Este trabalho investiga a decodificação turbo de códigos produto construídos a partir de códigos de Reed-Solomon sobre constelações QAM. Por meio da geometria euclidiana da constelação utilizada e das relações dos elementos de campo de Galois utilizados na codificação Reed-Solomon com os símbolos pertencentes ao alfabeto de modulação, é proposto um algoritmo de decodificação que utiliza a localização geométrica dos símbolos recebidos no processo de decodificação turbo. Tanto a primeira etapa da decodificação SISO baseada no algoritmo de Chase, como a extração da informação extrínseca baseada no algoritmo proposto por Pyndiah, são tratadas pelo uso de uma abordagem geométrica sobre o espaço euclidiano. Os resultados de simulação utilizando o algoritmo proposto coincidem com aqueles usando a decomposição e análise pragmática binária, sendo que a abordagem apresentada conduz a simplificações e otimizações em relação à metodologia binária no que ser refere à implementação dos possíveis esquemas de decodificação. / This work investigates the turbo decoding of product codes built using Reed- Solomon codes in QAM constellations. Using the euclidian geometry of the constellation and the relations of the Galois field elements used in the Reed-Solomon code and the modulation alphabet, a decoding algorithm for the turbo decoding process is proposed using the geometric localization of the received symbol. Both the first stage of the SISO decoding based on the Chase algorithm, as the calculation of the extrinsic information based on the Pyndiah algorithm, are treated using the geometric approach in the euclidian space. The simulations show that this algorithm gives similar performance results as the pragmatic binary decomposition approach, and leads to simplifications and optimizations in decoding implementations schemes compared to the former.

Dans cette thèse, nous nous intéressons au problème de la reconnaissance de code. Ce problème se produit principalement lorsqu'une communication est observée dans un milieu non-coopératif. Une liste de mots bruités issus d'un code inconnu est obtenue, l'objectif est alors de retrouver l'information contenue dans ces mots bruités. Pour cela, le code utilisé est reconstruit afin de décoder les mots observés. Nous considérons ici trois instances de ce problème et proposons pour chacune d'elle une nouvelle méthode. Dans la première, nous supposons que le code utilisé est un turbo-code et nous proposons une méthode pour reconstruire la permutation interne (les autres éléments du turbo-codeur pouvant être facilement reconstruits grâce aux méthodes existantes). Cette permutation est reconstruite pas à pas en recherchant l'indice le plus probable à chaque instant. Plus précisément, la probabilité de chaque indice est déterminée avec l'aide de l'algorithme de décodage BCJR. Dans la seconde, nous traitons le problème de la reconnaissance des codes LDPC en suggérant une nouvelle méthode pour retrouver une liste d'équations de parité de petits poids. Celle-ci généralise et améliore les méthodes existantes. Finalement, avec la dernière méthode, nous reconstruisons un code convolutif entrelacé. Cette méthode fait appel à la précédente pour retrouver une liste d'équations de parité satisfaites par le code entrelacé. Puis, en introduisant une représentation sous forme de graphe de l'intersection de ces équations de parité, nous retrouvons simultanément l'entrelaceur et le code convolutif. / In this PhD, we focus on the code reconstruction problem. This problem mainly arises in a non-cooperative context when a communication consisting of noisy codewords stemming from an unknown code is observed and its content has to be retrieved by recovering the code that is used for communicating and decoding with it the noisy codewords. We consider here three possible scenarios and suggest an original method for each case. In the first one, we assume that the code that is used is a turbo-code and we propose a method for reconstructing the associated interleaver (the other components of the turbo-code can be easily recovered by the existing methods). The interleaver is reconstructed step by step by searching for the most probable index at each time and by computing the relevant probabilities with the help of the BCJR decoding algorithm. In the second one, we tackle the problem of reconstructing LDPC codes by suggesting a new method for finding a list of parity-check equations of small weight that generalizes and improves upon all existing methods. Finally, in the last scenario we reconstruct an unknown interleaved convolutional code. In this method we used the previous one to find a list of parity-check equations for this code. Then, by introducing a graph representing how these parity-check equations intersect we recover at the same time the interleaver and the convolutional code.

