Particle Velocity Underwater Data Communication: Physics, Channels, System and Experiments

The largely unexplored underwater world has strong and multifaceted ties with our lives. There are numerous ocean-related areas and applications, such as oceanography, climate, pollution, and environmental monitoring, that have created increasing demand for wireless acoustic data communication among underwater sensors, platforms, and autonomous vehicles. Contrary to wireless transmission in air, electromagnetic waves are strongly attenuated in water, whereas acoustic waves are proper carriers of information in water, since compared to electromagnetic waves, they typically incur less attenuation in water. However, the underwater bandwidth is usually highly limited. Here, we demonstrate that it is possible to multiplex multiple data streams over acoustic particle velocity field components using a proposed compact vector transmitter over the same bandwidth. In existing underwater communication systems, data are conventionally modulated on acoustic pressure, i.e., scalar component of the acoustic field, using one scalar transmitter. Arrays of several spatially-separated scalar transmitters are also used to transmit multiple data streams simultaneously. However, given the large size of equipment carrying an array of several transmitters, many modern underwater platforms, such as autonomous underwater vehicles, cannot use multiple transmitters. Our experimental results demonstrate that using the developed vector transmitter, together with the proposed physics-based particle velocity modulation method over co-located underwater vector field components, multiple data streams can be concurrently transmitted, without requiring additional bandwidth. Using our findings, small-size underwater acoustic systems, modems, and equipment can be built that benefit from the acoustic vector field components.