Technology ensures direct communication between submarine and aircraft
American researchers at MIT have developed a technique that allows submarines to communicate with aircraft. Normally, submarines cannot transmit data from the water to the air, but the scientists have found a solution.
The researchers simulated the situation of a submarine and an airplane by placing a speaker in a swimming pool and pointing it at the surface of the water. The sound waves from the speaker mimic the sonar of submarines and as soon as the pressure waves hit the water surface, they create small vibrations. They cannot simply be detected; a special highly sensitive radar must be used for this. It can detect the changes on the water surface caused by the sound waves. To make the technology work, the researchers overcame a number of challenges, such as making the radar ‘recognize’ the water’s surface and detecting the small waves emanating from the sonar.
The technology is called translational acoustic-RF communication and works because the sonar signal causes small vibrations at different frequencies. They correspond to the zeros and ones of binary data. A radar, operating at frequencies from 30GHz to 300GHz, can detect the small changes on the water surface, after which the bits can be converted into meaningful data.
For the time being, however, rough seas are a bummer for this communication technology. Algorithms are used to process the signals and to distinguish between the small vibrations of the sonar and larger ones that come from, for example, waves in the sea. The water waves must not be larger than 16 centimeters for the time being, otherwise the system will not be able to decode the signals. The researchers hope to further develop the system so that it also works with larger waves.
The team of MIT scientists recognizes that the technology is still in its infancy. For example, no more than a few hundred bits per second can be sent for the time being; a technique called Orthogonal Frequency Division Multiplexing is used for this. And for the time being it only concerns an uplink: the technology cannot be used to enable communication from an aircraft to the submarine.
The researchers state that the technique is promising and can not only be used to allow submarines to send data to aircraft. For example, the technology can be used to find aircraft that have fallen into the sea and cannot be found. It can also be used for sensors under the water’s surface that can directly transmit data about the condition of, for example, coral reefs. And if data can be sent directly to aircraft, buoys on the surface are no longer needed to pick up the sonar waves and transmit the information in the form of radio signals.
The research is published under the title Networking across Boundaries: Enabling Wireless
Communication through the Water-Air Interface.