Clustered Cell-Free Multi-User MIMO Systems with Rate-Splitting

TL;DR

This paper introduces a clustered cell-free multi-user MIMO system employing rate-splitting to mitigate imperfect channel information effects and reduce computational loads, demonstrating superior sum-rate performance over existing methods.

Contribution

It proposes a novel clustered CF multi-user MIMO framework with rate-splitting and new linear precoders, addressing performance degradation and complexity issues.

Findings

Outperforms existing approaches in sum-rate.

Provides closed-form sum-rate expressions.

Reduces computational and signaling loads.

Abstract

In this paper, we address two crucial challenges in the design of cell-free (CF) systems: degradation in the performance of CF systems by imperfect channel state information at the transmitter (CSIT) and high computational/signaling loads arising from the increasing number of distributed antennas and parameters to be exchanged. To mitigate the effects of imperfect CSIT, we employ rate-splitting (RS) multiple-access, which separates the messages into common and private streams. Unlike prior works, we present a clustered CF multi-user multiple-antenna framework with RS, which groups the transmit antennas in several clusters to reduce the computational and signaling loads. The proposed RS-CF system employs one common stream per cluster to exploit the network diversity. Furthermore, we propose new cluster-based linear precoders for this framework. We then devise a power allocation strategy for the common and private streams within clusters and derive closed-form expressions for the sum-rate performance of the proposed cluster-based RS-CF system. Numerical results show that the proposed clustered RS-CF system and algorithms outperform existing approaches. % in terms of the sum-rate.