Cette thèse s'inscrit dans le domaine du Smart Grid. Les SGs améliorent la sécurité des réseaux électriques et permettent une utilisation adaptée de l'énergie disponible de manière limitée. Ils augmentent également l'efficacité énergétique globale en réduisant la consommation. L'utilisation de cette technologie est la solution la plus appropriée car elle permet une gestion plus efficace de l'énergie. Dans ce contexte, des compagnies comme Hydro-Québec déploient des réseaux de capteurs pour contrôler les principaux équipements. Pour réduire les coûts de déploiement et la complexité du câblage, un réseau de capteurs semble être une solution optimale. Cependant, son déploiement nécessite une connaissance approfondie de l'environnement. Les postes à haute tension sont des points stratégiques du réseau électrique et génèrent un bruit impulsif qui dégrade les performances des communications sans fil. Les travaux dans cette thèse sont centrés sur le développement de protocoles de communication performants dans ces milieux fortement perturbés. Nous avons proposé une première approche basée sur la concaténation du code à métrique de rang et le code convolutif avec la modulation OFDM. C'est une technique très efficace pour réduire l'effet du bruit impulsif tout en ayant un niveau de complexité assez faible. Une autre solution basée sur un système multi-antennaire est développée. Nous avons aussi proposé un système MIMO coopératif codé en boucle fermée basée sur le code à métrique de rang et le précodeur max-dmin. La deuxième technique est également une solution optimale pour améliorer la fiabilité du système et réduire la consommation énergétique dans les réseaux de capteurs. / This thesis is mainly in the Smart Grid domain. SGs improve the safety of electrical networks and allow a more adapted use of electricity storage, available in a limited way. SGs also increase overall energy efficiency by reducing peak consumption. The use of this technology is the most appropriate solution because it allows more efficient energy management. In this context, manufacturers such as Hydro-Quebec deploy sensor networks in the nerve centers to control major equipment. To reduce deployment costs and cabling complexity, the option of a wireless sensor network seems the most obvious solution. However, deploying a sensor network requires in-depth knowledge of the environment. High voltages substations are strategic points in the power grid and generate impulse noise that can degrade the performance of wireless communications. The works in this thesis are focused on the development of high performance communication protocols for the profoundly disturbed environments. For this purpose, we have proposed an approach based on the concatenation of rank metric and convolutional coding with orthogonal frequency division multiplexing. This technique is very efficient in reducing the bursty nature of impulsive noise while having a quite low level of complexity. Another solution based on a multi-antenna system is also designed. We have proposed a cooperative closed-loop coded MIMO system based on rank metric code and max-dmin precoder. The second technique is also an optimal solution for both improving the reliability of the system and energy saving in wireless sensor networks.

Orientador: Prof. Dr. Luiz Alberto L. Almeida / Coorientador: Prof. Dr. Ricardo Suyama / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia da Informação, Santo André, 2018. / Em diversas aplicações práticas, o QR Code é utilizado para codificar informações importantes, como por exemplo, informações técnicas sobre o equipamento no qual está afixado, ou dados para identificação de pacientes em hospitais, de maneira que é importante garantir a correta leitura da etiqueta que a contém. Entretanto, devido a degradações na própria etiqueta ou mesmo no processo de aquisição da imagem, modeladas como um ruído presente na imagem digital, é possível que o dado não seja corretamente decodificado. Dessa forma, no presente trabalho é proposta uma nova abordagem para a redução de ruído em imagens, visando minimizar erros de leitura de QR Codes. Considerando que o ruído apresenta característica impulsiva, foi desenvolvido um filtro adaptativo, capaz de minimizar as degradações na imagem e permitir a correta leitura da informação codificada. O método, embora simples, se mostrou bastante eficiente na redução do ruído, permitindo a recuperação da informação mesmo em condições bastante severas de degradação, mostrando-se significativamente mais eficiente do que a abordagem tradicional envolvendo o uso do filtro de mediana. / In several practical applications, the QR Code is used to encode important information, such as technical information about the equipment on which it is fixed or patient ID information in hospitals, and it is important to guarantee that the tag is correctly read. However, due to physical degradations in the tag or due to the image aquisition process, which are modeled as a noise, it is possible that read errors occur. Therefore, in this work, a new approach for image denoising is proposed, aiming to minimize read errors in QR Codes. Assuming that the noise, in such applications, has an impulsive characteristic, a new adaptive filter was developed, capable of minimizing image degradations and increasing the QR Code successful scan rate. Simulation results indicate that the proposed method is significantly more efficient than traditional approaches using median filters.