Communication through Air Water Interface Using Multiple Light Sources

Underwater wireless networks (UWNs) conventionally have been interfaced to remote control centers through floating nodes that serve as gateways. A gateway will have an acoustic transceiver to communicate with underwater nodes and interact with command nodes over radio airwaves. This paper presents a novel approach that avoids the need for surface gateways and enables effective communication through the air water interface using free space optics. We first analyze the effect of optical transmission angle on the underwater signal range. Based on such analysis we determine the optical beam angle and underwater node position for best signal strength. We further develop a scheme for extending the coverage by beamforming of multiple light sources to mitigate the effect of water current on the receiver position and enable the establishment of robust communication links between underwater nodes and an air-borne base-station.