Phase Shift Design for RIS-Aided Cell-Free Massive MIMO with Improved Differential Evolution

TL;DR

This paper introduces a novel phase shift design for RIS-assisted cell-free massive MIMO systems, optimizing uplink throughput using channel statistics and an improved differential evolution algorithm, showing significant performance gains.

Contribution

It presents a new phase shift design method leveraging channel statistics and an enhanced differential evolution algorithm for better throughput in RIS-assisted systems.

Findings

Achieves higher uplink sum ergodic throughput compared to benchmarks.

Effective in scenarios with high probability of direct links.

Provides solutions with reasonable computational effort.

Abstract

This paper proposes a novel phase shift design for cell-free massive multiple-input and multiple-output (MIMO) systems assisted by reconfigurable intelligent surface (RIS), which only utilizes channel statistics to achieve the uplink sum ergodic throughput maximization under spatial channel correlations. Due to the non-convexity and the scale of the derived optimization problem, we develop an improved version of the differential evolution (DE) algorithm. The proposed scheme is capable of providing high-quality solutions within reasonable computing time. Numerical results demonstrate superior improvements of the proposed phase shift designs over the other benchmarks, particularly in scenarios where direct links are highly probable.