Wireless Spectrum Sharing: Opportunities for Interdisciplinary Research


August 15, 2012


Anant Sahai




Under the current static system of frequency assignment, a great deal of spectrum remains underused. This seeming waste represents an opportunity for frequency-agile cognitive radios to improve performance. Understanding this opportunity forces us to take a closer look at the whole question of “regulatory overhead.” Until recently, cognitive radios represented the “Medical Marijuana” of wireless research — rhetoric on both sides characterized by distrust, wishful thinking, and vested interests, but the underlying “technology” in question was still very much illegal. Regulatory changes were required before research in this area could truly impact practice. Recent steps taken by the FCC in the TV Whitespaces demonstrate that the government is serious about change, and just last month, the President’s Council of Advisers on Science and Technology (PCAST) released a report that advocated expanding this approach beyond the TV bands. However, the problem is that while we have a rough sense of what we want to achieve at a high level, as a community, we do not yet know what this regulatory change should entail at the detailed level and more troubling, even how we would recognize the right answer if we saw it.
The full scope of the problem weaves together information theory, signal processing, economics, and law in a nontrivial way (and probably also cryptography and social networks). In this talk, I will give an introduction to the opportunity in the context of the TV Whitespaces. I’ll use some simulations based on real FCC data and realistic propagation models to give a quantitative sense of the tradeoffs involved, and then show idealized models that enable a conceptual understanding of the “overhead” in the context of spectrum sensing. I will then elucidate what “light handed regulation” could mean in the cognitive radio context, giving a simple criminal-law inspired model to reveal something about the overhead and tradeoffs involved. I’ll close with some interesting future research directions.


Anant Sahai

Anant Sahai (BS ’94 UC Berkeley, MS ’96 MIT, PhD ’01 MIT) is an Associate Professor in the Department of Electrical Engineering and Computer Sciences at the University of California at Berkeley, where he joined the faculty in 2002. He is a member of the Berkeley Wireless Research Center (BWRC) and the Wireless Foundations Center (WiFo). In 2001, he spent a year at the wireless startup Enuvis developing adaptive signal processing algorithms for extremely sensitive GPS receivers implemented using software defined radio. Prior to that, he was a graduate student at the Laboratory for Information and Decision Systems (LIDS) at the Massachusetts Institute of Technology (MIT). His research interests are in wireless communication, decentralized control, and information theory. He is particularly interested in delay, feedback, and complexity from an information-theoretic perspective and in cognitive radio from a regulatory perspective.