Improving IEEE 802.11 power saving mechanism

This paper presents an optimization of the power saving mechanism in the Distributed Coordination Function (DCF) in an Independent Basic Service Set (IBSS) of the IEEE 802.11 standard. In the power saving mode specified for DCF, time is divided into so-called beacon intervals. At the start of each beacon interval, each node in the power saving mode periodically wakes up for a duration called the ATIM Window. Nodes are required to be synchronized to ensure that all nodes wake up at the same time. During the ATIM window, the nodes exchange control packets to determine whether they need to stay awake for the rest of the beacon interval. The size of the ATIM window has a significant impact on energy saving and throughput achieved by the nodes. This paper proposes an adaptive mechanism to dynamically choose a suitable ATIM window size. We also allow the nodes to stay awake for only a fraction of the beacon interval following the ATIM window. On the other hand, the IEEE 802.11 DCF mode requires nodes to stay awake either for the entire beacon interval following the ATIM window or not at all. Simulation results show that the proposed approach outperforms the IEEE 802.11 power saving mechanism in terms of throughput and the amount of energy consumed. This research is supported in part by National Science Foundation grant 01-25859. Eun-Sun Jung received a Ph.D. degree in Computer Science from Texas A&M University, USA, an M.S. degree in Information Security from University of London, UK, and a B.S degree in Computer Science and Statistics from Dankook University, Seoul, Korea. From 1995 to 1996 she was a member of technical staff in Hanwha Corporation, Seoul, Korea. In 1999, she was employed by Korea Information Security Agency as a research scientist. Since 2005, she has been with Samsung Advanced Institute of Technology, Korea, as a senior researcher. Her research interests include Wireless Networks, Mobile Computing, and Network Security. Nitin Vaidya received the Ph.D. 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, as well as a faculty position at the Texas A&M University. His current research is in wireless networking and mobile computing. He co-authored papers that received awards at the ACM MobiCom and Personal Wireless Communications (PWC) conferences. Nitin’s research has been funded by various agencies, including the National Science Foundation, DARPA, Motorola, Microsoft Research and Sun Microsystems. Nitin Vaidya is a recipient of a CAREER award from the National Science Foundation. Nitin has served on the committees of several conferences, including as program co-chair for 2003 ACM MobiCom and General Chair for 2001 ACM MobiHoc. He has served as an editor for several journals, and presently serves as the Editor-in-Chief for the IEEE Transactions on Mobile Computing. He is a senior member of the IEEE and a member of the ACM. For more information, please visit .     

A randomized energy-conservation protocol for resilient sensor networks*

In this paper we present PEAS, a randomized energy-conservation protocol that seeks to build resilient sensor networks in the presence of frequent, unexpected node failures. PEAS extends the network lifetime by maintaining a necessary set of working nodes and turning off redundant ones, which wake up after randomized sleeping times and replace failed ones when needed. The fully localized operations of PEAS are based on each individual node's observation of its local environment but do not require per neighbor state at any node; this allows PEAS to scale to very dense node deployment. PEAS is highly robust against node failures due to its simple operations and randomized design; it also ensures asymptotic connectivity. Our simulations and analysis show that PEAS can maintain an adequate working node density in presence of as high as 38% node failures, and a roughly constant overhead of less than 1% of the total energy consumption under various deployment densities. It extends a sensor network's functioning time in linear proportional to the deployed sensor population. Fan Ye received his B.E. in Automatic Control in 1996 and M.S. in Computer Science in 1999, both from Tsinghua University, Beijing, China. He received his Ph.D. in Computer Science in 2004 from UCLA. He is currently with IBM Research. His research interests are in wireless networks, sensor networks and security. Honghai Zhang received his BS in Computer Science in 1998 from University of Science and Technology of China. He received his MS and Ph.D. in Computer Science from University of Illinois at Urbana-Champaign. He is currently with the Wireless Advanced Technology Lab of Lucent Technologies. His research interests are wireless networks, WiMAX, and VoIP over wireless networks. Songwu Lu received both his M.S. and Ph.D. from University of Illinois at Urbana-Champaign. He is currently an associate 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 UCLA’s 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. Jennifer C. Hou received the Ph.D. degree in Electrical Engineering and Computer Science from The University of Michigan, Ann Arbor in 1993 and is currently a professor in the Department of Computer Science at University of Illinois at Urbana Champaign (UIUC). Prior to joining UIUC, she has taught at Ohio State University and University of Wisconsin - Madison. Dr. Hou has worked in the the areas of network modeling and simualtion, wireless-enabled software infrastructure for assisted living, and capacity optimization in wireless networks. She was a recipient of an ACM Recognition of Service, a Cisco University Research Award, a Lumley Research Award from Ohio State University, and a NSF CAREER award. ^*A Shorter version of this paper appeared in ICDCS 2003.     

