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.
@article{arxiv.2308.06539,
title = {Phase Shift Design for RIS-Aided Cell-Free Massive MIMO with Improved Differential Evolution},
author = {Trinh Van Chien and Cuong V. Le and Huynh Thi Thanh Binh and Hien Quoc Ngo and Symeon Chatzinotas},
journal= {arXiv preprint arXiv:2308.06539},
year = {2023}
}