Robust Precoding Designs of RSMA for Multiuser MIMO Systems

TL;DR

This paper introduces a robust precoding method for RSMA in multiuser MIMO systems that effectively manages imperfect CSI, reducing computational complexity while maintaining high sum rate performance.

Contribution

It proposes a novel, computationally efficient robust precoding design for RSMA in MU-MIMO systems that handles imperfect CSI using a new optimization framework.

Findings

Achieves comparable sum rate performance to traditional methods.

Significantly reduces computational complexity.

Demonstrates robustness against imperfect channel information.

Abstract

Rate-splitting multiple access (RSMA) has been studied for multiuser multiple-input multiple-output (MUMIMO) systems especially in the presence of imperfect channel state information (CSI) at the transmitter. However, its precoding designs that maximize the sum rate normally have high computational complexity. To implement an efficient RSMA scheme for the MU-MIMO system, in this work, we propose a novel robust precoding design, which can handle imperfect CSI. Specifically, we first adopt the generalized mutual information to construct a lower bound of the objective function in the sum rate maximization problem. Then, we apply a smooth lower bound of the non-smooth sum rate objective function to construct a new optimization problem. By revealing the relationship between the generalized signal-to-interference-plus-noise ratio and the minimum mean square error matrices, we transform the constructed problem into a tractable one. After decomposing the transformed problem into three subproblems, we investigate a new alternating precoding design based on sequential solutions. Simulation results demonstrate that the proposed precoding scheme achieves comparable performance to conventional methods, while significantly reducing the computational complexity.