No description available.

This Diploma thesis deals with Turbo code problems. The Turbo codes belong to the group of error correction codes, sometimes referred to as forward error correcting (FEC) codes or channel codes. This thesis can be thematically divided into two basic parts. The first part describes turbo code encoder and decoder block diagram with the illustration of two most frequently used iterative decoding algorithms (SOVA and MAP). The end of this part contains best known turbo codes, which are used in present communication systems. The second part pursues simulation results for the turbo codes using Binary Phase Shift Keying (BPSK) over Additive White Gaussian Noise (AWGN) channels. These simulations were created in the MATLAB/SIMULINK computer program. It will be shown here, that there exist many different parameters, greatly affecting turbo codes performance. Some of these parameters are: number of decoding iterations used, the input data frame length, generating polynoms and RSC encoders constraint lengths, properly designed interleaving block, decoding algorithm used, etc.

<p>Turbo codes was first presented in 1993 by C. Berrou, A. Glavieux and P. Thitimajshima. Since then this class of error correcting codes has become one of the most popular, because of its good properties. The turbo codes are able to come very close to theoretical limit, the Shannon limit. Turbo codes are for example used in the third generation of mobile phone (3G) and in the standard IEEE 802.16 (WiMAX).</p><p>There are some drawbacks with the algorithm for decoding turbo codes. The deocoder uses a Maximum A Posteriori (MAP) algorithm, which is a complex algorith. Because of the use of many variables in the decoder the decoding circuit will consume a lot of power due to memory accesses and internal communication. One way in which this can be reduced is to make early decisions.</p><p>In this work I have focused on making early decision of the encoder states. One major part of the work was also to be sure that the expressions were written in a way that as few variables as possible are needed. A termination condition is also introduced. Simulations based on estimations of the number of memory accesses, shows that the number of memory accesses will significantly decrease.</p>

Turbo codes was first presented in 1993 by C. Berrou, A. Glavieux and P. Thitimajshima. Since then this class of error correcting codes has become one of the most popular, because of its good properties. The turbo codes are able to come very close to theoretical limit, the Shannon limit. Turbo codes are for example used in the third generation of mobile phone (3G) and in the standard IEEE 802.16 (WiMAX). There are some drawbacks with the algorithm for decoding turbo codes. The deocoder uses a Maximum A Posteriori (MAP) algorithm, which is a complex algorith. Because of the use of many variables in the decoder the decoding circuit will consume a lot of power due to memory accesses and internal communication. One way in which this can be reduced is to make early decisions. In this work I have focused on making early decision of the encoder states. One major part of the work was also to be sure that the expressions were written in a way that as few variables as possible are needed. A termination condition is also introduced. Simulations based on estimations of the number of memory accesses, shows that the number of memory accesses will significantly decrease.

