several joint research projects with the University of Waterloo and the University of Toronto on IEEE 802.16-Wimax, MIMO technology, interworking of IEEE 802.11 WLAN and 3G cellular networks, and next generation wireless networks. Prior to joining Bell Canada, Dr. Saleh worked as a faculty member at different universities and was Dean and Chairman of Department for several years. Dr. Saleh is a Fellow of IEE and a Senior Member of IEEE.     

Mobile multi-layered IPsec

To achieve high throughput in wireless networks, smart forwarding and processing of packets in access routers is critical for overcoming the effects of the wireless links. However, these services cannot be provided if data sessions are protected using end-to-end encryption as with IPsec, because the information needed by these algorithms resides inside the portion of the packet that is encrypted, and can therefore not be used by the access routers. A previously proposed protocol, called Multi-layered IPsec (ML-IPsec) modifies IPsec in a way so that certain portions of the datagram may be exposed to intermediate network elements, enabling these elements to provide performance enhancements. In this paper we extend ML-IPsec to deal with mobility and make it suitable for wireless networks. We define and implement an efficient key distribution protocol to enable fast ML-IPsec session initialization, and two mobility protocols that are compatible with Mobile IP and maintain ML-IPsec sessions. Our measurements show that, depending on the mobility protocol chosen, integrated Mobile IP/ML-IPsec handoffs result in a pause of 53–100 milliseconds, of which only 28–75 milliseconds may be attributed to ML-IPsec. Further, we provide detailed discussion and performance measurements of our MML-IPsec implementation. We find the resulting protocol, when coupled with SNOOP, greatly increases throughput over scenarios using standard TCP over IPsec (165% on average). By profiling the MML-IPsec implementation, we determine the bottleneck to be sending packets over the wireless link. In addition, we propose and implement an extension to MML-IPsec, called dynamic MML-IPsec, in which a flow may switch between plaintext, IPsec and MML-IPsec. Using dynamic MML-IPsec, we can balance the tradeoff between performance and security. Heesook Choi is a Ph.D. candidate in the Department of Computer Science and Engineering at the Pennsylvania State University. She received her B.S. degree in Computer Science and Statistics and M.S. degree in Computer Science from the Chungnam National University, Korea, in 1990 and 1992 respectively. She was a senior research staff in Electronics and Telecommunications Research Institute (ETRI) in Korea before she enrolled in the Ph.D. program at the Pennsylvania State University in August 2002. Her research interests lie in security and privacy in distributed systems and wireless mobile networks, focusing on designing algorithms and conducting system research. Hui Song is a Ph.D. candidate in the Department of Computer Science and Engineering at the Pennsylvania State University, University Park. He received the M.E. degree in Computer Science from Tsinghua University, China in 2000. His research interests are in the areas of network and system security, wireless ad-hoc and sensor networks, and mobile computing. He was a recipient of the research assistant award of the Department of Computer Science and Engineering at the Pennsylvania State University in 2005. Guohong Cao received his BS degree from Xian Jiaotong University, Xian, China. He received the MS degree and Ph.D. degree in computer science from the Ohio State University in 1997 and 1999 respectively. Since then, he has been with the Department of Computer Science and Engineering at the Pennsylvania State University, where he is currently an Associate Professor. His research interests are wireless networks and mobile computing. He has published over one hundred papers in the areas of sensor networks, wireless network security, data dissemination, resource management, and distributed fault-tolerant computing. He is an editor of the IEEE Transactions on Mobile Computing and IEEE Transactions on Wireless Communications, a guest editor of special issue on heterogeneous wireless networks in ACM/Kluwer Mobile Networking and Applications, and has served on the program committee of many conferences. He was a recipient of the NSF CAREER award in 2001. Thomas F. La Porta received his B.S.E.E. and M.S.E.E. degrees from The Cooper Union, New York, NY, and his Ph.D. degree in Electrical Engineering from Columbia University, New York, NY. He joined the Computer Science and Engineering Department at Penn State in 2002 as a Full Professor. He is the Director of the Networking and Security Research Center at Penn State. Prior to joining Penn State, Dr. La Porta was with Bell Laboratories since 1986. He was the Director of the Mobile Networking Research Department in Bell Laboratories, Lucent Technologies where he led various projects in wireless and mobile networking. He is a Bell Labs Fellow. Dr. La Porta was the founding Editor-in-Chief of the IEEE Transactions on Mobile Computing and served as Editor-in-Chief of IEEE Personal Communications Magazine. He is currently the Director of Magazines for the IEEE Communications Society and is a member of the Communications Society Board of Governors. He has published over 50 technical papers and holds 28 patents. His research interests include mobility management, signaling and control for wireless networks, mobile data systems, and protocol design.     

