GRAdient Broadcast: A Robust Data Delivery Protocol for Large Scale Sensor Networks

Although data forwarding algorithms and protocols have been among the first set of issues explored in sensor networking, how to reliably deliver sensing data through a vast field of small, vulnerable sensors remains a research challenge. In this paper we present GRAdient Broadcast (GRAB), a new set of mechanisms and protocols which is designed specifically for robust data delivery in face of unreliable nodes and fallible wireless links. Similar to previous work [12,13], GRAB builds and maintains a cost field, providing each sensor the direction to forward sensing data. Different from all the previous approaches, however, GRAB forwards data along a band of interleaved mesh from each source to the receiver. GRAB controls the width of the band by the amount of credit carried in each data message, allowing the sender to adjust the robustness of data delivery. GRAB design harnesses the advantage of large scale and relies on the collective efforts of multiple nodes to deliver data, without dependency on any individual ones. We have evaluated the GRAB performance through both analysis and extensive simulation. Our analysis shows quantitatively the advantage of interleaved mesh over multiple parallel paths. Our simulation further confirms the analysis results and shows that GRAB can successfully deliver over 90% of packets with relatively low energy cost, even under the adverse conditions of 30% node failures compounded with 15% link message losses.Fan Ye received his B.E. in Automatic Control in 1996 and MS in Computer Science in 1999, both from Tsinghua University, Beijing, China. After that, he has been pursuing a Ph.D. degree at UCLA. His research interests are in network protocol design, with focus on data forwarding, power management and security in large scale sensor networks.Gary Zhong is currently pursuing M.S. degree in computer science at University of California, Los Angeles. He received his B.S. degree in computer science and engineering from University of California, Davis. His research interests include wireless networking, mobile computing, and large scale sensor networks.Songwu Lu received both his M.S. and Ph.D. from University of Illinois at Urbana-Champaign. He is currently an assistant professor at UCLA Computer Science. He received NSF CAREER award in 2001. His research interests include wireless networking, mobile computing, wireless security, and computer networks.Lixia Zhang received her Ph.D in computer science from the Massachusetts Institute of Technology. She was a member of the research staff at the Xerox Palo Alto Research Center before joining the faculty of UCLAs Computer Science Department in 1995. In the past she has served on the Internet Architecture Board, Co-Chair of IEEE Communication Society Internet Technical Committee, the editorial board for the IEEE/ACM Transactions on Networking, and technical program committees for many networking-related conferences including SIGCOMM and INFOCOM. Zhang is currently serving as the vice chair of ACM SIGCOMM.     

Priority Scheduling in Wireless Ad Hoc Networks

Ad hoc networks formed without the aid of any established infrastructure are typically multi-hop networks. Location dependent contention and hidden terminal problem make priority scheduling in multi-hop networks significantly different from that in wireless LANs. Most of the prior work related to priority scheduling addresses issues in wireless LANs. In this paper, priority scheduling in multi-hop networks is discussed. We propose a scheme using two narrow-band busy tone signals to ensure medium access for high priority source stations. The simulation results demonstrate the effectiveness of the proposed scheme. Xue Yang received the B.E. degree and the M.S. degree from University of Electronic Science and Technology of China. She is currently a Ph.D. candidate at University of Illinois at Urbana-Champaign (UIUC). She is awarded Vodafone-U.S. Foundation Graduate Fellowship from 2003 to 2005. Her current research is in the areas of wireless networking and mobile computing, with the focus on medium access control, quality of service and topology control. Her research advisor is Prof. Nitin Vaidya at UIUC. For more information, please visit Nitin H. Vaidya received the PhD degree from the University of Massachusetts at Amherst. He is presently an Associate Professor of Electrical and Computer Engineering at the University of Illinois at Urbana-Champaign (UIUC). He has held visiting positions at Microsoft Research, Sun Microsystems and the Indian Institute of Technology-Bombay. His current research is in the areas of wireless networking and mobile computing. His research has been funded by various agencies, including the National Science Foundation, DARPA, BBN Technologies, Microsoft Research, and Sun Microsystems. Nitin Vaidya is a recipient of a CAREER award from the National Science Foundation. Nitin has served on the program committees of several conferences and workshops, and served as program co-chair for the 2003 ACM MobiCom. He has served as editor for several journals, and presently serves as Editor-in-Chief for IEEE Transactions on Mobile Computing, and as editor-in-chief of ACM SIGMOBILE periodical MC2R. He is a senior member of IEEE and a member of the ACM. For more information, please visit     

Energy-Efficient, Collision-Free Medium Access Control for Wireless Sensor Networks