[pt] Esta tese pode ser segmentada em duas partes distintas, porém complementares. A primeira parte trata do problema que tange ao desenvolvimento da maioria dos sistemas de marcação d água digital: a necessidade de primeiramente selecionar a técnica de modulação não codificada que fará parte de uma arquitetura codificada. Assim, para proceder adequada seleção, os limitantes de desempenho das técnicas não codificadas são ferramentas importantes para otimização de sistemas codificados, objetivando operação próximo à capacidade. Esta parte da tese introduz um novo limitante inferior para técnicas binárias de marcação d água digital, fundamentado em uma simples equivalência com um sistema de comunicação binário. A segunda parte desta tese introduz uma nova metodologia para o projeto e análise de sistemas de marcação d água digital que, sob o ponto de vista da teoria da informação, incorpora a fragilidade e a robustez. A metodologia proposta é desenvolvida com foco no comportamento da curva de desempenho em sistemas codificados, e considera não somente o ganho de codificação, mas também a robustez e a fragilidade do sistema. Este novo conceito introduz a necessidade de revisitar o projeto de sistemas codificados de marcação digital para incorporar também os requisitos de robustez e/ou de fragilidade. Neste contexto, o código turbo atende de imediato aos requisitos para implementação de um sistema de marcação d água digital robusto, e um sistema frágil pode também ser implementado através da introdução de um esquema de polarização. Este novo esquema de polarização, com o emprego da codificação turbo, também permite a implementação de técnicas semi-frágeis e híbridas, alcançando a robustez e a fragilidade do sistema com apenas uma marcação d água. Resultados de simulação experimental apóiam a metodologia proposta, e possibilita o aprofundamento da discussão do proposto esquema de polarização em sistemas de marcação d água digital. / [en] This thesis can be segmented in two distinct but complementary parts. The first part addresses the problem pertinent to coded digital watermarking systems development require namely the selection of a (uncoded) modulation technique to be part of a coded architecture. Therefore, performance bounds for uncoded techniques are an important tool for coded system optimization, aiming at operation close to capacity. This part introduces a new performance lower bound for uncoded binary watermarking modulation techniques, based on a simple equivalence with a binary communication system, considering an additive gaussian attack model. New M-ary unidimensional and multidimensional Spread Spectrum based modulation techniques are introduced, including their improved versions. The performances of the proposed techniques are determined, and the performance lower bounds for the corresponding techniques classes are determined as well. The second part of this thesis, introduces a new methodology for the design and analysis of digital watermarking systems which, from an information theoretic point of view, incorporates robustness and fragility. The proposed methodology is developed by focusing on the probability of error versus watermark-to-noise ratio curve, describing the technique performance, and a scenario for coded techniques which takes into account not only the coding gain, but also the robustness or fragility of the system. This new concept requires that coded digital watermarking systems design be revisited to also include the robustness and fragility requirements. Turbo codes, which appropriately meet these requirements, can be used straightforwardly to construct robust watermarking systems. Fragile systems can also be constructed by introducing the idea of polarization scheme. This new idea has allowed the implementation of hybrid techniques achieving fragility and robustness with a single watermark embedding. Simulation results supports the introduced methodology and allowed us to enhance the discussion on the polarization scheme.

