Secrecy Analysis and Optimization for IRMA- and Jammer-Aided Visible Light Communications

This letter investigates the physical-layer security (PLS) of an indoor visible light communication system having a transmitter, a jammer, an intelligent reflecting mirror array (IRMA), a legitimate user, and an eavesdropper. Two scenarios are investigated for the non-negative input: one is having an average optical intensity constraint only, and the other is with both average and peak optical intensity constraints. By the entropy-power inequality and variational method, we derive closed-form expressions of secrecy-capacity lower bounds for the two scenarios, respectively. Based on the derived lower bound, we formulate a constrained secrecy-capacity maximization problem to further improve the PLS performance, and then transform it into a tractable problem by objective function approximation. After that, an optimization algorithm is proposed to solve the problem. Numerical results show the necessity of considering both IRMA and jammer, and also verify the effectiveness of the proposed algorithm.