Novel Spread Spectrum Based Underwater Acoustic Communication Technology for Low Signal-to-Noise Ratio Environments

Underwater acoustic channels are unstable and acoustic waves when propagating in the ocean are subjected to variety of interference, such as noise, reflections, scattering and so on. To cope with this severe interference, spread spectrum communication technology is used. The traditional spread spectrum communication technology can communicate reliably in a lower signal-to-noise ratio environment, but at the cost of lower data rate. This paper thus proposes an underwater acoustic spread spectrum communication technology, which combines direct sequence spread spectrum and cyclic shift keying modulation to improve the data rate. Besides, a time-frequency two-dimensional search algorithm is used to realize the synchronization of this system. In order to reduce the bit error rate, the hybrid system is improved by adjusting power allocation of the transmitted signal. The performance of the proposed system is analyzed by the simulation and is verified by the experiment.