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The future role of unmanned underwater vehicles (UUVs) is expected to include autonomous tasks in environmental assessmenl, route survey, mine hunting, and battlefield preparation. Depending on the mission, there will be a need for a robust communication link between the mother ship and the UUV, with a low probability of intercept by third parties. The overall goal of the joint European project "UUV Covert Acoustic Communications" with contributions from Denmark, Finland, Italy, The Netherlands, Germany, Norway and Sweden is to develop covert communication algorithms to enable such a communication link. The present paper describes intlial results of the project's first sea trials, conducted in the Baltic and North Sea environments in September 2006. The main purpose of these trials is characterization of Íhe communication channel. A variety of probe signals were transmitted with a mobile projector, and recorded on a vertical hydrophone array deployed from a moored platform. The data analysis focuses on aspects relevant to acoustic communication, such as ambient noise, multi-path propagation, Doppler effects, and their time variability. The outcome of the analysis will be used for the development of a filter model, designed to model the underwater acoustic communication channel in a realistic fashion. |
