Iterative Soft Intra-Cluster Interference Cancellation for Cell-Free Massive MIMO Networks

This work proposes soft iterative parallel interference cancellation (PIC) for clustered cell-free massive multi-input multi-output (MIMO) networks to mitigate intra-cluster interference. In particular, we derive new closed-form expressions for minimum mean square error linear receive filters with PIC (MMSE-PIC) receivers by assuming the presence of inter-cluster interference (ICI), channel estimation errors and additive white Gaussian noise. The derived expressions are used to develop the resulting receivers by varying the number of iterations and assuming perfect and imperfect channel state information. By determining the mean and variance of the detected signals, new closed-form expressions for the Gaussian approximation of the likelihood function are also obtained. Simulations evaluate both clustered and full cell-free mMIMO networks equipped with the proposed cluster-based MMSE-PIC and linear MMSE receivers in terms of bit error rate (BER) and complexity.