Study of AP Association and Users and Power Allocation for Cell-Free Massive MIMO Systems

This paper introduces an access point-user (AP-UE) association strategy combined with pilot power allocation to mitigate multiuser interference and enhance spectral efficiency (SE) in clustered cell-free massive MIMO (CCF-mMIMO) networks. We propose a dynamic channel-based clustering method that groups APs according to their channel correlation, ensuring users are associated with APs exhibiting similar channel characteristics. The proposed approach exploits hierarchical clustering, enabling flexible cluster sizing to improve interference management and overall SE. Moreover, we present a power control (PC) technique that is based on a weighted sum-rate maximization (WSRM) algorithm to ensure consistent service quality across users. Numerical results demonstrate that the proposed method achieves superior SE and robust performance in high-density multi-user environments as compared to competing approaches.