This paper focuses on the effect of the receiver’s tilted angle on the capacity of a clear ocean water Underwater Wireless Optical Communication (UWOC) system. To achieve this goal, the relationship between the channel capacity and the receiver’s tilted angle is investigated. First, we propose a double-exponential fading model with pointing error which can more accurately depict the channel of clear ocean water UWOC instead of the traditional Beer’s law model. Based on this channel model, we present the close-form expression of the capacity bounds of the UWOC system. Then, an optimization problem is formulated to improve the capacity by tilting the receiving plane. Both theoretical analyses and simulation results verify that the capacity bounds of UWOC can be enhanced dramatically by tilting the receiver plane at an optimal angle. Thus, in practice, we can provide an effective design strategy for a UWOC system.

This paper focuses on investigating the effect of the receiver’s tilted angle on the channel capacity of an underwater wireless optical communication (UWOC) system, in which an avalanche photodiode (APD) detector is adopted as the receiver. Under the non-negativity, peak power, and average power constraints, the lower bounds on the capacity of UWOC are derived in detail according to different average-to-peak power ratios. With modeling achieving the maximum of the lower bounds of the capacity as an optimization object, we prove that the proposed optimization issue is in fact a simple convex optimization about the tilted angle of the APD receiver, and then present related theoretical solution for it. Both theoretical analysis and simulation results show that by appropriately tilting the receiver, we can significantly enhance the final capacity performance of the UWOC with APD receiver.