Secure Cooperative Hybrid VLC-RF Systems

In this paper, a cooperative hybrid visible light communication (VLC)-radio frequency (RF) system with spatially random terminals is considered. Specially, a source node (S) with a group of light emitting diode (LED) lamps transmits its information bits to a destination (D), which locates out of S’s coverage area, via a relay node (R). R is equipped with a photodetector and an antenna to set up VLC link between S and R, and radio frequency (RF) link between R and D, respectively. Meanwhile, an eavesdropper (E) tries to overhear the information delivery over RF link by equipping with an antenna. Furthermore, threshold decode-and-forward relaying scheme is adopted at R, so as to save the system resource consumed in the case that the information delivery over S – R link fails. By employing stochastic geometry, we first characterize the probability density function and cumulative distribution function of the received signal-to-noise-ratio over both VLC and RF links, while considering the randomness of the locations of both R and D. Then, the secrecy performance of the target system is studied by deriving the approximated closed-form expression for the probability of intercept. Finally, the proposed analytical model is verified via Monte-Carlo simulations.