Artificial-Noise-Aided Precoding Design for Multi-User Visible Light Communication Channels

Secure transmission is becoming an essentially important aspect in visible light communication (VLC). In this paper, we investigate the designs of artificial noise (AN)-aided precoding to improve physical layer security in a multi-user single eavesdropper wiretap VLC channels. The AN-aided precoding is designed to solve the max-min fairness signal- to-interference-plus-noise ratio (SINR) problem among users in two different scenarios: unknown and known eavesdropper's channel state information (CSI) at the transmitter. In the former case, we adopt the traditional null- space AN scheme and then study the impact of the AN power on the fairness performance. In the case of known eavesdropper's CSI, the AN-aided precoding is designed in such a way that keeps the SINR of the eavesdropper below a predefined threshold. Numerical results show that in both cases, the design could significantly degrade the quality of the eavesdropper's channel, thus enhancing communication secrecy.