MAC Layer Admission Control and Priority Re-allocation for Handling QoS Guarantees in Non-cooperative Wireless LANs

Providing QoS guarantee with appropriate service differentiation in IEEE 802.11 wireless LANs is quite desirable. However, users may be selfish and thus rigorously try to maximize their performance by demanding high services even though the network has already saturated. On the other hand, user misbehaviors such as misuse of priority and over-rate transmission pose further harm to performance of existing flows. These application layer non-cooperation makes successful resource allocation very challenging with existing contention based CSMA/CA channel access. In this paper, we propose a MAC layer coordinated QoS framework of admission control and priority re-allocation for quality of services of real-time applications in wireless LANs. Our focus is on priority based MAC schedulers where each user can set its flow priority in order to receive appropriate level of services. With channel condition information such as available bandwidth and mean delay exchanged among neighboring stations, users can enforce admission control based on the perceived channel status and may re-allocate their priorities to accommodate existing flows as desired. User misbehaviors are identified by estimating the flow transmitting rate and matching priority setting, or even punished by assigning appropriate low priorities. Extensive simulations results show that the proposed framework can effectively coordinate wireless users on keeping reserved transmission rate, using appropriate MAC priority, and allocating sufficient resource. Ming Li received his B.S. and M.S. in Engineering from Shanghai Jiao Tong University, China, in 1995 and 1998, respectively. He is currently a Ph.D. candidate in department of Computer Science, University of Texas at Dallas, where he received M.S. degree in Computer Science in Dec. 2001. His research interest includes QoS schemes for mobile ad-hoc networks and multimedia over wireless networks. B. Prabhakaran is with the faculty of Computer Science Department, University of Texas at Dallas. He has been working in the area of multimedia systems: animation & multimedia databases, authoring & presentation, resource management, and scalable web-based multimedia presentation servers. Dr. Prabhakaran received the prestigious National Science Foundation (NSF) CAREER Award in 2003 for his proposal on Animation Databases. He has published several research papers in various refereed conferences and journals in this area. He has served as guest-editor (special issue on Multimedia Authoring and Presentation) for ACM Multimedia Systems journal. He is also serving on the editorial board of Multimedia Tools and Applications journal, Kluwer Academic Publishers. He has also served as program committee member on several multimedia conferences and workshops. B. Prabhakaran has served as a visiting research faculty with the Department of Computer Science, University of Maryland, College Park. He also served as a faculty in the Department of Computer Science, National University of Singapore as well as in the Indian Institute of Technology, Madras, India.     

