Japan has one of the world's largest exclusive economic zones, and has the potential to become an ocean resource power. In future marine resource surveys, expectations may increase for the use of radio waves in the sea, such as for remote control of underwater robots and under-seabed exploration.

In this paper, the authors propose an underwater channel sounder, which is a system for measuring radio wave propagation characteristic in the sea and evaluate the usefulness of the developed underwater channel sounder in the actual sea area.

The authors explain the development process and technical features of the underwater channel sounder, and then describe the difficulty of making measurements in the sea. The authors also propose a method for measuring radio wave propagation characteristics with high accuracy and reproducibility in the sea. Furthermore, the authors conducted a wireless communication experiment in the sea and measured the bit error rate with respect to the distance between the transmitting and receiving antennas in the 10MHz band, showing that the measurement results were consistent with the theoretical values.

In this paper, the authors are developing a system based on basic research on the measurement of radio wave propagation characteristics in the sea and the evaluation of communication performance.　In addition, the authors conducted experiments in the sea area using the proposed underwater channel sounder and demonstrated its usefulness. In the future, it is expected that the use of radio wave utilization systems in the sea will greatly contribute to the survey and utilization of Japan's oceans. For the above reasons, this paper can be highly evaluated as a paper worthy of this award.