Challenges to Use RF Signals in Underwater

Japan has one of the largest exclusive economic zones in the world and has the potential to become a major marine resource power.

In response to the growing need for radio communications for remote control of underwater robots and seafloor exploration in marine resource development, NICT is researching and developing underwater wireless communications and seafloor sensing technologies in cooperation with JAMSTEC (Japan Agency for Marine-Earth Science and Technology) and other organizations.

When using underwater, long-distance and high-capacity radio communications are considered extremely difficult due to its high attenuation; it is largely affected by waves and salt, among other factors. To overcome such issues NICT researched modeling and analyzed radio propagation in the sea using electromagnetic field simulations, measurements of radio propagation in the sea, high-speed communications in the sea using multi-level modulations, and seafloor sensing using electromagnetic waves (frequencies from 10 kHz to 10 MHz). We developed underwater antennas and measurement systems, and achieved positive results with underwater experiments.

In the most recent underwater experiment, a communication speed of about 1 Mbps was achieved at a distance of 1.5 m. Further development is expected in the future.