Non‐orthogonal multiple access relaying with truncated ARQ

In this study, the authors propose a non-orthogonal multiple access (NOMA) relaying protocol with truncated automatic repeat request (ARQ), where the source simultaneously transmits two signals to the relay and the destination using superposition coding technique in the power domain. The successive interference cancelation technique is adopted by the relay, who should first decode its own data and then cancel it for the decoding of destination data. If either the data intended for the relay or the destination is erroneously received by the relay, it will be retransmitted by the source using full power. After correctly decoding the source data intended for the destination, the relay will forward it and the retransmission is performed when the data is erroneously received by the destination. The authors derive the system throughput and investigate the impacts of several parameters, such as power allocation factor, target rate, and distance between terminals etc. In terms of throughput, the authors' proposed scheme can greatly outperform the conventional relaying scheme with truncated ARQ.