Maximizing weighted sum of SLNR and SINR for LEO satellite communications with massive MIMO-NOMA

In a low earth orbit (LEO) satellite communication system with massive multiple input multiple output and non-orthogonal multiple access (MIMO-NOMA) transmission, how to reduce the inter-cluster interference as the same time to ensure the receiving performance of each user within a cluster is an important problem in downlink design. Hence, a beamforming scheme to maximize the weighted sum of signal to leakage plus noise ratio (SLNR) and signal to interference plus noise ratio (SINR) under the transmit power constraint is proposed in this paper. First, a user grouping strategy is adopted based on the spatial angle according to the characteristics of the channel from satellite to ground. Then, an alternating direction method of multipliers (ADMM) based solving procedure is designed to handle the beamforming problem by utilizing the advantage of ADMM in solving a multi-objective problem. The simulation shows that the proposed scheme gets a better sum rate than the baseline linear beamformers due to its more efficient optimization objective.