Downlink Analysis for Reconfigurable Intelligent Surfaces Aided NOMA Networks

TL;DR

This paper analyzes the downlink performance of RIS-aided NOMA networks using stochastic geometry, revealing performance improvements and the potential to alter SIC order through RIS configuration.

Contribution

It introduces a new path loss model and angle distribution analysis for RIS channels, and derives coverage probability expressions for RIS-aided NOMA systems.

Findings

RIS-aided NOMA outperforms traditional NOMA in coverage.

RIS can alter SIC order by changing channel gains.

Closed-form coverage probability expressions are provided.

Abstract

By activating blocked users and altering successive interference cancellation (SIC) sequences, reconfigurable intelligent surfaces (RISs) become promising for enhancing non-orthogonal multiple access (NOMA) systems. This work investigates the downlink performance of RIS-aided NOMA networks via stochastic geometry. We first introduce the unique path loss model for RIS reflecting channels. Then, we evaluate the angle distributions based on a Poisson cluster process (PCP) framework, which theoretically demonstrates that the angles of incidence and reflection are uniformly distributed. Lastly, we derive closed-form expressions for coverage probabilities of the paired NOMA users. Our results show that 1) RIS-aided NOMA networks perform better than the traditional NOMA networks; 2) the SIC order in NOMA systems can be altered since RISs are able to change the channel gains of NOMA users.