An effective adaptive equalization algorithm for underwater acoustic communications

A effective adaptive equalization algorithm has been proposed. The algorithm, which combining modified normalized LMS algorithm with decision feedback equalizer structure, realizes the adaptive equalization of various underwater acoustic channels and is prone to hardware realization on the premise of non-increasing computational complexity. At the same time, a second order digital phase-locked loop (2DPLL) is introduced to track and compensate phase rotation. The steady-state MSE of the proposed algorithm is close to that of RLS-DFE algorithm, but it overcomes the fact problem of great computational complexity which existed in RLS-DFE algorithm. And then, the carrier recovery performance of the proposed algorithm is better than that of the LMS-DFE-2DPLL algorithm, which is verified by computer simulation. In addition, MULAN Lake experiment shows that the performance of the proposed algorithm is better than that of the LMS-DFE algorithm in terms of bit error rate (BER) by comparing the influences caused filter order and step size.