IRS-Aided Multi-Cell Massive MIMO Systems With Impairments: SE Analysis and Optimization

Abstract

We consider the uplink of a hardware-impaired intelligent-reflective surfaces (IRS)-aided multi-cell massive multiple-input multiple-output (mMIMO) system with mobile user equipments, whose channels age with time. We propose a novel distortion-and-aging-aware minimum-mean-square-error (DAA-MMSE) receiver that not only provides a higher spectral efficiency (SE) than conventional maximal ratio combiner (MRC) and distortion-unaware MMSE (DU-MMSE) receivers, but also reduces the pilot overhead. We also derive an SE lower bound for this system with MRC and DAA-MMSE receivers. We develop a novel low-complexity SE optimization framework using the weighted-MMSE and minorization-maximization (MM) techniques, which provide closed-form expressions for optimal power and phase allocations. The MM technique requires construction of a surrogate function, which we do in this work. We numerically characterize the i) UE velocities for which IRS deployment can tangibly increase their SE; ii) reduced pilot overhead with DAA-MMSE receiver along with IRS.