In this paper, we propose simultaneous transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) assisted non-orthogonal multiple access (NOMA) networks. The considered STAR-RIS utilizes the mode switching (MS) protocol to serve multiple NOMA users located on both sides of the RIS surface. Based on the MS protocol, each STAR-RIS element can operate in full transmission or reflection mode. Within this perspective, we propose a novel algorithm to partition the STAR-RIS surface among the available users. This algorithm aims to determine the proper number of transmitting/reflecting elements needs to be assigned to each user in order to maximize the system sum-rate while guaranteeing the quality-of-service requirements for individual users. For the proposed system, we derive closed-form analytical expressions for the outage probability (OP) and its corresponding asymptotic behavior under different user deployments. Finally, Monte Carlo simulations are performed in order to verify the correctness of the theoretical analysis. It is shown that the proposed system outperforms the classical NOMA and orthogonal multiple access systems in terms of OP and sum-rate.

翻译：本文提出了一种基于同时透射与反射可重构智能表面（STAR-RIS）辅助的非正交多址接入（NOMA）网络。所研究的STAR-RIS采用模式切换（MS）协议，为分布于RIS表面两侧的多个NOMA用户提供服务。根据MS协议，每个STAR-RIS单元可工作于全透射或全反射模式。在此框架下，我们提出了一种新颖的算法，用于在可用用户间划分STAR-RIS表面。该算法旨在确定分配给每个用户的透射/反射单元数量，以在保证单个用户服务质量要求的同时最大化系统总速率。针对所提系统，我们推导了不同用户部署场景下中断概率（OP）及其渐近行为的闭式解析表达式。最后，通过蒙特卡洛仿真验证了理论分析的正确性。结果表明，所提系统在中断概率和总速率方面均优于传统NOMA与正交多址接入系统。