Energy-efficient scheduling with individual packet delay constraints over a fading channel

This article focuses on energy-efficient packet transmission with individual packet delay constraints over a fading channel. The problem of optimal offline scheduling (vis-à-vis total transmission energy), assuming information of all packet arrivals and channel states before scheduling, is formulated as a convex optimization problem with linear constraints. The optimality conditions are analyzed. From the analysis, a recursive algorithm is developed to search for the optimal offline scheduling. The optimal offline scheduler tries to equalize the energy-rate derivative function as much as possible subject to causality and delay constraints, in contrast to the equalization of transmission rates for optimal scheduling in static channels. It is shown that the optimal offline schedulers for fading and static channels have a similar symmetry property. Combining the symmetry property with potential idling periods, upper and lower bounds on the average packet delay are derived. The properties of the optimal offline schedule and the impact of packet sizes, individual delay constraints, and channel variations are demonstrated via simulations. A heuristic online scheduling algorithm, assuming causal traffic and channel information, is proposed and shown via simulations to achieve energy and delay performances comparable to those of the optimal offline scheduler in a wide range of scenarios.

Michael J. NeelyEmail:

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Wanshi Chen   received the B.S. degree (with highest honors) from Southwest Jiaotong University, Chengdu, China, the M.S. degree from the Ohio State University, Columbus, and the Ph.D. degree from the University of Southern California, Los Angeles, respectively. From 2000 to 2006, he was with Ericsson working on CDMA2000 related research, implementation, and standard development. Since May 2006, he has been with Qualcomm, where he is involved in research and development of the long-term evolution of third-generation wireless standards. His research interests include topics in resource allocation, communication theory, cooperative transmissions, and wireless networking. Urbashi Mitra   received the B.S. and the M.S. degrees from the University of California at Berkeley in 1987 and 1989 respectively, both in Electrical Engineering and Computer Science. From 1989 until 1990 she worked as a Member of Technical Staff at Bellcore in Red Bank, NJ. In 1994, she received her Ph.D. from Princeton University in Electrical Engineering. From 1994 to 2000, Dr. Mitra was a member of the faculty of the Department of Electrical Engineering at The Ohio State University, Columbus, Ohio. In 2001, she joined the Department of Electrical Engineering at the University of Southern California, Los Angeles, where she is currently a Professor. Dr. Mitra is currently an Associate Editor for the IEEE Transactions on Information Theory and the Journal of Oceanic Engineering. She was an Associate Editor for the IEEE Transactions on Communications from 1996 to 2001. Dr. Mitra is serving a second term as a member of the IEEE Information Theory Society’s Board of Governors. She is the recipient of: IEEE Fellow (2007), Texas Instruments Visiting Professor (Fall 2002, Rice University), 2001 Okawa Foundation Award, 2000 Lumley Award for Research (OSU College of Engineering), 1997 MacQuigg Award for Teaching (OSU College of Engineering), 1996 National Science Foundation (NSF) CAREER Award, 1994 NSF International Post-doctoral Fellowship, 1998 Lockheed Leadership Fellowship, 1987 California Microelectronics Fellowship. She has co-chaired the IEEE Communication Theory Symposium at ICC 2003 in Anchorage, AK and the first ACM Workshop on Underwater Networks at Mobicom 2006, Los Angeles, CA. Dr. Mitra was the tutorials Chair for IEEE ISIT 2007 in Nice, France and is currently the Finance Chair for IEEE ICASSP 2008 in Las Vegas, NV. She has held visiting appointments at: the Eurecom Institute, Rice University and Stanford University. Dr. Mitra is currently co-Director of the Communication Sciences Institute at the University of Southern California. Michael J. Neely   received B.S. degree in both Electrical Engineering and Mathematics from the University of Maryland, College Park, in 1997. He was then awarded a 3 year Department of Defense NDSEG Fellowship for graduate study at the Massachusetts Institute of Technology, where he received an M.S. degree in 1999 and a Ph.D. in 2003, both in Electrical Engineering. In 2004 he joined the faculty of the Electrical Engineering department at the University of Southern California, where he is currently an Assistant Professor. His research is in the area of stochastic network optimization for satellite and wireless networks, mobile ad-hoc networks, and queueing systems.