Beamforming Optimization for Intelligent Reflecting Surface Assisted MIMO: A Sum-Path-Gain Maximization Approach

TL;DR

This paper proposes a sum-path-gain maximization approach for optimizing beamforming in IRS-assisted MIMO systems, effectively enhancing spectral efficiency with a low-complexity algorithm and near-optimal performance.

Contribution

It introduces a novel sum-path-gain maximization criterion and an efficient ADMM-based algorithm for joint source precoding and IRS phase shift design in IRS-assisted MIMO systems.

Findings

Achieves near-optimal spectral efficiency performance.

Reduces computational complexity compared to existing methods.

Demonstrates effectiveness through numerical simulations.

Abstract

Recently, intelligent reflecting surface (IRS) has emerged as an appealing technique that enables wireless communications with low hardware cost and low power consumption. In this letter, we consider an IRS-assisted point-to-point multi-input multi-output (MIMO) system, where a source communicates with its destination with the help of an IRS. Our goal is to maximize the spectral efficiency of this system by jointly optimizing the (active) precoding at the source and the (passive) phase shifters (PSs) at the IRS. However, this turns out to be an intractable mixed integer non-convex optimization problem. To circumvent the intractability, we propose a new sum-path-gain maximization (SPGM) criterion to obtain a high-quality and efficient suboptimal solution to this problem. Specifically, the PSs are first designed based on a simplified optimization problem, which aims to maximize the sum-gains of the spatial paths between the source and the destination. Then, a low-complexity alternating direction method of multipliers (ADMM) algorithm is utilized to solve this simplified problem. Finally, with the above obtained PSs, the source precoding is derived by performing the singular value decomposition (SVD) on the effective channel between the source and the destination. Numerical results demonstrate that the proposed scheme can achieve near-optimal performance.