The traffic-adaptive medium access protocol (TRAMA) is introduced for energy-efficient collision-free channel access in wireless sensor networks. TRAMA reduces energy consumption by ensuring that unicast and broadcast transmissions incur no collisions, and by allowing nodes to assume a low-power, idle state whenever they are not transmitting or receiving. TRAMA assumes that time is slotted and uses a distributed election scheme based on information about traffic at each node to determine which node can transmit at a particular time slot. Using traffic information, TRAMA avoids assigning time slots to nodes with no traffic to send, and also allows nodes to determine when they can switch off to idle mode and not listen to the channel. TRAMA is shown to be fair and correct, in that no idle node is an intended receiver and no receiver suffers collisions. An analytical model to quantify the performance of TRAMA is presented and the results are verified by simulation. The performance of TRAMA is evaluated through extensive simulations using both synthetic- as well as sensor-network scenarios. The results indicate that TRAMA outperforms contention-based protocols (CSMA, 802.11 and S-MAC) and also static scheduled-access protocols (NAMA) with significant energy savings. This work was supported in part by the NSF-NGI grant number ANI-9813724 and by the Jack Baskin Chair of Computer Engineering at UCSC. Venkatesh Rajendran received the B.E. degree in Electronics and Communication Engineering from the Anna University in 2001, and M.S. in Computer Engineering from the University of California, Santa Cruz (UCSC) in 2003. He is currently working towards his Ph.D at UCSC. He is a graduate student researcher at the Inter-networking Research Lab (INRG). His research interests are in wireless communication system design, energy-aware media access control protocols for wireless ad hoc networks, smart sensor networks, reliable multi-casting, wireless multi-carrier communications, digital signal processing, adaptive modulation, and smart antenna systems. Katia Obraczka received the B.S. and M.S. degrees in electrical and computer engineering from the Federal University of Rio de Janeiro, Brazil, and the M.S. and Ph.D. degrees in computer science from the University of Southern California (USC). She is an Assistant Professor of Computer Engineering at the University of California, Santa Cruz. Before joining UCSC, she held a research scientist position at USC's Information Sciences Institute and a research faculty appointment at USC's Computer Science Department. Her research interests include computer networks, more specifically, network protocol design and evaluation in wire-line as well as wireless (in particular, multi-hop ad hoc) networks, distributed systems, and Internet information systems. J.J. Garcia-Luna-Aceves received the M.S. and Ph.D. degrees in electrical engineering from the University of Hawaii, Honolulu, HI, in 1980 and 1983, respectively. He is the Baskin Professor of Computer Engineering at the University of California, Santa Cruz (UCSC). Dr. Garcia-Luna-Aceves directs the Computer Communication Research Group (CCRG), which is part of the Information Technologies Institute of the Baskin School of Engineering at UCSC. He has been a Visiting Professor at Sun Laboratories and a consultant on protocol design for Nokia. Prior to joining UCSC in 1993, he was a Center Director at SRI International (SRI) in Menlo Park, California. Dr. Garcia-Luna-Aceves has published a book and more than 250 refereed papers and three U.S patents, and has directed more than 18 Ph.D. theses at UCSC. He has been Program Co-Chair of ACM MobiHoc 2002 and ACM Mobicom 2000; Chair of the ACM SIG Multimedia; General Chair of ACM Multimedia '93 and ACM SIGCOMM '88; and Program Chair of IEEE MULTIMEDIA '92, ACM SIGCOMM '87, and ACM SIGCOMM '86. He has served in the IEEE Internet Technology Award Committee, the IEEE Richard W. Hamming Medal Committee, and the National Research Council Panel on Digitization and Communications Science of the Army Research Laboratory Technical Assessment Board. HE has been on the editorial boards of the IEEE/ACM Transactions on Networking, the Multimedia Systems Journal, and the Journal of High Speed Networks. He received the SRI International Exceptional-Achievement Award in 1985 and 1989, and is a senior member of the IEEE.     

Algorithmic Aspects of the Time Synchronization Problem in Large-Scale Sensor Networks

We study the time synchronization problem for large-scale wireless sensor networks in the high-density regime. Our interest in this problem arises from a sensor networking application, where a large number of power-constrained radio transmitters coordinate their access to a Gaussian multiple access channel to cooperate in generating a waveform stronger than any individual node would be able to generate. In a companion paper to this one, we study theoretical aspects of a time synchronization mechanism that is optimal in the limit of asymptotically high network densities. In this work we summarize those results, and explore practical implementation issues of that mechanism in the context of networks with large, but finite, numbers of nodes. Through simulations, we find that the synchronization mechanism performs very well for finite (and relatively small) networks, maintaining tight clock synchronization indefinitely.Work supported by the National Science Foundation, under awards CCR- 0238271 (CAREER), CCR-0330059, and ANR-0325556. An-swol Hu was born in Mt. Kisco, New York on February 24, 1980. He received his B.S. in Electrical Engineering from Stanford University in 2002. Currently he is a Ph.D. candidate in the School of Electrical and Computer Engineering at Cornell University. His research interests include information theory and statistical signal processing, with applications to sensor networks. Sergio D. Servetto was born in Argentina, on January 18, 1968. He received a Licenciatura en Informática from Universidad Nacional de La Plata (UNLP, Argentina) in 1992, and the M.Sc. degree in Electrical Engineering and the Ph.D. degree in Computer Science from the University of Illinois at Urbana-Champaign (UIUC), in 1996 and 1999. From 1991 to 1994 he worked as a programmer for IBM Argentina. From 1994 to 1999 he was a Graduate Research Assistant at UIUC. From 1999 to 2001 he worked at the Ecole Polytechnique Fédérale de Lausanne (EPFL), Switzerland. Since Fall 2001, he has been an Assistant Professor in the School of Electrical and Computer Engineering, Cornell University. He is also a member of the field of Applied Mathematics at Cornell. His research interests are centered around information theoretic aspects of networked systems, with a current emphasis on problems that arise in the context of large-scale sensor networks.Sergio was the recipient of the 1998 Ray Ozzie Fellowship, given to “outstanding graduate students in Computer Science”, and of the 1999 David J. Kuck Outstanding Thesis Award, for the best doctoral dissertation of the year, both from the Dept. of Computer Science at UIUC. He is also the recipient of a 2003 NSF CAREER Award. He has served on the technical program committee of various conferences (IEEE Infocom, Globecom, ICC, SECON; ACM MobiCom, MobiHoc, SenSys, WSNA). He will present a tutorial at ACM MobiHoc 2004, on the topic of “Efficient Architectures for Information Transport in Wireless Sensor Networks”. He is currently writing a book, tentatively entitled “Digital Communications over Packet-Switched Networks”, to be published by Kluwer.This revised version was published online in August 2005 with a corrected cover date.     

