Conceptual Design and Propagation Characteristics of an Underwater Electromagnetic Communication System for Ocean Environment Sensor Systems

As an attempt to protect the ocean environment, a system design for fixed-point observation in a small-scale blue carbon test site is presented. Designed system requires an underwater wireless communication system for data transmission, and electromagnetic (EM) waves are effective for this purpose from the viewpoint of cost and targeted underwater environment. We assume 1-Kbps data rate based on the above use case, select 50-kHz and 100-kHz carrier frequencies, and investigate the propagation of EM waves near seabed at these frequencies by an experiment and numerical calculations. As a result, we show that the closer the distance to the seabed and the lower the frequency, the less attenuation and the wider the coverage area. We also show that low-conductivity layers below the surface layer of seabed affect the propagation, indicating that the layer configuration of seabed is important in the link budget of proposed system.