Performance Analysis of NOMA-Enabled RIS-Assisted Backscatter Communication

Backscatter communication (BackCom), which allows the passive wireless sensors to transmit via modulation and reflection of an incident radio-frequency (RF) signal, is a promising solution for the sustained operation of Internet-of-Things (IoT) nodes. Moreover, to address the inherent coverage and data rate limitations of contemporary BackCom systems, reconfigurable intelligent surfaces (RISs) have come to the forefront for the adaptive configuration of wireless environments. Meanwhile, BackCom systems can incorporate non-orthogonal multiple access (NOMA) to achieve higher spectral efficiency for massive connectivity. Hence, we consider a NOMA-enabled bistatic BackCom system, where multiple backscatter nodes (BSNs) are grouped by the NOMA principle and served with the assistance of an RIS. Using the method of moments (MoM), we analyze and obtain the bit error rate (BER) expressions of a 2 -BSN NOMA cluster under imperfect successive interference cancellation (SIC). The validity of the derived expressions is corroborated through extensive numerical simulations. Furthermore, the performance of the proposed system is evaluated in comparison with the conventional NOMA-BackCom system. Our results reveal the superior performance of the RIS-assisted NOMA system, and demonstrate the influence of the number of RIS elements and the choice of reflection coefficients on the BER performance of the proposed system.