Performance analysis of an improved modal dispersion compensation receiver for low-frequency and long-range shallow water communication experiment

Low-frequency acoustic signal will suffer from dispersion effect when propagating in long-range shallow water waveguide, which leads to multi-mode and waveform expanding. Longer transmission range and shallower waveguide will result in more serious dispersion effect. In this paper, we propose an improved modal dispersion compensation receiver, and evaluate its performance for a shallow water acoustic communication experiment. The receiver not only exploits time-frequency analysis approach to compensate the waveform expanding effect of each mode simultaneously, but also combines the modified multi-mode energy to enhance symbol estimation accuracy. The experiment is conducted by a differential-binary-phase-shift-keying modulated direct-sequence-spread-spectrum communication system, which is suitable for long-range transmission. With this receiver, we obtain no error demodulation results without coding in the experiment. The experimental data analysis also shows that the proposed receiver can obtain about 3 dB gain than the conventional one, which is of significant importance for long-range communications.