Joint Design of Hybrid Beamforming and Phase Shifts in RIS-Aided mmWave Communication Systems

TL;DR

This paper proposes a novel joint optimization framework for hybrid beamforming and RIS phase shifts in mmWave systems, significantly reducing power consumption while satisfying SINR constraints.

Contribution

It introduces a penalty-based manifold optimization algorithm for joint design, outperforming existing methods and demonstrating the benefits of combined RIS and beamforming optimization.

Findings

Proposed algorithm outperforms state-of-the-art methods.

Joint optimization yields better performance than separate optimization.

Simulation confirms power reduction and improved SINR satisfaction.

Abstract

This paper considers a reconfigurable intelligent surface (RIS)-aided millimeter wave (mmWave) downlink communication system where hybrid analog-digital beamforming is employed at the base station (BS). We formulate a power minimization problem by jointly optimizing hybrid beamforming at the BS and the response matrix at the RIS, under signal-to-interference-plus-noise ratio (SINR) constraints. The problem is highly challenging due to the non-convex SINR constraints as well as the non-convex unit-modulus constraints for both the phase shifts at the RIS and the analog beamforming at the BS. A penalty-based algorithm in conjunction with the manifold optimization technique is proposed to handle the problem, followed by an individual optimization method with much lower complexity. Simulation results show that the proposed algorithm outperforms the state-of-art algorithm. Results also show that the joint optimization of RIS response matrix and BS hybrid beamforming is much superior to individual optimization.