Research On Channel Equalization Of Underwater Acoustic Communication

Sound going through various channels to reach the receiving end causing severe multi-path effects in underwater acoustic channels, make the transmission signal frequency selective fading in the communication band. For single-carrier coherent communication, the multi-path effects will cause the front and rear slot signals are superimposed, that the phenomenon known as multi-path interference. For long-range underwater acoustic communication, the multi-path interference is unavoidable.Channel equalization on the received sequence by adjusting the tap coefficient weights,which can restore the original transmitting information, is an effective anti-multi-path signal processing technology. For underwater acoustic communication, the equalizer is the core technology in receiver signal processing system. The thesis chooses single-carrier communication as a carrier to study linear equalizer, decision feedback equalizer, blind equalizer and fractionally spaced equalizer in time invariant under water acoustic channel conditions. Study the impact of adaptive algorithm parameters to the equalizer. Compare the difference between the linear equalizer and decision feedback equalizers, potter-spaced equalizer and the fractionally spaced equalizer performance. Compare the good points and weak points between the different kinds of equalizers. In addition to multi-path interference,the underwater acoustic communication as well as suffer from the Doppler shift, strong noise and other interference interferences. Therefore, the equalizers need to combine with phase-locked loop, time reversal mirror and space diversity techniques to overcome these interferences. The equalizer severs as the core of the signal processing system improvements.To improve the communication rate, the paper design MIMO systems combination of space-time coding techniques, the single-channel high-speed data is converted into multiple parallel low-speed data transmission. At the receiving end, use decision feedback equalizer to decode the information. Simulation results show the proposed algorithm can achieve relatively high quality communication under high SNR. And the communication rate is higher than that of SI SO system.Finally, the test results of the of Songhua River and Lianhua Lake experiences show that decision feedback equalizer combination with phase-locked loop can compensate for the distortion of the phase with and combination with time reversal mirror technique can restrain inter-symbol interference suppression Information BER for different output array elements are combined treatment further reduced, indicating that the equalizer can be used with other technologies to ensure the performance of underwater acoustic communication between nodes.