Experimental Results of Underwater Acoustic Communication with Nonlinear Frequency Modulation Waveform

In this paper, we propose underwater acoustic (UWA) communications using a generalized sinusoidal frequency modulation (GSFM) waveform, which has a distinct ambiguity function (AF) and correlation function characteristic. For these reasons, it is more robust in multipath channels than the conventional chirp spread spectrum (CSS) with a linear frequency modulation (LFM) waveform. Four types of GSFM waveforms that are orthogonal to each other are applied for each symbol in the proposed method. To evaluate the performance of the proposed method, we compared the performances of the proposed method and conventional method by conducting diverse experiments: simulations, lake trials and sea trials. In the simulation results, the proposed method shows better performance than the conventional method. The lake trial was conducted with a distance of 300 similar to 400 m between the transmitter and receiver. As a result of the experiment, the average bit error rate (BER) of the proposed method is 3.52x10(-2) and that of the conventional method is 3.52x10(-1), which shows that the proposed method is superior to the conventional method. The sea trial was conducted at a distance of approximately 20 km between the transmitter and receiver at a depth of 1500 m, and the receiver was composed of 16 vertical line arrays (VLAs) with a hydrophone. The proposed method had a BER of 0.3x10(-2) in one channel and was error free in the other.

Automated summary

This paper proposes underwater acoustic communication using a generalized sinusoidal frequency modulation (GSFM) waveform, showing better performance in multipath channels compared to conventional linear frequency modulation (LFM) waveform with chirp spread spectrum (CSS). Through simulations, lake trials, and sea trials, experiments demonstrated the superior performance of the proposed GSFM method over the traditional CSS method, with lower bit error rates and higher reliability.