Research on multi-channel time frequency shift keying for underwater acoustic communication

Long-range underwater acoustic communication (UWAC) faces many difficulties such as great propagation loss, high ambient noise and long multipath delay. In order to design an excellent long-range UWAC system, it is necessary to increase signal-to-noise ratio (SNR), suppress inter-symbol interface (ISI) and alleviate frequency selective fading. In this paper, a novel time frequency shift keying scheme named as Multi-channel Hex Four Time Four Frequency Shift Keying (McH-4T4FSK) is presented. The scheme is designed by two aspects: high-array modulation at transmitter to improve spectral efficiency and multi-channel processing at receiver to enhance signal-to-noise ratio of received signal. Based on the two aspects mentioned above, there are four time slots and four frequencies in each symbol. Shallow water sea trials are conducted at Taiwan Strait with 30km distance. The results indicate that McH-4T4FSK is a kind of underwater acoustic communication scheme with low BER and good robustness.