Rate-Splitting Multiple Access With Backward Retransmission for Underwater Acoustic Networks: Efficient and Reliable Communication

The underwater acoustic networks (UANs) hold great promise for the development of the ocean and effectively support future communication demands for seamless global coverage. Nevertheless, limited underwater frequency resources and conventional orthogonal multiple access techniques cannot fulfill the exploding demand for data transmission, posing great challenges to the efficient operation of UANs. Fortunately, rate splitting multiple access (RSMA) with retransmission protocol can achieve concurrent connections and high reliability. Therefore, in this article, we first summarize representative multiple access solutions for UANs and illustrate the advantages and suitability of RSMA in underwater. Then, a cluster-based UAN architecture is presented as a case study to evaluate the characteristics and diverse applications in underwater. Furthermore, we introduce a RSMA scheme with backward retransmission (BRQ) and describe the integration of the two mechanisms in detail, aiming at managing serious interference and maintaining link stability. Simulation results demonstrate the feasibility and effectiveness of the proposed scheme compared with other benchmarks. Open issues and future directions are also discussed for UANs adopting nonorthogonal retransmission.