Reconfigurable intelligent surfaces (RIS) are capable of beneficially ameliorating the propagation environment by appropriately controlling the passive reflecting elements. To extend the coverage area, the concept of simultaneous transmitting and reflecting reconfigurable intelligent surfaces (STAR-RIS) has been proposed, yielding supporting 360^circ coverage user equipment (UE) located on both sides of the RIS. In this paper, we theoretically formulate the ergodic sum-rate of the STAR-RIS assisted non-orthogonal multiple access (NOMA) uplink in the face of channel estimation errors and hardware impairments (HWI). Specifically, the STAR-RIS phase shift is configured based on the statistical channel state information (CSI), followed by linear minimum mean square error (LMMSE) channel estimation of the equivalent channel spanning from the UEs to the access point (AP). Afterwards, successive interference cancellation (SIC) is employed at the AP using the estimated instantaneous CSI, and we derive the theoretical ergodic sum-rate upper bound for both perfect and imperfect SIC decoding algorithm. The theoretical analysis and the simulation results show that both the channel estimation and the ergodic sum-rate have performance floor at high transmit power region caused by transceiver hardware impairments.

翻译：可重构智能表面（RIS）能够通过适当调控无源反射元件来有效改善传播环境。为扩展覆盖范围，同步透射与反射可重构智能表面（STAR-RIS）的概念被提出，从而支持位于RIS两侧的360度覆盖用户设备（UE）。本文在存在信道估计误差和硬件损伤（HWI）的情况下，理论推导了STAR-RIS辅助非正交多址接入（NOMA）上行链路的遍历和速率。具体而言，基于统计信道状态信息（CSI）配置STAR-RIS的相移，随后采用线性最小均方误差（LMMSE）方法对从UE到接入点（AP）的等效信道进行信道估计。之后，AP利用估计的瞬时CSI执行串行干扰消除（SIC），我们推导了理想SIC与非理想SIC解码算法下的理论遍历和速率上界。理论分析与仿真结果表明，在高发射功率区域，由收发机硬件损伤导致的信道估计和遍历和速率均存在性能平层。