Artificial Noise Design in Time Domain for Indoor SISO DCO-OFDM VLC Wiretap Systems

In this paper, we investigate physical-layer security for the indoor single-input single-output (SISO) DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM) visible light communication (VLC) wiretap systems. To increase system security, we propose a precoding scheme using time-domain artificial noise (AN) to exploit the degrees of freedom (DOFs) provided by the cyclic prefix (CP) of OFDM. We further propose a convex optimization method to restrict the increase of peak to average power ratio (PAPR) introduced by AN precoding and then maximize the secrecy rates. Numerical results suggest that the proposed scheme can significantly boost the secrecy performance and alleviate the impact of PAPR increment.