A user matching and power allocation scheme for downlink MIMO-NOMA communication system

Abstract Non-orthogonal multiple access (NOMA) combined with multiple-input multiple-output (MIMO) can greatly increase the system throughput, but it will cause additional interference. Generally, the interference can be eliminated by utilizing the precoding technology. The previous studies preferentially focused on the channel difference between users, and neglected the lowly correlated scenarios, leading to the decline of users’ throughput. A low-complexity user matching and power allocation scheme is proposed for such scenarios. Firstly, users with higher channel correlations are matched, and the remaining users are matched in terms of channel difference. Furthermore, the objective function is established to maximize the system throughput while assuring users’ quality of service (QoS). Eventually, with the objective function in the Karush-Kuhn–Tucker (KKT) conditions being solved, the power allocation factors are achieved. The simulation results quantify that the proposed scheme has an advantage over the conventional MIMO-NOMA scheme.