This work investigates the design of Hybrid Automatic Repeat Request (HARQ) strategies for downlink Rate-Splitting Multiple Access (RSMA). The existence of private and common stream as well as their conditioning for Successive Interference Cancellation (SIC), gives rise to an expanded set of opportunities for retransmission of failed packets. Specifically, we devise a scheme in which the retransmissions are scheduled through the common stream, which offers a higher success probability. With this, the common stream needs to carry both new and retransmitted bits, which leads to a layered HARQ (L-HARQ) strategy which is capable of trading off throughput and reliability. Simulation results demonstrate that the devised HARQ scheme outperforms RSMA with conventional HARQ, where each retransmission is handled independently through its own stream. It also helps in closing the throughput gap between HARQ and Adaptive Modulation and Coding (AMC) in the high SNR regime while also achieving a decreased Packet Error Rate (PER) and a lower latency.

翻译：本文研究了下行链路速率分割多址接入（RSMA）中混合自动重传请求（HARQ）策略的设计问题。私有流与公共流的存在及其对连续干扰消除（SIC）的约束条件，为失败数据包的重传提供了更丰富的机遇。具体而言，我们设计了一种方案，将重传任务通过公共流进行调度，从而获得更高的成功概率。由此，公共流需要同时承载新数据位与重传数据位，这催生了一种能够权衡吞吐量与可靠性的分层HARQ（L-HARQ）策略。仿真结果表明，与依赖各自独立流处理每次重传的传统RSMA-HARQ方案相比，所设计的HARQ方案性能更优。该方案还有助于在高信噪比（SNR）条件下缩小HARQ与自适应调制编码（AMC）之间的吞吐量差距，同时实现更低的分组错误率（PER）与更低的延迟。