Low-power underwater communication

MIT researchers have demonstrated a technology that can transmit underwater signals much farther than existing methods, using only about a millionth as much power.

The system is based on backscatter communication, a method of encoding data in sound waves that are reflected from the sound source, or interrogator, back to a receiver in the same location. The underwater backscatter device uses nodes made from piezoelectric materials, which produce an electrical signal when a mechanical force-including sound waves-is applied. The nodes use that charge to scatter some of the acoustic energy back to the receiver.

To make the system more efficient, the researchers used a 70-year-old technology called a Van Atta array, in which symmetric pairs of antennas are connected so that energy is reflected back in the direction it came from, and placed a transformer between pairs of connected nodes. It can be used with data-collecting sensors and send data to a ship or onshore station.

In tests, the device achieved ranges of 300 meters, more than 15 times longer than previously demonstrated-and a model suggests that kilometer-scale ranges are possible. That could make it suitable for things like coastal hurricane prediction and climate modeling.

There are still a few interesting technical challenges to address, but there is a clear path from where we are now to deployment," says Fadel Adib, director of the Signal Kinetics group in the MIT Media Lab and the senior author of two papers on the work.