Basic at‐sea experiment for long horizontal time‐reversal communication in deep ocean

Abstract

In our research program, a long cruising autonomous underwater vehicle (AUV) has been developed and a project on a second AUV is planned, for wide‐areal observation in the deep ocean. In such AUV operation, it is preferred to ensure acoustic communication with AUV even at low data‐transmission rate. Time‐reversal techniques have a possibility to achieve such long horizontal communication. We have proposed a method of combining time reversal and an adaptive equalizer to realize communication even with a sparse time‐reversal array (TRA) and communication with a moving target. To verify the performance of such time‐reversal communication, at‐sea experiments were executed at the various distances. In the experiment of 10 km at a water depth of 1000 m, bidirectional time‐reversal communication between the focus point and TRA was achieved successfully and the effects of the TRA depth and its channel number are investigated. In the experiments of 20, 30, 40 km at the slight sloping area, the performance on the distances are discussed. In the experiment of 100 km at a water depth of 4000 m, the convergence by passive time reversal was verified.