Long-baseline Hydro-acoustic positioning using D-MAC communication protocol

Long-baseline (LBL) acoustic positioning systems, widely covered in various scientific publications, are based on specific protocols and were designed to solve one particular task, namely the positioning of remote targets. This paper proposes a solution that extends the application range of such systems by combining them with underwater acoustic communication systems. Both systems can share the same electro-acoustic circuit for transmitting and receiving signals and the same signal processing module. The same acoustic signal can be used for both transmission of digital information and estimation of its source position. A significant challenge for combining LBL positioning with digital communication is the media access control (MAC) protocol. This paper suggests a new protocol for LBL positioning, based on the use of hybrid MAC protocol, namely the D-MAC protocol. In particular, the D-MAC protocol provides an opportunity to send short messages, called instant messages, their timing being controlled by the higher level protocols. This allows to implement custom media access schemes that require precise synchronization of network nodes. LBL positioning algorithms, described in this paper, are based on broadcast synchronous instant messages of the D-MAC protocol. Combining the functions of underwater LBL positioning with digital acoustic communication allows to access each node of an underwater acoustic network for diagnostics, remote configuration or for executing other specific tasks that require an acoustic communication link.