基于PPM硬判决的ARQ-FSO系统误码性能分析

Performance of ARQ-FSO system based on PPM hard decision in turbulence channel

基于PPM(Pulse Position Modulation)硬判决检错的ARQ-FSO(Automatic Repeat Request-Free Space Optical)通信系统结合了PPM硬判决和新的ARQ协议.该系统以PPM硬判决的结果代替了传统ARQ的监督码元作为数据的检错依据,同时只重传数据包里面译码失败部分的PPM符号,消除了传统ARQ中用来检错的信息冗余,提高了系统的效率.理论分析表明该方案能够有效地改善硬判决误码率,其通过率也优于传统ARQ,适用于较低误码率、低复杂度的自由空间光通信场景.

We present an ARQ-FSO system, which consists of pulse position modulation （PPM） hard decision and a novel automatic repeat request （ARQ） protocol.Instead of traditional ARQ＇s data error detection,the PPM hard decision results are used to find data error.Then the transmitter only retransmits the failed decoded portion of the packet.These measures can eliminate the information redundancy of traditional ARQ and enhance the system effi- ciency.Theoretical analysis shows that the ARQ-FSO system can effectively improve the BER performance of the di- rect hard decision PPM system.Additionally,the proposed system significantly improves the average throughput effi- ciency compared with traditional ARQ systems.These characteristics make this ARQ-FSO system suitable to apply in low BER and low complexity FSO communications.