Recently, reconfigurable intelligent surface (RIS) has gained research and development interests in modifying wireless channel characteristics in order to improve the performance of wireless communications, especially when the quality of the line-of-sight channel is not that good. In this work, for the first time in the literature, we have used simultaneously transmitting and reflecting RIS (STAR-RIS) in a non-orthogonal multiple-access visible light communication system to improve the performance of the system. Achievable rates of the users are derived for two data recovery schemes, single-user detection (SUD) and successive interference cancellation (SIC). Then, the sum-rate optimisation problem is formulated for two operating modes of STAR-RIS, namely energy-splitting and mode-switching cases. Moreover, a sequential parametric convex approximation method is used to solve the sum-rate optimisation problems. The authors have also compared energy-splitting and mode-switching cases and showed that these two modes have the same performance. Finally, numerical results for SUD and SIC schemes and two benchmarking schemes, time-sharing and max-min fairness, are presented, and spectral- and energy-efficiency, number of STAR-RIS elements, the position of users, and access point are discussed.

中文翻译：

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同时发射和反射可重构智能表面的上行光无线通信性能分析

最近，可重构智能表面（RIS）在修改无线信道特性以提高无线通信性能方面引起了研究和开发兴趣，特别是在视距信道质量不太好的情况下。在这项工作中，我们在文献中首次在非正交多址可见光通信系统中使用同时发射和反射RIS（STAR-RIS）来提高系统的性能。针对两种数据恢复方案（单用户检测（SUD）和连续干扰消除（SIC））导出了用户可达到的速率。然后，针对 STAR-RIS 的两种操作模式，即能量分裂和模式切换情况，制定了总速率优化问题。而且，使用顺序参数凸逼近方法来解决和率优化问题。作者还比较了能量分裂和模式切换情况，并表明这两种模式具有相同的性能。最后，给出了 SUD 和 SIC 方案以及两种基准方案（分时和最大最小公平性）的数值结果，并给出了频谱效率和能源效率、STAR-RIS 元件数量、用户位置和接入点讨论过。