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

Journal of Huaiyin Institute of Technology

Research on Structure Method of an Improved Type of Low-Density-Parity-Check-Codes

Kuixi Yin

Published Jan 1, 2007• 0 citations
OpenAlex

Abstract

Low-Density-Parity-Check-Codes taken as a kind of advanced channel coding mode,have become the powerful competitor of the fourth generation of communication system.The LDPC advanced by Gallager has standard Tanner figure structure,and the advantage of the performance can be materialized after the length of the codes become longer.When the length is short or of medium sized,the performance of coding will fall down in a way because of the existence of short girth in the Tanner figure.With the improvement of structure method advanced by Gallager,the short girth in which length is 4 can be eliminated,thus the performance of coding can be raised.

Related papers

An software construction method restricting short girth of LDPC codes

Xiaoqi Yin

Low-Density-Parity-Check-Codes(LDPC) taken as a kind of advanced channel coding mode,has become the powerful competitor of the fourth generation communication system.The LDPC advanced by Gallager have standard Tanner figure structure,the performance of coding will fall down in a way because of the existence of short girth in the Tanner figure.It is advanced the improvement of structured method based on Gallager,the short girth that length is 4 was eliminated and the flow chart was given.Simulation result shows that performance of coding is raised.

Journal of Hunan University of Science & Technology•Jan 1, 2011•0 citations

Increasing the local girth of irregular low-density parity-check codes based on degree-spectrum analysis

Francis C. M. Lau, Wai M. Tam, Chi Kong Tse

A low-density parity-check (LDPC) code can be described by a Tanner graph composed of symbol nodes and check nodes. Short cycles in the Tanner graph should be avoided because such cycles will degrade the performance of the decoder and hence increase the error rate. In most of the circumstances, cycles of length 4 can be totally eliminated in the Tanner graph when the LDPC code has been designed properly. Locally, for each variable node in the Tanner graph, the girth may take the value of 6 or 8, or even higher. In this study, the authors attempt to increase the local girths of a Tanner graph with an aim to improving the error performance of the code. The authors propose and analyse the ‘degree spectrum’ of the symbol nodes connecting to each of the check nodes. Based on the analysis, the authors can determine if the local girths can be further increased. The authors also propose simple ways to construct codes with higher local girths. Finally, the authors show the characteristics and the error performance of the codes constructed with the proposed methods.

IET Communications•Jul 22, 2011•2 citations

The Design of Structured Low-Density Parity-Check Codes With Large Girth

Jing Long

This paper,based on algebra and graph,proposes a method for constructing structured low-density parity-check(LDPC) codes.In this method,the authors design a connected graph with three kinds of special path to ensure that the Tanner graph of the parity check matrix mapped from the connected graph is without short cycles.The construction method results in two classes of(3,k)-regular quasi-cyclic LDPC codes with girth 8 and 12 respectively.Furthermore,by extending this construction method,two classes of LDPC codes with column weight 2,whose girths are respectively 16 and 24,can be obtained.The simulation studies show that these codes can achieve better performance than randomly constructed regular LDPC codes over AWGN channels with iterative decoding.At the BER of 10-5,the new proposed(3,6)-regular(4356,2205) QC-LDPC code performs 1.48dB from the Shannon limit.Moreover,it outperforms the random regular LDPC code of comparable parameters by 0.1dB.For the new proposed structured LDPC codes with column weight 2,they can achieve about 2dB coding gains with respect to the random regular LDPC codes with similar block lengths and code rates.

Chinese Journal of Computers•Jan 1, 2007•1 citation

The Design of Structured(n,3,k) LDPC Codes with Large Girth

DU Xing-min

Eliminating short cycles has been an important measure to improve Low Density Parity-Check(LDPC) codes performance,based on regular (n,2,k) LDPC codes without short cycles,a constructing method of practical regular(n,3,k) LDPC codes without cycle 4,6 and 8 is proposed.The simulation results over AWGN channels prove the validity of the method,and the produced codes with girth 10 reach the outstanding performance.

