The hardware sub-system of the transmitter and the receiver includes the modules of FEC coding and decoding , DPPM modulation and demodulation , signal deserialization module and time slot synchronization .
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Simultaneously , a theoretical analyses and research of the implementations of an Forward Error Correction ( FEC ) sub-system and a Differential Pulse Position Modulation ( DPPM ) sub-system are done in this paper .
同时本文对前向纠错（FEC）编码和差分脉冲位置调制（DPPM）子系统的实现做了详细理论分析研究。
3 ) By the description on the PPM theory of the atmosphere laser emergency communication system and the comparison to the L-PPM , DPPM and multiple pluse PPM , the thesis proposes the scheme of the L-PPM modulator and demodulator .
