M-QAM系统中QC_LDPC译码性能研究

摘要

研究了M-QAM与QC-LDPC结合的调制编码系统的性能。详细推导M-QAM软解调的后验概率计算公式,得出正方形星座软解调时,解映射搜索点数由M可降低为M～（1/2）的结论。通过仿真,对调制阶数对系统性能的影响进行了评估。QC-LDPC译码采用M.Mansour最新提出的P-TDMP算法,仿真结果显示,P-TDMP算法比传统的置信传播译码算法有一定的性能增益,它还提高了硬件实现的并行度,降低了系统的开销。%M-QAM modulation/demodulation with the QC-LDPC coding/decoding system is studied.For M-QAM soft demodu-lation,the detailed derivation of posterior probability formula is given.Through derivation,we can get the conclusion that the computational complexity is cut down from O M～（1/2） to OM for square constellation;A simulation experiment is done to estimate performance of different modulation order.The P-TDMP decoding algorithm is adopted as the QC-LDPC decoding scheme,through simulation,a conclusion can be made that P-TDMP decoding has a performance advantage over classic decoding algorithm.