Underwater Visible Light Communications in Cascaded Gamma-Gamma Turbulence

In this paper, we investigate the performance of vertical underwater visible light communication (VLC) links in the presence of moderate and strong turbulence conditions using Gamma-Gamma (GG) probability density function. In vertical links, refractive index changes with depth eventually affecting the variance of turbulence-induced fading. Considering such variations with respect to depth, we first develop a statistical turbulence channel model based on the cascaded structure of fading coefficients. Then, we use this expression to formulate a closed form expression for bit error rate performance. We confirm the analytical derivations through simulations.