Rate-Splitting Meets Cell-Free MIMO Communications

TL;DR

This paper introduces a novel rate-splitting approach for cell-free MIMO systems to improve sum-rate performance under imperfect channel state information, demonstrating up to 10% gain over existing methods.

Contribution

It proposes a new CF architecture employing rate splitting with linear precoders and derives closed-form expressions for sum-rate performance, addressing CSI imperfections.

Findings

RS-CF outperforms existing systems in sum-rate.

Up to 10% higher sum-rate gain achieved.

Closed-form expressions for performance evaluation.

Abstract

Multiuser multiple-input multiple-output wireless communications systems have the potential to satisfy the performance requirements of fifth-generation and future wireless networks. In this context, cell-free (CF) systems, where the antennas are distributed over the area of interest, have attracted attention because of their potential to enhance the overall efficiency and throughput performance when compared to traditional networks based on cells. However, the performance of CF systems is degraded by imperfect channel state information (CSI). To mitigate the detrimental effects of imperfect CSI, we employ rate splitting (RS) - a multiple-access scheme. The RS approach divides the messages of the users into two separate common and private portions so that interference is managed robustly. Unlike prior works, where the impact of RS in CF systems remains unexamined, we propose a CF architecture that employs RS with linear precoders to address deteriorated CSI. We derive closed-form expressions to compute the sum-rate performance of the proposed RS-CF architecture. Our numerical experiments show that our RS-CF system outperforms existing systems in terms of sum-rate, obtaining up to $10$% higher gain.