End-to-end QoS framework for heterogeneous wired-cum-wireless networks

With information access becoming more and more ubiquitous, there is a need for providing QoS support for communication that spans wired and wireless networks. For the wired side, RSVP/SBM has been widely accepted as a flow reservation scheme in IEEE 802 style LANs. Thus, it would be desirable to investigate the integration of RSVP and a flow reservation scheme in wireless LANs, as an end-to-end solution for QoS guarantee in wired-cum-wireless networks. For this purpose, we propose WRESV, a lightweight RSVP-like flow reservation and admission control scheme for IEEE 802.11 wireless LANs. Using WRESV, wired/wireless integration can be easily implemented by cross-layer interaction at the Access Point. Main components of the integration are RSVP-WRESV parameter mapping and the initiation of new reservation messages, depending on where senders/receivers are located. In addition, to support smooth roaming of mobile users among different basic service sets (BSS), we devise an efficient handoff scheme that considers both the flow rate demand and network resource availability for continuous QoS support. Furthermore, various optimizations for supporting multicast session and QoS re-negotiation are proposed for better performance improvement. Extensive simulation results show that the proposed scheme is promising in enriching the QoS support of multimedia applications in heterogeneous wired-cum-wireless networks. Ming Li received his B.S. and M.S. in Engineering from Shanghai Jiao Tong University, China, in 1995 and 1998, respectively. He is currently a Ph.D. candidate in department of Computer Science, University of Texas at Dallas, where he received M.S. degree in Computer Science in Dec. 2001. His research interest includes QoSschemes for mobile ad-hoc networks and multimedia over wireless networks. Hua Zhu received the Ph.D. degree in Electrical Engineering from the University of Texas at Dallas, Texas. Since 2005, he has been working for San Diego Research Center, Inc., San Diego, CA, as a Research Engineer. His research interests include all layers of wireless communication systems. His particular interest is in L2/3 air interface design, performance analysis, and optimization for ad hoc and sensor networks. Imrich Chlamtac is the President of CREATE-NET and the Bruno Kessler Professor at the University of Trento, Italy. He has held various honorary and chaired professorships in USA and Europe including the Distinguished Chair in Telecommunications Professorship at the University of Texas at Dallas, Sackler Professroship at Tel Aviv University and has been on faculty at Technion, and UMass. Dr. Imrich Chlamtac has made significant contribution to various networking technologies as scientist, educator and entrepreneur. Dr. Chlamtac is the recipient of multiple awards and recognitions including Fellow of the IEEE, Fellow of the ACM, Fulbright Scholar, the ACM Award for Outstanding Contributions to Research on Mobility and the IEEE Award for Outstanding Technical Contributions to Wireless Personal Communications. Dr. Chlamtac published over three hundred and fifty refereed journal, book, and conference articles and is the co-author of four books. Dr. Chlamtac has widely contributed to the scientific community as founder and Chair of ACM Sigmobile, founder and steering committee chair of some of the lead conferences in networking including Mobicom, OptiComm, Mobiquitous, Broadnets, Securecomm. Dr. Chlamtac also serves as the founding Editor in Chief of the ACM/URSI/Springer Wireless Networks (WINET), the ACM/Springer Journal on Special Topics in Mobile Networks and Applications (MONET). B. Prahbakaran is with the faculty of Computer Science Department, University of Texas at Dallas. He has been working in the area of multimedia systems: animation & multimedia databases, authoring & presentation, resource management, and scalable web-based multimedia presentation servers. Dr. Prabhakaran received the prestigious National Science Foundation (NSF) CAREER Award in 2003 for his proposal on Animation Databases. He has published several research papers in various refereed conferences and journals in this area. He has served as guest-editor (special issue on Multimedia Authoring and Presentation) for ACM Multimedia Systems journal. He is also serving on the editorial board of Multimedia Tools and Applications journal, Kluwer Academic Publishers. He has also served as program committee member on several multimedia conferences and workshops. B. Prabhakaran has served as a visiting research faculty with the Department of Computer Science, University of Maryland, College Park. He also served as a faculty in the Department of Computer Science, National University of Singapore as well as in the Indian Institute of Technology, Madras, India.     

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.     

Scalable Multiple Channel Scheduling with Optimal Utility in Wireless Local Area Networks

