Seleção de Pontos de Acesso, Pré-Codificação MMSE e Alocação de Potência Iterativa para Sistemas de Múltiplas Antenas Livres de Células

In this work, we propose iterative access point (AP) selection (APS), linear minimum mean-square error (MMSE) precoding and power allocation for Cell-Free multiple-input multiple-output (MIMO) systems. We consider the downlink channel with single-antenna users and multiple-antenna APs. A sophisticated downlink strategy is developed which implies MMSE precoding in combination with uniform power allocation or optimized power allocation that maximizes the minimum rate per user. Simulations show that the proposed approach outperforms existing conjugate beamforming (CB) and zero-forcing (ZF) schemes and that performance remains excellent with APS, in the presence of perfect and imperfect channel state information (CSI).