Remote Underwater Acoustic Communication Technology

With the rapid exploitation of ocean, the need of unmanned underwater vehicle (UUV) increases rapidly, and attracts much attention to the research of UUV. Underwater acoustic communication technique over long-range underwater acoustic channel is one of the key techniques of UUV. Because of the adverse characteristic of underwater acoustic channel, it becomes a challenge for long-range, high data-rate, high reliable information transmission over underwater acoustic channels.Long-range underwater acoustic communication techniques which applied on unmanned underwater vehicle were introduced in this paper. The characteristics of underwater acoustic channel and it effect on long-range acoustic communication were introduced at first. Two common channel models were referred, and ray model was used to calculate channel, and parameters of four multipath channels were given. According to the system requirements of unmanned underwater vehicle, the MC-PSK modulation technique was present in this paper, some key techniques were discussed. More attentions were imposed on adaptive equalization techniques for acoustic communication system, structures and algorithms of adaptive equalization were introduced. The equalizer applied for long-range acoustic channel was designed, and the simulation results were given latter. Synchronization of system, delay estimation, Doppler estimation and compensation were deeply investigated. Two methods were employed to improve symbol timing and estimation of channel delay. The Doppler shift in the received signals was estimated based on data packet duration, and interpolation was used to remove Doppler shift. The simulation results predicted that the long-range acoustic communication system which based on MC-PSK modulation could satisfaction the requirements of the information transmission system. At last the designs of FIR and FFT algorithms in DSP were given.