Research On Semi-blind Equalization Algorithm In Underwater Acoustic Channel Abstract

In the process of underwater wireless communication, due to the complexity of underwater environment, the signal will produce distortion during the transmission which led to the decrease of the quality of the communication, even using the modulation or coding method and so on can out improve it effectively, while doing the underwater sensor network position, the distortion of signal made the positioning accuracy lower. On the receiving end of underwater acoustic signal distortion is serious, and positioning accuracy is going low, this project proposed an improved variable step-size semi-blind equalization algorithm.This article respectively did balanced processing of two practical measured signals by CMA and MCMA based on analyzing and researching the Bussgang blind equalization algorithm, compared with the equilibrium effect when setting different initial value of equalizer. In order to make the initial value of algorithm more targeted, doing some research on the transmission characteristics of underwater acoustic channel, designed the simulation interface based on eigen-rays model which can obtain experiment channel impulse response by setting acoustic environment parameters. Combined the acoustic transmission channel modeling and the simulation results, did further equalization with CMA and MCMA.And in order to solve the contradiction between convergence speed and steady residual error of the semi-blind equalization, semi-blind equalization algorithms is improved. Equalized the measured signals with the improved algorithm, calculated the distance between the two receivers, and analyzed the error value. Final made some optimization for the improved algorithm to facilitate the realization of the algorithm on the hardware.After balanced the practical measured signals by the improved variable step-size semi-blind CMA and MCMA, the simulation results show that the amplitude of received signals obviously compensated and basely recovered the signal waveform; the distance measurement error is 5.75% and 5.6% respectively, measurement accuracy improve by 0.45% and 0.3%; Optimized the improved algorithm, the operation speed is improved obviously.