Design and Evaluation of a QoS-aware Framework for HIPERLAN/2 Networks

Recent advances on wireless technology are enabling the design and deployment of multiservice wireless networks. In order to be able to meet the QoS requirements of the various applications, it is essential to deploy QoS provisioning mechanisms. In this paper, we present a QoS framework to support various types of services in a wireless networking environment. Under this QoS framework, we propose various resource request mechanisms. We carry out a comparative study of the proposed schemes. Our simulation results show the effectiveness of the mechanisms when supporting different services, such as video, voice, best-effort and background traffic. Francisco M. Delicado This author received his M.Sc. degree in Physics (Electronics and Computer Science) from the University Complutense of Madrid, Madrid, Spain in 1995. He is currently a Ph.D. degree student in the Department of Computer Engineering at the University of Castilla-La Mancha. His research interests include high-performance networks, specially wireless LAN, QoS over WLAN, video compression, video transmission and error-resilient protocol architectures. Pedro Cuenca This author received his M.Sc. degree in Physics (Electronics and Computer Science, award extraordinary) from the University of Valencia in 1994. He got his Ph.D. degree in Computer Engineering in 1999 from the Polytechnic University of Valencia, Spain. In 1995 he joined the Department de Computer Engineering at the University of Castilla-La Mancha. He is currently an Associate Professor of Communications and Computer Networks. He has also been a visiting researcher at The Nottingham Trent University, Nottingham (England) and at the Multimedia Communications Research Laboratory, University of Ottawa (Canada). His research topics are centered in the area of high-performance networks, wireless LAN, video compression, QoS video transmission and error-resilient protocol architectures. He has served in the organization of International Conferences as Session Chair. He has been reviewer for several Journals and for several International Conferences. He is a member of the IFIP 6.8 Working Group and a member of the IEEE. Luis Orozco-Barbosa This author received the B.Sc. degree in electrical and computer engineering from Universidad Autonoma Metropolitana, Mexico, in 1979, the Diplome d'Etudes Approfondies from ENSIMAG, France, in 1984 and the Doctorat de l'Universite from Universite Pierre et Marie Curie, France, in 1987, both in computer science. From 1991 to 2002, he was a Faculty Member of Computer Engineering at the School of Information Technology and Engineering (SITE), University of Ottawa, Canada. In 2002, he joined the Department of Computer Engineering at Universidad de Castilla La Mancha (SPAIN) where he is currently Director of the Albacete Research Institute of Informatics. He has published over 180 papers in international Journals and Conferences on computer networks and performance evaluation. His current research interests include Internet protocols, video communications, wireless networks, traffic modeling and performance evaluation. He is a member of the IEEE. Antonio Garrido This author received the degree in physics (electronics and computer science) and the Ph.D. degrees from the University of Granada, Spain, in 1986 and University of Valencia, Spain, in 1991, respectively. In 1986, he joined the Department of Computer Engineering at the University of Castilla-La Mancha, where he is currently a Full Professor of Computer Architecture and Technology and Dean of the EscuelaPolitecnica Superior de Albacete (School of Computer Engineering). His research interests include high-performance networks, telemedicine, video compression, and video transmission. He has published over 40 papers in international journals conferences on performance evaluation of parallel computer and communications systems and compression and transmission in high-speed networks. He has led several research projects in telemedicine, computer networks and advanced computer system architectures.     

QoS-driven asynchronous uplink subchannel allocation algorithms for space-time OFDM-CDMA systems in wireless networks

