Study On The Coding And Synchronization Techniques In Underwater Acoustic Communication

In the past 10 years, the rapid development has happened in the study of underwater acoustic (UWA) communication techniques, with more attention to the underwater acoustic communication systems. The dissertation begins with the introduction of the underwater acoustic communication system, and is compactly devoted to the study on the synchronization and coding techniques in underwater acoustic communication, based on the analysis of the characteristics of UWA channels.The three main characteristics of UWA channels are studied thoroughly, and their influence on the UWA communication system are completely analyzed. Aimed at the features of the UWA, the LFM(linear frequency-modulated) pulse synchronization is proposed, in which LFM is the frame synchronization signal, and realize accurate synchronization by using replica correlation in receiving end. The LFM pulse time delay coding method is also proposed in dissertation, which increases the speed of transmitting signal in UWA.The UWA modulatory technique based on Frequency Shift Keying(FSK) is systematically and in-depth studied. Associated with the LFM frame synchronization method, the three methods: periodogram method, Welch's method and higher-order cumulant method are completed analyzed. In combination with the characteristics of UWA, Differential Phase Shift Keying(DPSK) is studied. The two demodulation methods: differential demodulation method and cross spectra demodulation method are deeply studied. With the LFM pulse frame synchronization method, the performance of UWA communication system based on DPSK is apparently improved.