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-04-20T12:09:28Z No. of bitstreams: 1 thiagorodriguesoliveira.pdf: 2429204 bytes, checksum: b1904f2bde31b546890c5bfa77d58c80 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-04-20T12:44:42Z (GMT) No. of bitstreams: 1 thiagorodriguesoliveira.pdf: 2429204 bytes, checksum: b1904f2bde31b546890c5bfa77d58c80 (MD5) / Made available in DSpace on 2017-04-20T12:44:42Z (GMT). No. of bitstreams: 1 thiagorodriguesoliveira.pdf: 2429204 bytes, checksum: b1904f2bde31b546890c5bfa77d58c80 (MD5) Previous issue date: 2010-09-28 / Esta dissertação apresenta, de forma detalhada, um conjunto de metodologias e técnicas destinadas à análise de redes de energia elétrica como meio de transmissão de dados (power line communication - PLC). As características das redes elétricas que influenciam um sistema de comunicação de dados consideradas neste trabalho são as seguintes: a impedância de acesso à rede elétrica, a resposta ao impulso e o ruído. Para tanto, técnicas de processamento de sinais para estimação da resposta em frequência, estimação do comprimento efetivo da resposta ao impulso, detecção e segmentação de ruídos impulsivos e análise espectral de ruídos aditivos são propostas e discutidas na presente contribuição. Os desempenhos objetivos e a apreciação subjetiva das técnicas propostas, a partir de dados sintéticos e medidos, evidenciam a adequação destas técnicas para a análise em questão. Além disso, formulações matemáticas para a resposta ao impulso de canais PLC invariantes, variantes e periodicamente variantes no tempo, derivadas a partir do modelo de multi-propagação para canais PLC, são apresentadas. Tais formulações proporcionam de forma simples e objetiva a emulação dos possíveis comportamentos temporais de canais PLC reais e, portanto, podem se constituir como ferramentas de grande utilidade para o projeto e a avaliação de sistemas de comunicações baseados na tecnologia PLC. / This thesis addresses a set of methodologies and techniques for the analysis of electric grids as a medium for data communications (power line communications - PLC). The main features influencing a communication system that are considered in this work are the input impedance, the channel impulse response, and the noise. In this regards, signal processing-based techniques are investigated, proposed and analyzed for the estimations of the channel frequency response and the effective length of the channel impulse response; the detection and segmentation of impulsive noise; and the power spectral analysis of the additive noise at the channel output. The numerical performance and subjective analysis regarding the use of the proposed techniques in synthetic and measured data indicate that those techniques fit well in the thesis purposes. In addition, mathematical formulation for invariant, time-varying, and periodically time-varying PLC channel models, which are based on multi-path channel model approach, are presented. These formulations are simple and elegant ones for the emulation of possible temporal behavior of existing PLC channels and, as a result, can constitute a useful tool for the design and analysis of PLC systems.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-04-20T12:33:06Z No. of bitstreams: 1 analuizasiqueiraferreira.pdf: 2299159 bytes, checksum: 4a5563c4c2ee9592b3902e4440a2031b (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-04-20T12:45:20Z (GMT) No. of bitstreams: 1 analuizasiqueiraferreira.pdf: 2299159 bytes, checksum: 4a5563c4c2ee9592b3902e4440a2031b (MD5) / Made available in DSpace on 2017-04-20T12:45:20Z (GMT). No. of bitstreams: 1 analuizasiqueiraferreira.pdf: 2299159 bytes, checksum: 4a5563c4c2ee9592b3902e4440a2031b (MD5) Previous issue date: 2011-04-11 / O uso de banda ultra-larga (ultra wideband - UWB) vem sendo tema de pesquisa na área da comunicação sem fio há cerca de 20 anos e os bons resultados obtidos tem levado à introdução de novas tecnologias no mercado de transmissão de dados a curtas distâncias. No entanto, o uso de UWB para a transmissão de dados através da rede elétrica (power line communications - PLC) ainda é uma questão de investigação em aberto, interessante e promissora para um conjunto específico de aplicações que demandam elevada taxa de transmissão em curtas distâncias e baixo custo, tais como impressoras, monitores, etc. Neste contexto, a presente dissertação analisa diferentes aspectos da transmissão UWB através de cabos de distribuição de energia elétrica. Um sistema UWB impulsivo é analisado quando i) o canal PLC é outdoor, linear e variante no tempo; ii) o canal PLC é indoor, linear