Multisource Transmission for Wireless Relay Networks With Linear Complexity
Liangbin Li, Yindi Jing, Hamid Jafarkhani · IEEE Transactions on Signal Processing · 2011
This paper considers transmission schemes in multiaccess relay networks (MARNs) whereJsingle-antenna sources send independent information to oneN-antenna destination through oneM-antenna relay. For complexity considerations, we propose a linear framework, where the relay linearly transforms its received signals to generate the forwarded signals without decoding and the destination uses its multiantennas to fully decouple signals from different sources before decoding, by which the decoding complexity is linear in the number of sources. To achieve a high symbol rate, we first propose a scheme called ConcurrentS→R→D-ICDin which all sources' information streams are concurrently transmitted in both the source-relay link and the relay-destination link. In this scheme, distributed space-time coding (DSTC) is applied at the relay, which satisfies the linear constraint. DSTC also allows the destination to conduct the zero-forcing interference cancellation (IC) scheme originally proposed for multiantenna systems to fully decouple signals from different sources. Our analysis shows that the symbol rate of ConcurrentS→R→D-ICDis 1/2 symbols/source/channel use and the diversity gain of the scheme is upperbounded byM-J+1. To achieve a higher diversity gain, we propose another scheme called ConcurrentR→D-ICDin which the sources time-share the source-relay link. The relay coherently combines the signals on its antennas to maximize the signal-to-noise ratio (SNR) of each source, then concurrently forwards all sources' information. The destination performs zero-forcing IC. It is shown through both analysis and simulation that whenN≥ 2J-1, ConcurrentR→D-ICDachieves the same maximum diversity gain as the full TDMA scheme in which information streams from each source are assigned to orthogonal channels in both links, but with a higher symbol rate.