This paper studies scheduling algorithms for an infra-structure based wireless local area network with multiple simultaneous transmission channels. A reservation-based medium access control protocol is assumed where the base station (BS) allocates transmission slots to the system mobile stations based on their requests. Each station is assumed to have a tunable transmitter and tunable receiver. For this network architecture, the scheduling algorithms can be classified into two categories: contiguous and non-contiguous, depending on whether slots are allocated contiguously to the mobile stations. The main objective of the scheduling algorithms is to achieve high channel utility while having low time complexity. In this paper, we propose three scheduling algorithms termed contiguous sorted sequential allocation (CSSA), non-contiguous round robin allocation (NCRRA) and non-contiguous sorted round robin allocation (NCSRRA). Among these, CSSA schedules each station in contiguous mode, while other two algorithms, NCRRA and NCSRRA, schedule stations in non-contiguous mode. Through extensive analysis and simulation, the results demonstrate that the CSSA with only slightly increased complexity can achieve much higher channel utility when compared to the existing contiguous scheduling algorithms. The NCRRA and NCSRRA on the other hand, results in significantly lower complexity, while still achieving the optimal channel utility compared to existing non-contiguous scheduling algorithms. Chonggang Wang received a B.Sc. (honors) degree from Northwestern Polytechnic University, Xi'an, China, in 1996, and M.S. and Ph. D. degrees in communication and information system from University of Electrical Science and Technology in China, Chengdu, China, and Beijing University of Posts and Telecommunications, Beijing, China, in 1999 and 2002, respectively. From September 2002 to November 2003 he has been with the Hong Kong University of Science and Technology, Hong Kong, where he is an associate researcher in the Department of Computer Science. He is now a post-doctoral research fellow in University of Arkansas, Arkansas. His current research interests are in wireless networks with QoS guarantee, sensor networks, peer-to-peer and overlay networks. Bo Li received the B.S. (summa cum laude) and M.S. degrees in the Computer Science from Tsinghua University, Beijing, P. R. China, in 1987 and 1989, respectively, and the Ph.D. degree in the Electrical and Computer Engineering from University of Massachusetts at Amherst in 1993. Between 1994 and 1996, he worked on high performance routers and ATM switches in IBM Networking System Division, Research Triangle Park, North Carolina. Since January 1996, he has been with Computer Science Department, the Hong Kong University of Science and Technology, where he is an associated professor and co-director for the ATM/IP cooperate research center, a government sponsored research center. Since 1999, he has also held an adjunct researcher position at the Microsoft Research Asia (MSRA), Beijing, China. His current research interests include wireless mobile networking supporting multimedia, video multicast and all optical networks using WDM, in which he has published over 150 technical papers in referred journals and conference proceedings. He has been an editor or a guest editor for 16 journals, and involved in the organization of about 40 conferences. He was the Co-TPC Chair for IEEE Infocom'2004. He is a member of ACM and a senior member of IEEE. Krishna M. Sivalingam (ACM ‘93) is an Associate Professor in the Dept. of CSEE at University of Maryland, Baltimore County. Previously, he was with the School of EECS at Washington State University, Pullman from 1997 until 2002; and with the University of North Carolina Greensboro from 1994 until 1997. He has also conducted research at Lucent Technologies' Bell Labs in Murray Hill, NJ, and at AT&T Labs in Whippany, NJ. He received his M.S. and Ph.D. degrees in Computer Science from State University of New York at Buffalo in 1990 and 1994 respectively; and his B.E. degree in Computer Science and Engineering in 1988 from Anna University, Chennai (Madras), India. While at SUNY Buffalo, he was a Presidential Fellow from 1988 to 1991. His research interests include wireless networks, optical wavelength division multiplexed networks, and performance evaluation. He holds three patents in wireless networks and has published several research articles including more than twenty-five journal publications. He has published an edited book on Wireless Sensor Networks in 2004 and on optical networks in 2000 and in 2004. He is a member of the Editorial Board for ACM Wireless Networks Journal, IEEE Transactions on Mobile Computing, and KICS Journal of Computer Networks. He has served as a Guest Co-Editor for special issues of ACM MONET on “Wireless Sensor Networks” in 2003 and 2004 and an issue of IEEE Journal on Selected Areas in Communications on optical WDM networks (2000). He is co-recipient of the Best Paper Award at the IEEE International Conference on Networks 2000 held in Singapore. His work has been supported by several sources including AFOSR, NSF, Cisco, Intel and Laboratory for Telecommunication Sciences. He is a member of the Editorial Board for ACM Wireless Networks Journal, IEEE Transactions on Mobile Computing, and KICS Journal of Computer Networks. He is serving as Technical Program Co-Chair for the First IEEE Conference on Sensor Communications and Networking to be held in Santa Clara, CA in 2004. He has served as General Co-Chair for SPIE Opticomm 2003 (Dallas, TX) and for ACM Intl. Workshop on Wireless Sensor Networks and Applications (WSNA) 2003 held on conjunction with ACM MobiCom 2003 at San Diego, CA. He served as Technical Program Co-Chair of SPIE/IEEE/ACM OptiComm conference at Boston, MA in July 2002; and as Workshop Co-Chair for WSNA 2002 held in conjunction with ACM MobiCom 2002 at Atlanta, GA in Sep 2002. He is a Senior Member of IEEE and a member of ACM. Kazem Sohraby received the BS, MS and PhD degrees in electrical engineering and the MBA from the Wharton School, University of Pennsylvania, Philadephia. He is a Professor of the Electrical Engineering Department, College of Engineering, University of Arkansas, Fayetteville. Prior to that, he was with Bell Laboratories, Holmdel, NJ. His areas of interest include computer networking, signaling, switching, performance analysis, and traffic theory. He has over 20 applications and granted patents on computer protocols, wireless and optical systems, circuit and packet switching, and on optical Internet. He has several publications, including a book on The Performance and Control of Computer Communications Networks (Boston, MA: 1995). Dr Sohraby is a Distinguished Lecturer of the IEEE Communications Society, and serves as its President's representative on the Committee on Communications and Information Policy (CCIP). He served on the Education Committee of the IEEE Communications Society, is on the Editorial Boards of several publications, and served as Reviewer and Panelist with the National Science Foundation, the US Army and the Natural Sciences and Engineering Research Council of Canada.     

