Mobile underwater acoustic communication based on passive time reversal

Chirp slope keying (CSK) modulation based on linear frequency modulation signal (LFM) and hyperbolic frequency modulation signal (HFM) combined with passive time reversal (PTR) for mobile underwater acoustic communication is proposed in this paper. For CSK modulation, the carriers are LFM and HFM signals, and the bit information is represented by different signals. A PTR processor is designed at the receiver before demodulation. There are two advantages of the proposed method due to the focusing of PTR and the good Doppler tolerance of chirp signal: enhancement of signal to noise ratio (SNR) and good performance against the interference caused by multipath, and good performance against Doppler effect. Simulations and pool experiments have been carried out. The results confirmed the feasibility of the method whose data rate is 100–400bps with M=2-16 where the duration of the symbol is 10ms and the bit error rate (BER) is below 10−4.