Technical Talk

Title : Parity-Forwarding Strategies for the Relay Channel
Speaker : Dr. Wei Yu, University of Toronto
When:Thursday, Feb. 20, 2008 from 1:30pm-2:30pm
Where:McMaster University, Room JHE/265
Abstract : Decode-and-forward and quantize-and-forward are two fundamental strategies for the relay channel. Both can be considered as parity-forwarding strategies, in which the relay summarizes its observation by forming parity bits and forwards them to the destination. In the first part of this talk, we generalize parity-forwarding to relay networks with multiple relays. We show that a relay network can be degraded in more than one way and decode-and-forward can achieve the capacity of new classes of degraded relay networks. In the second part of this talk, we describe efficient implementation of parity-forwarding using low-density parity-check (LDPC) codes. We show that capacity-achieving codes in this case need to be "bi-layer" and need to simultaneously operate at two different SNRs: the SNR at the relay and at the destination. Using an EXIT-chart-based design methodology, it is demonstrated that a bi-layer LDPC code can approach the theoretical decode-and-forward rate to within a fraction of dB to capacity. The third part of this talk focuses on quantize-and-forward, and provides an example of a modulo-sum channel for which quantize-and-forward is capacity achieving. In this class of channels, the relay observes a corrupted version of the noise only and has a separate channel to the destination. This is a first example of a relay channel for which the well-known cut-set bound is not tight.
(joint work with Peyman Razaghi and Marko Aleksic)
Speaker Bio : Wei Yu received the B.A.Sc. degree in Computer Engineering and Mathematics from the University of Waterloo, Waterloo, Ontario, Canada in 1997 and M.S. and Ph.D. degrees in Electrical Engineering from Stanford University, Stanford, CA, in 1998 and 2002, respectively. Since 2002, he has been an Assistant Professor with the Electrical and Computer Engineering Department at the University of Toronto, Toronto, Ontario, Canada, where he holds a Canada Research Chair. His main research interests include multiuser information theory, optimization, wireless communications and broadband access networks. Prof. Wei Yu was an Editor for IEEE Transactions on Wireless Communications from 2004 to 2007, and a Guest Editor of IEEE Journal on Selected Areas in Communications for a special issue on "Nonlinear Optimization of Communications Systems'' in 2006. He received an Early Researcher Award from Ontario in 2006, and an Early Career Teaching Award from the Faculty of Applied Science and Engineering, University of Toronto, in 2007.