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.     

Maximizing Lifetime for Data Aggregation in Wireless Sensor Networks

This paper studies energy efficient routing for data aggregation in wireless sensor networks. Our goal is to maximize the lifetime of the network, given the energy constraint on each sensor node. Using linear programming (LP) formulation, we model this problem as a multicommodity flow problem, where a commodity represents the data generated from a sensor node and delivered to a base station. A fast approximate algorithm is presented, which is able to compute (1−ε)-approximation to the optimal lifetime for any ε > 0. Then along this baseline, we further study several advanced topics. First, we design an algorithm, which utilizes the unique characteristic of data aggregation, and is proved to reduce the running time of the fastest existing algorithm by a factor of K, K being the number of commodities. Second, we extend our algorithm to accommodate the same problem in the setting of multiple base stations, and study its impact on network lifetime improvement. All algorithms are evaluated through both solid theoretical analysis and extensive simulation results. Yuan Xue received her B.S. in Computer Science from Harbin Institute of Technology, China in 1994 and her M.S. and Ph.D. in Computer Science from the University of Illinois at Urbana-Champaign in 2002, and 2005. Currently she is an assistant professor at the Department of Electrical Engineering and Computer Science of Vanderbilt University. Her research interests include wireless and sensor networks, mobile systems, and network security. Yi Cui received his B.S. and M.S. degrees in 1997 and 1999, from Department of Computer Science, Tsinghua University, China, and his Ph.D. degree in 2005 from the Department of Computer Science, University of Illinois at Urbana-Champaign. Since then, he has been with the Department of Electrical Engineering and Computer Science at Vanderbilt University, where he is currently an assistant professor. His research interests include overlay network, peer-to-peer system, multimedia system, and wireless sensor network. Klara Nahrstedt (M ' 94) received her A.B., M.Sc degrees in mathematics from the Humboldt University, Berlin, Germany, and Ph.D in computer science from the University of Pennsylvania. She is an associate professor at the University of Illinois at Urbana-Champaign, Computer Science Department where she does research on Quality of Service(QoS)-aware systems with emphasis on end-to-end resource management, routing and middleware issues for distributed multimedia systems. She is the coauthor of the widely used multimedia book ‘Multimedia:Computing, Communications and Applications’ published by Prentice Hall, and the recipient of the Early NSF Career Award, the Junior Xerox Award and the IEEE Communication Society Leonard Abraham Award for Research Achievements, and the Ralph and Catherine Fisher Professorship Chair. Since June 2001 she serves as the editor-in-chief of the ACM/Springer Multimedia System Journal. An erratum to this article is available at .     

