Achievable Rate Analysis of Non-Ideal Cell-Free Massive MIMO Systems with RSMA

Abstract

Cell-free massive multiple-input multiple-output (CF-mMIMO) is a promising architecture for future wireless networks, yet its practical deployment is severely hindered by hardware impairments and time-varying channel conditions. To address these challenges, we investigate downlink transmission in a rate-splitting multiple access (RSMA)-aided CF-mMIMO system under multiple classes of non-idealities, including channel aging, local oscillator phase noise, and analog-to-digital converter quantization distortion. By explicitly modeling these practical impairments, we first derive the linear minimum mean square error channel estimator and subsequently obtain tight closed-form expressions for the achievable rate under imperfect channel state information. Extensive numerical results validate the accuracy of our theoretical analysis and quantify the performance degradation induced by the joint effects of multi-class impairments. Furthermore, the results demonstrate that owing to its flexible interference management, RSMA exhibits significantly stronger robustness and superior spectral efficiency compared to the conventional space-division multiple access strategy under non-ideal conditions.