Dissertations / Theses on the topic 'Canal de transmission'
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Souhard, Benoît. "Codage conjoint source canal : application à la transmission d'images fixes sur canal ionospérique." Poitiers, 2004. http://www.theses.fr/2004POIT2253.
Ho, Ka Ming. "Transmission distribuée dans le canal multi-antennaire à interférences." Phd thesis, Télécom ParisTech, 2010. http://pastel.archives-ouvertes.fr/pastel-00574250.
Hamidouche, Wassim. "Stratégies de transmission vidéo sur un canal MIMO réaliste." Poitiers, 2010. http://theses.edel.univ-poitiers.fr/theses/2010/Hamidouche-Wassim/2010-Hamidouche-Wassim-These.pdf.
This work focus on video transmission over mobile a hoc net-works. Several schemes have been proposed in order to improve and guarantee a high quality of service of applications integrating video transmission over ad hoc networks. The performance of these schemes is assessed by using network simulator tools such as NS-2 and GLOMOSIM. However, the physical layer usually used in network simulators does not properly model the propagation phenomenon as in a real urban environment. We have proposed a realistic physical layer which considers all specificities of mobile wireless channel. This physical layer uses a ray tracer propagation mo-del and allows assessing a SISO and MIMO wireless links following the IEEE 802. 11a and IEEE 802. 11n standards, respectively. This work clearly shows that we should consider a realistic physical layer in network simulator to assess the performance of video transmission schemes. On the other hand, we have pro-posed an original joint source-channel coding solution for a hierarchical trans-mission of scalable video coder, known as H. 264/SVC. This solution exploits a spatial diversity of a MIMO channel jointly with a hierarchy provided by the H. 264/SVC coder in order to guarantee the best quality of the received video regardless the channel conditions. The proposed solution uses a precoder designs for an optimal power allocation toward transmitted antennae in order to minimize the received video distortion
ALID, MOSTAFA. "Transmission de donnees sur canaux selectifs en frequence : application aux transmissions sur canal acoustique sous-marin." Rennes 1, 1993. http://www.theses.fr/1993REN10059.
Ramirez, Acosta Alejandro Aluaro. "Codage conjoint source-canal pour la transmission de la parole." Brest, 2000. http://www.theses.fr/2000BRES2051.
Liénard, Martine. "Télécommunications sol-véhicules en tunnel : caractérisation du canal de transmission." Lille 1, 1993. http://www.theses.fr/1993LIL10014.
Malinowski, Simon Guillemot Christine. "Codes joints source-canal pour transmission robuste sur canaux mobiles." Rennes : [s.n.], 2008. ftp://ftp.irisa.fr/techreports/theses/2008/malinowski.pdf.
Malinowski, Simon. "Codes joints source-canal pour transmission robuste sur canaux mobiles." Rennes 1, 2008. ftp://ftp.irisa.fr/techreports/theses/2008/malinowski.pdf.
Joint source-channel coding has been an area of recent research activity. This is due in particular to the limits of Shannon's separation theorem, which states that source and channel coding can be performed separately in order to reach optimality. Over the last decade, various works have considered performing these operations jointly. Source codes have hence been deeply studied. In this thesis, we have worked with these two kind of codes in the joint source-channel coding context. A state model for soft decoding of variable length and quasi-arithmetic codes is proposed. This state model is parameterized by an integer T that controls a trade-off between decoding performance and complexity. The performance of these source codes on the aggregated state model is then analyzed together with their resynchronisation properties. It is hence possible to foresee the performance of a given code with respect to the aggregation parameter T. A robust decoding scheme exploiting side information is then presented. The extra redundancy is under the form of partial length constraints at different time instants of the decoding process. Finally, two different distributed coding schemes based on quasi-arithmetic codes are proposed. The first one is based on puncturing the output of the quasi-arithmetic bit-stream, while the second uses a new kind of codes : overlapped quasi-arithmetic codes. The decoding performance of these schemes is very competitive compared to classical techniques using channel codes
Coatélan, Stéphane. "Conception et évaluation d'un système de transmission sur canal acoustique sous-marin horizontal petits fonds." Brest, 1996. http://www.theses.fr/1996BRES2001.
