Energy-Efficient Multi-Pair Computation for Intra Cell-Free Massive MIMO Communications

Cell-free massive MIMO (CF-mMIMO) networks have been extensively researched in the literature with a focus on separately designing either their uplink or downlink transmission schemes. However, a joint design of the uplink and downlink transmission can yield superior performance, particularly in CF-mMIMO networks with intra-cloud communications. This letter proposes an end-to-end transmission scheme for intra-network communication in a CF-mMIMO network, which does not split the transmission into uplink and downlink in the classical sense. It characterizes the performance of the scheme under perfect and imperfect channel state information (CSI), and then optimizes its energy efficiency while considering fronthaul capacity and power constraints, access point power constraints, and user power and spectral efficiency constraints. Numerical evaluations demonstrate that the proposed scheme achieves significantly improved energy efficiency compared to the state-of-art.