Weighted Sum-Rate Maximized Power Allocation in Downlink MIMO-NOMA Systems

Non-orthogonal multiple access (NOMA) is one of the key technology of the fifth generation mobile communication systems to increase the network capacity and data rate. The combination of multi-input multi-output (MIMO) technique and non-orthogonal multiple access (NOMA) systems can further improve the spectrum efficiency. In this paper, we investigate the power allocation problem in downlink MIMO-NOMA system. We first formulate the power allocation problem as a weighted sum rate maximization problem. Then, a series transformations based on quadratic transformation and Lagrange dual transformation are introduced to convert the original problem into a convex problem. Moreover, we propose an iterative algorithm to obtain the optimal solution of power allocation. Numerical results show the excellent convergence of our proposed power allocation approach and reveal that the proposed scheme improves the weighted sum rate significantly in MIMO-NOMA systems.