Research on M-ary Chaotic Phase Modulation Orthogonal Multi-carrier Spread Spectrum for Underwater Acoustic Communication

Abstract

Long-range underwater acoustic communication (UWAC) faces many difficulties such as band-limited channel, great propagation loss, high ambient noise and large-scale multipath delay, which greatly limit the communication rate and bit error performance. Conventional spread spectrum modulation is capable to resist the multipath interference as well as the high-level noise due to its spread spectrum gain. However, such benefit is on the cost of low spectrum efficiency, thus it’s difficult to carry out high speed communication. In this paper, a novel M-ary Chaotic Phase Modulation Orthogonal Multi-Carrier Spread Spectrum (M-ary CPM-OMCSS) modulation is presented. The scheme is designed by two aspects: orthogonal multi-carrier modulation to improve the spectrum efficiency and frequency domain spread spectrum modulation to enhance the bit error performance. Based on the two aspects mentioned above, chaotic phase modulation is explored to decrease the inter-carrier interference (ICI) due to the excellent cross-correlation property of chaotic sequence. Shallow water sea trials were conducted at Bohai with 12km distance. The results indicate that M-ary CPM-OMCSS is a kind of underwater acoustic communication with low bit error rate and good robustness.