Optimal Relay Placement for Relay-assisted Underwater Wireless Optical Communication Systems over Weak Turbulence Channel

In this paper, based on the principle of optimal performance, we investigate relay placement in a relay-assisted underwater wireless optical communication (UWOC) system with a single relay over a log-normal turbulence channel. To evaluate the system performance, outage probability is deduced where the system adopts a decode-and-forward (DF) relay, and the effect of depth on solar noise is considered. Then, a two-dimensional Cartesian coordinate system is established to describe the optimization model. Due to the non-convex objective function, it cannot be solved directly using convex optimization methods. Hence, we consider an alternating iteration method to iteratively solve the relay’s position and obtain a suboptimal solution. Through simulations, the proposed solution method is verified to be able to obtain the optimal position, and the UWOC system using optimal relay placement (ORP) has a significantly better performance.