Impact of Phase-Noise and Spatial Correlation on Double-RIS-Assisted Multiuser MISO Networks

TL;DR

This paper analyzes how phase-noise and spatial correlation affect the performance of double-RIS-assisted multiuser MISO systems, providing closed-form expressions for achievable rates and optimal phase-shifts, highlighting the impact of system parameters.

Contribution

It derives closed-form achievable rate expressions and optimal phase-shift designs for double-RIS MISO systems considering phase-noise and spatial correlation effects.

Findings

Phase-noise severely degrades performance without direct links.

High spatial correlation at RISs boosts achievable rates.

Analytical expressions are validated by numerical results.

Abstract

We study the performance of a phase-noise impaired double reconfigurable intelligent surface (RIS)-aided multiuser (MU) multiple-input single-output (MISO) system under spatial correlation at both RISs and base-station (BS). The downlink achievable rate is derived in closed-form under maximum ratio transmission (MRT) precoding. In addition, we obtain the optimal phase-shift design at both RISs in closed-form for the considered channel and phase-noise models. Numerical results validate the analytical expressions, and highlight the effects of different system parameters on the achievable rate. Our analysis shows that phase-noise can severely degrade the performance when users do not have direct links to both RISs, and can only be served via the double-reflection link. Also, we show that high spatial correlation at RISs is essential for high achievable rates.