Secrecy outage probability analysis in a free-space optical system based on partially coherent beams through anisotropic non-Kolmogorov turbulent atmosphere

Abstract

In this paper, the secrecy outage probability of a partially coherent beam free-space optical communication system considering the combined effect of anisotropic non-Kolmogorov strong turbulent atmosphere and the eavesdropper’s position is investigated. The Fisher–Snedecor distribution is chosen to model the atmospheric turbulence because it is not only suitable for weak to strong turbulence conditions but is also mathematically simple. Based on the fading channel model and the generalized pointing error model, we derive analytical expressions for the lower bounded secrecy outage probability. Also, we obtain asymptotic closed-form expression at a high signal-to-noise regime. The obtained expressions are corroborated by Monte Carlo simulations. The calculation results based on the analytical expressions show that increasing the source coherence parameter makes the secrecy interruption probability performance first better and then worse for a given condition, and an optimal value is observed. The anisotropic coefficient and power law have a positive effect on the secrecy outage probability of the free-space optical communication system. Under the given conditions, the performance of the secrecy outage probability is significantly improved by the divergent beam, although the increased spot size at the receiver makes it easier for eavesdroppers to tap the link. The secrecy outage probability performance deteriorates as the vertical component of Bob, the jitter variance, and the refractive index structure constant increase.