This article focuses on the exploitation of reconfigurable intelligent surfaces (RISs) in multiuser networks employing orthogonal multiple access (OMA) or non-orthogonal multiple access (NOMA), with an emphasis on investigating the interplay between NOMA and RIS. Depending on whether the RIS reflection coefficients can be adjusted only once or multiple times during one transmission, we distinguish between static and dynamic RIS configurations. In particular, the capacity region of RIS-aided single-antenna NOMA networks is discussed and compared with the OMA rate region from an information-theoretic perspective, revealing that the dynamic RIS configuration is capacity-achieving. Then, the impact of the RIS deployment location on the performance of different multiple access schemes is investigated, which reveals that asymmetric and symmetric deployment strategies are preferable for NOMA and OMA, respectively. Furthermore, for RIS-aided multiple-antenna NOMA networks, three novel joint active and passive beamformer designs are proposed based on both beamformer-based and cluster-based strategies. Finally, open research problems for RIS-NOMA networks are highlighted.

中文翻译：

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可重构智能表面辅助多用户网络：NOMA 和 RIS 之间的相互作用

本文侧重于在采用正交多址 (OMA) 或非正交多址 (NOMA) 的多用户网络中利用可重构智能表面 (RIS)，重点研究 NOMA 和 RIS 之间的相互作用。根据一次传输期间 RIS 反射系数是否只能调整一次或多次，我们区分静态和动态 RIS 配置。特别是，从信息论的角度讨论了 RIS 辅助单天线 NOMA 网络的容量区域，并与 OMA 速率区域进行了比较，揭示了动态 RIS 配置是容量实现的。然后，研究了 RIS 部署位置对不同多址方案性能的影响，这表明非对称和对称部署策略分别对 NOMA 和 OMA 更可取。此外，对于 RIS 辅助的多天线 NOMA 网络，基于基于波束形成器和基于集群的策略，提出了三种新颖的联合有源和无源波束形成器设计。最后，强调了 RIS-NOMA 网络的开放研究问题。