Design of Protograph-based LDPC Code Ensembles with Fast Convergence Properties

Conference: SCC 2017 - 11th International ITG Conference on Systems, Communications and Coding
02/06/2017 - 02/09/2017 at Hamburg, Germany

Proceedings: ITG-Fb. 268: SCC 2017

Pages: 6Language: englishTyp: PDF

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Mulholland, Ian P.; Flanagan, Mark F. (School of Electrical and Electronic Engineering, University College Dublin, Dublin, Ireland)
Paolini, Enrico (Department of Electrical, Electronic, and Information Engineering “G. Marconi”, University of Bologna, Cesena (FC), Italy)

The design of protograph-based low-density parity-check (LDPC) code ensembles optimized for a finite number of decoder iterations is investigated. We show by example that protograph-based EXIT (PEXIT) analysis is not sufficiently reliable in the finite-iteration case, and develop a new technique which, similarly to PEXIT analysis, uses the mutual information (MI) as a tool in order to predict the performance of ensembles based on protographs. In contrast to PEXIT analysis, in which a critical value of the MI is used to define the decoding threshold, in our technique we examine the behavior of the MI over a range of channel parameters in order to define the threshold. Using this new definition of the iteration-constrained threshold, we perform a search over a large family of protographs in order to find the protograph with the highest iteration-constrained threshold for a finite number of iterations over the BEC.