A method to improve the update rate of underwater acoustic positioning system

Underwater positioning system obtains relative position between a transponder and a transceiver by measuring round trip time (RTT) and angle of arrival. The position update rate (PUR) cannot be greater than 1/RTT, and when one transceiver locates multiple transponders, the PUR becomes smaller. This paper proposes a method to increase the PUR. The proposed method minimizes “idle time” by allowing the transceiver to send additional pings without packet transmission-reception collisions, rather than waiting for the response to the previous ping sent to the transponder. It is essential that the reception (transmission) of the ping and the transmission (reception) of the response should not be overlapped in the transponder (transceiver). In order to avoid these collisions, the ping transmission time is adaptively determined by considering the bound of packet reception times drawn by ping duration (PD), response signal duration (RD), and the maximum relative speed. In addition, the transceiver assigns a delay before sending the response signal upon receiving each ping. These adaptive features effectively adapt to changes due to mobility. We derive a theoretical upper bound of the PUR and verify this bound by computer simulations. [Work supported by KIMST funded by the Agency of Korea Coast Guard (KIMST-20210547).]