User selective relaying in multiple access relay channels

Network coding has recently received significant attention as an innovative approach to improve the throughput of wireless communication systems. The multiple access relay channel (MARC), in which multiple users communicate with a common destination via a relay, is one of the important network coding applications for wireless cooperative communications. In this paper, selective relaying approach which combats performance degradation due to error propagation in digital relaying based wireless networks has been adopted to the MARC model. In the proposed scheme, the information of the some of the user terminals are transmitted to the destination through both direct and relay channel utilizing ideas from network coding while the other terminals employ only the direct link. The optimal subset of all user terminals whose transmissions will be listened and retransmitted by the relay are determined by the destination terminal in a manner to minimize the overall end to end bit error rate of the system and sent to the relay through the feedback link. Simulation results for Rayleigh fading channels show that the proposed selection relaying scheme outperform the noncooperative system that involves direct transmissions and overcome the diversity gain reduction due to error propagation.