New Modified Constant Modulus Algorithm for Underwater Acoustic Communications

Abstract

In digital communications, the modified constant modulus algorithm (MCMA) is known to outperform the constant modulus algorithm (CMA) considerably. However in underwater acoustic communications which occur seriously multipath fading and Doppler frequency shift, the MCMA only achieves moderate convergence rate and steady-state mean square error (MSE). So a new modified constant modulus algorithm is presented which is suitable for high-data-rate underwater acoustic communications. The proposed approach uses a novel constant function to channel the modulus of received signals to match the statistical modulus, which can reduce the incorrect decision and decrease the inter-symbol interference (ISI) more effectively. Compared with MCMA the proposed algorithm has faster convergence rate and lower steady-state MSE. The efficiency of the method is proved by computer simulations in underwater acoustic channels.