La croissance exponentielle du trafic de données sans fils, causée par l'Internet mobile et les smartphones, contraint les futurs systèmes radio à inclure des modulations/formes d'ondes plus avancées offrant un débit plus élevé et une utilisation efficace des ressources spectrales. Les transmissions dites Faster-Than-Nyquist (FTN), introduites en 1975, sont parmi les meilleurs candidates pour répondre à ces besoins. En transmettant les symboles à une cadence plus rapide que celle définie par le critère de Nyquist, FTN peut théoriquement augmenter le débit mais en introduisant des interférences en contrepartie. Dans cette thèse, nous explorons le concept des transmissions FTN à travers un canal AWGN (Additive White Gaussian Noise) dans le contexte des modulations OFDM/OQAM (Orthogonal Frequency Division Multiplexing with Offset Quadrature Amplitude Modulation).L'objectif principal de cette thèse est de présenter un système OFDM/OQAM qui permet de transmettre l'information au-delà de la cadence de Nyquist tout en tenant en compte la complexité globale du système. Tout d'abord, nous proposons une nouvelle implémentation efficace des systèmes OFDM/OQAM appliquant le concept FTN, désignée ici par FTN-OQAM, qui garde la même complexité que les systèmes OFDM/OQAM et qui permet un gain en débit très proche du gain théorique. Vu que la condition de Nyquist n'est plus respectée, le signal transmis est maintenant perturbé par des interférences. Pour remédier à ce problème, nous proposons un récepteur basé sur le principe de l'égalisation linéaire sous le critère minimum erreur quadratique moyenne avec annulation d'interférences appelé MMSE LE-IC. Le but de notre système est d'augmenter le débit de transmission, ce qui signifie que des constellations d'ordres élevés seront ciblées. Dans ce contexte, le MMSE LE-IC, dont la complexité est indépendante de la constellation, représente un bon compromis entre efficacité et complexité. Puisque la modulation OFDM/OQAM utilise différents types de formes d'ondes, nous proposons pour plusieurs d'entre elles un algorithme pour déterminer la valeur minimale du facteur d'accélération, en fonction de l'ordre de constellation, qui apporte un gain en efficacité spectrale tout en gardant les mêmes performances que les systèmes respectant le critère de Nyquist à un SNR fixé. Ensuite, nous étudions l'amélioration du traitement itératif de l'émetteur-récepteur. La méthode proposée consiste à combiner un précodeur avec le système FTN-OQAM afin de réduire les interférences causées par du FTN à l'émission. Nous proposons un modèle de précodage dispersé, car il est difficile de précoder conjointement tous les symboles transmis. Nous présentons trois familles de précodeurs avec les récepteurs correspondants. En outre, nous modifions différents blocs de l'émetteur FTN-OQAM tels que le codage canal, le mappage des bits et le mappage des symboles afin d'améliorer davantage le transmetteur FTN-OQAM. Les résultats présentés révèlent le potentiel important des systèmes proposés. / The exponential growth of wireless data traffic driven by mobile Internet and smart devices constrains the future radio systems to include advanced modulations/waveforms offering higher data rates with more efficient bandwidth usage. One possibility is to violate the well known Nyquist criterion by transmitting faster than the Nyquist rate, i.e., using a technique also known as Faster-Than-Nyquist (FTN) signaling. Nyquist-based systems have the advantage of simple transmitter and receiver architectures at the detriment of bandwidth efficiency. The idea of signaling beyond the Nyquist rate to trade the interference-free transmission for more throughput goes back to 1975. In this dissertation, we investigate the concept of FTN signaling over Additive White Gaussian Noise (AWGN) channel in the context of Orthogonal Frequency Division Multiplexing with Offset Quadrature Amplitude Modulation OFDM/OQAM modulation.The main objective of our work is to present an OFDM/OQAM system signaling faster than the Nyquist one and explore its potential rate improvement while keeping under consideration the overall system complexity. First, we propose a new efficient FTN implementation of OFDM/OQAM systems, denoted by FTN-OQAM, that has the same complexity as OFDM/OQAM systems, while approaching very closely the FTN theoretical rate improvement. As the Nyquist condition is no longer respected, severe interference impacts the transmitted signals. To deal with the introduced interferences, we propose a turbo-like receiver based on Minimum Mean Square Error Linear Equalization and Interference Cancellation, named MMSE LE-IC. The aim of our system is to boost the transmission rate, which means that high constellation orders will be targeted. In this respect, the MMSE LE-IC, whose complexity is independent of the constellation, turns out to be a good candidate. Since OFDM/OQAM modulation can be equipped with different types of pulse shapes, we propose an algorithm to find, for different constellation orders, the minimum achieved FTN packing factor for various pulse shapes. Then, we aim at improving the iterative processing of the introduced transceiver. The proposed method involves combining a precoder with the FTN-OQAM system in order to remove FTN-induced interference at the transmitter. We also present a sparse precoding pattern as it is difficult to jointly precode all the transmitted symbols. We introduce three families of precoders along with the corresponding receivers. Furthermore, we propose several modifications of the FTN-OQAM transmitter concerning different blocks such as channel coding, bits mapping and symbols mapping to further enhance the FTN-OQAM transceiver design. Presented results reveal the significant potential of the proposed methods.

