Outage performance analysis of IRS-assisted cell-free massive MIMO-URLLC systems

Abstract

This paper investigates the outage performance of an IRS-assisted cell-free massive multiple-input multiple-output (MIMO) system for ultra-reliable low-latency communication (URLLC) scenarios. The direct and cascaded channels are modeled using Rician fading distributions, and maximum ratio transmission (MRT) precoding is adopted at the access points (APs). Under both perfect and imperfect channel state information (CSI) conditions, this article analyzes the statistical characteristics of instantaneous signal-to-interference-plus-noise ratio (SINR) and derives a closed-form expression for the outage probability. The analysis shows that the SINR follows a non-central F distribution with fixed degrees of freedom, while channel estimation errors mainly affect the non-centrality parameter and consequently degrade the outage performance. Numerical and simulation results validate the theoretical derivations and demonstrate the impacts of the number of APs, IRS reflecting elements, and CSI imperfections on system reliability.