Data-link protocol for underwater acoustic networks

The physical properties of acoustic channels essentially differ from those of conventional wireless communication channels. This motivates a substantial redesign of algorithms and techniques of underwater data telemetry concerning both their physical layer and their data-link layer, as well. The sound velocity in water is much less than the velocity of electromagnetic oscillations in radio. The propagation of acoustic signals underwater is characterized with extremely complex and quickly varying reverberation. The Sweep-Spread Carrier communication method, recently developed for underwater data telemetry, provides an opportunity to process the multipath arrivals separately and in this way to carry out all necessary adaptations of the receiver to the rapid fluctuations of the transmitting channel. To provide an effective data telemetry, a development of a new data-link layer protocol is required; especially the protocol, which would compensate long waiting times characteristic for acoustic transmission channels. The paper represents an appropriate solution of the problem, as well as the simulation and experimental results.