e invariante no tempo; iii) há ruído AWGN (additive white Gaussian noise) e iv) há ruído AIGN (additive impulsive Gaussian noise). Além disso, são respondidas questões referentes à adequação do pulso UWB ao canal de comunicação, considerando o espectro do mesmo quando o canal PLC é outdoor ou indoor. As modulações UWB investigadas são pela posição do pulso (pulse position modulation - PPM) e pela amplitude do pulso (pulse amplitude modulation - PAM). Além de apresentar diretrizes para o projeto de um sistema UWB para aplicações PLC, a presente dissertação analisa diversas estratégias e técnicas para recepção e redução da complexidade computacional do receptor UWB. Os resultados indicam que o uso de UWB é interessante para algumas aplicações específicas que envolvam elevada taxa de transmissão, através de curtas distâncias e baixo custo. / Ultra wideband modulation (UWB) has been a subject of research in the wireless field for nearly 20 years and the good results achieved have led to the introduction of new technologies in the market of short distances data communication. However, the employment of UWB for data transmission over power lines (PLC) is still an open, interesting and promising research theme for a specific set of applications which require high throughput over short distances and low cost, such as printers, computer monitors, etc. In this context, this dissertation examines several aspects of the UWB transmission through electricity distribution cables. An UWB impulsive system is analyzed when i) the PLC channel is outdoor, linear and time invariant; ii) the PLC channel is indoor, linear and time invariant; iii) there is AWGN (additive white gaussian noise) and iv) there is AIGN (additive impulsive gaussian noise) noise. Moreover, many questions regarding the adequacy of UWB pulse for the communication channel are answered, taking into account its spectrum when the PLC channel is outdoor or indoor. The UWB modulations investigated are pulse position modulation (PPM) and pulse amplitude modulation (PAM). Apart from presenting some guidelines to project a UWB system, this work analyzes different strategies and techniques for reception that reduce the computational complexity of the UWB receiver. The results point out that UWB is interesting for some specific applications which require high data transmission rate in short distances and low cost.

Cette thèse a pour cadre les transmissions sur les réseaux CPL-BE et les réseaux de capteurs à faible capacité. L'état de l'art classique sur la protection de l'information dans la transmission par réseaux de capteurs fait référence à l'utilisation de codage distribué où les relais implémentent des opérations de parité (mélange des flux) sur les data issues des capteurs. Cependant, il est difficile, de par la nature variable de la qualité des liens en liaisons sans fil, de contrôler la qualité du codeur équivalent construit et de maintenir ses performances au cours du temps. C'est pourquoi nous nous sommes orientés dans cette thèse vers la recherche de schémas de codage différents qui résistent mieux à la variation de qualité des liaisons à travers le réseau. Notre choix s'est porté sur le codage par sous-espace inspiré des travaux de Gabidulin. Le but est de former un code qui utilise une métrique simple et résistante pour sécuriser les transmissions sur le réseau. Les codes à métrique de rang répondent bien à ce besoin car il n'y a qu'à contrôler le rang de la matrice obtenue en réception pour vérifier l'intégrité de la transmission. Les codes à métrique de rang et leur algorithme de décodage ont été étudiés dans un premier temps. Puis, les performances du code LRPC proposé concaténé avec les codes convolutifs sont testées dans des schémas de transmission des contextes différents. / This thesis considers the context of transmissions on CPL-BE networks and low-capacity sensor networks. The state of the art on information protection intransmission by sensor networks refers to the use of distributed coding, where therelays implement parity operations (mixing of streams) on data transmitted by thesensors. However, due to the varying nature of the quality of the wireless links, it is difficult to control the quality of the equivalent encoder constructed and to maintain its performance over time. Therefore, in this thesis, we have focused on the search for different coding schemes that are better resist the variation in the quality of the links across the network. Our choice was based on the sub-space coding inspired by Gabidulin's work. The goal is to form a code that uses a simple and resistant metric to secure transmission across the network. Rank metric codes respond well to this need because it only has to control the rank of the matrix obtained in reception to verify the integrity of the transmission. The rank metric codes and their decoding algorithm were studied in a first step. Then, the performance of the proposed LRPC code concatenated with the convolutional codes is tested in transmission schemes of different contexts.

