Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

IEEE Communications Letters

Construction of QC-LDPC Codes Based on Pre-Masking and Local Optimal Searching

Dongdong Wang, Liqian Wang, Xue Chen, Aimei Fei, Chen Ai Ju, Zhirong Wang

Published Sep 25, 2017• 9 citations
Publisher

Abstract

In this letter, we consider the construction of quasi-cyclic (QC) low-density parity-check (LDPC) codes by jointly optimizing the girth g and the number of g-cycles. We first propose a sub-array detection method to accelerate the detection of cycles, and by detecting the non-repeated automatic enumerative cycles in the frame of sub-arrays, cycle detection time can be greatly reduced. Furthermore, a local optimal searching algorithm combined with pre-masking is presented, by orderly searching the local optimal p j,l for each circulant permutation matrix (CPM), a class of QC-LDPC codes with possibly enlarged g, less number of g-cycles, and arbitrary attainable degree distribution could be constructed. Simulation results show that the codes constructed by the proposed method perform well in error floor region.

DOI
10.1109/lcomm.2017.2756640

Related papers

Construction of Quasi-Cyclic LDPC Codes via Masking With Successive Cycle Elimination

Hengzhou Xu, Dan Feng, Rui Luo +1 more

In this letter, we study the construction of quasi-cyclic (QC) low-density parity-check (LDPC) codes by array dispersion and masking. We first propose a class of arrays of circulant permutation matrices (CPMs) of arbitrary size obtained by dispersion. Based on this class of arrays of CPMs, a class of QC-LDPC codes is constructed. For these resulting codes, we analyze their cycle structure and derive the numbers, which indicate how many cycles pass through each CPM in their parity-check matrices. Following the indication numbers with the order from largest to smallest, we replace the corresponding CPMs with zero matrices (ZMs) of the same size one by one until a targeted masking termination condition is satisfied. Then, the resultant arrays of CPMs and ZMs give a large class of QC-LDPC codes. Numerical results show that the codes constructed perform well over the additive white Gaussian noise (AWGN) channel when decoded with the sum-product algorithm.

IEEE Communications Letters•Sep 21, 2016•50 citations

Superposition Construction of Q-ary LDPC Codes by Jointly Optimizing Girth and Number of Shortest Cycles

Hengzhou Xu, Baoming Bai

In this letter, we consider the construction of q-ary low-density parity-check (LDPC) codes by jointly optimizing the girth and number of shortest cycles in the frame of superposition. We begin with constructing binary quasi-cyclic LDPC codes by superposition. By replacing the nonzero entries of the parity-check matrices of the resulting binary codes with the nonzero elements of GF(q), a class of q-ary LDPC codes is obtained. Furthermore, we analyze the cycle structure of the constructed codes for a given degree distribution and code length, and present a search algorithm for finding q-ary LDPC codes with few cycles of length g, where g is the optimized girth value. Simulation results show that the proposed codes perform well under the iterative decoding algorithms.

IEEE Communications Letters•Jan 1, 2016•25 citations

Construction and Performance Evaluation of QC-LDPC Codes With Low Error Floor

Ying Wang, Xiaojian Liu, Ming Jiang +1 more

In the paper, we propose a novel construction method for quasi-cyclic (QC) low-density parity-check (LDPC) codes with lower error floor. This approach aims at eliminating the most harmful substructures by choosing proper shift values for cyclic permutation matrices (CPM). To search these harmful substructures, we introduce a high-efficiency searching algorithm, based on cycle combination and leaf cutting. In addition, a high throughput decoding platform based on multi-core CPU with SIMD instruction sets are implemented and utilized to reach the error floors of different LDPC codes efficiently. Simulation results show that for given base matrices, our method can achieve excellent performance in the high SNR region.

