Distributed MMSE-based uplink receive combining, downlink transmit precoding and optimal power allocation in cell-free massive MIMO systems

Abstract In cell-free massive multiple-input multiple-output systems, a large number of distributed wireless access points (AP) simultaneously serve user equipments (UEs). This setup has recently been introduced as promising alternative for the current 5G cellular networks. The ability to offer good quality service, especially UEs on cell edges, be it that there is still need low-complexity signal processing algorithms. this paper, problem optimal power allocation combined with uplink receive combining and downlink transmit precoding tackled by providing efficient MMSE-based necessary fronthaul communications estimate combining/precoding vectors large-scale channel statistics are reduced minimum rely in-network summation can accomplished whenever APs arranged into tree-topology. Non-weighted max-sum max–min used utilities allocation, but algorithms not limited these cases. Simulations show proposed outperform heuristic methods, both in downlink.