Novel blind equalization algorithm for multipath fading underwater acoustic channel

In underwater acoustic digital communications, two main factors which affect the performance of communication systems seriously are multipath fading and Doppler frequency shift. A blind equalizer based on fractionally-spaced decision-feedback structure, which efficiently combats the multipath fading effects of underwater acoustic channels, is discussed. Towards the time-varying Doppler underwater acoustic channels, a modified constant modulus fractionally-spaced decision-feedback equalization and second-order digital phase-locked loop combined algorithm, which can efficiently correct the channel-introduced carrier phase rotation, is proposed. Finally the performance of the proposed algorithm is compared with a constant modulus baud-spaced decision-feedback blind equalization algorithm by computer simulation, and the simulation results confirm the effectiveness of the proposed algorithm.