Information Communication Technologies Conference (ICTC)•May 17, 2023•0 citations

Construction of Quasi-Cyclic LDPC codes with large girth based on circulant permutation matirx

Peng Yang, Xiaoxiao Bao, Hui Zhao

In this paper, we propose an algorithm for removing short-cycles in Quasi-Cyclic (QC) Low-density parity-check (LDPC) codes. First using an algorithm with lower computational complexity, all the cycles in the parity check matrix H are found. Then following a ruler, we adjust the shift value of circulant permutation matrix (CPM) to remove the short-cycles. This algorithm could ensure that the code after cycle removal process preserves the quasi-cyclic structure. Simulation results show that: comparing with the codes (504,252) and (1008, 504), we achieve 0.1dB improvement both.

Wireless and Optical Communications Conference•May 1, 2013•4 citations

New Construction of Large-girth QC-LDPC Codes by Classification of Cycles and Heuristic Search Strategy

Jianhua Zhang

By classifying cycle types within the parity-check matrix of a quasi-cyclic(QC) low-density parity-check(LDPC) code,a method without repetition or omission is proposed to detect all the cycles with lengths smaller than twelve.Based on this cycle detection method,a new approach is presented to construct large girth QC-LDPC codes by using some heuristic strategies.The approach includes three steps.Firstly,under the infinite cyclic permutation matrix(CPM) size condition,two integer sequences satisfying the girth constraint are found using a heuristic strategy.Secondly,according to the designed code rate,several integer pairs are extracted from the two sequences so as to form a shift matrix.Finally,by employing the recently proposed theoretical lower bound by Zhang et.al,a range of consecutive CPM sizes in which the girth never decrease is accurately computed from the shift matrix.Compared with Liu-Han's method,the new approach possesses two advantages in the sense that:(1) Not only girth-10+ QC-LDPC codes but also girth-12 ones can be constructed to have consecutive CPM sizes;(2) girth-10+ and girth-12 QC-LDPC codes can be generated with very high code rates,due to the new cycle detection method which significantly accelerates the sequence search procedure.

Space Electronic technology•Jan 1, 2013•0 citations

On the Low Complexity Construction of Quasi-Cyclic Low-Density Parity-Check Codes by Progressive-Block Growth

Qiangy Yuan, Pinyi Ren, Yilin Feng +1 more

In this paper, we propose a novel method with low complexity for constructing quasi-cyclic LDPC codes. The algorithm chooses every circulant permutation matrix sequentially, and makes sure that the current circulant permutation matrix forms no cycles of length 4 and 6 with the existent matrices, finally a family of $(3,L)$ QC-LDPC codes with girth at least 8 is obtained. The main complexity of the algorithm is checking cycles of length 6, the number of which is no more than $L^2$. Simulation results show that, when block length is 1008 and using the iterative belief propagation decoding, the LDPC code constructed by the proposed algorithm out performs the random code about 0.1dB at the bit-error-rate of $ 10^{ - 5}$.