Non-Cooperative Games for Service Differentiation in CDMA Systems

In this paper, we address the problem of user-class based service differentiation in CDMA networks. Users are categorized into three classes who get differentiated services based on their expected quality of service (QoS) from the service provider and the price they are willing to pay. We adopt a game theoretic approach for allocating resources through a two-step process. During a service admission, resource distribution is determined for each class. Then, the resource allocated to each class is distributed among the active users in that class. We devise a utility function for the providers which considers the expected revenue and the probability of users leaving their service provider if they are not satisfied with the service. Our model demonstrates how power can be controlled in a CDMA network to differentiate the service quality. Also, we show the impact of admitting high paying users on other users. Mainak Chatterjee received his Ph.D. from the department of Computer Science and Engineering at The University of Texas at Arlington in 2002. Prior to that, he completed his B.Sc. with Physics (Hons) from the University of Calcutta in 1994 and M.E. in Electrical Communication Engineering from the Indian Institute of Science, Bangalore, in 1998. He is currently an Assistant Professor in the department of Electrical and Computer Engineering at the University of Central Florida. His research interests include economic issues in wireless networks, applied game theory, resource management and quality-of-service provisioning, ad hoc and sensor networks, CDMA data networking, and link layer protocols. He serves on the executive and technical program committee of several international conferences. Haitao Lin received the BE degree in radio engineering from Southeast University, Nanjing, China, in 1996, the MS degree in computer applications from the Beijing University of Posts and Telecommunications, Beijing, China, in 2000, and Ph.D. in Computer Science and Engineering from The University of Texas at Arlington in 2004. He is currently with Converged Multimedia Services System Engineering at Nortel, Richardson, Texas. His research interests include wireless network performance evaluation and enhancement, wireless link adaptation, wireless network resource management, and applied game theory. Sajal K. Das received B.S. degree in 1983 from Calcutta University, M.S. degree in 1984 from Indian Institute of Science, Bangalore, and Ph.D. degree in 1988 from University of Central Florida, Orlando, all in Computer Science. He is currently a Professor of Computer Science and Engineering and also the Founding Director of the Center for Research in Wireless Mobility and Networking (CReWMaN) at the University of Texas at Arlington (UTA). Prior to 1999, he was a professor of Computer Science at the University of North Texas (UNT), Denton where he founded the Center for Research in Wireless Computing (CReW) in 1997, and also served as the Director of the Center for Research in Parallel and Distributed Computing (CRPDC) during 1995–97. Dr. Das is a recipient of the UNT Student Association's Honor Professor Award in 1991 and 1997 for best teaching and scholarly research; UNT's Developing Scholars Award in 1996 for outstanding research; UTA's Outstanding Faculty Research Award in Computer Science in 2001 and 2003; and the UTA College of Engineering Research Excellence Award in 2003. He is also frequently invited as a keynote speaker at international conferences and symposia. Dr. Das' current research interests include mobile wireless communications, resource and mobility management in wireless networks, mobile and pervasive computing, wireless multimedia, ad hoc and sensor networks, mobile internet architectures and protocols, distributed and grid computing, performance modeling and simulation. He has published over 350 research papers in these areas in international journals and conferences, directed numerous industry and government funded projects, and holds five US patents in wireless mobile networks. He received four Best Paper Awards in the ACM MobiCom'99, ICOIN'01, ACM MSWiM'00, and ACM/IEEE PADS'97. He as the Editor in Chief of the Pervasive and Mobile Computing (PMC) journal and also as an Associate Editor of IEEE Transactions on Mobile Computing, ACM/Kluwer Wireless Networks, Parallel Processing Letters, Journal of Parallel, Distributed and Emerging Systems. He served as General Chair of IEEE WoWMoM'05, PerCom'04, IWDC'04, MASCOTS'02, ACM WoWMoM'00-02; General Vice Chair of IEEE PerCom'03, ACM MobiCom'00 and IEEE HiPC'00-01; Program Chair of IWDC'02, WoWMoM'98-99; TPC Vice Chair of ICPADS'02; and as TPC member of numerous IEEE and ACM conferences. He is Vice Chair of the IEEE Computer Society's TCPP and TCCC Executive Committees.     

SOLONet: Sub-optimal location-aided overlay network for MANETs

Overlay networks have made it easy to implement multicast functionality in MANETs. Their flexibility to adapt to different environments has helped in their steady growth. Overlay multicast trees that are built using location information account for node mobility and have a low latency. However, the performance gains of such trees are offset by the overhead involved in distributing and maintaining precise location information. As the degree of (location) accuracy increases, the performance improves but the overhead required to store and broadcast this information also increases. In this paper, we present SOLONet, a design to build a sub-optimal location aided overlay multicast tree, where location updates of each member node are event based. Unlike several other approaches, SOLONet doesn’t require every packet to carry location information or each node maintain location information of every other node or carrying out expensive location broadcast for each node. Our simulation results indicate that SOLONet is scalable and its sub-optimal tree performs very similar to an overlay tree built by using precise location information. SOLONet strikes a good balance between the advantages of using location information (for building efficient overlay multicast trees) versus the cost of maintaining and distributing location information of every member nodes. Abhishek Patil received his BE degree in Electronics and Telecommunications Engineering from University of Mumbai (India) in 1999 and an MS in Electrical and Computer Engineering from Michigan State University in 2002. He finished his PhD in 2005 from the Department of Computer Science and Engineering at Michigan State University. He is a research engineer at Kiyon, Inc. located in San Diego, California. His research interests include wireless mesh networks, UWB, mobile ad hoc networks, application layer multicast, location-aware computing, RFIDs, and pervasive computing. Yunhao Liu received his BS degree in Automation Department from Tsinghua University, China, in 1995, and an MA degree in Beijing Foreign Studies University, China, in 1997, and an MS and a Ph.D. degree in Computer Science and Engineering at Michigan State University in 2003 and 2004, respectively. He is now an assistant professor in the Department of Computer Science at Hong Kong University of Science and Technology. His research interests include wireless sensor networks, peer-to-peer and grid computing, pervasive computing, and network security. He is a senior member of the IEEE Computer Society. Li Xiao received the BS and MS degrees in computer science from Northwestern Polytechnic University, China, and the PhD degree in computer science from the College of William and Mary in 2002. She is an assistant professor of computer science and engineering at Michigan State University. Her research interests are in the areas of distributed and Internet systems, overlay systems and applications, and sensor networks. She is a member of the ACM, the IEEE, the IEEE Computer Society, and IEEE Women in Engineering. Abdol-Hossein Esfahanian received his B.S. degree in Electrical Engineering and the M.S. degree in Computer, Information, and Control Engineering from the University of Michigan in 1975 and 1977 respectively, and the Ph.D. degree in Computer Science from Northwestern University in 1983. He was an Assistant Professor of Computer Science at Michigan State University from September 1983 to May 1990. Since June 1990, he has been an Associate Professor with the same department, and from August 1994 to May 2004, he was the Graduate Program Director. He was awarded ‘The 1998 Withrow Exceptional Service Award’, and ‘The 2005 Withrow Teaching Excellence Award’. Dr. Esfahanian has published articles in journals such as IEEE Transactions, NETWORKS, Discrete Applied Mathematic, Graph Theory, and Parallel and Distributed Computing. He was an Associate Editor of NETWORKS, from 1996 to 1999. He has been conducting research in applied graph theory, computer communications, and fault-tolerant computing. Lionel M. Ni earned his Ph.D. degree in electrical and computer engineering from Purdue University in 1980. He is Chair Professor and Head of Computer Science and Engineering Department of the Hong Kong University of Science and Technology. His research interests include wireless sensor networks, parallel architectures, distributed systems, high-speed networks, and pervasive computing. A fellow of IEEE, Dr. Ni has chaired many professional conferences and has received a number of awards for authoring outstanding papers.     

