Implementation of Chaotic DSSS Technique for Underwater Acoustic Communication System

This paper proposes a novel modulation scheme for underwater acoustic communications based on chaotic signal. The proposed method is Chaotic Direct-sequence spread spectrum (DSSS). The conventional modulation techniques often encounter challenges related to spectral efficiency, robustness against noise, and security. In contrast, chaotic modulation harnesses the unique properties of chaotic signals to achieve improved performance in these aspects. In this study, the Logistic map is used as the spreading sequence code for BPSK signal for direct sequence spread spectrum communications. In contrast to conventional methods employing chirp signals for synchronization, this approach utilizes a chaotic signal to achieve synchronization. Additionally, demodulator incorporates a Doppler shift compensator capable of addressing shifts of up to 10 m/s. This compensator operates on a bank of Doppler shifts. To assess the impact of the underwater acoustic channel on our proposed acoustic signal, the simulations in MATLAB were conducted. The channel was characterized by the inclusion of white Gaussian noise, multipath propagation and the Doppler effect.