In order to support the diverse Quality of Service (QoS) requirements for differentiated data applications in broadband wireless networks, advanced techniques such as space-time coding (STC) and orthogonal frequency division multiplexing (OFDM) are implemented at the physical layer. However, the employment of such techniques evidently affects the subchannel-allocation algorithms at the medium access control (MAC) layer. In this paper, we propose the QoS-driven cross-layer subchannel-allocation algorithms for data transmissions over asynchronous uplink space-time OFDM-CDMA wireless networks. We mainly focus on QoS requirements of maximizing the best-effort throughput and proportional bandwidth fairness, while minimizing the upper-bound of scheduling delay. Our extensive simulations show that the proposed infrastructure and algorithms can achieve high bandwidth fairness and system throughput while reducing scheduling delay over wireless networks. Xi Zhang (S’89-SM’98) received the B.S. and M.S. degrees from Xidian University, Xi’an, China, the M.S. degree from Lehigh University, Bethlehem, PA, all in electrical engineering and computer science, and the Ph.D. degree in electrical engineering and computer science (Electrical Engineering—Systems) from The University of Michigan, Ann Arbor, USA. He is currently an Assistant Professor and the Founding Director of the Networking and Information Systems Laboratory, Department of Electrical and Computer Engineering, Texas A&M University, College Station, Texas, USA. He was an Assistant Professor and the Founding Director of the Division of Computer Systems Engineering, Department of Electrical Engineering and Computer Science, Beijing Information Technology Engineering Institute, Beijing, China, from 1984 to 1989. He was a Research Fellow with the School of Electrical Engineering, University of Technology, Sydney, Australia, and the Department of Electrical and Computer Engineering, James Cook University, Queensland, Australia, under a Fellowship from the Chinese National Commission of Education. He worked as a Summer Intern with the Networks and Distributed Systems Research Department, Bell Laboratories, Murray Hills, NJ, and with AT&T Laboratories Research, Florham Park, NJ, in 1997. He has published more than 80 technical papers. His current research interests focus on the areas of wireless networks and communications, mobile computing, cross-layer designs and optimizations for QoS guarantees over mobile wireless networks, wireless sensor and Ad Hoc networks, wireless and wireline network security, network protocols design and modeling for QoS guarantees over multicast (and unicast) wireless (and wireline) networks, statistical communications theory, random signal processing, and distributed computer-control systems. Dr. Zhang received the U.S. National Science Foundation CAREER Award in 2004 for his research in the areas of mobile wireless and multicast networking and systems. He is currently serving as an Editor for the IEEE Transactions on Wireless Communications, an Associated Editor for the IEEE Transactions on Vehicular Technology, and and Associated Editor for the IEEE Communications Letters, and is also currently serving as a Guest Editor for the IEEE Wireless Communications Magazine for the Special Issues of “Next Generation of CDMA vs. OFDMA for 4G Wireless Applications”. He has served or is serving as the Panelist on the U.S. National Science Foundation Research-Proposal Review Panel in 2004, the WiFi-Hotspots/WLAN and QoS Panelist at the IEEE QShine 2004, as the Symposium Chair for the IEEE International Cross-Layer Designs and Protocols Symposium within the IEEE International Wireless Communications and Mobile Computing Conference (IWCMC) 2006, the Technical Program Committee Co-Chair for the IEEE IWCMC 2006, the Poster Chair for the IEEE QShine 2006, the Publicity Co-Chair for the IEEE WirelessCom 2005, and as the Technical Program Committee members for IEEE GLOBECOM, IEEE ICC, IEEE WCNC, IEEE VTC, IEEE QShine, IEEE WoWMoM, IEEE WirelessCom, and IEEE EIT. He is a Senior Member of the IEEE and a member of the Association for Computing Machinery (ACM). Jia Tang (S’03) received the B.S. degree in electrical engineering from Xi’an Jiaotong University, Xi’an, China, in 2001. He is currently a Research Assistant working towards the Ph.D. degree in the Networking and Information Systems Laboratory, Department of Electrical and Computer Engineering, Texas A&M University, College Station, Texas, USA. His research interests include mobile wireless communications and networks, with emphasis on cross-layer design and optimizations, wireless quality-of-service (QoS) provisioning for mobile multimedia networks, wireless diversity techniques, and wireless resource allocation. Mr. Tang received the Fouraker Graduate Research Fellowship Award from the Department of Electrical and Computer Engineering, Texas A&M University in 2005.     

Proportional Service Differentiation in Wireless LANs Using Spacing-based Channel Occupancy Regulation