Real-time traffic support in heterogeneous mobile networks

Multi-hop mobile wireless networks have been proposed for a variety of applications where support for real-time multimedia services will be necessary. Support for these applications requires that the network is able to offer quality of service (QoS) appropriate for the latency and jitter bounds of the real-time application constraints. In this paper, we analyze the primary challenges of realizing QoS in mobile wireless networks with heterogeneous devices and propose a QoS framework for real-time traffic support. We address the problem in three ways: estimate the path quality for real-time flows, mitigate the impact of node heterogeneity on service performance, and reduce the impact of interfering non-real-time traffic. Specifically, our proposed QoS framework first utilizes a call setup protocol at the IP layer to discover paths for real-time flows, as well as to perform admission control by accurate service quality prediction. The underlying routing protocol also enables transparent path selection among heterogeneous nodes to provide stable paths for real-time traffic delivery. We then use a prioritized MAC protocol to provide priority access for flows with real-time constraints to reduce interference from unregulated non-real-time traffic. We foresee the utility of our proposed solution in heterogeneous mobile networks, such as campus or community-wide wireless networks. In these environments, resource-rich or fixed wireless routers may be leveraged to achieve better service quality when heterogeneity of node capability and movement is significant. Through experimental results, we demonstrate the utility and efficiency of our approach. Yuan Sun received her Ph.D. from the Department of Computer Science at the University of California, Santa Barbara in 2005. She worked with Prof. Elizabeth Belding-Royer in the MOMENT Lab. Her thesis work focused on providing QoS for mobile networks. Dr. Sun is currently employed at Google. Elizabeth M. Belding-Royer is an Associate Professor in the Department of Computer Science at the University of California, Santa Barbara. Elizabeth’s research focuses on mobile networking, specifically ad hoc and mesh networks, multimedia, monitoring, and advanced service support. She is the founder of the Mobility Management and Networking (MOMENT) Laboratory (moment.cs.ucsb.edu) at UCSB. Elizabeth is the author of over 50 papers related to mobile networking and has served on over 40 program committees for networking conferences. Elizabeth served as the TPC Co-Chair of ACM MobiCom 2005 and IEEE SECON 2005, and is currently on the editorial board for the IEEE Transactions on Mobile Computing. Elizabeth is the recipient of an NSF CAREER award, and a 2002 Technology Review 100 award, awarded to the world’s top young investigators. See ebelding for further details. Xia Gao is currently a Staff Engineer at Ubicom. He received his Ph.D of ECE from the University of Illinois at Urbana-Champaign in 2001. Before joining Ubicom, he had worked in DoCoMo Communications Laboratory for 4 years where he conducted research on 3G-4G wireless communication system and handset technologies and WiFi systems. He has published more than 30 conference and journal papers. He has chaired several International conferences and served as TPC members for many others. He is a member of IEEE and a honored member of Sigma Xi. James Kempf is a Research Fellow at DoCoMo USA Laboratories. He holds a Ph.D. from the University of Arizona, Tucson, AZ. Previously, James worked at Sun Microsystems for 13 years, and contributed to numerous research projects involving wireless networking, mobile computing, and service discovery. James is a former member of the Internet Architecture Board, and co-chaired the SEND and Seamoby IETF Working Groups. James continues to be an active contributor to Internet standards in the areas of security and mobility for next generation, Internet protocol-based mobile systems.     

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.     

