Fundamental Limits on Wide Bandwidth Signal Acquisition (A Convexity and Optimization Perspective)

SPEAKER: Professor Moe Z. Win, MITABSTRACT: Signal acquisition is a challenging task in wide bandwidth transmission systems. The problem involves searching for a location of sequence-phase within a required accuracy, which is inversely proportional to the transmission bandwidth. To address this, we propose a search technique that takes advantage of multipath, which has long been regarded as deleterious for efficient communication, to aid the sequence acquisition in dense multipath channels. Using optimization and convexity theories, we determine the fundamental limits of achievable mean acquisition times (MATs) for a class of serial-search strategies. In particular, we derive both the minimum and maximum MATs and the conditions for achieving these limits. We prove that a fixed-step serial search, a form of non-consecutive serial search, achieves the near-optimal MAT. Our results also show that the conventional serial search, in which consecutive cells are tested serially, should be avoided since it results in the maximum MAT. We also consider a randomized search strategy and show that the corresponding MAT is at most two times the MAT of the optimal serial search. These results are valid for all signal-to-noise ratio values, regardless of the specifics of the detection layer and the fading distributions.Joint work with Watcharapan Suwansantisuk.Bio: Moe Win is an Associate Professor at the Laboratory for Information & Decision Systems (LIDS), Massachusetts Institute of Technology (MIT). Prior to joining MIT, he spent 5 years at AT&T Research Laboratories and 7 years at the Jet Propulsion Laboratory. As a Presidential Fellow at USC, he received both an M.S. degree in Applied Mathematics and the Ph.D. degree in Electrical Engineering in 1998. His main research interests are the application of mathematical and statistical theories to communication, detection, and estimation problems. Specific current research topics include measurement and modeling of time-varying channels, design and analysis of multiple antenna systems, ultra-wide bandwidth (UWB) communications systems, optical communications systems, and space communications systems.Dr. Win has been involved actively in organizing and chairing a number of international conferences. He is the current chair and past secretary (2002-2004) for the Radio Communications Committee of the IEEE Communications Society. He served as Area Editor (2003-2006) for Modulation and Signal Design and Editor (1998-2006), both for the IEEE TRANSACTIONS ON COMMUNICATIONS. He was Guest-Editor for the 2002 IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS (Special Issue on Ultra-Wideband Radio in Multiaccess Wireless Communications). He received the IEEE Antennas and Propagation Society Sergei A. Schelkunoff Transactions Prize Paper Award in 2003. In 2004, he received the Fulbright Fellowship, the Institute of Advanced Study Natural Sciences and Technology Fellowship, and the Presidential Early Career Award for Scientists and Engineers from the White House. In 2006 he was co-recipient (jointly with Professor Robert A. Scholtz) of the Eric E. Sumner Award, an IEEE Technical Field Award, "for pioneering contributions to ultra-wide band communications science and technology." Professor Win is an IEEE Distinguished Lecturer and elected Fellow of the IEEE, cited "for contributions to wideband wireless transmission."Host: Prof. Robert Scholtz, scholtz@usc.edu

Location: Frank R. Seaver Science Center (SSC) - 319

Audiences: Everyone Is Invited

Contact: Mayumi Thrasher