Mixed quality of service in cell-free massive MIMO

A mixed quality-of-service (QoS) problem is investigated in the uplink of a cell-free massive multiple-input multiple-output system where the minimum rate of non-real time users is maximized with per user power constraints while the rates of the real-time users (RTUs) meet their target rates. The original mixed QoS problem is formulated in terms of receiver filter coefficients and user power allocations, which can iteratively be solved through two sub-problems, namely, receiver filter coefficient design and power allocation. Numerical results show that, while the rates of RTUs meet the QoS constraints, the 90%-likely throughput improves significantly, compared with a simple benchmark scheme.