Stochastic geometry approach to secrecy analysis in visible light communication in the presence of randomly located eavesdroppers

This paper investigates the physical layer security of indoor visible light communication (VLC) systems in the presence of randomly located eavesdroppers using a stochastic geometry framework. Unlike traditional LOS-only or perfect-CSI assumptions, this work incorporates a more realistic setting where the eavesdropper’s channel state information (CSI) is unknown, and both line-of-sight (LOS) and first-order non-line-of-sight (NLOS) reflections are accounted for in the channel modelling. The analysis further integrates device orientation randomness and evaluates security under eavesdroppers employing selection combining (SC) and maximum ratio combining (MRC). Closed-form expressions for the channel gain, SNR distribution, and secrecy outage probability (SOP) are derived by exploiting the spatial statistics of a bounded Poisson point process (PPP). Results show that incorporating NLOS components significantly enhances legitimate SNR and improves secrecy performance, while eavesdropper collaboration using maximum ratio combining presents the worst-case security threat. Monte Carlo simulations validate the analytical derivations, demonstrating close agreement across various system parameters. The study offers an accurate and practical secrecy analysis framework for next-generation VLC deployments in realistic indoor environments.