Dans un nombre croissant d'applications, les perturbations rencontrées s'éloignent fortement des modèles classiques qui les modélisent par une gaussienne ou un mélange de gaussiennes. C'est en particulier le cas des bruits impulsifs que nous rencontrons dans plusieurs domaines, notamment celui des télécommunications. Dans ce cas, une modélisation mieux adaptée peut reposer sur les distributions alpha-stables. C'est dans ce cadre que s'inscrit le travail de cette thèse dont l'objectif est de concevoir de nouvelles méthodes robustes pour l'estimation conjointe état-bruit dans des environnements impulsifs. L'inférence est réalisée dans un cadre bayésien en utilisant les méthodes de Monte Carlo séquentielles. Dans un premier temps, cette problématique a été abordée dans le contexte des systèmes de transmission OFDM en supposant que les distorsions du canal sont modélisées par des distributions alpha-stables symétriques. Un algorithme de Monte Carlo séquentiel a été proposé pour l'estimation conjointe des symboles OFDM émis et des paramètres du bruit $\alpha$-stable. Ensuite, cette problématique a été abordée dans un cadre applicatif plus large, celui des systèmes non linéaires. Une approche bayésienne non paramétrique fondée sur la modélisation du bruit alpha-stable par des mélanges de processus de Dirichlet a été proposée. Des filtres particulaires basés sur des densités d'importance efficaces sont développés pour l'estimation conjointe du signal et des densités de probabilité des bruits / In signal processing literature, noise's sources are often assumed to be Gaussian. However, in many fields the conventional Gaussian noise assumption is inadequate and can lead to the loss of resolution and/or accuracy. This is particularly the case of noise that exhibits impulsive nature. The latter is found in several areas, especially telecommunications. $\alpha$-stable distributions are suitable for modeling this type of noise. In this context, the main focus of this thesis is to propose novel methods for the joint estimation of the state and the noise in impulsive environments. Inference is performed within a Bayesian framework using sequential Monte Carlo methods. First, this issue has been addressed within an OFDM transmission link assuming a symmetric alpha-stable model for channel distortions. For this purpose, a particle filter is proposed to include the joint estimation of the transmitted OFDM symbols and the noise parameters. Then, this problem has been tackled in the more general context of nonlinear dynamic systems. A flexible Bayesian nonparametric model based on Dirichlet Process Mixtures is introduced to model the alpha-stable noise. Moreover, sequential Monte Carlo filters based on efficient importance densities are implemented to perform the joint estimation of the state and the unknown measurement noise density

Le travail présenté dans cette thèse a pour objectif de proposer et d'évaluer les performances de différentes techniques de suppression de bruit impulsif de type asynchrone adaptées aux transmissions sur courants porteurs en lignes (CPL) indoor. En effet, outre les caractéristiques physiques spécifiques à ce type de canal de transmission, le bruit impulsif asynchrone reste la contrainte sévère qui pénalise les systèmes CPL en terme de QoS. Pour remédier aux dégradations dues aux bruits impulsifs asynchrones, les techniques dites de retransmission sont souvent très utilisées. Bien qu'elles soient efficaces, ces techniques de retransmission conduisent à une réduction de débit et à l’introduction de délais de traitement supplémentaires pouvant être critiques pour des applications temps réel. Par ailleurs, plusieurs solutions alternatives sont proposées dans la littérature pour minimiser l'impact du bruit impulsif sur les transmissions CPL. Cependant, le nombre de techniques, qui permettent d'obtenir un bon compromis entre capacité de correction et complexité d'implantation reste faible pour les systèmes CPL. Dans ce contexte, nous proposons dans un premier temps d'utiliser un filtre linéaire adaptatif : le filtre de Widrow, nommé aussi ADALINE (ADAptive LInear NEuron), que nous utilisons comme méthode de débruitage pour les systèmes CPL. Pour améliorer les performances du débruitage effectué à l'aide d'ADALINE, nous proposons d'utiliser un réseau de neurones (RN) non linéaire comme méthode de débruitage. Le réseau de neurones est un bon outil qui est une généralisation de la structure du filtre ADALINE. Dans un deuxième temps, pour améliorer les performances du débruitage par un réseau de neurones, nous proposons un procédé d'annulation du bruit impulsif constitué de