A cross-layer design of network coded retransmissions in wireless relay channels

In this paper we investigate the multiple-access relay channels with feedback available at relay, and we concentrate on designing retransmission protocol at relay. The feedback contains the realized Signal-to-Noise Ratio (SNR) of each packet from different users. The relay utilizes such information from the physical layer and decides what to retransmit with the help of network coding. The objective is to ensure each packet has its SNR larger than some predetermined value so that certain Bit-Error Rate (BER) can be guaranteed. Simulation results show that such a cross-layer design leads to significant throughput improvement.