MIT researchers have taken a step toward solving a long-standing challenge with wireless communication: direct data transmission between underwater and airborne devices. Their findings could have applications for the military, search and rescue, and marine research.
Today, underwater sensors cannot share data with those on land, as both use different wireless signals that only work in their respective mediums.
Radio signals that travel through air die very rapidly in water. Acoustic signals, or sonar, sent by underwater devices mostly reflect off the surface without ever breaking through. This causes inefficiencies and other issues for a variety of applications, such as submarine-to-plane communication and ocean exploration.
MIT Media Lab researchers have designed a system that tackles this problem in a novel way. 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.
“Trying to cross the air-water boundary with wireless signals has been an obstacle. Our idea is to transform the obstacle itself into a medium through which to communicate,” says Fadel Adib, an assistant professor in the Media Lab, who is leading this research. He co-authored the paper with his graduate student Francesco Tonolini.
The system, called “translational acoustic-RF communication” (TARF), is still in its early stages, Adib says. But it represents a “milestone,” he says, that could open new capabilities in water-air communications.
Using the system, military submarines, for instance, wouldn’t need to surface to communicate with aeroplanes, compromising their location. And underwater drones that monitor marine life wouldn’t need to constantly resurface from deep dives to send data to researchers.
Another promising application is aiding searches for planes that go missing underwater. “Acoustic transmitting beacons can be implemented in, say, a plane’s black box,” Adib says. “If it transmits a signal every once in a while, you’d be able to use the system to pick up that signal.”
The researchers hope that their system could eventually enable an airborne drone or plane flying across a water’s surface to constantly pick up and decode the sonar signals as it flies over.