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Experiment Results of Time-Reversal Communication at the Range of 300 km

We have researched on long horizontal time-reversal communication in the deep ocean, to be used for communication with autonomous underwater vehicle (AUV) in future, and proposed the method of combining time reversal with adaptive equalization. The pervious at-experiments were carried out at the ranges from 10 to 100 km with a virtual time-reversal array. In our latest sea trial, the experiment for passive time-reversal communication was executed with a real receiver array at the range of 300 km. This was the first implementation of time-reversal communication at such a range as an experiment intended for communication including the source movement. In this experiment, the source was suspended from the research vessel, thus drifted due to the ship motion. The proposed method could achieve error-free demodulation in spite of such drifting motion. The M-sequence signal and chirp pulse were used as the probe signal for passive time reversal. The results in case of M-sequence were better than those in case of chirp pulse.