Channel Modeling, Performance Analysis, and Probabilistic Shaping for Underwater Wireless Optical Communications

Recently, underwater wireless optical communication (UWOC) has emerged to support the high data rate requirements of oceanic exploration. In this paper, we propose an accurate and closed-form UWOC channel model to understand the effects of dynamic ocean environment on optical signal propagation. The model takes into account the impairments induced by oceanic path-loss, oceanic turbulence, pointing error loss and link interruption due to angle-of-arrival (AoA) fluctuations jointly. We further derive analytical expressions for various outage performance metrics. To boost the system robustness to dynamic ocean environment, we design a probabilistic shaping (PS)-based strategy with unipolar pulse amplitude modulation (PAM), which maximizes the ergodic constellation constrained capacity. Furthermore, considering the limitation of computational resources in real ocean environment, we simplify the PS-based scheme to alleviate the problem. Numerical results verify the accuracy of the proposed channel model and the outage performance analysis. Moreover, the simplified PS-based unipolar M-PAM scheme is validated to be a promising solution for the development and deployment of high speed adaptive UWOC systems.