An Approach to Improving DSSS Modulation in Underwater Acoustic Communications Using Chaotic Signals

This paper proposes a modulation scheme for QPSK Direct-Sequence Spread Spectrum (DSSS) modulation that utilizes chaotic signals as a spreading signal. Unlike traditional techniques that use pseudo-random noise (PN) sequences as spreading signals, this approach suggests the use of chaotic signals generated through the Logistic map. Conventional modulation techniques often face challenges related to spectral efficiency, noise robustness, and security. Chaotic modulation techniques that address these issues typically suffer from low data rates. By employing QPSK modulation, compared to previously used BPSK and DCSK modulation schemes, the data rate, channel capacity, and synchronization are improved. On the other hand, the use of chaotic signals enhances security, increases resistance to noise and multipath fading, reduces the probability of detection, and it is environmentally friendly.To test the proposed solution, simulations were conducted in MATLAB. The simulation results show improvements and successful demodulation.