Energy Consumption Minimization of Air-to-Water Visible Light Communications

As offshore industries and the Internet of Underwater Things (IoUT) continue to expand, air-to-water communication is needed to connect various underwater sensors and things to the outside world. Visible light communication (VLC) has the potential to provide higher data rates and longer transmission distances than radio frequency and other air-to-water communication techniques. This paper presents an air-to-water VLC system where a light emitting diode (LED) transmitter carried by a hovering unmanned aerial vehicle (UAV) transmits data to an underwater receiver. We minimize the UAV energy consumption that includes both LED transmission and UAV propulsion energy consumption by optimizing the LED transmit power while guaranteeing that the average received signal-to-noise ratio (SNR) at the underwater receiver is above the required SNR. A sequential quadratic programming (SQP)-based algorithm is proposed to solve this problem. Simulation results show that our optimized LED transmit power reduces the total UAV energy consumption by up to 45% as compared to the benchmark schemes without increasing the transmission time for a given data volume.