Impact of Orthogonal Multiple Access and Non Orthogonal Multiple Access for the Performance of IRS-Aided Downlink Systems

The rapid expansion of communicating devices has brought with a need of higher capacity, low latency wireless communication systems. Which has led to interest in advanced multiple access techniques such as NOMA. The NOMA technique allows multiple users to transmit over the same channel using power-domain multiplexing and SIC approach. This allows for an increase inconnectivity and spectral efficiency over traditional OMA. However, NOMA suffers from inter-user interference and a decline in performance in multipath environments. In order to eliminate such constraints, IRS emerged as a potential solution. This paper examines, how the IRS can be applied in conjunction with NOMA. Specifically, what effect does it have on user data rates. The Simulation is done for the cases of direct NOMA, IRS-Aided NOMA and OMA with varying number of Reflecting Elements. The results show improvements in data rates, in comparison with conventional NOMA and OMA schemes. Simulation also shows improvement in data rates with increase in Reflecting Elements. Moreover, this paper outlines some crucial research gaps and future directions.