Intelligent Reflecting Surface-Assisted Uplink SCMA System

Abstract

Intelligent reflecting surface (IRS) is a promising technique to enhance performance of wireless systems due to its ability to smartly reconfigure the signal propagation environment. Sparse code multiple access (SCMA) is code-domain non-orthogonal multiple access technique suitable for the next-generation wireless networks. In this letter, we consider IRS-assisted uplink SCMA (I-SCMA) for energy and spectrally-efficient wireless systems. Message passing algorithm (MPA)-based signal detection is proposed to detect multiple users’ symbols in uplink I-SCMA. The diversity orders of I-SCMA for random and coherent phase shifting are derived. The symbol error rate and the sum-rate performance of the uplink I-SCMA system are analyzed. Further, the impact of overloading factor, the number of reflecting surfaces, the number of phase shifts of reflected signals are studied. Simulation results demonstrate the benefits of I-SCMA in terms of the spectral and energy efficiency over conventional SCMA and other NOMA techniques.