Experiment results of time-reversal communication in the deep ocean at the range of 300 km.

Abstract

The research is being conducted to realize communication with a long cruising AUV in the deep ocean using time reversal. We have proposed the method of combining time reversal and adaptive equalization. In our previous at‐sea experiments, the performance of time‐reversal communication was confirmed at the range of 10–100 km with a virtual array. In our latest sea‐trial, experiments of passive time‐reversal communication were executed at the range of 300 km with a real receiver array. As a probe signal, chirp pulses and M‐sequence pulses were used. The data transmission speed was 50 and 100 bps. The source was suspended from the research vessel and the 20 channel receiver array was moored. Thus, Doppler effect was induced due to the ship drifting at the speed of approximately 0.25 m/s at maximum. Nevertheless, such effect is compensated and demodulation with no error is achieved with the proposed method. The results of using chirp pulses are inferior to the results of using M‐sequences because of sidelobes of the chirp correlation. The results of using longer M‐sequence are degraded due to Doppler effect.