Fujita: Communication is highly stable when using a wired connection. However, cables can become entangled in unexpected obstacles on the seafloor, leading to cable cuts, or in the worst-case scenario, the loss of the marine robot itself. On the other hand, stable underwater acoustic communication often requires a large number of receivers, leading to an increase in equipment scale. Operation was prone to instability when using a small number of receivers, so you had to communicate with the marine robot while regulating its speed.

Yoshimura: We conducted this experiment in cooperation of many people, including employees at OKI Com-Echoes Co., Ltd. and the captain of the small vessel towing the receiver. I was in charge of coordinating with the people who cooperated with the experiment as well as managing the experiment on the day of the test, including monitoring the progress of the experiment. As opposed to the laboratory, unexpected things can happen in marine experiments. Therefore, I tried to control the whole process calmly, including the timing of communication, in order to obtain reliable results.

Fujita: My research focuses on underwater acoustic communication technologies effective in harsh environments and the testing of those technologies. Then, I operated a device that sends signals from a transmitter to a receiver and retrieves the data, and then I analyzed that data. This research is based the outcomes that have been accumulated in Professor Kubo’s laboratory over the years, and it made full use of the knowledge of Mr. Yoshimura, Mr. Hashimoto, and their colleagues.

Hashimoto: I rode on the vessel that towed the receiver, where I communicated closely with the captain while controlling the equipment. I also analyzed the propagation environment to determine how the sound waves reached the receiver, and I made minor improvements to our experimental methods.

Yoshimura: Since its inception, our laboratory has been working toward the goal of communicating in a mobile environment at a speed of three knots. Our predecessors conducted many experiments, starting with a communication test at a distance of five meters on Lake Biwa about 10 years ago, followed by a long-distance test at 370 meters off the coast of Izu, and a low-speed travel test at one knot. In this process, we have inherited many things from alumni, such as simulators for evaluating communication methods in advance, methods for measuring the actual environment and analyzing its impact on communication, and know-how on conducting experiments.

Yoshimura: The figures from the simulation did not directly indicate that bubbles would be an issue, but our partners at OKI Com-Echoes told us to watch out for bubbles. Actually, Hashimoto also suspected that bubbles might be a problem during the environmental evaluation process, and this concern was right on target.

Fujita: To be honest, the sense was this was not a very serious issue. On the other hand, if we could overcome this problem, it would mean that we could establish our acoustic communication technology under even harsher conditions. What makes research enjoyable is coming to understand those things you don’t know. For this reason, we engaged in a lot of dialogue to fine-tune our approach ahead of the next experiment.

Hashimoto: I also did not take the issue too seriously. I was confident that I could fine-tune the experiment based on previous simulations and the results of this experiment, so I was able to turn my sights to the next experiment without letting it become a mental burden. That being said, the toughest aspect was the drain on our physical health, seeing as we conducted the experiments in September, when it was extremely hot, and in November, when it was extremely cold. (laughs)

Fujita: I had no interest in the communications field until high school, but before I chose which laboratory to join, it was the words of Professor Kubo that drew me to his laboratory: "Underwater acoustic communication is the last frontier.” After that, I decided to pursue a master's degree to further my study of acoustic communication.

Yoshimura: I have always been interested in marine life, so I thought that if effective acoustic communication could be established, it could increase the range of motion of marine robots and lead to the discovery of new marine creatures. I became increasingly fascinated by acoustic communication, and I have been researching underwater acoustic communication to this day.

Hashimoto: When I was in high school, I had the opportunity to experience telecommunications in an IT class. But I had trouble establishing communications back then. So, when I entered university, I was ready to tackle the challenge again. I was drawn to Professor Kubo’s laboratory by the joy everyone felt after their first successful communication test and the fact that underwater acoustic communication is an interesting field.

Fujita: During my time in Professor Kubo’s laboratory, I gained experience in theory, manufacturing, and field testing. In particular, working on this experiment taught me a valuable lesson: that it is up to me to recognize the important information contained in the data. I would like to analyze everyday phenomena while keeping my eyes open to a wide array of possibilities.

Yoshimura: By working on this experiment, I think I have gained the ability to see the big picture. Successfully completing such a difficult experiment has also given me confidence. Since I have been assigned to a production engineering position at a manufacturer, I hope I can utilize my experience from the experiment to take a bird's eye view of the whole process when handling any task and to do work that is beneficial to others.

Hashimoto: In our acoustic experiments, we found solutions to problems based on data from the experimental environment that we analyzed from various angles. This made me realize the importance of deepening mutual understanding by looking at things from perspectives other than my own and by discussing things together rather than going it alone. I would like to use this experience to find solutions to difficult problems.