•Jan 1, 2009•1 citation
In this letter, we consider the construction of quasi-cyclic (QC) low-density parity-check (LDPC) codes by jointly optimizing the girth g and the number of g-cycles. We first propose a sub-array detection method to accelerate the detection of cycles, and by detecting the non-repeated automatic enumerative cycles in the frame of sub-arrays, cycle detection time can be greatly reduced. Furthermore, a local optimal searching algorithm combined with pre-masking is presented, by orderly searching the local optimal p j,l for each circulant permutation matrix (CPM), a class of QC-LDPC codes with possibly enlarged g, less number of g-cycles, and arbitrary attainable degree distribution could be constructed. Simulation results show that the codes constructed by the proposed method perform well in error floor region.
In this letter, we study the construction of quasi-cyclic (QC) low-density parity-check (LDPC) codes by array dispersion and masking. We first propose a class of arrays of circulant permutation matrices (CPMs) of arbitrary size obtained by dispersion. Based on this class of arrays of CPMs, a class of QC-LDPC codes is constructed. For these resulting codes, we analyze their cycle structure and derive the numbers, which indicate how many cycles pass through each CPM in their parity-check matrices. Following the indication numbers with the order from largest to smallest, we replace the corresponding CPMs with zero matrices (ZMs) of the same size one by one until a targeted masking termination condition is satisfied. Then, the resultant arrays of CPMs and ZMs give a large class of QC-LDPC codes. Numerical results show that the codes constructed perform well over the additive white Gaussian noise (AWGN) channel when decoded with the sum-product algorithm.
In this letter, we consider the construction of q-ary low-density parity-check (LDPC) codes by jointly optimizing the girth and number of shortest cycles in the frame of superposition. We begin with constructing binary quasi-cyclic LDPC codes by superposition. By replacing the nonzero entries of the parity-check matrices of the resulting binary codes with the nonzero elements of GF(q), a class of q-ary LDPC codes is obtained. Furthermore, we analyze the cycle structure of the constructed codes for a given degree distribution and code length, and present a search algorithm for finding q-ary LDPC codes with few cycles of length g, where g is the optimized girth value. Simulation results show that the proposed codes perform well under the iterative decoding algorithms.
In the paper, we propose a novel construction method for quasi-cyclic (QC) low-density parity-check (LDPC) codes with lower error floor. This approach aims at eliminating the most harmful substructures by choosing proper shift values for cyclic permutation matrices (CPM). To search these harmful substructures, we introduce a high-efficiency searching algorithm, based on cycle combination and leaf cutting. In addition, a high throughput decoding platform based on multi-core CPU with SIMD instruction sets are implemented and utilized to reach the error floors of different LDPC codes efficiently. Simulation results show that for given base matrices, our method can achieve excellent performance in the high SNR region.
In this paper, we propose an algorithm for removing short-cycles in Quasi-Cyclic (QC) Low-density parity-check (LDPC) codes. First using an algorithm with lower computational complexity, all the cycles in the parity check matrix H are found. Then following a ruler, we adjust the shift value of circulant permutation matrix (CPM) to remove the short-cycles. This algorithm could ensure that the code after cycle removal process preserves the quasi-cyclic structure. Simulation results show that: comparing with the codes (504,252) and (1008, 504), we achieve 0.1dB improvement both.
By classifying cycle types within the parity-check matrix of a quasi-cyclic(QC) low-density parity-check(LDPC) code,a method without repetition or omission is proposed to detect all the cycles with lengths smaller than twelve.Based on this cycle detection method,a new approach is presented to construct large girth QC-LDPC codes by using some heuristic strategies.The approach includes three steps.Firstly,under the infinite cyclic permutation matrix(CPM) size condition,two integer sequences satisfying the girth constraint are found using a heuristic strategy.Secondly,according to the designed code rate,several integer pairs are extracted from the two sequences so as to form a shift matrix.Finally,by employing the recently proposed theoretical lower bound by Zhang et.al,a range of consecutive CPM sizes in which the girth never decrease is accurately computed from the shift matrix.Compared with Liu-Han's method,the new approach possesses two advantages in the sense that:(1) Not only girth-10+ QC-LDPC codes but also girth-12 ones can be constructed to have consecutive CPM sizes;(2) girth-10+ and girth-12 QC-LDPC codes can be generated with very high code rates,due to the new cycle detection method which significantly accelerates the sequence search procedure.
In this paper, we propose a novel method with low complexity for constructing quasi-cyclic LDPC codes. The algorithm chooses every circulant permutation matrix sequentially, and makes sure that the current circulant permutation matrix forms no cycles of length 4 and 6 with the existent matrices, finally a family of (3,L)(3,L)(3,L) QC-LDPC codes with girth at least 8 is obtained. The main complexity of the algorithm is checking cycles of length 6, the number of which is no more than L2L^2L2. Simulation results show that, when block length is 1008 and using the iterative belief propagation decoding, the LDPC code constructed by the proposed algorithm out performs the random code about 0.1dB at the bit-error-rate of $ 10^{ - 5}$.