应用于无人机测控传输系统的多元LDPC码

针对无人机巡查区域地理环境复杂、信道特性多变、突发衰减严重的问题，设计了一种基于多元低密度奇偶校验(Q-LDPC)码的无人机测控传输系统。为减小置信传播(BP)类译码算法中振荡变量节点引入的错误传播，采用加权因子校正迭代前后的变量信息，从而减小短环对遥测、遥控等中短码字译码性能的影响，提高无人机测控传输系统可靠性。基于突发衰减信道建立系统仿真模型，仿真结果表明，所提方案通过将连续的突发比特错误转换为数量较小的符号错误，能够有效抵御快速衰落，降低误码率，为无人机对地观测提供安全保障。

Q-LDPC code for UAV TT&C transmission system

In unmanned aerial vehicle(UAV) inspection,wireless communication is one of most challenging tasks because the channels are often subject to geographical environment complexity,channel characteristic varying and severe burst fading. Here in this paper a UAV TT&C transmission system is specifically designed based on Q-LDPC code. In order to decrease error propagation brought by oscillating variable nodes in Log-FFT-BP decoding algorithm,weight factor is introduced to check previous priori probabilities and current posteriori probabilities after iteration. And consequently it reduces effects of small girth on decoding performance of short and middle length codes(telemetry and remote control data,etc.),as well as improves the reliability of UAV TT&C system. A system simulation model driven by burst fading channel is established. Simulation results show that the proposed scheme can not only efficiently withstand burst error,but also reduce bit error rate(BER) through converting continuous bit error to less symbol error. Accordingly,the proposed scheme can supply better guarantee for UAV earth observation.