Research and Development of Wireless Communication Technologies for Undersea and Underwater IoT

Underwater and undersea communications have generally been based on acoustic communication. However, a project is currently underway to challenge the preconception that radio-wave communication is not possible underwater or undersea as well as to establish medium-range or long-range communication technologies on this front. We interviewed Prof. Yuki Fukumoto, who is conducting research and development to meet new needs, regarding the focus and goal of this project.

Has wireless communication never been used before underwater or undersea?

Fukumoto: Radio-wave communication has not been used in an undersea setting in the past. Acoustic communication, i.e., communication using sound waves, has been the norm as far as undersea wireless communication is concerned. Although communications using light and radio waves have been explored on a research level, such technologies were far from being commercialized. The reason for this is that it was common knowledge among those working with radio waves that seawater is a conductor and that radio waves cannot propagate undersea. I believe this explains why there has been no development of undersea radio-wave communications.

Do you mean this project is focused on technologies that have not been developed previously?

Fukumoto: I mentioned that radio waves cannot propagate undersea, but it is more accurate to say that they do not propagate well at high frequencies. However, at frequencies below 1 MHz, radio waves can propagate several meters. Still, while radio waves can propagate at lower frequencies, the amount of information that can be transmitted in this way is minimal and insufficient for communication with IoT devices. Therefore, we thought it would be possible to carry out communication transmission at speeds of 1 Mbps or higher, which would allow for video transmission by using orthogonal frequency division multiplexing (OFDM) technology that utilizes a wide bandwidth within the lower frequency band. Since we possess the relevant key technologies, specifically undersea electromagnetic wave analysis technology, antenna technology, and OFDM modulation/demodulation technology in the medium- to short-wave bands, we decided to attempt to achieve this goal by mobilizing all of these technologies in this project.

What do you hope to achieve from the results of this project?

Fukumoto: Over the course of this project, we have talked to many people involved in the fishing industry, coastal engineering, and marine engineering. Through our conversations, it became clear that there is a massive need that exists in areas where acoustic communication cannot be used and settings where radio-wave communication is superior. These include, for instance, long-term, low-cost video recording at aquaculture facilities in the fishing industry, as well as the collection of IoT sensor information for the maintenance of coastal facilities in coastal engineering. Indeed, these are settings where acoustic communication performs poorly. We can thus take advantage of short-range, high-speed communication in such settings. Moreover, such undersea communication systems are capable of long-term operation, in addition to their lower cost and superior ease of maintenance. Introducing IT undersea is still an unexplored domain, and we feel that there is a massive need in this field. Rather than comparing it with acoustic communication, radio-wave communication demonstrates great promise as a communication technology in areas where acoustic communication cannot be used.

What are your R&D goals going forward?

Fukumoto: One goal is to achieve medium-range communication (1 Mbps over a distance of 4 m) that allows for video transmission underwater and undersea by FY2024, and to establish the technology by conducting experiments in large aquariums and the open sea. After that, we also aim to establish the technology for long-range communication systems (multi-hop communication with 10 or more hops) that are designed for data collection using undersea relay stations through integration with medium-range communication.

Thank you very much.