Method of detecting a stray diver using underwater ultrasonic-band multicast communication

Recent years have seen a growing interest in underwater communication and have brought some progress in this area. However, underwater communication is still far behind terrestrial communication. Since the underwater environment is intrinsically not suitable for electric wave-based communication, ultrasonic waves are mainly used for communication. Ultrasonic waves cannot provide sufficient communication speed or capacity. In particular, communication in shallow water is still an undeveloped area. As a result, no communication technology is employed in the environment where people enjoy scuba diving. This paper proposes a method of detecting a stray recreational diver. This method adjusts the transmission power to adjust the size of a multicast communication space in which communication is possible. It monitors the number of hops to determine the position of each node, thereby detecting any stray node. We have implemented this method in a network simulator and evaluated the detection rate.