Distributed joint receiver design for uplink cell-free massive MIMO

The majority of works on cell-free massive multiple-input multiple-output (MIMO) adopt uncoordinated transmit/receive strategies at the base stations (BSs) to avoid extensive channel state information (CSI) exchange via backhaul signaling. However, significant performance gains can be achieved by allowing coordination among the BSs. This paper proposes a distributed joint receiver design for uplink cell-free massive MIMO based on over-the air (OTA) signaling, which entirely eliminates the need for backhaul signaling for CSI exchange. The proposed scheme is flexible and scalable, as the amount of OTA signaling does not grow with the number of BSs or user equipments. Numerical results show fast convergence and remarkable performance gains with respect to uncoordinated joint reception.