NeTS: Small: Enabling Long-Range Underwater Backscatter via Van-Atta Acoustic Networks

The ability to perform low-power long-range underwater sensing can have transformative impact on climatology, oceanography, marine biology, food security, defense, and even extra-terrestrial exploration. Motivated by the fact that over 95% of the ocean has not been observed or explored, this project aims to push the limits of scalable and low-power ocean sensing in order to scalably measure the ocean’s vital signs (temperature, pressure, salinity) for climate models, weather prediction, disaster response, and marine life discovery. Scalable and low-power underwater sensing also has important applications in food security, where it can support the world's fastest-growing food sector, aquaculture (seafood farming). To this end, the project will develop fundamental technologies that advance the ability for scalable ocean sensing and disseminate these technologies to the academic community, industry, and the broader public through publications, technology transfer, and public-facing videos about the developed technologies to increase public education and engagement with science, technology, and climate. The goal of this proposal is to design, build, and evaluate a low-power, long-range underwater backscatter network. Underwater backscatter is a new communication technology that consumes 5-6 orders of magnitude lower power than prior low-power underwater acoustic communication technologies. However, existing designs for underwater backscatter are limited in their communication range to within few to tens of meters, which restricts their scalability and application domains. To overcome this range limitation, this project explores retroreflective designs for underwater backscatter. In contrast to existing architectures which are inefficient because they backscatter underwater sound in all directions, the proposed designs will achieve much higher efficiency by backscattering sound retroreflectively to the sender. This retrodirectivity enables boosting the signal-to-noise ratio of the backscatter packets, which in turn boosts communication range, throughput, and scalability. To realize retroreflective underwater backscatter, the proposal will design Van-Atta architectures, which have been demonstrated over the past 50 years in the wireless RF (Radio Frequency) domain, but have never been applied before in underwater environments or acoustic networks. The proposal will explore designs that enable 2D and 3D retrodirectivity through Van-Atta arrays, implement these designs into practical systems, and develop them into end-to-end scalable networks for both underwater communication and localization. If successful, the resulting system will be the first to enable low-power long-range underwater backscatter, paving the way for scalable networked sensing of underwater environments. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.