Robust Beamforming Design for STAR-RIS Aided RSMA Network with Hardware Impairments

TL;DR

This paper develops a robust beamforming strategy for STAR-RIS aided RSMA networks that accounts for hardware impairments, improving sum rate performance and robustness over traditional schemes.

Contribution

It introduces a fractional programming-based optimization method for robust beamforming in STAR-RIS RSMA systems considering hardware impairments, which enhances performance and robustness.

Findings

Proposed scheme outperforms other multiple access schemes.

Considering hardware impairments improves robustness.

Achieves higher sum rate than conventional passive RIS.

Abstract

In this article, we investigate the robust beamforming design for a simultaneous transmitting and reflecting reconfigurable intelligent surface (STAR-RIS) aided downlink rate-splitting multiple access (RSMA) communication system, where both transceivers and STAR-RIS suffer from the impact of hardware impairments (HWI).A base station (BS) is deployed to transmit messages concurrently to multiple users, utilizing a STAR-RIS to improve communication quality and expand user coverage. We aim to maximize the achievable sum rate of the users while ensuring the constraints of transmit power, STAR-RIS coefficients, and the actual rate of the common stream for all users. To solve this challenging high-coupling and non-convexity problem, we adopt a fractional programming (FP)-based alternating optimization (AO) approach, where each sub-problem is addressed via successive convex approximation (SCA) and penalty function (PF) methods. Numerical results demonstrate that the proposed scheme outperforms other multiple access schemes and conventional passive RIS in terms of the achievable sum rate. Additionally, considering the HWI of the transceiver and STAR-RIS makes our algorithm more robust than when such considerations are not included.