Acoustic communication between two autonomous underwater vehicles

Abstract

This paper describes a project designed to iiivestigate and demonstrate cominuiiicatioii between two Autonomous Underwater Vehicles (AUVs). T h e basic coiicept of multiple cooperatiiig AUVa iiiiplies tliat tliese systems must, of necessity, be able to coiniriuiiicate with each other iii soiiie ineaiiiiigful way. This paper preserits the results of in-water Aeld experiiiieiits iii wliicli two AUV systems were able to coiii-" m a t e witli each other using acoustic iiiodems wllile coiiductirig a simple riiission. The AUVs used in t h i s project were t w o EAVE I11 systenis developed by the Marine Systeiris Engineering Laboratory (MSEL). A pair of Acoustic Telemetry Modems (ATMs) acquired frorn Datasonics, Inc. provided tlie communication c1l;ulnel.The experiiiierits successfully deliionstrated (1) siiiiultaiieous navigation of two AUVY within a siiigle transponder network, (2) acoustic exchange of data (both ways) betweeii the two vehicles, (3) runtime modiAcatioris of acoustic liiik parameters (BPS rate, packet size), and (4) rriodiflcatiori of oiie vehicle's niissioii by the other vehicle while underway via coinuiuriicutiori over the acoustic cliaiiiic.1. ~3 A C K G I t O U N DAiitononious Underwater Vehicle ( A U V ) technology has evolved to the point whcre such sy.jteiiis arc: uow viewed as near tc,rni realixt.ic ~u o l a for iiiariy iiiiderwater applications. Oceaii scientists h a v e recognized the potential impact of AUV systems i l s a means of collecting the vast quantities of data necessary to understand global processes [l], [2]. 111 the effort to realize such capability, systems of varying degrees of ability and performance have been developed over tlie past decade by university laboratories, industry, the military, and other government or gait i z ;I tioils.Wliile the autonomy of such systems frees them from umbilical coniiections to the surface dlowiug them to go wliere it is too tlarigerous or expensive to send manned systems, there will certainly be situations whcn it would Le hcrirficial for a remote A 02534 operator to be able to communicate with the AUV. As AUV systems expand into larger, more complex, and more capable multi-AUV systems, it will be essential tliat the participating AUVs be able to communicate with each other and their operators. This program had a goal of demonstrating coinniunication betweeii two AUVs operatiiig i n the siiiiic local arcil.T h e development of acoustic cornniunication systems is l i nited by the environment in which they operate. This is characterized by low bits per second (BPS) rates, time delays due to sound propagation velocities, ray bending due to temperature gradients, and multipath problenis to name but a few. Currently, there are development breaktlirouglis being accomplished [3], [4], [5] which show promise of providing acoustic links with data rates of tens of kilo-BPS in the narrow water channel ertvironment. Bit rates of this magnitude will allow much broader bandwidth coinniuriication with arid between AUV systems. PROJECT DESCRIPTION A . CoalsT...

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