deux algorithmes : EMD (Empirical Mode Decomposition) associé à un réseau de neurones de type perceptron multicouches. L'EMD effectue le prétraitement en décomposant le signal bruité en signaux moins complexes et donc plus facilement analysables. Après quoi le réseau de neurones effectue le débruitage. Enfin, nous proposons une méthode d'estimation du bruit impulsif utilisant la méthode GPOF (Generalized Pencil Of Function). L'efficacité des deux méthodes, EMD-RN et la technique utilisant l'algorithme GPOF, est évaluée en utilisant une chaîne de simulation de transmission numérique compatible avec le standard HPAV. / The aim of our thesis is to propose and to evaluate the performances of some asynchronous impulsive noise mitigation techniques for transmission over indoor power lines. Indeed, besides the particular physical properties that characterize this transmission channel type, asynchronous impulsive noise remains the difficult constraint to overcome on power lines communications (PLC). Usually, the impact of asynchronous impulsive disturbances over power lines is partly compensated by means of retransmission mechanisms. However, the main drawbacks of the use of retransmission solutions for impulsive noise mitigation are the bitrate loss and the induced time delays that may be prohibitive for real-time services. Although several other countering strategies are proposed in the literature, only very few of them have a good compromise between correction capability and implementing complexity for PLC systems. In this context, we proposed an adaptive linear filter, the Widrow filter, also known as ADALINE (Adaptive LInear neurons), as a denoising method for PLC systems. To improve the performance of the denoising method using ADALINE, we proposed to use a neural network (NN) as a nonlinear denoising method. The neural network is a good generalization of the ADALINE filter. In a second step, to improve the performances of denoising by NN, we proposed a combined denoising method based on EMD (Empirical Mode Decomposition) and MLPNN (Multi Layer Perceptron Neural Network). The noised signal is pre-processed by EMD which decomposes it into signals less complex and therefore more easily analyzed. Then the MLPNN denoises it. Finally, we proposed an asynchronous impulsive noise estimation method using the GPOF method (Generalized Pencil Of Function). The performances of the two methods, EMD-MLPNN and GPOF technique, are evaluated using a PLC transmission chain compatible with the HPAV standard.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-04-24T15:28:35Z No. of bitstreams: 1 paolajohanasaboyalopez.pdf: 1042873 bytes, checksum: a46dd95de00e062cba39ef4b9b642462 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-04-24T17:09:24Z (GMT) No. of bitstreams: 1 paolajohanasaboyalopez.pdf: 1042873 bytes, checksum: a46dd95de00e062cba39ef4b9b642462 (MD5) / Made available in DSpace on 2017-04-24T17:09:24Z (GMT). No. of bitstreams: 1 paolajohanasaboyalopez.pdf: 1042873 bytes, checksum: a46dd95de00e062cba39ef4b9b642462 (MD5) Previous issue date: 2013-06-03 / A presente dissertação tem por objetivo propor e avaliar cinco técnicas de detecção de ruídos impulsivos para a melhoria da transmissão digital de dados via redes de energia elétrica (do inglês, Power Line Communications) (PLC). As técnicas propostas contemplam a detecção de ruídos impulsivos no domínio do tempo discreto, no domínio da transformada wavelet discreta (do inglês, Discrete Wavelet Transform) (DWT) e no domínio da transformada discreta de Fourier (do inglês, Discrete Fourier Transform) (DFT). Tais técnicas fazem uso de métodos de extração e seleção de características, assim como métodos de detecção de sinais baseados na teoria de Bayes e redes neurais. Análises comparativas explicitam as vantagens e desvantagens de cada uma das técnicas propostas para o problema em questão, e ainda indicam que estas são bastante adequadas para a solução do mesmo. / This dissertation aims to propose and evaluate five techniques for impulsive noise detection in order to improve digital communications through power line channels. The imput signals for the proposed detection techniques are impulsive noise signals on discrete-time domain, on the Discrete Wavelet Transform domain and on the Discrete Fourier Transform domain and it makes use of feature extraction and selection techniques, as well as detection techniques supported on Bayes Theory and Multi-layer Perceptron Neural Networks. Comparative analysis show some advantages and disadvantages of each proposed technique and the relevance of them to solve the impulsive noise detection problem.