Diversity Analysis of Multi-Aperture UWOC System Over EGG Channel With Pointing Errors

The existing single-aperture reception for underwater wireless optical communication (UWOC) is insufficient to deal with oceanic turbulence caused by the combined effect of temperature gradient and air bubbles. This letter analyzes the performance of multi-aperture reception for UWOC under channel irradiance fluctuations characterized by the mixture exponential-generalized gamma (EGG) distribution. We analyze the system performance by employing selection combining (SC) and maximum ratio combining (MRC) receivers. In particular, we derive the exact outage probability expression for the SC-based multi-aperture UWOC receiver and obtain an upper bound on the outage probability for the MRC-based multi-aperture UWOC receiver. With the help of the derived results, we analytically obtain the diversity order of the considered multi-aperture UWOC systems outperforming the single-aperture-based system by a factor of the number of multi-aperture elements. The simulation results validate the accuracy of derived analytical expressions and demonstrate that the low-complexity SC technique effectively improves the performance of the UWOC system under oceanic turbulence with pointing errors at a moderately high transmit power.