Interference Cancellation in a Linear Multi-Access Relay Network

Monday, May 3, 2010 - 10:00 a.m. to Tuesday, May 4, 2010 - 10:55 a.m.
Engineering Gateway 3161
CPCC Seminar

Featuring Liangbin Li

Ph.D. Candidate, Electrical Engineering and Computer Science

The Henry Samueli School of Engineering, UC Irvine



Free and open to the public



Abstract:

In this talk, we present transmission and detection schemes in multi-access relay (MARN) network with linear constraints. In a (J, R, N) MARN, J single-antenna user nodes send independent messages to one N-antenna destination node by two hops of transmission through one R-antenna relay node. For complexity considerations, the network is studied under two linear constraints. For one, the relay generates forwarded signals by linearly transforming its received signals. For the other, the receiver decodes multi-user symbols with linear complexity in the number of users. To obtain high communication reliability and linear multi-user decoding, distributed space-time codes (DSTCs) and zero-forcing interference cancellation (IC) are applied to this multi-user relay network. Different from conventional protocols that assign multi-users to orthogonal channels, our proposed two protocols allow multi-user concurrent transmission in both or part of the two hops to enhance spectrum efficiency. The first proposed protocol is called DSTC-ICRec, which allows concurrent transmission in both the source-relay link and the relay-receiver link. Analysis shows that the diversity gain of DSTC-ICRec can be upperbounded as d \le R - J + 1. This relation shows the tradeoff between the number of users and the diversity by DSTC-ICRec. To gain higher diversity, another protocol called TDMA-ICRec is proposed in which users time-share the source-relay link. Multi-user concurrent transmission is used in the relay-receiver link. It is shown through both analysis and simulation that when N \ge 2J - 1, TDMA-ICRec achieves the maximum interference-free (int-free) diversity of R, but with a loss of symbol-rate compared to DSTC-ICRec. The proposed two protocols tradeoff among diversity, symbol rate, and the number of users under linear network constraints. 



About the Speaker:

Liangbin Li received his B.S. and M.S. degrees in electrical engineering from Fudan University, Shanghai, China in 2005 and 2008, respectively. He is currently working toward the Ph.D. degree at the University of California, Irvine. His research interests include communication theory and multi-user wireless networks.