Association of Access Points 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 mit-igate 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 character-istics. The proposed approach exploits hierarchical clustering, enabling flexible cluster sizing to improve interference manage-ment 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.