Enhancing secrecy rates in visible-light communications with signal-dependent noise: exploring optical jamming technique

Abstract This research investigates the security of a visible light communication (VLC) system in an indoor setting. The system consists of multiple transmitters (referred to as Alice), a legitimate receiver (referred to as Bob), and a passive adversary (referred to as Eve). A scheme is proposed to enhance secrecy by using optical jamming signals alongside the confidential signal, under constraints of nonnegativity and average optical intensity. The optical jamming signals follow a truncated Gaussian distribution to adhere to predefined constraints. The analysis takes into account both noise independent of the signal and noise dependent on the signal. The study obtains lower and upper bounds on secrecy rate through the application of the variational method, the dual expression of secrecy rate, and the notion of ‘the optimal input distribution that tends towards infinity’. An asymptotic analysis reveals a minimal performance difference between the upper and lower bounds under large optical intensity. Introducing a peak optical intensity constraint enables further scrutiny of both the exact and asymptotic secrecy-rate bounds. Numerical results are provided to validate the obtained secrecy-rate bounds.