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Construction method of LDPC check matrix for navigation signals

A technology of LDPC code and check matrix, which is applied in the field of satellite navigation system signal design, and can solve the problem of destroying the lower triangle structure of the check matrix

Inactive Publication Date: 2014-04-16
HUAZHONG UNIV OF SCI & TECH
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  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, the construction algorithm given in this article cannot explain why "-1" appears in the base matrix in a given result, and may destroy the original lower triangular structure of the check matrix

Method used

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  • Construction method of LDPC check matrix for navigation signals
  • Construction method of LDPC check matrix for navigation signals
  • Construction method of LDPC check matrix for navigation signals

Examples

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example

[0047] The following describes an example of constructing a parity check matrix with a codeword length of N=1200, a parity bit length of M=600, and a submatrix size of 60×60.

[0048] Need to generate 10 sparse sequences. Get their last 600 digits first 1,2 ~s 10,2 , most of the elements are "0", and the following table 1 shows the position of "1":

[0049] The position where "1" appears in the last 600 bits of the sparse sequence in Table 1

[0050]

Where "1" appears

Where "1" appears

s 1,2

2,591

s 6,2

6,7

s 2,2

1,2,3

s 7,2

7,8

s 3,2

3,4

s 8,2

8,9

s 4,2

4,5

s 9,2

9,10

s 5,2

5,6

s 10,2

10,591

[0051] The first 600 bits of the sparse sequence are obtained by a loop with an outer loop count of 10,

[0052] Table 2 below shows where "1" occurs:

[0053] Table 2 The position where "1" appears in the first 600 bits of the sparse sequence

[0054]

...

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Abstract

The invention discloses a construction method of an LDPC check matrix for navigation signals. The method includes the following steps that (1) the size z*z of a submatrix of the LDPC check matrix to be constructed and the size m*n of a basis matrix of the LDPC check matrix to be constructed are obtained, and (2) m sparse sequences [S1, S2, ..., Sm] composed of 0 and 1 and with lengths of nz bits are constructed according to results obtained from the step (1), and the LDPC check matrix H is obtained by means of the constructed m sparse sequences. A quasi-cyclic check matrix H is constructed by a method of searching for the sparse sequences, the generation method of rear M sparse sequences determines the situation that the obtained check matrix is of a structure approximate to a lower triangle, and an encryption algorithm based on the H is simpler. Constraint conditions of front N-M sparse sequences and mutual correlation constraint conditions of the different sparse sequences guarantee that a ring with the length of 4 cannot appear in the check matrix H. According to the method, the check matrix with the quasi-cyclic characteristic and of the lower triangle structure can be constructed quickly and efficiently.

Description

technical field [0001] The invention belongs to the field of satellite navigation system signal design, and more specifically relates to a method for constructing an LDPC code parity check matrix for navigation signals. Background technique [0002] Low density parity code (Low density parity code, referred to as LDPC code) is an error correction code first proposed by Gallager in 1962. It is a linear block code with a sparse check matrix. The research results show that using iterative The probabilistic decoding algorithm, LDPC codes can achieve performance close to the Shannon limit. [0003] With the development of the global navigation satellite system (GNSS for short) signal system, new ideas continue to emerge. This includes the introduction of forward error correction (Forward error correction, FEC for short) codes such as convolutional coding and LDPC codes to improve the robustness of the signal. The traditional navigation signal GPS C / A only uses Hamming code to p...

Claims

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Application Information

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IPC IPC(8): H03M13/11
Inventor 魏蛟龙唐祖平杨溢张小清刘昌建
Owner HUAZHONG UNIV OF SCI & TECH
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