Relay-Aided Physical Layer Security in Multi-User VLC With Single Light Source Using Cooperative Jamming

Traditional physical layer security (PLS) schemes for multi-user visible light communication (MuVLC) are designed with multiple light sources, rendering them inapplicable to MuVLC with single light source. To address this limitation, we propose an innovative relay-aided PLS scheme based on cooperative jamming for MuVLC with single light source. First, we randomly select parts of relays for cooperative jamming, modeling their locations as a Poisson point process (PPP). Then, a jamming signal introduced through these selected relays significantly decreases the signal-to-interference-plus-noise-ratio of the randomly located eavesdroppers, thereby increasing the security capacity. By modeling the eavesdropper locations as another independent PPP, we analyze the security performance by deriving closed-form expressions for the cumulative distribution function of security capacity, security outage probability, its lower and upper bounds, and ergodic security capacity. These theoretical expressions are verified via Monte Carlo simulations. Numerical results show that our scheme achieves high-level communication security. Furthermore, increasing relay density, decreasing eavesdropper density, reducing target security capacity, or lowering relay plane height can effectively reduce security outage probability, offering valuable insights for designing secure MuVLC with single light source.