Optimal FOV of Angular Diversity Receiver for Underwater Visible Light Communications

Abstract

Recently, underwater visible light communications (UVLC) have attracted much attention for searching and excavating undersea resources effectively. While UVLC suffers from background noise from sunlight, the application of UVLC has been limited to the deep ocean. To realize the UVLC in shallow water, UVLC with the maximal-ratio combining scheme applied to angle diversity receiver with multiple Photodiodes (PDs) at different angles was proposed and, in particular, the optimization of PD placement has been studied. However, as the field of view (FOV) of each PD was fixed at 90 degrees, its optimization has not been studied. Therefore, this paper investigates the optimal FOV of PDs that maximize the average SNR of a square communication area of $n$ centered at the initial position of the receiver. As a result, in an area of $k$, narrowing the FOV of the receiver with evenly distributed PDs to 25 degrees improved the average SNR by about 3 dB compared to the case where the FOV was set to 90 degrees. In the $i$ area, narrowing the FOV of the receiver with PDs placed on the sides to 75 degrees improved the average SNR by about 0.8 dB compared to the case where the FOV was set to 90 degrees.