MIT system could enable submarine-to-aircraft communications

The development, which is still at a very early stage, could someday allow submarines to communicate directly with aircraft. Known as TARF (translational acoustic-RF communication), it uses a combination of sonar and highly sensitive radar to send and receive the signals. An underwater transmitter first sends data packets to the surface via sonar. Above the surface, the ultra-sensitive radar can detect the minute disturbances in the water, allowing the receiver to decode the data.

“Trying to cross the air-water boundary with wireless signals has been an obstacle,” said lead researcher Fadel Adib, an assistant professor in the MIT Media Lab. “Our idea is to transform the obstacle itself into a medium through which to communicate.”

TARF includes an underwater acoustic transmitter that sends sonar signals using a standard acoustic speaker. The signals travel as pressure waves of different frequencies corresponding to different data bits. For example, when the transmitter wants to send a 0, it can transmit a wave travelling at 100Hz; for a 1, it can transmit a 200Hz wave. When the communications signal hits the surface, it causes tiny ripples in the water, only a few micrometres in height, corresponding to those frequencies.