Research On Underwater Acoustic Communication Using Pseudo-Time-Reserval

In recent years, digital underwater acoustic communication develops rapidly internationally. There is a novel method-time reversal, which draws much attention in underwater acoustic academe.With 863 project of Underwater Instruments and Underwater Acoustic Data Transportation and CSIC (China Ship Industry Corp.) supported research of Underwater Acoustic Network Node Technique Research, through comparison and analysis of horizon underwater acoustic channel, I proposed the pseudo-time reversal and spectrum techniques, which is the key part of my research.There are severe Multipath Effects and Doppler Spread in unde rwater acoustic channels. The channel is treated as a filter between the transmitter and receiver, and accordingly I deduced the signal equation in both time domain and frequency domain. Before transmitting data, the probe signal is transmitted first to estimate the channel, and then the data sequences. With spectrum technique, BPSK modulated information is spread by 255 chips, and then is transmitted after convolution with probe signal. In receiver, the probe signal filtered by channel and convoluted data sequences are processed with conjugation method, and the channel effects on the phases of BPSK modulated information are restrained. Channel estimation and system synchronization are achieved by LFM signal. The transmitted information is detected by replica correlation.Based on theory, the underwater acoustic channel simulator is proposed. Through simulation on MATLAB platform, pseudo-time reversal and spectrum techniques performances are tested, and the curves figure of several methods are given. From simulation: time reversal and spectrum techniques are able to be used in long distance underwater acoustic communication, and Mutipath Effects can be restrained efficiently, and Doppler Spread interference still can not be fully resolved.Finally, underwater acoustic data collected from sea trials is processed by the PC (personal computer), differences of the two methods are showed in figures. Conclusion according to the results of sea trials: time reversal and spectrum techniques are able to be used in long distance underwater acoustic communication, and able to restrain the Multipath Effects in underwater acoustic...