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Time-invariant and switch-type hybrid iterative decoding of low-density parity-check codes

Décodage Itératif des Codes de Parité À Faible Densité par une Méthode Hybride À Invariance Dans Le Temps Ou À Basculement

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Abstract

Hybrid decoding is to combine different iterative decoding algorithms with the aim of improving error performance or decoding complexity. This, e.g., can be performed by using a specific blend of different algorithms in every iteration (time-invariant hybrid: HTI), or by switching between different algorithms throughout the iteration process (switch-type hybrid: HST). In this work, we study HTI and HST algorithms both asymptotically, usingdensity-evolution, and at finite block lengths, using simulations, and show that these algorithms perform considerably better than their constituent algorithms. We also investigate the convergence properties of HTI and HST algorithms, under both the assumption of perfect knowledge of the channel, and the lack of it, and show that compared to HST algorithms, such as Gallager’s algorithm B, HTI algorithms are far less sensitive to channel conditions and thus can be practically more attractive.

Résumé

Le décodage hybride consiste à combiner différents algorithmes de décodage itératif avec pour but d’améliorer la performance en termes d’erreur et de complexité de décodage. Cela peut être réalisé, par exemple, en utilisant un mélange spécifique de différents algorithmes à chaque itération (hybride invariant dans le temps : HTI), ou en basculant entre différents algorithmes tout au long du processus itératif (hybride de type basculement: HST). Dans ce travail, nous étudions les algorithmes HTI et HST à la fois asymptotiquement, à travers l’évolution de densité, et pour des blocs de longueur finie, au travers de simulations, et nous montrons que ces algorithmes ont des performances considérablement supérieures à celles de leurs algorithmes constitutifs. Nous examinons également les propriétés de convergence des algorithmes HTI et HSJ dans des conditions de connaissance parfaite du canal d’une part et dans des conditions où les propriétés du canal sont inconnues d’autre part, et nous montrons que comparés aux algorithmes HST, tels que l’algorithme B de Gallager, les algorithmes HTl sont bien moins sensibles aux conditions du canal, et donc beaucoup plus attrayants d’un point de vue pratique.

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Authors and Affiliations

  1. Broadband Communications and Wireless Systems (BCWS) Centre, Department of Systems and Computer Engineering, Carleton University, 1125 Colonel By Drive, K1S 5B6, Ottawa, Ontario, Canada

    Pirouz Zarrinkhat, Amir H. Banihashemi & Hua Xiao

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  1. Pirouz Zarrinkhat
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  2. Amir H. Banihashemi
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  3. Hua Xiao
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Additional information

This work was supported in part by an Ontario Graduate Scholarship (ogs).

Pirouz Zarrinkhat received the M.Sc. degree in electrical engineering in 1997 from Sharif University of Technology, Tehran, Iran. He is currently working towards the Ph.D. degree in the Department of Systems and Computer Engineering at Carleton University, Ottawa, ON, Canada.

Amir H. Banihashemi received the Ph.D. degree in electrical engineering in 1997 from University of Waterloo, Waterloo, ON, Canada. He is currently an Associate Professor in the Department of Systems and Computer Engineering at Carleton University, Ottawa, ON, Canada.

Hua Xiao received the M.Eng. degree in information and systems science from Carleton University, Ottawa, ON, Canada in 2002. He is currently working towards the Ph.D. in the Department of Systems and Computer Engineering, Carleton University.

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Zarrinkhat, P., Banihashemi, A.H. & Xiao, H. Time-invariant and switch-type hybrid iterative decoding of low-density parity-check codes. Ann. Télécommun. 60, 103–131 (2005). https://doi.org/10.1007/BF03219809

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