Privacy Protection via Beamforming Optimization in MISO NOMA Networks

Non-orthogonal multiple access (NOMA) is a promising approach for 5G. However, the privacy between users may be compromised due to the superposition of all users’ signals to successive interference cancellation (SIC) receivers. In this paper, we propose a scheme based on beamforming optimization for the downlink NOMA that can enhance the security of a specific private user while guaranteeing other users' quality of service (QoS). Specifically, we intend to maximize the secrecy rate of the private user, under the constraint that the other users’ QoS is satisfied. Owing to the non-convexity, we first convert it into convex forms and then, an iterative algorithm based on the concave-convex procedure is proposed to attain their solutions. Extensive simulation results are presented to evaluate the effectiveness of the proposed scheme.