Gabay, Abraham. "Codage conjoint source-canal : application a la transmission d'images par satellite." Paris, ENST, 2001. http://www.theses.fr/2001ENST0007.
Gabay, Abraham. "Codage conjoint source canal : application à la transmission d'images par satellites /." Paris : École nationale supérieure des télécommunications, 2001. http://catalogue.bnf.fr/ark:/12148/cb38820427d.
Marquet, Alexandre. "Transmission au delà de la cadence de Nyquist sur canal radiomobile." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAT104/document.
With an increasing number of mobile terminals coupled with a large spreading of so-called "smart devices", we can see a growing demand for effective communication means in any place and in any situation.This goes with a more and more overcrowded spectrum.In this context, multicarrier modulations are good candidates to allow effective communication in any place.However current techniques, OFDM in particular, suffer from a bad time--frequency localization and peak-to-average power ratio, limiting their relevancy in an embedded context, or in scenarios with severe spectral constraints.In this thesis, we study faster-than-Nyquist multicarrier modulations.This kind of modulation allow for an increase in spectral efficiency by means of an increase in signaling density.This, in compensation, comes at the price of unavoidable self-interference, which makes demodulation harder.On an additive white Gaussian noise channel, we show how to carefully chose pulse-shapes that maximize signal-to-interference-plus-noise ratio.We show that these particular pulse-shapes yields a linear turbo-equalization of self-interference minimizing the mean squared error.Next, our work highlights the capability of these optimal pulse-shapes to reduce peak-to-average power ratio as density rises.Lastly, on frequency selective channels, we confirm that low complexity equalization using one tap by subcarrier is still possible.These results show how this new modulation technique helps increasing spectral efficiency while keeping what made multicarrier modulations popular: good adaptation to transmission channels
Sawaya, Wadih. "Codage et modulation pour le canal satellite /." Paris : Ecole nationale supérieure des télécommunications, 1994. http://catalogue.bnf.fr/ark:/12148/cb357672671.
Basilio, Giovanna Garcia. "Heurística para otimizar a alocação de canal e potência em redes sem fio." Universidade Tecnológica Federal do Paraná, 2015. http://repositorio.utfpr.edu.br/jspui/handle/1/1409.
Devido a crescente demanda por conectividade, um maior número de APs tendem a ser utilizados para que, em todo um ambiente, os clientes de uma rede sem fio possam receber o sinal de rádio. Contudo, a distribuição desorganizada destes APs no ambiente pode reduzir a qualidade do sinal. Esta qualidade é influenciada pelo aumento da interferência que os APs exercem entre si. Por este motivo, encontrar uma forma de reduzi-la vem sendo motivo de pesquisas. Dentre as soluções encontradas, a otimização de canal e potência estão entre as mais eficientes. Neste trabalho, é proposto um algoritmo heurístico para otimizar a configuração de canal e potência para APs pertencentes a rede. Este algoritmo realiza uma avaliação da rede, utilizando modelos analíticos de propagação e técnicas para otimização de canal e potência a fim de encontrar uma solução que aumente a qualidade da rede. Nos resultados obtidos, o algoritmo proposto teve um desempenho muito próximo da melhor solução encontrada com o método exaustivo.
With the crescent demand for connectivity, a large number of access points may be used to cover the entire environment, of a wireless network, with radio signal. But, the disorganized distribution of these access points may reduce the quality of the signal. This quality is influenced by the interference of nearby access points, and therefore many researchers are seeking a method to reduce it. The channel and power optimization are efficient methods to reduce interference. In this work, an heuristic algorithm to find a better configuration of channel and transmission power for those access points in the network is proposed. This algorithm evaluates the network, using analytical models, and techniques to optimize the channel and the transmission power to increase the quality of the signal in the environment. In the results, the algorithm arrives at solution close to the optimal.
Ait, Sab Omar. "Turbo codes et codage conjoint source-canal : application à la transmission d'images." Brest, 1998. http://www.theses.fr/1998BRES2005.
