![]() The transformer, which transfers electric energy from one circuit to another, allows the nodes to reflect the maximum amount of energy back to the source. The researchers avoided this problem by placing a transformer between pairs of connected nodes. To overcome this challenge, the researchers leveraged a 70-year-old radio device called a Van Atta array, in which symmetric pairs of antennas are connected in such a way that the array reflects energy back in the direction it came from.īut connecting piezoelectric nodes to make a Van Atta array reduces their efficiency. The nodes use that charge to scatter some of the acoustic energy back to the source, transmitting data that a receiver decodes based on the sequence of reflections.īut because the backscattered signal travels in all directions, only a small fraction reaches the source, reducing the signal strength and limiting the communication range. When sound waves strike the nodes, they vibrate and convert the mechanical energy to an electric charge. These materials produce an electric signal when mechanical force is applied to them. Underwater backscatter communication devices utilize an array of nodes made from “piezoelectric” materials to receive and reflect sound waves. The MobiCom paper is also written by co-lead authors Akbar and Allam. Adib, senior author on both papers, is joined on the SIGCOMM paper by co-lead authors Aline Eid, a former postdoc who is now an assistant professor at the University of Michigan, and Jack Rademacher, a research assistant as well as research assistants Waleed Akbar and Purui Wang, and postdoc Ahmed Allam. The researchers shared these findings in two papers which will be presented at this year’s ACM SIGCOMM and MobiCom conferences. The model, which they validated using experimental data, showed that their retrodirective system could communicate across kilometer-scale distances. To better understand the limits of underwater backscatter, the team also developed an analytical model to predict the technology’s maximum range. ![]() However, the experiments were limited by the length of the docks available to the researchers. When tested in a river and an ocean, the retrodirective device exhibited a communication range that was more than 15 times farther than previous devices. These innovations enable reflected signals to be more precisely directed at their source.ĭue to this “retrodirectivity,” less signal scatters in the wrong directions, allowing for more efficient and longer-range communication. Underwater backscatter enables low-power communication by encoding data in sound waves that it reflects, or scatters, back toward a receiver. ![]() 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, associate professor in the Department of Electrical Engineering and Computer Science and director of the Signal Kinetics group in the MIT Media Lab. “What started as a very exciting intellectual idea a few years ago - underwater communication with a million times lower power - is now practical and realistic. By expanding their battery-free system’s communication range, the researchers have made the technology more feasible for applications such as aquaculture, coastal hurricane prediction, and climate change modeling. This technique, which the researchers began developing several years ago, uses about one-millionth the power that existing underwater communication methods use. ![]() MIT researchers have demonstrated the first system for ultra-low-power underwater networking and communication, which can transmit signals across kilometer-scale distances. ![]()
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