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.