Optimizing Spectral Efficiency in RIS-Assisted Cell-Free Massive MIMO NOMA Systems

The core message of this article is to propose a joint optimization framework to maximize the sum spectral efficiency of a reconfigurable intelligent surface (RIS)-assisted cell-free massive multiple-input multiple-output (mMIMO) non-orthogonal multiple access (NOMA) system, considering imperfect channel state information and imperfect successive interference cancellation.