一种新颖的LDPC编码系统码率识别方法

Novel Coding Identification Algorithm for LDPC Codes

LDPC码编码识别是信道编码识别中的难点。随着LDPC码在通信领域的广泛应用,LDPC码编码识别技术也引起越来越多的关注。针对在低信噪比条件下,现有算法对LDPC码编码参数识别率低的问题,首先利用信道输出的软信息,将编码校验关系映射到对数似然比域,并定义编码校验对数似然比(Check log-likelihood ratio,CLLR)。然后,分析CLLR模值的统计特性,建立CLLR与待识别LDPC码参数之间的联系。最后,充分利用在不同校验矩阵下CLLR统计特性的区别,设计一种综合CLLR均值和方差特征的最大均方比判决器。从仿真结果看,在给定先验编码集合的闭集应用模式下,本文算法明显优于已有算法,识别增益在低信噪比环境下可达2～5dB。而且对于高码率LDPC码的识别,本算法可以显著提高识别性能。

LDPC code recognition is a difficult issue in channel coding recognition.With the widespread application of LDPC code in communication field,LDPC code recognition technology has been attracted more and more attention.Aiming at the problem that the existing methods have been suffering weak identification performance in low SNR environment,a LDPC coding method with maximum mean square ratio is proposed in this paper.Firstly,the coded verification relation is mapped to the log-likelihood ratio domain using the soft information output in the channel,and the parity check log-likelihood ratio(CLLR)is defined.Then,the modulus statistical properties of CLLR are analyzed,and the relationship between CLLR and the parameters of LDPC code is established.Finally,using the difference of statistical properties of CLLR under different check matriices,a method of maximum mean and variance ratio based decision device is proposed.The simulation results show that the proposed algorithm is superior to the existing algorithms in the finite set application model,and the recognition gain can reach 2 dB to 5 dB in the low SNR environment.Moreover,for the recognition of high bit rate LDPC codes,the algorithm can significantly improve the recognition performance.