Outage probability analysis of vertical underwater wireless optical links under varying turbulence with pointing errors and attenuation losses

In this paper, we investigate the outage probability performance of underwater wireless optical communication for a vertical link. Due to temperature and salinity variations, turbulence in the vertical link ranges from strong to weak. The vertical link turbulence is modeled using a cascade of the gamma-gamma and hyperbolic tangent log-normal distributions. In addition to turbulence, we consider the impact of attenuation losses in the underwater medium and pointing errors at the receiver for outage probability analysis. A closed-form expression for the outage probability of the vertical link is derived. Outage probability results are presented for different water types, signal-to-noise ratio thresholds, degrees of pointing errors, and data rates. Additionally, an asymptotic analysis is provided to offer insights at high transmitted power. The accuracy of the derived closed-form expression is validated using Monte Carlo simulations.