A Low Complexity Block Turbo Decoder Architecture

International audienceWe present a low-complexity architecture designed for the decoding of block turbo codes. In particular we simplify the implementation of Pyndiah's algorithm by not memorizing any of the concurrent codewords generated by the Chase search

Turbo codes et estimation paramétrique pour les communications à haut débit

In this work, we focus on channel coding, which is used to correct the errors due to the channel in digital transmissions. Turbo codes are the last advance in channel coding, and they reach the limit predicted by C.E. Shannon in 1948. We introduce an improvement for the implementation of the turbo decoder designed by R. Pyndiah. We also introduce two synchronization algorithms taking advantage of the informations provided by a turbo decoderDans ce travail, nous nous intéressons au problème du codage canal, dont le but est de corriger les erreurs dûes au canal lors d'une transmission numérique. En particulier, les turbo codes constituent la dernière avancée dans ce domaine et atteignent la borne prédite par C.E. Shannon en 1948. Nous présentons une simplification de la mise en oeuvre du turbo décodeur de R. Pyndiah, ainsi que des systèmes de synchronisation profitant des informations apportées par le turbo décodeur

Turbo codes et estimation paramétrique pour les communications à haut débit

In this work, we focus on channel coding, which is used to correct the errors due to the channel in digital transmissions. Turbo codes are the last advance in channel coding, and they reach the limit predicted by C.E. Shannon in 1948. We introduce an improvement for the implementation of the turbo decoder designed by R. Pyndiah. We also introduce two synchronization algorithms taking advantage of the informations provided by a turbo decoderDans ce travail, nous nous intéressons au problème du codage canal, dont le but est de corriger les erreurs dûes au canal lors d'une transmission numérique. En particulier, les turbo codes constituent la dernière avancée dans ce domaine et atteignent la borne prédite par C.E. Shannon en 1948. Nous présentons une simplification de la mise en oeuvre du turbo décodeur de R. Pyndiah, ainsi que des systèmes de synchronisation profitant des informations apportées par le turbo décodeur

Turbo codes et estimation paramétrique pour les communications à haut débit

Dans ce travail, nous nous intéressons au problème du codage canal, dont le but est de corriger les erreurs dûes au canal lors d'une transmission numérique. En particulier, les turbo codes constituent la dernière avancée dans ce domaine et atteignent la borne prédite par C.E. Shannon en 1948. Nous présentons une simplification de la mise en oeuvre du turbo décodeur de R. Pyndiah, ainsi que des systèmes de synchronisation profitant des informations apportées par le turbo décodeurIn this work, we focus on channel coding, which is used to correct the errors due to the channel in digital transmissions. Turbo codes are the last advance in channel coding, and they reach the limit predicted by C.E. Shannon in 1948. We introduce an improvement for the implementation of the turbo decoder designed by R. Pyndiah. We also introduce two synchronization algorithms taking advantage of the informations provided by a turbo decoderCACHAN-ENS (940162301) / SudocSudocFranceF

Block turbo codes for multicarrier local loop transmission

International audienceWe investigate the performance of different block turbo codes in the context of Enhanced VDSL. We first describe the VDSL system used in our simulation link. We then propose an iterative decoding algorithm based on Pyndiah's (1998) SISO decoder for product turbo block codes that can be implemented with reasonable complexity. We also illustrate several results for various QAM modulation schemes. The coding gains obtained for the different codes and modulations then allow us to predict the attainable bit rates as a function of the line length. We show that such a turbo block decoding outperforms the classical Reed Solomon hard decoding used in the ADSL system

An iterative phase synchronization scheme for general QAM constellations

(IEEE Cat. No.04CH37577)International audienceThis paper concerns a new synchronizing scheme designed for block turbo coded system. The phase estimation relies on the feedback of the extrinsic information. A near optimum version of the algorithm based on the block turbo decoder devised by Pyndiah allows easy implementation. We display various results showing that the proposed algorithm is able to track frequency shifts and that it works very well in the case of general Quadrature Amplitude Modulation (QAM) constellations. We also show that this turbo synchronizer works at low Signal to Noise Ratios (SNR) taking completely advantage of the turbo coding possibilities

A new iterative phase tracking scheme

International audienc

A Block Turbo Phase Synchronization Scheme

International audienceThis letter presents an original phase synchronization scheme designed for block turbo coded systems. This is a low-complexity scheme. It copes with low signal-to-noise ratios, taking complete advantage of the turbo coding possibilities. We display various results, showing that the proposed algorithm is able to process blocks of a few hundreds bits and that it tackles the case of large quadrature amplitude modulation constellations very well and with no phase ambiguity

Joint estimation of QAM carrier phase with block turbo decoding

International audienceThis paper concerns a new synchronizing scheme designed for block turbo coded system. The phase estimation relies on the feedback of reliability information from the output of the turbo decoder. It is based on the fact that the power of the lower reliability values is strongly dependent on the carrier phase offset. A near optimum version of the algorithm based on a Pyndiah like block turbo decoder allows easy implementation.We display various results showing that the proposed algorithm is able to track frequency shifts and that it works very well in the case of general Quadrature Amplitude Modulation (QAM) constellations. We also show that this turbo synchronizer works at law Signal to Noise Ratios (SNR) taking completely advantage of the turbo coding possibilities

Synchronisation de phase - Boucle à remodulation souple

National audienceThe phase estimation is a really important step in digital communication systems. Without a good synchronization, using error correction codes and turbo-codes is suboptimum. This paper describes a new synchronizing algorithm which can update the phase of each received symbol. The estimated phase is calculated with a Soft Decision Feedback Loop. This loop uses the Log-Likelihood Ratio (LLR) provided by the turbo-decoder’s soft output. A forward-backward loop improves phase estimation. This algorithm can be applied on every QAM’s constellations and good performance is achieved till near Shannon’s limit SNRs.Les performances des systèmes de transmission numérique dépendent de nombreux facteurs. Parmi ceux-ci, l’étape de synchronisation est déterminante pour la qualité de réception de l’information numérique transmise. En effet, les améliorations apportées par les codes correcteurs d’erreurs et les turbo-codes en particulier sont fortement tributaires de l’étape de synchronisation. Nous présentons dans cet article un algorithme permettant d’estimer et de compenser la phase de la porteuse du signal reçu en exploitant l’information souple fournie par tout turbo-décodeur. La méthode proposée permet de faire une mise à jour de la phase à chaque symbole grâce à une boucle adaptative utilisant les log-vraisemblances de chaque bit reçu fournies par un turbo-décodeur. De plus, une boucle “aller-retour” permet d’améliorer sensiblement le comportement de cet estimateur de phase et ainsi d’obtenir des performances, en termes d’Erreur Quadratique Moyenne, proches de la boucle à symboles connus