Ultra-Low-Power Underwater Imaging

Researchers at MIT have developed and demonstrated the first ultra-low-power underwater networking and communication system, capable of transmitting signals across multiple kilometres. The system is now ready to be tested across longer ranges.

The system is a significant technological innovation that builds off of existing underwater communication methods, but uses one-millionth of the power required to run currently operating systems. The innovation will have a wide array of applications in the areas of aquaculture, climate change modelling and coastal weather pattern predictions.

‍Fadel Adib, MIT Department of Electrical Engineering and Computer Science associate professor and Abdul Latif Jameel Water and Food Systems Lab (J-WAFS) affiliated researcher, is a member of the team behind the research, which received funding from Community Jameel, the Office of Naval Research, the Sloan Research Fellowship, the National Science Foundation, the MIT Media Lab, and the Dohert Chair in Ocean Utilization. Fadel says, "What started as a very exciting intellectual idea a few years ago - underwater communication with a million times lower power - is now practical and realistic. There are still a few interesting technical challenges to address, but there is a clear path from where we are now to deployment."

Underwater backscatter communication devices use nodes made from "piezoelectric" materials. When a sound wave comes into contact with these nodes, they produce an electric signal and convert the mechanical energy into electric charge. The charge then scatters some of the acoustic energy back to the source, where data is decoded based on a series of reflections. Since backscatter occurs in all directions, signal strength and communication range is limited. Therefore, researchers employed the 70-year-old radio technology, Van Atta array, which positions pairs of antennas in a way that energy is reflected in the position it came from. To overcome the challenge of reduced efficiency caused by connecting the piezoelectric nodes in a Van Atta array, researchers placed a transformer between the node pairs, enabling maximum energy to be reflected back to its source.

The technology has been tested in more than 1,500 experimental trials, reaching a communication range of 300 meters, however testing has been limited to the length of the docks in the Atlantic coast and river ways until now. It is now being tested through an analytical model developed by the researchers, who hope to continue proving the technology's long-range capabilities through underwater testing using boats. As researchers move towards commercialising the technology, they plan to make tools and datasets available for other researchers to build on the innovation.