On the Performance of STAR-RIS-Aided NOMA at Finite Blocklength

Simultaneous refracting/transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) has emerged as a potential technology for future-generation wireless communication that enhances the signal quality and provides 360 degrees coverage area. In this letter, we provide a finite blocklength (FBL) analysis of a STAR-RIS-aided downlink communication system with non-orthogonal multiple access (NOMA), where the base station (BS) transmits a superimposed signal to two users with the aid of a STAR-RIS. First, we derive the probability density function (PDF) and cumulative distribution function (CDF) of the signal-to-interference-plus-noise ratio (SINR) of each user, and then we analyze the system performance by deriving analytical expressions for their block error rate (BLER) and goodput. Finally, using Monte-Carlo simulations, we validate the accuracy of the derived analytical expressions, and highlight the impact of key system parameters such as blocklength, and the number of refracting and reflecting elements on the system performance.