MIT Media Lab researchers have designed a system that allows underwater and airborne sensors to directly share data. An underwater transmitter directs a sonar signal to the water’s surface, causing tiny vibrations that correspond to the 1s and 0s transmitted. Above the surface, a highly sensitive receiver reads these minute disturbances and decodes the sonar signal.
Image: Christine Daniloff/MIT

Submarines can’t normally communicate directly with anything above the water due to the physical limits of their signal, but that might change in the near future. As MIT researchers have developed a wireless system that can transmit data from an underwater source to the air.

Most wireless communication on earth happens via radio waves, which propagate easily through the air. However, they dissipate quickly after hitting the water. Meanwhile, submarines and other underwater device rely on sonar — sound waves that can travel through water over long distances. These two systems normally don’t connect. Fadel Adib and Francesco Tonolini of MIT Media Lab have created an interlink called Translational Acoustic-RF communication, or TARF.

Using an underwater transmitter, researchers sent a sonar signal to the surface of a swimming pool, causing tiny vibrations. These were picked up by a sensitive radar, that decoded the 1s and 0s that were transmitted as vibrations. The system is a “milestone,” according to co-author of the research paper Fadel Adib, an assistant professor in the Media Lab.

 

 

The system is called “translational acoustic-RF communication” or TARF. MIT says it can be used to find airplanes that go missing underwater, to allow military submarines to communicate with airplanes without surfacing and giving away their position, and to allow underwater drones to continuously monitor marine life without having to surface to transmit data.

However, the system can take a long time to send a large amount of data – and it does not work when there are waves taller than 16cm (6in) in the water.

“It can deal with calm days and deal with certain water disturbances. But… we need this to work on all days and all weathers,”

– Fadel Adib, from the MIT Media Lab.

The researchers hope to develop algorithms that can eliminate the “noise” of a wavy ocean and isolate the tiny ripples from the sonar messages.