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Chaotic modulations for digital underwater acoustic communications

MPSK and MFSK are two common modulation schemes for coherent and incoherent digital communications respectively. Despite wide applications in underwater acoustic communications, they are not suitable for confidential application scenarios due to their well-known generating processes and signal features. In this paper, two corresponding chaotic modulation methods are proposed to improve their security, namely Chaotic MPSK (CMPSK) and Chaotic MFSK (CMFSK). By applying chaotic sequences to the modulation procedures, it is nearly impossible to demodulate CMPSK and CMFSK signals without knowledge of the key sequences. So the CMPSK and CMFSK are able to prevent unauthorized receivers from extracting information from the intercepted signals even with high SNR.