Unified Statistical Channel Model for Turbulence-Induced Fading in Underwater Wireless Optical Communication Systems

TL;DR

This paper introduces a unified statistical model using the Exponential-Generalized Gamma distribution to accurately characterize turbulence-induced fading in underwater optical channels affected by air bubbles and temperature gradients, supported by experimental data.

Contribution

It presents the first comprehensive model for underwater optical turbulence, enabling analytical performance evaluation of UWOC systems under various conditions.

Findings

Model fits experimental data perfectly across conditions

Provides closed-form expressions for performance metrics

Simplifies analysis of UWOC system performance

Abstract

A unified statistical model is proposed to characterize turbulence-induced fading in underwater wireless optical communication (UWOC) channels in the presence of air bubbles and temperature gradient for fresh and salty waters, based on experimental data. In this model, the channel irradiance fluctuations are characterized by the mixture Exponential-Generalized Gamma (EGG) distribution. We use the expectation maximization (EM) algorithm to obtain the maximum likelihood parameter estimation of the new model. Interestingly, the proposed model is shown to provide a perfect fit with the measured data under all channel conditions for both types of water. The major advantage of the new model is that it has a simple mathematical form making it attractive from a performance analysis point of view. Indeed, we show that the application of the EGG model leads to closed-form and analytically tractable expressions for key UWOC system performance metrics such as the outage probability, the average bit-error rate, and the ergodic capacity. To the best of our knowledge, this is the first-ever comprehensive channel model addressing the statistics of optical beam irradiance fluctuations in underwater wireless optical channels due to both air bubbles and temperature gradient.