A Novel HARQ Design for RSMA Networks

Rate splitting multiple access (RSMA) has a variety of advantages, including higher throughput, enhanced capacity, and network efficiency, which makes it suitable for beyond fifth generation (5G) networks. Since the combining and splitting operations are performed on the transmitter side, one of the challenging aspects of RSMA is how a retransmission can be accomplished. In this article, an efficient hybrid automatic repeat request (HARQ) design for RSMA networks is presented in which three novel retransmission strategies are developed. More specifically, the main idea is choosing among RSMA, nonorthogonal multiple access (NOMA), and space division multiple access (SDMA) during the HARQ retransmission round, respectively, to do the retransmission. Therefore, a new link adaptation approach is proposed. The effectiveness of the proposed design is analyzed in terms of the average number of retransmissions, energy efficiency (EE), and achievable sum rate. Simulation results confirm the superiority of the proposed protocol in terms of packet error rate, EE, and sum-rate improvement up to 70%, 81%, and 76%, respectively, as compared to the conventional RSMA.