Density Evolution Based on Two-Type Degree Distribution Framework of Raptor-Like LDPC
Density Evolution Based on Two-Type Degree Distribution Framework of Raptor-Like LDPC
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DOI：
10.1109/tvt.2018.2877134
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发表时间：
2018-12
影响因子：
6.8
通讯作者：
Genning Zhang;Yin Xu;Dazhi He;Jun Sun;Wenjun Zhang
中科院分区：
文献类型：
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作者：
Genning Zhang;Yin Xu;Dazhi He;Jun Sun;Wenjun Zhang
传统的度分布框架是分析非规则低密度奇偶校验（LDPC）码的有效工具。然而，它不能用于分析raptor-like LDPC码，因为它不能描述raptor-like LDPC码的最重要的结构特征，即任何校验节点最多连接到一个度一的变量节点。本文提出了一种两类度分布的Raptor-like LDPC码结构。该框架通过将校验节点划分为两个不同的集合来描述raptor-like LDPC码的特殊结构特征。一个是连接到那些度为1的变量节点的校验节点的集合，另一个是不连接到那些度为1的变量节点的校验节点的集合。在此基础上，提出了两类离散密度演化算法和两类高斯近似密度演化算法，用于估计raptor-like LDPC码的门限。在解码分析过程中，所提出的算法对属于两个单独集合的校验节点进行不同的处理。与传统的多边缘类型（MET）算法相比，所提出的算法允许我们更快地计算阈值，而不会牺牲太多的准确性。对于高级电视系统委员会3.0（ATSC3.0）标准中采用的一些raptor-like LDPC码，本文提出的算法估计的门限可以非常接近传统MET算法估计的门限。误差小于0.07dB。同时，由于两类度分布框架和高斯近似，所提出的算法可以大大降低计算复杂度。
The traditional degree distribution framework is a useful tool to analyze irregular low density parity check (LDPC) code. However, it cannot be used to analyze raptor-like LDPC code as it cannot describe the most important structural feature of raptor-like LDPC code, which is that any check node is connected to at most one degree-one variable node. In this paper, we propose a two-type degree distribution framework for raptor-like LDPC code. The proposed framework can describe the special structural feature of raptor-like LDPC code by dividing the check nodes into two different sets. One is the set of check nodes connected to those degree-one variable nodes, the other is the set of check nodes unconnected to those degree-one variable nodes. Furthermore, we propose a two-type discrete density evolution algorithm and a two-type Gaussian approximation density evolution algorithm based on the proposed two-type degree distribution framework to estimate the threshold of raptor-like LDPC code. During the decoding analysis, the proposed algorithms treat the check nodes belonging the two separate sets differently. Compared with the traditional multi-edge type (MET) algorithm, the proposed algorithms allow us to calculate the threshold more quickly without much sacrifice in accuracy. For some raptor-like LDPC codes adopted by the Advanced Television Systems Committee 3.0 (ATSC3.0) standard, the thresholds estimated by the proposed algorithms can be very close to the thresholds estimated by the traditional MET algorithm. The deviations are less than 0.07 dB. Meanwhile, the proposed algorithms can tremendously reduce the computation complexity because of the two-type degree distribution framework and the Gaussian approximation.