直扩通信系统信噪比估计在LDPC译码中的应用

针对LDPC码的信噪比误差使置信传播(BP)译码算法性能下降的问题,提出一种扩频码辅助的直接序列扩频信号信噪比最大似然估计算法,并利用解扩后的相关值序列对存在的小多普勒频偏情况进行修正。仿真结果表明,该算法在较低信噪比时仍可以达到比较好的估计精度,采用估计信噪比作为BP译码先验概率对译码性能影响非常小。

SNR Estimation of Direct Sequence Spread Spectrum Signals in LDPC Decoding

Aiming at the problem that the Low-density paritychick codes BP decoding performances will loss when SNR mismatches,the SNR estimation algorithm of direct series spread spectrum signals based on ML estimation theory is proposed and the correlation values are used to correct the estimation when Doppler frequency shift presented.Simulation results show that it reaches good precision in low SNR Surrounding,and the performance loss of BP decoder is little when the estimated SNR is used as initial prior probability.