Performance of a Cell-Free MIMO Under RF Mismatch

Cell-free wireless communications systems are characterized by the absence of base stations responsible for covering a specifically region and, then, all access points ideally can communicate with all user equipments. In this work, the performance analysis of cell-free systems subject to gain mismatches of the transceiver radio frequency circuits is presented at the access points, when they operate in the downlink mode. We also adapt a LMMSE channel estimation for this scenario. The analyses consider scenarios with two levels of mismatch, as well as the presence of pilot interference. The results have shown that the average system transmission rates are reduced when there is RF mismatch at the access points operating in transmission mode. It also demonstrated that increasing of mismatch level reduces system's achievable rates. The comparison between curves which consider or not RF mismatch during precoding have shown that the precoder which considers the mismatch gives achievable rates slightly higher.