Turán-Theoretic Bounds on Several Elementary Trapping Sets in LDPC Codes

Fuente: arXiv
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Main Authors: Zhao, Ziyang, Xiong, Haoran, Ye, Zicheng, Yan, Guiying
Format: Preprint
Published: 2026
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author Zhao, Ziyang
Xiong, Haoran
Ye, Zicheng
Yan, Guiying
author_facet Zhao, Ziyang
Xiong, Haoran
Ye, Zicheng
Yan, Guiying
contents LDPC codes have attracted significant attention because of their superior performance close to the Shannon limit. Elementary trapping sets are the main cause of the error floor phenomenon in LDPC codes. We consider typical graphs related to trapping sets, including theta graphs, dumbbell graphs, and short cycles with chords. Based on the Turán numbers of $θ(2,2,2)$, $θ(1,3,3)$ and $D(4,4;0)$, we prove that any $(a,b)$-ETS with $g=8$ variable-regular $γ$ satisfies the inequality $b\geq aγ-\frac{a(\sqrt{24a-23}-1)}{4}$, provided that any two 8-cycles in the Tanner graph do not share common variable node. In addition, we can also eliminate ETSs by removing certain short-cycle structures with chords. The minimum sizes of ETSs obtained through these methods are significantly increased. To assess practical impact , we analyze spectral radii of the ETSs and construct QC-LDPC codes to show frame error rates in the error floor region.
format Preprint
id arxiv_https___arxiv_org_abs_2604_12332
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Turán-Theoretic Bounds on Several Elementary Trapping Sets in LDPC Codes
Zhao, Ziyang
Xiong, Haoran
Ye, Zicheng
Yan, Guiying
Information Theory
Combinatorics
LDPC codes have attracted significant attention because of their superior performance close to the Shannon limit. Elementary trapping sets are the main cause of the error floor phenomenon in LDPC codes. We consider typical graphs related to trapping sets, including theta graphs, dumbbell graphs, and short cycles with chords. Based on the Turán numbers of $θ(2,2,2)$, $θ(1,3,3)$ and $D(4,4;0)$, we prove that any $(a,b)$-ETS with $g=8$ variable-regular $γ$ satisfies the inequality $b\geq aγ-\frac{a(\sqrt{24a-23}-1)}{4}$, provided that any two 8-cycles in the Tanner graph do not share common variable node. In addition, we can also eliminate ETSs by removing certain short-cycle structures with chords. The minimum sizes of ETSs obtained through these methods are significantly increased. To assess practical impact , we analyze spectral radii of the ETSs and construct QC-LDPC codes to show frame error rates in the error floor region.
title Turán-Theoretic Bounds on Several Elementary Trapping Sets in LDPC Codes
topic Information Theory
Combinatorics
url https://arxiv.org/abs/2604.12332