Robust artificial noise-aided beamforming for a secure MISO-NOMA visible light communication system

Visible light communication (VLC) and non-orthogonal multiple access (NOMA) have been deemed two promising techniques in the next wireless communication networks. In this paper, secure communications in the presence of potential eavesdropper are investigated for a multiple-input single-output VLC system with NOMA. The artificial noise jamming and beamforming technologies are applied to improve secure performance. A robust resource allocation scheme is proposed to minimize the total transmit power taking into account the constraints on the quality of service requirement of the desired users and the maximum tolerable data rate of the eavesdropper, and the practical imperfect channel state information of both the desired users and the eavesdropper. The formulated non-convex optimization problem is tackled based on S-Procedure and semi-definite programming relaxation. Simulation results illustrate that our proposed resource allocation scheme can effectively guarantee communication security and achieve transmit power saving. Moreover, the height and number of LED can significantly affect system performance and the optimum LED height can be obtained for different LED numbers.