Abstract:

Abstract: In underwater acoustic communication, the channel of the multipath effect can cause severe inter-symbol interference. In view of the existing equalization algorithm dealing with inter-symbol interference, these algorithms have some problems such as slow convergence speed, huge steady-state error, complex algorithm and not easy to transplant hardware, presented a new variable step LMS algorithm with three adjustment parameter combined with the feed-forward equalizer and decision feed-back equalizer （FFE-DFE）structure. Firstly we made algorithm simulation of three adjustment parameter alpha, beta, gamma，then we compared our algorithm with traditional LMS algorithm ，modified arctangent based variable step LMS（MA-VSLMS） and hyperbolic secant function based variable step size LMS algorithm（HS-VSLMS）in the convergence and steady-state error. The simulation result confirms that our algorithm has 57.9% faster convergence speed and 2dB lower steady-state error than traditional LMS algorithm. Our algorithm has 26.3% faster convergence speed than HS-VSLMS, 15.8% faster than MA-VSLMS and 1~2dB lower steady-state error. Finally we transplanted our algorithm to the signal processing module, and tested our algorithm in underwater experiment, the experimental results show that the signal after the equalizer recovers very well. The equalizer effectively overcome the inter-symbol interference caused by multipath effect in the actual scene.