Multi-channel time frequency shift keying in underwater acoustic communication

Current long-range underwater acoustic communication (UWAC) faces many difficulties such as great propagation loss, high ambient noise and long multi-path delay. In order to design an excellent long-range UWAC system, it is necessary to increase signal-to-noise ratio (SNR), suppress inter-symbol interference (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. Both theoretical analysis and simulation over Bellhop multi-path channel model indicate that McH-4T4FSK exhibits lower bit error rate (BER) at the same SNR compared with traditional Frequency Shift Keying (FSK) regardless of diversity or not. Moreover, shallow water sea trial experiments at Xiamen Port with 15 km distance and at Taiwan Strait with 30 km distance confirm that McH-4T4FSK possesses lower BER and better robustness.