An Efficient Network-Coded ARQ Scheme for Two-Way Wireless Communication with Full-duplex Relaying

There has been renewed interest in using relaying systems as a low-cost solution in next generation wireless broadband networks. In this paper, we take a fresh look at relaying and propose a new retransmission protocol for a two-way wireless network with one base-station, one full-duplex relay and multiple users exchanging messages over fading channels. In this scenario, the relay and each user may hear the message from the base-station and other users. To improve the throughput, we apply network-coded ARQ with reverse-link assistance (NC-RLA) at the relay to exploit the overheard side-information acquired from both the downlink and uplink. We analyze the throughput performance enhancements of NC-RLA and validate our mathematical derivations with Monte Carlo simulation. The simulation results show that significant throughput improvements are obtained with the NC-RLA scheme for low/moderate SNRs. We also prove that full-duplex relay increases the throughput if it is located at the optimal position. Otherwise, it is not beneficial to add a relay, especially with a large number of users using network coding.