Hybrid precoding design based on alternating optimization in mmWave massive MIMO systems aided by intelligent reflecting surface

Abstract

Intelligent reflecting surface (IRS) offers a promising and revolutionizing solution to enhance spectrum and energy efficiency by leveraging massive low-cost passive elements that are able to reflect the incident signal with adjustable amplitude and phase. Different from the prior works focusing on MISO scenario, this paper considers the IRS-aided single-user mmWave massive MIMO systems. We formulate and solve new problems to maximize the spectral efficiency of the systems by jointly optimizing the active beamforming at both the base station and user equipment, as well as the passive beamforming at the IRS. To tackle this problem, we first give the closed-form solutions of active beamforming and passive beamforming in MISO scenario. Then, we divide the optimization problem into three sub-problems, and perform alternate optimization solutions in MIMO scenario. In addition, we analyze the performance of the proposed algorithms in more practical scenarios where each element of IRS can only take discrete phase-shift values and base station has imperfect CSI. Simulation results show that IRS-aided MIMO systems effectively improves the spectral efficiency and also verifies the superior performance of our proposed algorithms.