Two-Phase Channel Estimation for RIS-Aided Cell-Free Massive MIMO with Electromagnetic Interference

TL;DR

This paper introduces a two-phase channel estimation method for RIS-aided cell-free massive MIMO systems that accounts for electromagnetic interference, improving accuracy and spectral efficiency through novel pilot assignment and analysis.

Contribution

It proposes a new two-phase channel estimation scheme with fractional power control and derives closed-form spectral efficiency expressions considering EMI effects.

Findings

The proposed scheme improves estimation accuracy under EMI.

RIS and more access points enhance system performance.

Numerical results confirm the effectiveness of the method.

Abstract

This work considers a reconfigurable intelligent surface (RIS)-aided cell-free massive multiple-input multiple-output (MIMO) system with RIS spatial correlation and electromagnetic interference (EMI). We propose a two-phase channel estimation scheme with fractional power control-aided pilot assignment to improve the estimation accuracy and system performance of RIS-aided cell-free massive MIMO systems. Additionally, we derive the closed-form expressions of the downlink spectral efficiency (SE) with conjugate beamforming to evaluate the impact of EMI among RIS elements on the system performance. Numerical results validate that the proposed two-phase scheme can compensate for the performance degradation caused by EMI in terms of estimation accuracy and downlink SE. Moreover, the benefits of introducing RISs and increasing access points (APs) are illustrated.