RSMA for Overloaded MIMO Networks: Low-Complexity Design for Max-Min Fairness

TL;DR

This paper introduces a low-complexity RSMA design for overloaded MIMO downlink networks, providing optimal power and rate allocation solutions that outperform traditional SDMA schemes under various CSIT conditions.

Contribution

It offers closed-form solutions for max-min fairness in overloaded MIMO networks and proposes a practical RSMA system design for arbitrary user and antenna configurations.

Findings

RSMA achieves higher rates than SDMA in simulations.

The proposed solutions work under perfect and imperfect CSIT.

Low-complexity design simplifies implementation.

Abstract

Rate-Splitting Multiple Access (RSMA) is a robust multiple access scheme for multi-antenna wireless networks. In this work, we study the performance of RSMA in downlink overloaded networks, where the number of transmit antennas is smaller than the number of users. We provide analysis and closed-form solutions for optimal power and rate allocations that maximize max-min fairness when low-complexity precoding schemes are employed. The derived closed-form solutions are used to propose a low-complexity RSMA system design for precoder selection and resource allocation for arbitrary number of users and antennas under perfect and imperfect Channel State Information at the Transmitter (CSIT). We compare the performance of the proposed design with benchmark designs based on Space Division Multiple Access (SDMA) with and without user scheduling. By numerical results, we show that the proposed low-complexity RSMA design achieves a significantly higher rate compared to the SDMA-based benchmark designs under perfect and imperfect CSIT.