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.     

Performance Evaluation of Directional Adaptive Range Control in Mobile Ad Hoc Networks

This paper presents DARC (Directional Adaptive Range Control), a range control mechanism using directional antennas to be implemented across multiple layers. DARC uses directional reception for range control rather than directional transmission in order to achieve both range extension and high spatial reuse. It adaptively controls the communication range by estimating dynamically changing local network density based on the transmission activities around each network node. The experimental results using simulation with detailed physical layer, IEEE 802.11 DCF MAC, and AODV protocol models have shown the successful adaptation of communication range with DARC for varied network densities and traffic loads. DARC improves the packet delivery ratio by a factor of 9 at the maximum for sparse networks while it maintains the increased network capacity for dense networks. Further, as each node adaptively changes the communication range, the network delivers up to 20% more packets with DARC compared to any fixed range configurations.Mineo Takai is a Principal Development Engineer in the Computer Science Department at University of California, Los Angeles. He received his B.S., M.S. and Ph.D. degrees, all in electrical engineering, from Waseda University, Tokyo, Japan, in 1992, 1994 and 1997 respectively.Dr. Takai’s research interests include parallel and distributed computing, mobile computing and networking, and modeling and simulation of networked systems. He is a member of the ACM, the IEEE and the IEICE.Junlan Zhou received her B.S in Computer Science from Huazhong University of Science and Technology in 1998, her M.Eng in Computer Engineering from Nanyang Technological University in 2001 and her M.S in Computer Science from University of California, Los Angeles in 2003. She is currently a Ph.D candidate in the Computer Science Department at University of California, Los Angeles. Her research interests include modeling and simulation of wireless networks, protocol design and analysis of wireless networks, and broad areas of distributed computing.Rajive Bagrodia is a Professor of Computer Science at UCLA. He obtained a Bachelor of Technology in electrical engineering from the Indian Institute of Technology, Bombay and a Ph.D. in Computer Science from the University of Texas at Austin. Professor Bagrodia’s research interests include~wireless networks, performance modeling and~simulation, and nomadic computing. He has published over a hundred research papers on the preceding topics. The research has been funded by a variety of government and industrial sponsors including the National Science Foundation, Office of Naval Research, and the Defense Advanced Research Projects Agency. He is an associate editor of the ACM Transactions on Modeling and Computer Systems (TOMACS).     

On designing incentive-compatible routing and forwarding protocols in wireless ad-hoc networks

In many applications, wireless ad-hoc networks are formed by devices belonging to independent users. Therefore, a challenging problem is how to provide incentives to stimulate cooperation. In this paper, we study ad-hoc games—the routing and packet forwarding games in wireless ad-hoc networks. Unlike previous work which focuses either on routing or on forwarding, this paper investigates both routing and forwarding. We first uncover an impossibility result—there does not exist a protocol such that following the protocol to always forward others' traffic is a dominant action. Then we define a novel solution concept called cooperation-optimal protocols. We present Corsac, a cooperation-optimal protocol which consists of a routing protocol and a forwarding protocol. The routing protocol of Corsac integrates VCG with a novel cryptographic technique to address the challenge in wireless ad-hoc networks that a link’s cost (i.e., its type) is determined by two nodes together. Corsac also applies efficient cryptographic techniques to design a forwarding protocol to enforce the routing decision, such that fulfilling the routing decision is the optimal action of each node in the sense that it brings the maximum utility to the node. We evaluate our protocols using simulations. Our evaluations demonstrate that our protocols provide incentives for nodes to forward packets. Additionally, we discuss the challenging issues in designing incentive-compatible protocols in ad hoc networks. Part of this paper appeared in a conference version [49]. Sheng Zhong was supported in part by NSF grants ANI-0207399 and CNS-0524030. Yang Richard Yang was supported in part by NSF grants ANI-0207399, ANI-0238038, and CNS-0435201. This work was partly done while Sheng Zhong was at Yale University; Yanbin Liu was at University of Texas at Austin. Sheng Zhong is an assistant professor in the State University of New York at Buffalo. He received his PhD (2004) from Yale University and his ME (1999), BS (1996) from Nanjing University, China, all in computer science. His research interests include economic incentives and privacy protection, particularly incentive and privacy problems in mobile computing and data mining. Li Erran Li received his B.E. in Automatic Control from Beijing Polytechnic University in 1993, his M.E. in Pattern Recognition from the Institute of Automation, Chinese Academy of Sciences, in 1996, and his Ph.D. in Computer Science from Cornell University in 2001 where Joseph Y. Halpern was his advisor. He is presently a member of the Networking Research Center in Bell Labs. His research interests are in networking with a focus on wireless networking and mobile computing. He has served as a program committee member for several conferences including ACM MobiCom, ACM MobiHoc, IEEE INFOCOM and IEEE ICNP. He is a guest editor for JSAC special issue on Non-Cooperative Behavior in Networking. He has published over 30 papers. Yanbin Liu received her B.E. degree in Computer Science and Technology from Tsinghua University (1993), Beijing, China, in 1993, and her M.S. degree in Computer Science from the University of Texas at Austin (1998), where is a Ph.D. candidate. Since 2006, he has been with IBM TJ Watson Research Center, Hawthorne, NY. Her research interests are in real-time systems, grid computing, mobile computing, and computer networks. Yang Richard Yang received his B.E. degree in Computer Science and Technology from Tsinghua University, Beijing, China, in 1993, and his M.S. and Ph.D. degrees in Computer Science from the University of Texas at Austin in 1998 and 2001, respectively. Since 2001, he has been with the Department of Computer Science, Yale University, New Haven, CT, where currently he is an Associate Professor. His current research interests are in computer networks, mobile computing, and sensor networks. He leads the Laboratory of Networked Systems (LANS) at Yale University.     