Les huiles essentielles et les arômes des plantes constituent un réel potentiel pour l’industrie dans le but de substituer aux composés synthétiques ayant des effets néfastes sur la santé et l’environnement. Afin de contribuer aux principes de la chimie verte, cette étude porte sur l’éco-extraction et la valorisation des extraits naturels des plantes et le développement d’une nouvelle technologie «verte» pour l’extraction des composés aromatiques naturels. La première partie de ce manuscrit mets en évidence les propriétés biologiques des huiles essentielles et des arômes et l’importance de leurs applications dans différents domaines surtout le domaine agroalimentaire. Dans la deuxième partie, les études sur les propriétés biologiques des huiles essentielles des plantes des Alliacées montrent leurs bonnes activités antioxydantes et antimicrobiennes. Ces résultats encourageants ont permis dans la troisième partie de valoriser les sous-produits d’oignon issus de la turbo hydrodistillation et qui sont considérés normalement comme déchets. La technique offre une bonne extraction des composés phénoliques et des flavonoïdes utilisant l’eau comme solvant naturel. La quatrième et la dernière partie de ce travail s’est orientée vers l’optimisation et le développement d’une technologie « verte» utilisant les ultrasons et l’huile de tournesol comme solvant naturel pour l’extraction des composés aromatiques du thym. Cette nouvelle approche écologique permet l’extraction des absolues dépourvues de cire et des résidus de solvants pétroliers, contenant la teneur la plus élevée en thymol et exerçant la plus forte activité antioxydante. / Plant essential oils and aromas are a real potential for the industry to substitute the synthetic compounds that might have harmful effects on the human health and the environment. In order to contribute to the green chemistry principles, this study focuses on the “eco-extraction” and valorization of natural plant extracts and the development of a new «green» technology for the extraction of aromatic compounds. The first part of this manuscript highlights the biological properties of the essential oils and aromas and the importance of their applications in various sectors especially in the food industry. In the second part, studies on the biological properties of the essential oils from plants of the Alliaceae family show their good antioxidant and antimicrobial activities. These encouraging results have allowed in the third part to evaluate the onion by-products resulting from the turbo hydrodistillation, which are normally considered as waste. The technique offers a good extraction of flavonoids and phenols using water as natural solvent. The fourth and final part of this work deals with the optimization and the development of a «green» technology using ultrasound and sunflower oil as a natural solvent for the extraction of aromatic compounds from thyme. This new ecological approach allows the extraction of absolutes free from waxes and petroleum solvent residues, having the highest content in thymol and exerting the strongest antioxidant activity.

La investigación presenta un nuevo diseño de rotondas llamado turbo rotondas, estos tipos de rotondas se adoptan, debido a que las glorietas convencionales multicarril se encuentran relacionadas con problemas como lo son el comportamiento de los conductores en la entrada, carril circulatorio y zonas de salida de la rotonda; donde se observa el cambio e invasión de los carriles sin respetar las marcas divisorias de carril lo que genera mayor velocidad. Las turbo rotondas a comparación de las rotondas convencionales, poseen beneficios operativos y de seguridad, gracias a que tienen separadores de carril cuya principal función es de restringir los cambios de carril o malas maniobras de los conductores, reducir la velocidad y los puntos de conflictos. Para el caso de estudio se eligió a la rotonda Monitor por la congestión vehicular que presenta, la mala operación de la rotonda y la alta tasa de accidentes de tránsito, por lo que se plantea un rediseño físico y operacional mediante una turbo rotonda, donde se evaluará los niveles de servicio, las demoras y el nivel de seguridad a través de una microsimulación mediante el software Vissim 9 entre la rotonda actual y la propuesta. Finalmente, después de realizar varias corridas al programa se llega a la conclusión de que el replanteo físico y operacional de la rotonda Monitor Huáscar, a través de la Turbo Rotonda tipo rotor beneficia a los usuarios mejorando el nivel de servicio de F a C. Esto quiere decir, que las demoras y los tiempos de viaje se reducen significativamente. Además, de mejorar la seguridad vial reduciendo el número de puntos de conflicto. / The research presents a new roundabout design called turbo roundabouts, these types of roundabouts are adopted, due to specific multi-lane roundabouts are related to problems such as the behavior of drivers at the entrance, circulatory lane and exit areas of the roundabout where the change and invasion of the lanes is observed without respect the lane divisions marks which generates greater speed. The turbo roundabouts to the comparison of compact roundabouts, the features operational and safety benefits, thanks to the fact that they have rail separators whose main function is restricted lane changes or bad driver jaws, reduce speed and conflict points . In the case of the study, the roundabout Monitor was chosen because of the traffic congestion that shows inefficiency in the operation of the roundabout and high traffic accident rate, so a physical and operational redesign is proposed through a turbo roundabout, where it is evaluated service levels, delays and security level through microsimulation using Vissim 9 software between the current roundabout and the proposed one. Finally, after making several runs to the program, it is concluded that the physical and operational replacement of the Huáscar Monitor roundabout, through the Rotor-type Turbo Roundabout, benefits users by improving the service level from F to C. This wants That is, delays and travel times are significantly reduced. In addition, improve road safety by reducing the number of conflict points. / Tesis