Blind equalization of underwater acoustic channel using a novel double mode constant modulus algorithm

A novel double mode constant modulus algorithm (NDMCMA) is presented in this paper to compensate the defects of the least mean Kurtosis constant modulus algorithm (LMKCMA) and the sign algorithm (SA), to effectively utilize the underwater acoustic channel (UWAC) finite bandwidth, and to improve the underwater communication speed. The SA is applied to the LMKCMA and sign LMKCMA (SLMKCMA) is proposed. The SLMKCMA and the LMKCMA are fused to come into being the NDMCMA. Based on the decision of the equalizer´s output, iteration process of the NDMCMA switches between the LMKCMA and the SLMKCMA automatically. The NDMCMA is more robust than the SLMKCMA, and more computationally efficient than the LMKCMA. Therefore, it is very suitable for the recovery of the underwater data transmission. The performance of the NDMCMA is proven by computer simulation for the equalization of the UWAC.