A Practical Cross-Layer Mechanism For Fairness in 802.11 Networks

Many companies, organizations and communities are providing wireless hotspots that provide networking access using 802.11b wireless networks. Since wireless networks are more sensitive to variations in bandwidth and environmental interference than wired networks, most networks support a number of transmission rates that have different error and bandwidth properties. Access points can communicate with multiple clients running at different rates, but this leads to unfair bandwidth allocation. If an access point communicates with a mix of clients using both 1 Mb/s and 11 Mb/s transmission rates, the faster clients are effectively throttled to 1 Mb/s as well. This happens because the 802.11 MAC protocol approximate “station fairness”, with each station given an equal chance to access the media. We provide a solution to provide “rate proportional fairness”, where the 11 Mb/s stations receive more bandwidth than the 1 Mb/s stations. Unlike previous solutions to this problem, our mechanism is easy to implement, works with common operating systems and requires no change to the MAC protocol or the stations. Joseph Dunn received an M.S. in computer science from the University of Colorado at Boulder in 2003, and B. S. in coputer science and mathematics from the University of Arizona in 2001. His research interests are in the general area of computer systems, primarily focusing on security and scalability in distributed systems. He is currently working on his Ph.D. in computer science from the University of Colorado at Boulder. Michael Neufeld received a Ph.D. in Computer Science from the University of Colorado at Boulder in December of 2004, having previously received an M.S. in Computer Science from the University of Colorado at Boulder in 2000 and an A.B. in Computer Science from Princeton University in 1993. His research interests are in the general area of computer system, specifically concentrating on wireless networking, software defind/cognitive radio, and streerable antennas. He is currently a postdoc in the Computer Science department at the University of Calorado at Boulder pursuing research related to software defined radio and new MAC protocols for steerable phase array antennas. 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. He has been co-leading the development of the MANTIS operating system. He has co-authored three papers include MAC layer protocol design, energy-efficient wireless communication, and adapting communications to mobility. Dirk Grunwald received his Ph.D. from the University of Illinois in 1989 and joined the University of Colorado the same year. His work addresses research and teaching in the broad area of “computer systems”, which includes computer architecture, operating systems, networks, and storage systems. His interests also include issues in pervasive computing, novel computing models, and enjoying the mountains. He is currently an Associate Professor in the Department of Computer Science and in Electrical and Computer Engineering and is also the Director of the Colorado Center for Information Storage. John Bennett is a Professor of Computer Science with a joint appointment in Electrical and Computer Engineering at the University of Colorado at Boulder. He also serves as Associate Dean for Education in the College of Engineering and Applied Science. He joined the CU-Boulder faculty in 2000, after serving on the faculty of Rice University for 11 years. While at Rice, Bennett pioneered a course in engineering design for both engineering and non-engineering students that has been emulated at several universities and high schools. In addition to other teaching awards, Bennett received the Keck Foundation National Award for Engineering Teaching Excellence for his work on this course. Bennett received his Ph.D. in 1988 from the University of Washington. Prior to completing his doctoral studies, he was a U.S. Naval Officer for several years and founded and served as President of Pacific Mountain Research, Inc., where he supervised the design and development of a number of commercial computing systems. Bennett's primary research interests are broadly focused in the area of distributed systems, and more narrowly in distributed information management and distributed robotic macrosensors.     

