Rate-Splitting Multiple Access (RSMA) has emerged as a novel multiple access technique that enlarges the achievable rate region of Multiple-Input Multiple-Output (MIMO) broadcast channels with linear precoding. In this work, we jointly address three practical but fundamental questions: (1) How to exploit the benefit of RSMA under finite constellations? (2) What are the potential and promising ways to implement RSMA receivers? (3) Can RSMA still retain its superiority in the absence of successive interference cancellers (SIC)? To address these concerns, we first propose low-complexity precoder designs taking finite constellations into account and show that the potential of RSMA is better achieved with such designs than those assuming Gaussian signalling. We then consider some practical receiver designs that can be applied to RSMA. We notice that these receiver designs follow one of two principles: (1) SIC: cancelling upper layer signals before decoding the lower layer and (2) non-SIC: treating upper layer signals as noise when decoding the lower layer. In light of this, we propose to alter the precoder design according to the receiver category. Through link-level simulations, the effectiveness of the proposed precoder and receiver designs are verified. More importantly, we show that it is possible to preserve the superiority of RSMA over Spatial Domain Multiple Access (SDMA), including SDMA with advanced receivers, even without SIC at the receivers. Those results therefore open the door to competitive implementable RSMA strategies for 6G and beyond communications.

翻译：速率分割多址接入（RSMA）作为一种新型多址技术，可通过线性预编码扩展多输入多输出（MIMO）广播信道的可达速率区域。本文联合探讨三个实际且基础的问题：（1）如何在有限星座条件下利用RSMA优势？（2）实现RSMA接收机的潜在可行方案有哪些？（3）RSMA在无串行干扰消除器（SIC）时能否保持其优越性？针对这些问题，我们首先提出考虑有限星座的低复杂度预编码器设计方案，证明该设计相比假设高斯信号的设计能更好发挥RSMA潜力。随后研究适用于RSMA的若干实用接收机设计，发现这些设计遵循两种原则：（1）SIC型：在解码下层信号前消除上层信号干扰；（2）非SIC型：解码下层信号时将上层信号视为噪声。据此，我们提出根据接收机类型调整预编码器设计。通过链路级仿真验证了所提预编码器与接收机设计的有效性。更重要的是，我们证明在接收端无SIC的情况下，RSMA仍能保持对空分多址（SDMA）的优越性，包括采用先进接收机的SDMA方案。这些结果为面向6G及未来通信的竞争性RSMA可实施策略奠定了基础。