Quasi-cyclic low density parity check code (LDPC) construction method and device based on protographs

A technology of an LDPC code and a construction method, which is applied in the field of channel coding and can solve problems such as deteriorating the performance of LDPC codes.

Inactive Publication Date: 2013-06-12
PEKING UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Short rings, especially rings with a ring length of 4, will seriously deteriorate the performance of LDPC codes

Method used

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  • Quasi-cyclic low density parity check code (LDPC) construction method and device based on protographs
  • Quasi-cyclic low density parity check code (LDPC) construction method and device based on protographs
  • Quasi-cyclic low density parity check code (LDPC) construction method and device based on protographs

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Experimental program
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Effect test

Embodiment 1

[0049] The algorithm of the present invention is used in the existing AR4A series of original model diagrams with a code rate of 1 / 2, and three groups of code rates are constructed with 1 / 2, and the parameters are (576, 288), (1152, 576), ( 2304, 1152) quasi-cyclic LDPC code. The structure of the original model and the corresponding matrix are as Figure 8 Shown. Figure 8 ● and ○ are variable nodes, It is a check node, where ○ represents the variable node to be punched, and the maximum number of multiple edges of the original model graph is 3. Taking the construction of (576, 288) code as an example, the specific construction process is as follows:

[0050] The first step is to select the original model of the AR4A series with a code rate of 1 / 2, and the corresponding matrix size is 3×5. The protograph represents an LDPC code with a code length of 4 (the 5 columns of nodes in the matrix contain 1 column of punctured nodes, so the effective code length is 4).

[0051] The second...

Embodiment 2

[0067] The algorithm of the present invention is applied to the existing AR4A series of original models with code rates of 2 / 3, 1 / 2, and 1 / 4, among which the AR4A series of original models with code rates of 2 / 3 and 1 / 4 are as follows: Picture 10 , Picture 11 Shown. The length of the information bits of the three groups of quasi-cyclic LDPC codes is 300 bits, and the parameters are (450, 300), (600, 300), (1200, 300). The specific construction process is similar to Embodiment 1. The decoding performance of the constructed codeword is excellent, and the simulation results are as follows Picture 12 Shown.

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Abstract

The invention discloses a quasi-cyclic low density parity check code (LDPC) construction method and a device based on protographs. The protographs are expanded for two times in the construction method. A first expansion time L1 is smaller. A correcting progressive edge growth (PEG) algorithm is adopted to remove multiple edges of protographs. The girths of codes which are expanded are increased. A second expansion time is L2 and a cyclic shift offset is selected for connection which is established in the first expansion. Each connection corresponds to a unit cyclic matrix, wherein the size of the unit cyclic matrix is L2 * L2. The method references a local optimization idea of the PEG algorithm to construct a basis matrix of the quasi-cyclic LDPC code. The connection is established between each row of variable nodes and checking nodes and is confirmed in corresponding cyclic shift offset process. According to the correcting PEG algorithm, new rings formed in the basis matrix caused by the newly established connection are gone through. The fact that expansion factors A of the rings are larger than one is guaranteed. Thus, the rings with length of four are avoided. The number of short rings is reduced. The short rings which are small in connectivity emerge in a checking matrix are avoided by utilizing an ACE multiplication principle.

Description

Technical field [0001] The present invention relates to the technical field of channel coding, and more specifically, to a method for constructing a quasi-cyclic low-density check code (QC-LDPC) based on the expansion of the original pattern graph. Background technique [0002] Channel coding is a technique for reliably transmitting information in a communication system. Low Density Parity Check Codes (LDPC codes for short) is a channel code with sparse check matrix proposed by Gallager in his doctoral dissertation in 1962. The bipartite graph is an intuitive representation of the LDPC code, which corresponds to the check matrix H. figure 1 Is a bipartite graph representation of an LDPC code and its corresponding H matrix. [0003] The nodes in the bipartite graph are divided into variable nodes and check nodes, which correspond to the symbols and check equations of the LDPC code respectively. If the size of H is m×n, there are m check nodes and n variable nodes in the bipartite ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03M13/11
Inventor 董明科左君洪一帆乐天洪杰龙秋朦蒋伟罗武
Owner PEKING UNIV
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