Non-Orthogonal Multiple Access (NOMA) With Multiple Intelligent Reflecting Surfaces

Abstract

In this paper, non-orthogonal multiple access (NOMA) networks assisted by\nmultiple intelligent reflecting surfaces (IRSs) with discrete phase shifts are\ninvestigated, in which each user device (UD) is served by an IRS to improve the\nquality of the received signal. Two scenarios are considered according to\nwhether there is a direct link between the base station (BS) and each UD, and\nthe outage performance is analyzed for each of them. Specifically, the\nasymptotic expressions for the upper and lower bounds of the outage probability\nin the high signal-to-noise ratio (SNR) regime are derived. Following that, the\ndiversity order is obtained. It is shown that the use of discrete phase shifts\ndoes not degrade diversity order. More importantly, simulation results reveal\nthat a 3-bit resolution for discrete phase shifts is sufficient to achieve\nnear-optimal outage performance. Simulation results also imply the superiority\nof IRSs over full-duplex decode-and-forward relays.\n