Analysis of Uplink IRS-Assisted NOMA under Nakagami-m Fading via Moments Matching

TL;DR

This paper analyzes the uplink outage performance of IRS-assisted NOMA with Nakagami-m fading, using moments matching to derive tractable outage expressions and revealing conditions where IRS can either degrade or improve user performance.

Contribution

It introduces a moments matching approach to approximate received powers as Gamma variables, enabling flexible outage analysis in IRS-assisted NOMA under Nakagami-m fading.

Findings

IRS can degrade LOS-dominated user performance under certain conditions.

NLOS-dominated users always benefit from IRS assistance.

The approach provides tractable outage expressions for complex fading environments.

Abstract

This letter investigates the uplink outage performance of intelligent reflecting surface (IRS)-assisted non-orthogonal multiple access (NOMA). We consider the general case where all users have both direct and reflection links, and all links undergo Nakagami-m fading. We approximate the received powers of the NOMA users as Gamma random variables via moments matching. This allows for tractable expressions of the outage under interference cancellation (IC), while being flexible in modeling various propagation environments. Our analysis shows that under certain conditions, the presence of an IRS might degrade the performance of users that have dominant line-of-sight (LOS) to the base station (BS), while users dominated by non-line-of-sight (NLOS) will always benefit from it.