MDS-Mac: A Scheduled MAC for Localization, Time-Synchronisation and Communication in Underwater Acoustic Networks

In this paper we describe a design for an underwater MAC protocol which combines localization, time-synchronisation and communication. This protocol is designed for small-scale clustered networks in which all nodes are able to communicate with each other. We consider an integrated design of localization, time-synchronisation and communication important because scheduled communication, localization and time-synchronisation require estimation of propagation delays between nodes to operate accurately and efficiently. For localization we use multidimensional scaling because it does not require the use of reference nodes. Our MAC design consists of two phases, i.e. an unscheduled coordination phase and a communication phase. During the first phase, propagation delays are estimated, relative positions are calculated using multidimensional scaling, and timesynchronisation is performed. During the communication phase, sensor-data is transmitted using scheduled communication. Using simulation we evaluate the feasibility of such a design. By measuring the time required for the coordination phase at different modulation rates, we derive the required modulation rate for acceptable coordination phase times.