Journal of Air Force Engineering University•Jan 1, 2007•0 citations

A Class of Improved Low-Density Parity-Check Codes Constructed Based on Gallager's Form

Guangen Wu, Pinyi Ren

Focused on the problem that short cycles degrade the iterative decoding performance of finite length LDPC, a class of improved low density parity check (LDPC) codes constructed based on Gallager's form is designed. On the basis of keeping down the basic form of Gallager's construction, a quasi-cyclic form is used, then the new codes are free of cycles of length 4 and have good minimum distance. Simulation results demonstrated that the improved codes are better than Gallager's codes when block length is small

International Conference on Communications, Circuits and Systems•Jun 1, 2006•0 citations

On Lowering the Error Floor of Short-to-Medium Block Length Irregular Low Density Parity Check Codes

Umar-Faruk Abdu-Aguye

Gallager proposed and developed low density parity check (LDPC) codes in the early 1960s. LDPC codes were rediscovered in the early 1990s and shown to be capacity approaching over the additive white Gaussian noise (AWGN) channel. Subsequently, density evolution (DE) optimized symbol node degree distributions were used to significantly improve the decoding performance of short to medium length irregular LDPC codes. Currently, the short to medium length LDPC codes with the lowest error floor are DE optimized irregular LDPC codes constructed using progressive edge growth (PEG) algorithm modifications which are designed to increase the approximate cycle extrinsic message degrees (ACE) in the LDPC code graphs constructed. The aim of the present work is to find efficient means to improve on the error floor performance published for short to medium length irregular LDPC codes over AWGN channels in the literature. An efficient algorithm for determining the girth and ACE distributions in short to medium length LDPC code Tanner graphs has been proposed. A cyclic PEG (CPEG) algorithm which uses an edge connections sequence that results in LDPC codes with improved girth and ACE distributions is presented. LDPC codes with DE optimized/’good’ degree distributions which have larger minimum distances and stopping distances than previously published for LDPC codes of similar length and rate have been found. It is shown that increasing the minimum distance of LDPC codes lowers their error floor performance over AWGN channels; however, there are threshold minimum distances values above which there is no further lowering of the error floor performance. A minimum local girth (edge skipping) (MLG (ES)) PEG algorithm is presented; the algorithm controls the minimum local girth (global girth) connected in the Tanner graphs of LDPC codes constructed by forfeiting some edge connections. A technique for constructing optimal low correlated edge density (OED) LDPC codes based on modified DE optimized symbol node degree distributions and the MLG (ES) PEG algorithm modification is presented. OED rate-½ (n, k)=(512, 256) LDPC codes have been shown to have lower error floor over the AWGN channel than previously published for LDPC codes of similar length and rate. Similarly, consequent to an improved symbol node degree distribution, rate ½ (n, k)=(1024, 512) LDPC codes have been shown to have lower error floor over the AWGN channel than previously published for LDPC codes of similar length and rate. An improved BP/SPA (IBP/SPA) decoder, obtained by making two simple modifications to the standard BP/SPA decoder, has been shown to result in an unprecedented generalized improvement in the performance of short to medium length irregular LDPC codes under iterative message passing decoding. The superiority of the Slepian Wolf distributed source coding model over other distributed source coding models based on LDPC codes has been shown.

