DocumentCode :
151639
Title :
On characterization of elementary trapping sets of variable-regular LDPC codes
Author :
Karimi, Maryam ; Banihashemi, Amir H.
Author_Institution :
Dept. of Syst. & Comput. Eng., Carleton Univ., Ottawa, ON, Canada
fYear :
2014
fDate :
18-22 Aug. 2014
Firstpage :
62
Lastpage :
66
Abstract :
In this paper, we study the graphical structure of elementary trapping sets (ETS) of variable-regular low-density parity-check (LDPC) codes. ETSs are known to be the main cause of error floor in LDPC coding schemes. For the set of LDPC codes with a given variable node degree dl and girth g, we identify all the non-isomorphic structures of an arbitrary class of (a, b) ETSs, where a is the number of variable nodes and b is the number of odd-degree check nodes in the induced subgraph of the ETS. Our study leads to a simple characterization of dominant classes of ETSs (those with relatively small values of a and b) based on short cycles in the Tanner graph of the code. For such classes of ETSs, we prove that any set S in the class is a layered superset (LSS) of a short cycle, where the term “layered” is used to indicate that there is a nested sequence of ETSs that starts from the cycle and grows, one variable node at a time, to generate S. This characterization corresponds to a simple search algorithm that starts from the short cycles of the graph and finds all the ETSs with LSS property in a guaranteed fashion. Specific results on the structure of ETSs are presented for dl = 3, 4, 5, 6, g = 6, 8 and a, b ≤ 10. The results of this work can be used for the error floor analysis and for the design of LDPC codes with low error floors.
Keywords :
graph theory; parity check codes; ETS structure; elementary trapping sets; error floor analysis; layered superset; low-density parity-check codes; nonisomorphic structures; odd-degree check nodes; variable-regular LDPC codes; Bipartite graph; Charge carrier processes; Decoding; Information processing; Iterative decoding; Turbo codes;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Turbo Codes and Iterative Information Processing (ISTC), 2014 8th International Symposium on
Conference_Location :
Bremen
Type :
conf
DOI :
10.1109/ISTC.2014.6955086
Filename :
6955086
Link To Document :
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