HAL : inria-00119600, version 2

arXiv : cs.NI/0612063

DOI : 10.1109/TIT.2006.887512

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IEEE Transactions on Information Theory 53, 1 (2007) 368 - 377

Versions disponibles

v1 (11-12-2006)

v2 (13-12-2006)

Synchronization recovery and state model reduction for soft decoding of variable length codes

Simon Malinowski 1, Hervé Jégou 2, Christine Guillemot 1

(01/2007)

Variable length codes exhibit de-synchronization problems when transmitted over noisy channels. Trellis decoding techniques based on Maximum A Posteriori (MAP) estimators are often used to minimize the error rate on the estimated sequence. If the number of symbols and/or bits transmitted are known by the decoder, termination constraints can be incorporated in the decoding process. All the paths in the trellis which do not lead to a valid sequence length are suppressed. This paper presents an analytic method to assess the expected error resilience of a VLC when trellis decoding with a sequence length constraint is used. The approach is based on the computation, for a given code, of the amount of information brought by the constraint. It is then shown that this quantity as well as the probability that the VLC decoder does not re-synchronize in a strict sense, are not significantly altered by appropriate trellis states aggregation. This proves that the performance obtained by running a length-constrained Viterbi decoder on aggregated state models approaches the one obtained with the bit/symbol trellis, with a significantly reduced complexity. It is then shown that the complexity can be further decreased by projecting the state model on two state models of reduced size.

1 :	TEMICS (INRIA - IRISA)
	CNRS : UMR6074 – INRIA – Université de Rennes 1
2 :	LEAR (IMAG-INRIA Rhône-Alpes / GRAVIR)
	CNRS : UMR5527 – INRIA – Université Joseph Fourier - Grenoble I – Institut National Polytechnique de Grenoble (INPG)

Domaine

:

Informatique/Théorie de l'information et codage Mathématiques/Théorie de l'information et codage Informatique/Réseaux et télécommunications

Mots-clés : variable length codes – data compression – joint source/channel coding

inria-00119600, version 2

http://hal.inria.fr/inria-00119600

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Contributeur : Hervé Jégou <>

Soumis le : Mardi 12 Décembre 2006, 23:56:47

Dernière modification le : Vendredi 3 Décembre 2010, 10:34:27