Optimal Beamforming Structure for Rate Splitting Multiple Access

TL;DR

This paper introduces a novel toolbox-free method for optimizing beamforming and rate allocation in RSMA, achieving maximum weighted sum-rate with reduced computational complexity compared to traditional approaches.

Contribution

It identifies the optimal beamforming structure and common rate allocation for WSR maximization in RSMA using a new FP and Lagrangian duality approach, without relying on optimization toolboxes.

Findings

Achieves the same WSR performance as traditional methods.

Significantly reduces computational time.

Validates effectiveness through numerical simulations.

Abstract

In this paper, we aim at maximizing the weighted sum-rate (WSR) of rate splitting multiple access (RSMA) in multi-user multi-antenna transmission networks through the joint optimization of rate allocation and beamforming. Unlike conventional methods like weighted minimum mean square error (WMMSE) and standard fractional programming (FP), which tackle the non-convex WSR problem iteratively using disciplined convex subproblems and optimization toolboxes, our work pioneers a novel toolbox-free approach. For the first time, we identify the optimal beamforming structure and common rate allocation for WSR maximization in RSMA by leveraging FP and Lagrangian duality. Then we propose an algorithm based on FP and fixed point iteration to optimize the beamforming and common rate allocation without the need for optimization toolboxes. Our numerical results demonstrate that the proposed algorithm attains the same performance as standard FP and classical WMMSE methods while significantly reducing computational time.