Performance Analysis of MIMO-EGC System for the Underwater Vertical Wireless Optical Communication Link

In this paper, we have investigated the performance of an underwater vertical wireless optical communication (UVWOC) link employing multiple input-multiple output (MIMO) operating in conjunction with equal gain combing (EGC) techniques perturbed by weak and strong turbulence in the presence of pointing errors and attenuation losses. Vertical underwater turbulence, which varies from layer to layer due to temperature and salinity variation connected to depth, is modeled using hyperbolic tangent log-normal (HTLN) distribution in the case of weak underwater turbulence and gamma-gamma (GG) distribution in the case of strong underwater turbulence. Novel closed-form expressions quantifying the average bit error rate (BER) have been derived for the UVWOC MIMO EGC system for weak and strong turbulence regimes. The expression for the average BER associated with the UVWOC link for different values of pointing error, differing vertical layer depth, modulation types, and differing numbers of sources and detectors have been determined. In addition, closed-form expressions for the outage probability (OP) and ergodic channel capacity (ECC) have been derived for the UVWOC MIMO EGC system. The accuracy of all closed-form expressions derived in the paper has been verified using Monte Carlo simulations.