The effects of synchronization on topology-transparent scheduling

Topology-transparent scheduling is an attractive medium access control technique for mobile ad hoc networks (MANETs) and wireless sensor networks (WSNs). The transmission schedule for each node is fixed and guarantees a bounded delay independent of which nodes are its neighbours, as long as the active neighbourhood is not too dense. Most of the existing work on topology-transparent scheduling assumes that the nodes are synchronized on frame boundaries. Synchronization is a challenging problem in MANETs and in WSNs. Hence, we study the relationships among topology-transparent schedules, expected delay, and maximum delay, for successively weaker models of synchronization: frame-synchronized, slot-synchronized, and asynchronous transmission. For each synchronization model, we give constructive proofs of existence of topology-transparent schedules, and bound the least maximum delay. Perhaps surprisingly, the construction for the asynchronous model is a simple variant of the slot synchronized model. While it is foreseen that the maximum delay increases as the synchronization model is weakened, the bound is too pessimistic. The results on expected delay show that topology-transparent schedules are very robust to node density higher than the construction is designed to support, allowing the nodes to cope well with mobility, and irregularities of their deployment. Wensong Chu received his M.S. in Applied Mathematics from Shanghai Jiao Tong University, China, in 1993; received his M.S. in Computer Networks (Electrical Engineering) from the University of Southern California in 2000; received his Ph.D. in Mathematics from the University of Southern California in 2002. He was with the Department of Computer Science and Engineering at Arizona State University as a post-doctoral fellow from 2002 to 2003. Currently he is doing research at the CMS Bondedge in California. His research interests include sequence designs for communications, combinatorial coding methods, mobile ad hoc networks and sensor networks, financial engineering and combinatorial design theory. Charles J. Colbourn was born in Toronto, Canada in 1953. He completed his B.Sc. degree at the University of Toronto in 1976, M.Math. at the University of Waterloo in 1978, and Ph.D. at the University of Toronto in 1980, all in computer science. He has held faculty positions at the University of Saskatchewan, the University of Waterloo, and the University of Vermont, and is now Professor of Computer Science and Engineering at Arizona State University. He is co-editor of the CRC Handbook of Combinatorial Designs and author of Triple Systems and The Combinatorics of Network Reliability, both from Oxford University Press. He is editor-in-chief of the Journal of Combinatorial Designs. His research concerns applications of combinatorial designs in networking, computing, and communications. Violet R. Syrotiuk earned the Ph.D. degree in Computer Science from the University of Waterloo (Canada) in 1992. She joined Arizona State University in 2002 and is currently an Assistant Professor of Computer Science and Engineering. Dr. Syrotiuk’s research is currently supported by three grants from the National Science Foundation, and contracts from Los Alamos National Laboratory, and the Defence Science and Technology Organisation in Australia. She serves on the Editorial Board of Computer Networks, and on the Technical Program Committee of several major conferences including MobiCom and Infocom. Her research interests include mobile ad hoc and sensor networks, in particular MAC protocols with an emphasis on adaptation, topology-transparency, and energy efficiency, dynamic spectrum utilization, mobile network models, and protocol interaction and cross-layer design. She is a member of the ACM and the IEEE.     

Decentralized Utility-based Sensor Network Design

Wireless sensor networks consist of energy-constrained sensor nodes operating unattended in highly dynamic environments. In this paper, we advocate a systematic decentralized approach towards the design of such networks based on utility functions. A local utility function is defined for each sensor node in the network. While each sensor node “selfishly” optimizes its own utility, the network as a “whole” converges to a desired global objective. For the purpose of demonstrating our approach, we consider the following two separate case studies for data gathering in sensor networks: (a) construction of a load balanced tree and (b) construction of an energy balanced tree. Our work suggests a significant departure from the existing view of sensor networks as consisting of cooperative nodes, i.e. “selfish”sensor nodes is a useful paradigm for designing efficient distributed algorithms for these networks. Narayanan Sadagopan received the B.S. degree in computer science from the Regional Engineering College, Trichy, India, in 1998, and the M.S. degree in computer science from University of Southern California (USC), Los Angeles, in 2001. He is currently working toward the Ph.D. degree in the Computer Science Department, USC. His research is focused on theoretical aspects of wireless ad hoc and sensor networks. Mitali Singh received the BTech. degree in Computer Science and Engineering from the Indian Institute of Technology, New Delhi, India in 2000, and the M.S. degree in Computer Science from the University of Southern California, Los Angeles, USA. She is currently working towards the Ph.D. degree in Computer Science at the University of Southern California. Her research interests lie in the area of applied theory and networks. Presently, her work is focused on high level modeling and distributed algorithm design for wireless sensor systems. Bhaskar Krishnamachari received the B.E.E.E. degree from The Cooper Union for the Advancement of Science and Art, New York, in 1998, and the M.S.E.E. and Ph.D. degrees in electrical engineering from Cornell University, Ithaca, NY, in 1999 and 2002, respectively. He is now an Assistant Professor in the Department of Electrical Engineering, University of Southern California, Los Angeles, where he also holds a joint appointment in the Department of Computer Science. His current research is focused on the discovery of fundamental principles and the analysis and design of protocols for next-generation wireless sensor networks.     

