Robust beamforming for downlink non-orthogonal multiple access network

Abstract

In this paper, we study the robust beamforming design for a downlink non-orthogonal multiple access (NOMA) network. By considering the estimation errors of channel state information (CSI), we aim to design robust beamformer, which minimizes transmit power while satisfies the outage probability constraints. However, the robust beamforming design problem is non-convex and intractable. To overcome this difficulty, the probabilistic constraints are converted to deterministic form by using semidefinite relaxation (SDR) and the Bernstein-type Inequality, and thus the non-convex robust beamforming design problem is transformed to a convex problem, which can be solved using interior point algorithms. Simulations demonstrate that the proposed method significantly outperforms the existing methods in terms of the robustness and the power efficiency.