Location-aware resource management in mobile ad hoc networks

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

A Performance Evaluation of a Novel Energy-Aware Data-Centric Routing Algorithm in Wireless Sensor Networks

In this paper, we present a novel Energy-Aware Data-Centric Routing algorithm for wireless sensor networks, which we refer to as EAD. We discuss the algorithm and its implementation, and report on the performance results of several workloads using the network simulator ns-2. EAD represents an efficient energy-aware distributed protocol to build a rooted broadcast tree with many leaves, and facilitate the data-centric routing in wireless micro sensor networks. The idea is to turn off the radios of all leaf nodes and let the non-leaf nodes be in charge of data aggregation and relaying tasks. The main contribution of this protocol is the introduction of a novel approach based on a low cost backbone provisioning within a wireless sensor network in order to turn off the non backbone nodes and save energy without compromising the connectivity of the network, and thereby extending the network lifetime. EAD makes no assumption on the network topology, and it is based on a residual power. We present an extensive simulation experiments to evaluate the performance of our EAD forwarding-to-parent routing scheme over a tree created by a single EAD execution, and compare it with the routing scheme over a regular Ad hoc On-Demand Distance Vector (AODV) Protocol. Last but not least, we evaluate the performance of our proposed EAD algorithm and compare it to the Low-Energy Adaptive Clustering Hierarchy (LEACH) protocol, a cluster-based, energy-aware routing protocol specifically designed for sensor networks. Our results indicate clearly that EAD outperforms AODV and LEACH in energy conservation, throughput, and network lifetime extension.Dr. A. Boukerche was partially supported by NSERC, Canada Research Program, Canada Foundation for Innovation, and Ontario Innovation Funds/Ontario Distinguished Research Award.Azzedine Boukerche is a Full Professor and holds a Canada Research Chair Position at the University of Ottawa. He is also the Founding Director of PARADISE Research Laboratory at Ottawa U. Prior to this, he hold a faculty position at the University of North Texas, USA, and he was working as a Senior Scientist at the Simulation Sciences Division, Metron Corporation located in San Diego. He was also employed as a Faculty at the School of Computer Science McGill University, and taught at Polytechnic of Montreal. He spent a year at the JPL-California Institute of Technology where he contributed to a project centered about the specification and verification of the software used to control interplanetary spacecraft operated by JPL/NASA Laboratory.His current research interests include wireless networks, mobile and pervasive computing, wireless multimedia, QoS service provisioning, wireless ad hoc and sensor networks, distributed systems, distributed computing, large-scale distributed interactive simulation, and performance modeling. Dr. Boukerche has published several research papers in these areas. He was the recipient of the best research paper award at PADS’97, and the recipient of the 3rd National Award for Telecommunication Software 1999 for his work on a distributed security systems on mobile phone operations, and has been nominated for the best paper award at the IEEE/ACM PADS’99, and at ACM MSWiM 2001. Dr. A. Boukerche serves as an Associate Editor and on the editorial board for ACM/Springer Wireless Networks, the Journal of Parallel and Distributed Computing, The Wiley Journal of Wireless Communication and Mobile Computing. He served as a Founding and General Chair of the first Int’l Conference on Quality of Service for Wireless/Wired Heterogeneous Networks (QShine 2004), ACM/IEEE MASCOST 1998, IEEE DS-RT 1999-2000, ACM MSWiM 2000; Program Chair for ACM/IFIPS Europar 2002, IEEE/SCS Annual Simulation Symposium ANNS 2002, ACM WWW’02, IEEE/ACM MASCOTS 2002, IEEE Wireless Local Networks WLN 03-04; IEEE WMAN 04-05, ACM MSWiM 98–99, and TPC member of numerous IEEE and ACM conferences. He served as a Guest Editor for JPDC, and ACM/kluwer Wireless Networks and ACM/Kluwer Mobile Networks Applications, and the Journal of Wireless Communication and Mobile Computing.Dr. Boukerche serves as a Steering Committee Chair for ACM MSWiM, IEEE DS-RT, and ACM PE-WASUN Conferences.Xiuzhen Cheng is an Assistant Professor in the Department of Computer Science at the George Washington University. She received her MS and Ph.D. degrees in Computer Science from University of Minnesota—Twin Cities in 2000 and 2002, respectively. Her current research interests include localization, data aggregation services, and data storage in sensor networks, routing in mobile ad hoc networks, and approximation algorithm design and analysis. She is a member of the ACM and IEEE.Joseph Linus has recently graduated with a MSc Degree from the Department of Computer Sciences, University of North Texas. His current research interests include wireless sensors networks, and mobile ad hoc networks.