•Jan 1, 2018•0 citations
Low-Density-Parity-Check-Codes taken as a kind of advanced channel coding mode,have become the powerful competitor of the fourth generation of communication system.The LDPC advanced by Gallager has standard Tanner figure structure,and the advantage of the performance can be materialized after the length of the codes become longer.When the length is short or of medium sized,the performance of coding will fall down in a way because of the existence of short girth in the Tanner figure.With the improvement of structure method advanced by Gallager,the short girth in which length is 4 can be eliminated,thus the performance of coding can be raised.
Low-Density-Parity-Check-Codes(LDPC) taken as a kind of advanced channel coding mode,has become the powerful competitor of the fourth generation communication system.The LDPC advanced by Gallager have standard Tanner figure structure,the performance of coding will fall down in a way because of the existence of short girth in the Tanner figure.It is advanced the improvement of structured method based on Gallager,the short girth that length is 4 was eliminated and the flow chart was given.Simulation result shows that performance of coding is raised.
A low-density parity-check (LDPC) code can be described by a Tanner graph composed of symbol nodes and check nodes. Short cycles in the Tanner graph should be avoided because such cycles will degrade the performance of the decoder and hence increase the error rate. In most of the circumstances, cycles of length 4 can be totally eliminated in the Tanner graph when the LDPC code has been designed properly. Locally, for each variable node in the Tanner graph, the girth may take the value of 6 or 8, or even higher. In this study, the authors attempt to increase the local girths of a Tanner graph with an aim to improving the error performance of the code. The authors propose and analyse the ‘degree spectrum’ of the symbol nodes connecting to each of the check nodes. Based on the analysis, the authors can determine if the local girths can be further increased. The authors also propose simple ways to construct codes with higher local girths. Finally, the authors show the characteristics and the error performance of the codes constructed with the proposed methods.
This paper,based on algebra and graph,proposes a method for constructing structured low-density parity-check(LDPC) codes.In this method,the authors design a connected graph with three kinds of special path to ensure that the Tanner graph of the parity check matrix mapped from the connected graph is without short cycles.The construction method results in two classes of(3,k)-regular quasi-cyclic LDPC codes with girth 8 and 12 respectively.Furthermore,by extending this construction method,two classes of LDPC codes with column weight 2,whose girths are respectively 16 and 24,can be obtained.The simulation studies show that these codes can achieve better performance than randomly constructed regular LDPC codes over AWGN channels with iterative decoding.At the BER of 10-5,the new proposed(3,6)-regular(4356,2205) QC-LDPC code performs 1.48dB from the Shannon limit.Moreover,it outperforms the random regular LDPC code of comparable parameters by 0.1dB.For the new proposed structured LDPC codes with column weight 2,they can achieve about 2dB coding gains with respect to the random regular LDPC codes with similar block lengths and code rates.
Focused on the problem that short cycles degrade the iterative decoding performance of finite length LDPC, a class of improved low density parity check (LDPC) codes constructed based on Gallager's form is designed. On the basis of keeping down the basic form of Gallager's construction, a quasi-cyclic form is used, then the new codes are free of cycles of length 4 and have good minimum distance. Simulation results demonstrated that the improved codes are better than Gallager's codes when block length is small
Gallager proposed and developed low density parity check (LDPC) codes in the early 1960s. LDPC codes were rediscovered in the early 1990s and shown to be capacity approaching over the additive white Gaussian noise (AWGN) channel. Subsequently, density evolution (DE) optimized symbol node degree distributions were used to significantly improve the decoding performance of short to medium length irregular LDPC codes. Currently, the short to medium length LDPC codes with the lowest error floor are DE optimized irregular LDPC codes constructed using progressive edge growth (PEG) algorithm modifications which are designed to increase the approximate cycle extrinsic message degrees (ACE) in the LDPC code graphs constructed. The aim of the present work is to find efficient means to improve on the error floor performance published for short to medium length irregular LDPC codes over AWGN channels in the literature. An efficient algorithm for determining the girth and ACE distributions in short to medium length LDPC code Tanner graphs has been proposed. A cyclic PEG (CPEG) algorithm which uses an edge connections sequence that results in LDPC codes with improved girth and ACE distributions is presented. LDPC codes with DE optimized/’good’ degree distributions which have larger minimum distances and stopping distances than previously published for LDPC codes of similar length and rate have been found. It is shown that increasing the minimum distance of LDPC codes lowers their error floor performance over AWGN channels; however, there are threshold minimum distances values above which there is no further lowering of the error floor performance. A minimum local girth (edge skipping) (MLG (ES)) PEG algorithm is presented; the algorithm controls the minimum local girth (global girth) connected in the Tanner graphs of LDPC codes constructed by forfeiting some edge connections. A technique for constructing optimal low correlated edge density (OED) LDPC codes based on modified DE optimized symbol node degree distributions and the MLG (ES) PEG algorithm modification is presented. OED rate-½ (n, k)=(512, 256) LDPC codes have been shown to have lower error floor over the AWGN channel than previously published for LDPC codes of similar length and rate. Similarly, consequent to an improved symbol node degree distribution, rate ½ (n, k)=(1024, 512) LDPC codes have been shown to have lower error floor over the AWGN channel than previously published for LDPC codes of similar length and rate. An improved BP/SPA (IBP/SPA) decoder, obtained by making two simple modifications to the standard BP/SPA decoder, has been shown to result in an unprecedented generalized improvement in the performance of short to medium length irregular LDPC codes under iterative message passing decoding. The superiority of the Slepian Wolf distributed source coding model over other distributed source coding models based on LDPC codes has been shown.