Analyzing Visible Light Communication Through Air-Water Interface

In underwater wireless networks (UWNs), conventionally there is no direct communication between an underwater node and a remote command center. A floating base-station is often used to serve as an interface to a UWN; such a base-station would typically have both acoustic and radio modems to communicate with underwater nodes and off-shore centers, respectively. Although employing an airborne base-station would avoid the logistically-complicated surface nodes deployment, communication across the air-water interface becomes the main challenge since it involves two mediums. This paper promotes a novel way to interconnect UWNs to airborne base-stations through visible light communication (VLC) links. The paper analyzes the viability of VLC across the air-water interface by determining the coverage area and intensity inside the water for a light transmitter placed in the air. We show that enough intensity can be achieved for VLC communication even in the presence of a wavy water surface. We then provide guidelines for using single and multiple light sources to establish robust VLC links under rough environmental conditions like high water current and turbidity. Our approach is validated using simulation and a lab experiment is done to validate the simulation result for flat water surfaces.