IMPROVED PROPORTIONATE LEAST MEAN SQUARE/FOURTH BASED CHANNEL EQUALIZATION FOR UNDERWATER ACOUSTIC COMMUNICATIONS

An improved proportionate least mean square/fourth (IPLMS/F) equalizer is proposed in this paper, and applied to underwater acoustic communications in real experiment. In addition to improving the performance of least mean squares (LMS) equalizer, the proposed IPLMS/F equalizer maintains the simplicity and stability of LMS. The advantage of the proposed IPLMS/F equalizer is due to introduction of a proportional update matrix. The diagonal elements of this matrix are determined by the equalizer tap magnitudes to improve the sparsity level estimate, and thus, further improve the equalizer performance. The performance of IPLMS/F is verified by applying it to the experimental data from the 9(th) Chinese National Arctic Research Expedition. The results show that IPLMS/F exhibits fastest convergence speed and it has the lowest bit error rate compared with LMS and LMS/F, indicating its effectiveness and reliability in practical applications.