MIT researchers have successfully developed a groundbreaking system for ultra-low-power underwater networking and communication, showcasing its potential to revolutionize battery-free underwater communication across vast distances. This technology has the capacity to facilitate the monitoring of climate and coastal changes. Unlike existing underwater communication methods, this system utilizes a mere fraction of the power, approximately one millionth, making it an exceptional advancement.
The researchers have substantially extended the communication range of their battery-free system, rendering it highly suitable for a range of applications, including aquaculture, coastal hurricane prediction, and climate change modeling. Fadel Adib, an associate professor in the Department of Electrical Engineering and Computer Science and director of the Signal Kinetics group in the MIT Media Lab, highlighted the evolution of this concept from an exciting intellectual idea to a practical and realistic technology, despite some remaining technical challenges.
The key innovation in this system is the use of underwater backscatter, a method that encodes data in sound waves reflected back towards a receiver. This approach improves communication efficiency and range due to its retrodirectivity, reducing signal scattering in unintended directions. The researchers achieved communication ranges more than 15 times farther than previous methods during tests in rivers and oceans, although these experiments were constrained by the available dock lengths.
To better understand the technology’s limits, the researchers developed an analytical model to predict the maximum range of their retrodirective system, which they validated using experimental data. The results indicated the capability of communicating across kilometer-scale distances.
The research findings were presented in two papers at the ACM SIGCOMM and MobiCom conferences. The team employed piezoelectric materials to create nodes that receive and reflect sound waves for underwater backscatter communication. These materials generate an electric signal when subjected to mechanical force, converting the energy for data transmission.
To optimize signal reflection, the researchers incorporated a 70-year-old radio device known as a Van Atta array, which enhances the signal’s retrodirectivity. A transformer placed between node pairs enabled efficient reflection of energy back to the source. By alternating the polarities of connected nodes, the researchers could encode binary data in the reflected signal.
Additionally, the researchers developed a scalable design with staggered nodes to prevent signal blocking, allowing signals to reach the array from any direction. This design significantly increased communication range, with tests achieving ranges of up to 300 meters, over 15 times longer than previous demonstrations.
Motivated by these results, the researchers created an analytical model to predict the potential communication limits of underwater backscatter technology. This model considered parameters like node size and input power and accurately predicted the range of retrodirected acoustic signals.
Using the model, the researchers demonstrated the possibility of achieving kilometer-long communication ranges with underwater backscatter arrays. They plan to further study these arrays, potentially using boats for longer communication range evaluations, and aim to release tools and datasets to support further research and development. The researchers are also exploring the commercialization of this groundbreaking technology, which has the potential to transform underwater communication and enable applications such as underwater climate change monitoring and coastal monitoring.