Implementation of a low cost, solar charged RF modem for underwater wireless sensor networks

Underwater communication (UWC) has become an attractive research field over the past few decades. This is mainly due to the increase in underwater applications such as exploration, monitoring, and warning systems. Traditional communications techniques face many obstacles when used underwater. Optical communications require line of sight which is not always maintained underwater due to turbulence. Acoustic communication does not suffer from that, however, it can only operate with very low rates. While radio frequency (RF) communication can only operate over short distances due to the attenuation from the water, it can deliver relatively high data rates and does not require line of sight nor affected by turbulence. Additionally, it does not suffer much when crossing the air–water boundaries. Moreover, underwater nodes require a new method of powering as it is not feasible to change their batteries when they are depleted. And so, we have investigated underwater solar power harvesters as a means to power the underwater nodes. In this paper, we design, implement, integrate, and test a low cost solar powered RF underwater modem to be used as a building block of an underwater wireless sensor network. The system was tested with multiple nodes to allow multi-hop communications in order to increase the communication distance. Results show that the network operates with a moderate to high throughput from end to end.