Outage Probability Analysis of Reconfigurable Intelligent Surface (RIS)-Enabled NOMA Network

Non-orthogonal multiple access (NOMA) is a promising multiple access technique for the next generation of wireless networks. However, the random nature of wireless channels can significantly reduce performance. Recently, reconfigurable intelligent surfaces (RISs) have emerged as a passive smart solution to combat the effects of wireless radio links. Integrating NOMA with RIS is a smart solution to control the stochastic behaviour of wireless channels with improved coverage and enhanced throughput. It can substantially improve the outage probability (OP) of wireless networks. This paper investigates the outage performance of a multi-antenna downlink NOMA system with RIS assistance. We determine the OP utilising the statistical characteristics of the signal-to-noise ratio of the reflection channel from the base station to the users through RIS for both near and far users. The proposed RIS-aided system outperforms conventional NOMA and orthogonal multiple access (OMA) systems without RIS. We validate our analytical results using Monte Carlo simulations. The simulation results show that the RIS-aided NOMA system outperforms conventional systems and the scenario without RIS assistance.