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Speech quality enhancement for mobile radio systems by using a priori information at the receiver side

Abstract : In digital mobile radio systems, the speech quality can be severly degraded if the channel decoder produces residual bit errors due to heavy burst errors on the radio path. On the other hand, in most speech coding schemes some residual redundancy remains because of complexity and delay limitations. A solution for improving the speech quality consists in using a priori information based on source residual redundancy at the receiver side. In one approach, a priori information is used at the source decoder to perform optimal estimation of transmitted codec parameters. In another approach, a priori information is used at the channel decoder in oder to minimize the residual bit errors rate.We study both approaches and apply them to the GSM EFR. At the speech decoder level, we model the residual redundancy of speech codec parameters by using Gaussian mixtures. This model reduces the complexity when compared to state-of-art methods and provides a better representation of residual redundancy. At the channel decoder level, we introduce an efficient method to exploit intra-frame bit redundancy during the channel decoding process. In this method, the value of the bit being decoded is predicted from the bits already decoded along the treillis path.These methods are evaluated on simulations of radio transmission by an objective measure of speech quality. In all cases, the performance of the speech decoder using our residual redundancy model turns out to be better than the GSM EFR decoder with standard error concealment procedure. The performance of the channel decoder using residual redundancy is strongly dependent of the index assignment used by the quantifier.
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https://pastel.archives-ouvertes.fr/pastel-00001192
Contributor : Ecole Télécom Paristech <>
Submitted on : Monday, June 6, 2005 - 8:00:00 AM
Last modification on : Friday, July 31, 2020 - 10:44:07 AM
Long-term archiving on: : Saturday, November 26, 2016 - 3:22:44 PM

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  • HAL Id : pastel-00001192, version 1

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Christophe Veaux. Speech quality enhancement for mobile radio systems by using a priori information at the receiver side. domain_other. Télécom ParisTech, 2005. English. ⟨pastel-00001192⟩

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