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Next Generation Dynamic Spectrum Networks

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Today’s static spectrum assignment policy has led to a critical spectrum shortage. While innovative wireless networks such as WiMAX are denied from spectrum access, the majority of existing networks use only 10-15% of their assigned spectrum. To reuse “wasted” spectrum, the recent proposal on dynamic spectrum access allows unlicensed (secondary) users to sense the presence of legacy licensed spectrum holders (primary users such as TV broadcasts) and opportunistically utilize unused licensed spectrum on a non-interfering basis. This “creates” new capacity and commercial value from existing under-utilized spectrum.

While it shows great promise, the technology nderlying dynamic spectrum systems is still in its infancy. Issues in wireless communications and networking, once addressed in the context of fixed spectrum assignment, offer new research challenges in the realm of dynamic spectrum systems. In this talk, we describe some initial studies on dynamic spectrum systems. We begin by describing spectrum heterogeneity, a result of the dual-user nature of these systems that drastically complicates spectrum management. We then present three algorithms for secondary users to access spectrum fairly and efficiently. Specifically, we introduce (1) a centralized graph coloring approach that optimizes spectrum allocation for a static topology, (2) a distributed coordination approach where devices use local bargaining to adapt spectrum assignment over topology variations, and (3) a light-weight rule-based distributed solution that requires minimum coordination. We conclude by summarizing this work in context, and discussing current and future directions in combining these results with higher layer mechanisms to produce an end-to-end programmable and adaptive network.

Speaker Bio: Since August 2005, Heather Zheng has been an assistant professor at Department of Computer Science, University of California, Santa Barbara. Her research area includes wireless networking and communications, and multimedia computing. She currently focuses on Cognitive Radios and dynamic spectrum networks. Her research on Cognitive Radios was selected as one of the 10 Emerging Technologies of 2006 by MIT Technology Review Magazine, and the Best Student Paper in IEEE DySPAN 2007. Dr. Zheng was named as the MIT Technology Review’s Top 35 Innovators under the age of 35 in 2005. She also received 2006 World Technology Award (top 5 in communication), 2002 Bell-Labs President’s Gold Award, 1998-99 George Harhalakis Outstanding Graduate Student Award from University of Maryland, College Park. Dr. Zheng received her Ph.D. from University of Maryland, College Park in 1999 and then joined wireless research lab, Bell-Labs, Lucent Technologies. She then moved to Microsoft Research Asia as a project lead and researcher in March 2004 and later joined UCSB .

This talk is part of the Computer Laboratory Systems Research Group Seminar series.

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