(A Tiny Bit of) Progress in Understanding the Relay Channel

Speaker: Dr. Sergio D. Servetto, Cornell University

We consider the problem of communicating over a relay channel. I will first present a brief review of the state-of-the-art in the analysis of the discrete memoryless relay channel, with an emphasis on the Estimate-and-Forward (EAF) coding strategy developed by Cover and El Gamal in 1979. There are two aspects of the description of the rates achievable with EAF that make it hard to examine concrete instances of the problem: its dependence on an auxiliary variable whose distribution is such that the rate minimization problem becomes non-convex, and the presence of a feasibility constraint. I will then show how a carefully chosen auxiliary variable leads to a readily computable set of achievable rates. Using this choice, I will show examples of channels for which our EAF strictly outperforms Decode-and-Forward, and I will also show that the Gaussian choice for the auxiliary variable that is commonly used in Gaussian relaying can be strictly suboptimal. I will conclude with some discussion on the meaning of these results, and some speculation about their relevance in the context of very large networks.
Joint work with Ron Dabora (Cornell/ECE) Paper available here


Sergio D. Servetto was born in Argentina, on January 18, 1968. He received a Licenciatura en Inform'atica from Universidad Nacional de La Plata (UNLP, Argentina) in 1992, and the M.Sc. degree in Electrical Engineering and the Ph.D. degree in Computer Science from the University of Illinois at Urbana-Champaign (UIUC), in 1996 and 1999. Between 1999 and 2001, he worked at the \'Ecole Polytechnique F'ed'erale de Lausanne (EPFL), Lausanne, Switzerland. Since Fall 2001, he has been an Assistant Professor in the School of Electrical and Computer Engineering at Cornell University, and a member of the fields of Applied Mathematics and Computer Science. He was the recipient of the 1998 Ray Ozzie Fellowship, given to ``outstanding graduate students in Computer Science,'' and of the 1999 David J. Kuck Outstanding Thesis Award, for the best doctoral dissertation of the year, both from the Dept.\ of Computer Science at UIUC. He was also the recipient of a 2003 NSF CAREER Award. His research interests are centered around information theoretic aspects of networked systems, with a current emphasis on problems that arise in the context of large-scale sensor networks.

Presented On: Dec 15th, 2006
Video: QuickTime Streaming video