In this paper, we propose Spacing-based Channel Occupancy Regulation (SCORE) MAC protocol for wireless LANs that provides proportional service differentiation in terms of normalized throughput. As shown by our system model and simulation study, SCORE provides consistent, scalable and adjustable proportional differentiation for any network size, any service class distribution, any node data rate and any packet size. Compared to state-of-the-art prioritized service differentiation schemes like Enhanced Distributed Coordination Function (EDCF), SCORE can quantitatively control the channel sharing between different service classes. Moreover, SCORE obtains significant performance improvements in terms of higher network throughput, higher transmission efficiency, lower medium access delay and lower delay jitter. Dr. Qi Xue is now a senior systems engineer with Qualcomm Inc. since Feb. 2005. Qi Xue is currently a Ph.D. candidate in the department of Electrical and Computer Engineering, University of Massachusetts at Amherst. He received his M.S. degree in Electrical and Information Engineering from Huazhong University of Science and Technology, China, in 2000. His research interests include protocol design and performance analysis in wireless networks. Weibo Gong received his Ph.D degree from Harvard University in 1987, and have been with the Dept. of Electrical and Computer Engineering, University of Massachusetts, Amherst since then. He is also an adjunct professor in the Dept. of Computer Science at the same campus. His major research interests include control and systems methods in communication networks, network security, and network modeling and analysis. He is a receipient of the IEEE Transactions on Automatic Control’s George Axelby Outstanding paper award, an IEEE Fellow, and the Program Committee Chair for the 43rd IEEE Conference on Decision and Control. Aura Ganz received her B.Sc, M.Sc and Ph.D degrees in Computer Science from the Technion in Israel. She is currently an associate professor and Director of the Multimedia Networks Laboratory at the ECE Department, University of Massachusetts at Amherst. She has experience in topics related to all strata of networking technology, from work related to topics in the network infrastructure development to advanced user-space application development for mobile clients. The research results are validated by a combination of analytical, simulation and prototyping tools. She has published a book “Multimedia Wireless Networks: Technologies, Standards and QoS” (Prentice Hall) and authored over one hundred and fifty peer reviewed publications. Dr. Ganz is a senior member of IEEE     

A Receiver-Centric Transport Protocol for Mobile Hosts with Heterogeneous Wireless Interfaces

Numerous transport protocols have been proposed in related work for use by mobile hosts over wireless environments. A common theme among the design of such protocols is that they specifically address the distinct characteristics of the last-hop wireless link, such as random wireless errors, round-trip time variations, blackouts, handoffs, etc. In this paper, we argue that due to the defining role played by the wireless link on a connection’s performance, locating the intelligence of a transport protocol at the mobile host that is adjacent to the wireless link can result in distinct performance advantages. To this end, we present a receiver-centric transport protocol called RCP (Reception Control Protocol) that is a TCP clone in its general behavior, but allows for better congestion control, loss recovery, and power management mechanisms compared to sender-centric approaches. More importantly, in the context of recent trends where mobile hosts are increasingly being equipped with multiple interfaces providing access to heterogeneous wireless networks, we show that a receiver-centric protocol such as RCP can enable a powerful and comprehensive transport layer solution for such multi-homed hosts. Specifically, we describe how RCP can be used to provide: (i) a scalable solution to support interface specific congestion control for a single active connection; (ii) seamless server migration capability during handoffs; and (iii) effective bandwidth aggregation when receiving data through multiple interfaces, either from one server, or from multiple replicated servers. We use both packet level simulations, and real Internet experiments to evaluate the proposed protocol. In consideration of the typically prevalent server-client nature of traffic in the Internet, we term the protocol ‘receiver-centric’ although precisely it is the mobile host that drives the protocol operation. Note that in this paper, we define the sender and the receiver of a connection with respect to the direction of the data flow. Hung-Yun Hsieh received the B.S. and M.S. degrees in electrical engineering from National Taiwan University, Taipei, Taiwan, ROC, and the Ph.D. degree in electrical and computer engineering from Georgia Institute of Technology, Atlanta, Georgia, USA. He joined the Department of Electrical Engineering and the Graduate Institute of Communication Engineering at National Taiwan University as an Assistant Professor in August 2004. His research interests include wireless networks, mobile computing, and Internet protocols. E-mail: hungyun@ntu.edu.tw Kyu-Han Kim is currently a Ph.D student in the Department of Electrical Engineering and Computer Sicence at Univeristy of Michigan at Ann Arbor. He received his M.S. degree in computer science from Georgia Institute of Technology, where he worked in the GNAN Research Group under the guidance of Prof. Raghupathy Sivakumar. His main research interests are mobile computing, wireless networks, and network performance evaluation. E-mail: kyuhkim@eecs.umich.edu Yujie Zhu received her bachelor’s degree and master’s degree from the Electrical Engineering Department of Beijing University of Aeronautics and Astronautics in 1994 and 1997 respectively. After that she worked as a Network Engineer in ATM Network Management Center of China Telecom, Guangzhou Co. She is currently a Ph.D. student in the ECE department of Georgia Tech. Her research interest includes transport layer protocols, sensor networks and mobile ad-hoc networks. E-mail: zhuyujie@ece.gatech.edu Raghupathy Sivakumar received the BE degree in Computer Science from Anna University, India, in 1996 and master’s and doctoral degrees in Computer Science from the University of Illinois at Urbana-Champaign in 1998 and 2000 respectively. He joined the School of Electrical and Computer Engineering at the Georgia Institute of Technology as an Assistant Professor in August 2000. His research interests are in wireless network protocols, mobile computing, and network quality of service. E-mail: siva@ece.gatech.edu An erratum to this article is available at .