Ant-Based Distributed Topology Control Algorithms for Mobile Ad hoc Networks

By adjusting the transmission power of mobile nodes, topology control aims to reduce wireless interference, reduce energy consumption, and increase effective network capacity, subject to connectivity constraints. In this paper, we introduce the Ant-Based Topology Control (ABTC) algorithm that adapts the biological metaphor of Swarm Intelligence to control topology of mobile ad hoc networks. ABTC is a distributed algorithm where each node asynchronously collects local information from nearby nodes, via sending and receiving ant packets, to determine its appropriate transmission power. The operations of ABTC do not require any geographical location, angle-of-arrival, topology, or routing information, and are scalable. In particular, ABTC attempts to minimize the maximum power used by any node in the network, or minimize the total power used by all of the nodes in the network. By adapting swarm intelligence as an adaptive search mechanism, ABTC converges quickly to a good power assignment with respect to minimization objectives, and adapts well to mobility. In addition, ABTC may achieve common power, or properly assign power to nodes with non-uniform distribution. Results from a thorough comparative simulation study demonstrate the effectiveness of ABTC for different mobility speed, various density, and diverse node distributions.This work is supported in part by National Science Foundation under grant ANI-0240398.Chien-Chung Shen received his B.S. and M.S. degrees from National Chiao Tung University, Taiwan, and his Ph.D. degree from UCLA, all in computer science. He was a research scientist at Bellcore Applied Research working on control and management of broadband networks. He is now an assistant professor in the Department of Computer and Information Sciences of the University of Delaware, and a recipient of NSF CAREER Award. His research interests include ad hoc and sensor networks, control and management of broadband networks, distributed object and peer-to-peer computing, and simulation.Zhuochuan Huang received his B.E. degree in Computer Science and Technology from Tsinghua University, P.R. China, in 1998, and his M.S. degree in Computer Science from University of Delaware in 2000. He is currently a PhD candidate with the Department of Computer and Information Sciences at the University of Delaware. His current research interests include the design and simulation of protocols for mobile ad hoc networks.Chaiporn Jaikaeo received his B.Eng degree in computer engineering from Kasetsart University, Thailand, and his M.S. and Ph.D. degrees in computer and information sciences from the University of Delaware in 1996, 1999 and 2004, respectively. He is currently a lecturer in the Department of Computer Engineering at Kasetsart University. His research interests include unicast and multicast routing, topology control, peer-to-peer computing and network management for mobile wireless ad hoc and sensor networks.     

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.     

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.     

Localized Construction of Bounded Degree and Planar Spanner for Wireless Ad Hoc Networks

We propose a novel localized algorithm that constructs a bounded degree and planar spanner for wireless ad hoc networks modeled by unit disk graph (UDG). Every node only has to know its 2-hop neighbors to find the edges in this new structure. Our method applies the Yao structure on the local Delaunay graph [1] in an ordering that are computed locally. This new structure has the following attractive properties: (1) it is a planar graph; (2) its node degree is bounded from above by a positive constant ; (3) it is a t-spanner (given any two nodes u and v, there is a path connecting them in the structure such that its length is no more than · C_del times of the shortest path in the unit disk graph); (4) it can be constructed locally and is easy to maintain when the nodes move around; (5) moreover, we show that the total communication cost is O(n log n) bits, where n is the number of wireless nodes, and the computation cost of each node is at most O(d log d), where d is its 2-hop neighbors in the original unit disk graph. Here C_del is the spanning ratio of the Delaunay triangulation, which is at most . And the adjustable parameter α satisfies 0 < α ≤ π/3. Yu Wang is an assistant professor in the Department of Computer Science, University of North Carolina at Charlotte. He received his Ph.D. degree in computer science from Illinois Institute of Technology in 2004, his B.S. degree and M.S. degree in computer science from Tsinghua University, China, in 1998 and 2000. His current research interests include computer networks, wireless networks, mobile computing, algorithm design, and artificial intelligence. His recent work focuses on designing power efficient algorithms for wireless ad hoc networks and sensor networks. He published more than 40 papers in peer-reviewed journals and conferences. He served as program committee member for sevaral conferences (such as IEEE INFOCOM, IEEE MASS, IEEE ICCCN, etc.). He also served as reviewers for a number of international journals and conferences. His paper titled "Sparse Power Efficient Topology for Wireless Networks" won a Best Paper Award from the 35th IEEE Hawaii International Conference on System Sciences in 2002. He is a member of the ACM, IEEE, and IEEE Communication Society. For more information, please see http://www.cs.uncc.edu/~ywang32. Xiang-Yang Li has been an Assistant Professor of Computer Science at the Illinois Institute of Technology since 2000. He received M.S. (2000) and Ph.D. (2001) degree at Department of Computer Science from University of Illinois at Urbana-Champaign. He received his Bachelor degree at Department of Computer Science and Bachelor degree at Department of Business Management from Tsinghua University, P.R. China in 1995. He is a member of the Chinese national team prepared for the International Mathematics Olympics (IMO) from 1988 to 1990. His research interests span the wireless ad hoc networks, game theory, computational geometry, and cryptography and network security. Recently, he focuses on performing research on the cooperation, energy efficiency, and distributed algorithms for wireless ad hoc and sensor networks. He has published about 60 conference papers in top-quality conferences such as ACM MobiCom, ACM MobiHoc, ACM SODA, ACM STOC, IEEE INFOCOM, etc. He has more than 30 journal papers published or accepted for publish. He is a Member of the ACM, IEEE, and IEEE Communication Society. Xiang Yang Liserved various positions (such as conference chair, local arrangement chair, financial chair, session chair, TPC member) at a number of international conferences such as IEEE INFOCOM, ACM MobiHoc, ACM STOC. Li recently also co-organized a special issue of ACM MONET on non-cooperative computing in wireless networks. For more information, please see http://www.cs.iit.edu/~xli.     

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.     

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.