We consider the downlink of a massive multiple-input-multiple-output (mMIMO) system, where a base station (BS) serves multiple clusters of single-antenna user equipments (UEs) by using multiple single-antenna relays. The BS employs a novel rate-splitting multiple access (RSMA) private interference cancellation (PIC) protocol wherein, similar to RSMA, a UE first decodes its common message. To decode its private message, a UE then cancels interference not only from the common message but, unlike RSMA, also from the private messages of weaker UEs in its own cluster. The RSMA-PIC protocol integrates the benefits of non-orthogonal multiple access (NOMA) and RSMA protocols, and outperforms them in low and high signal-to-noise regime. The BS employs minimum-mean-squared-error precoder to cancel the inter-relay interference between multiple relays. We also develop a decentralized two layer iterative optimization framework to maximize the weighted sum energy efficiency metric.

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.