Different from conventional reconfigurable intelligent surfaces (RIS), a recent innovation called simultaneous transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) has emerged, aimed at achieving complete 360-degree coverage in communication networks. Additionally, fullduplex (FD) technology is recognized as a potent approach for enhancing spectral efficiency by enabling simultaneous transmission and reception within the same time and frequency resources. In this study, we investigate the performance of a STAR-RIS-assisted FD communication system. The STAR-RIS is strategically placed at the cell-edge to facilitate communication for users located in this challenging region, while cell-center users can communicate directly with the FD base station (BS). We employ a non-orthogonal multiple access (NOMA) pairing scheme and account for system impairments, such as self-interference at the BS and imperfect successive interference cancellation (SIC). We derive closed-form expressions for the ergodic rates in both the up-link and down-link communications and extend our analysis to bidirectional communication between cell-center and cell-edge users. Furthermore, we formulate an optimization problem aimed at maximizing the ergodic sum-rate. This optimization involves adjusting the amplitudes and phase-shifts of the STAR-RIS elements and allocating total transmit power efficiently. To gain deeper insights into the achievable rates of STAR-RIS-aided FD systems, we explore the impact of various system parameters through numerical results.

翻译：不同于传统可重构智能表面（RIS），近期出现了一种名为同时传输和反射可重构智能表面（STAR-RIS）的创新技术，旨在实现通信网络中的全360度覆盖。此外，全双工（FD）技术被视为一种有效提升频谱效率的方法，其通过在同一时间和频率资源内同时进行传输和接收来实现。在本研究中，我们探讨了STAR-RIS辅助FD通信系统的性能。STAR-RIS被策略性地部署在小区边缘，以促进位于这一挑战性区域用户的通信，而小区中心用户则可直接与FD基站（BS）通信。我们采用非正交多址接入（NOMA）配对方案，并考虑系统损伤，如基站处的自干扰和非完美连续干扰消除（SIC）。我们推导了上行和下行通信中遍历速率的闭式表达式，并将分析扩展至小区中心与小区边缘用户之间的双向通信。此外，我们构建了一个旨在最大化遍历和速率的优化问题。该优化涉及调整STAR-RIS单元的幅度和相移，并高效分配总发射功率。为更深入理解STAR-RIS辅助FD系统的可达速率，我们通过数值结果探索了各种系统参数的影响。