An underwater acoustic modem system is built by employing DSP Software based on M-ary frequency-shift-key (MFSK) modulation and non-coherent detection.

采用DSP软件方法，研制了一套基于MFSK调制和非相干能量检测的水声调制解调系统。

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Based on the characters of long rang underwater acoustic channels and MFSK modulation, a new Frequency Group Coding (FGC) method is proposed in this paper.

本文针对远程水下信道和MFSK调制的特点，提出了一种新的频率分组编码(FGC)方法。

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Because of limited frequency band of channel, spread spectrum and MFSK modulations can not resolve that high speed transmission is in contradiction with limited frequency band.

当进行高速水下通信时，由于水下信道的频带有限，扩频和MFSK调制方式无法解决高速率信息传输和可利用信道频带窄的矛盾。

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