El, Baz Abdessamad. "Décodage conjoint source-canal : optimisation d'une chaîne de transmission pour images fixes." Brest, 2002. http://www.theses.fr/2002BRES2008.
In this thesis we considered the optimisation of a still image transmission system over noisy channel. The transmission system adopts a vector quantizer as a source encoder. The codebook used is built using kohonen's self organisation feature map algorithm which confers a topological organisation to the codebook vectors. Those vectors are associated in an optimal way to the constellation points of 16-QAM modulation used to transmit the data. By this association, the system becomes robust to the transmission errors. We then introduced a BCH forward error correction (FEC) code without altering the transmission system robustness to the errors. For this reason we have constrained the channel encoder. An additional constraint is imposed to this encoder to exploit the statistics of the source. When computing the BCH decoding decision rule, we take into account the probability distribution of the vectors generated by the source which we first regarded as independent but with non uniform distribution, and which we modelled in a second step as a first order Markov chain. The gain obtained in terms of BER and PSNR of the decoded image over the Gaussian channel and Rayleigh channel which we considered, are appreciable. We then replaced BCH FEC code by a BCH block turbo code. We took into account the statistics of the source in the calculation of the decision rule and the extrinsic information. The additional gain obtained in terms of PSNR of Lenna image decoded when using the new algorithms approaches the 11dB for low signal noise ratios, as compared to the classical algorithms. Many other images have been considered and the results show that the gain is highly dependent of the characteristics of the images but remains superior to classical algorithms
Zaïbi, Sonia. "Optimisation conjointe du codage (décodage) source-canal pour la transmission d' images." Brest, 2004. http://www.theses.fr/2004BRES2002.
This thesis deals with joint optimization of source and channel coding for image transmission over noisy channels. The considered image transmission system includes an embedded source coder, achieving a progressive compression of the transmitted images. We propose a robust version of the SPIHT algorithm. A convolutional error correcting codes is introduced in the system. The List-Viterbi algorithm is used to decode it. Moreover error detection is integrated into the arithmetic coding process applied by he source coder, according to the method proposed by Boyd et al. The arithmetic decoder works then jointly with the list-Viterbi algorithm. In the last part of this work, we consider the optimization of the rate allocation between an embedded source coder and a channel coding scheme applying unequal error protection. A generalization of the dynamic programming method, proposed forst by Chande et al. , is applied to solve the optimization problem. This method is validate on an image transmission system using block turbo codes for channel coding
Zheng, Shuo. "Prise en compte des contraintes de canal dans les schémas de codage vidéo conjoint du source-canal." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLT005/document.
SoftCast based Linear Video Coding (LVC) schemes have been emerged in the last decade as a quasi analog joint-source-channel alternative to classical video coding schemes. Theoretical analyses have shown that analog coding is better than digital coding in a multicast scenario when the channel signal-to-noise ratios (C-SNR) differ among receivers. LVC schemes provide in such context a decoded video quality at different receivers proportional to their C-SNR.This thesis considers first the channel precoding and decoding matrix design problem for LVC schemes under a per-subchannel power constraint. Such constraint is found, e.g., on Power Line Telecommunication (PLT) channels and is similar to per-antenna power constraints in multi-antenna transmission system. An optimal design approach is proposed, involving a multi-level water filling algorithm and the solution of a structured Hermitian Inverse Eigenvalue problem. Three lower-complexity alternative suboptimal algorithms are also proposed. Extensive experiments show that the suboptimal algorithms perform closely to the optimal one and can reduce significantly the complexity. The precoding matrix design in multicast situations also has been considered.A second main contribution consists in an impulse noise mitigation approach for LVC schemes. Impulse noise identification and correction can be formulated as a sparse vector recovery problem. A Fast Bayesian Matching Pursuit (FBMP) algorithm is adapted to LVC schemes. Subchannels provisioning for impulse noise mitigation is necessary, leading to a nominal video quality decrease in absence of impulse noise. A phenomenological model (PM) is proposed to describe the impulse noise correction residual. Using the PM model, an algorithm to evaluate the optimal number of subchannels to provision is proposed. Simulation results show that the proposed algorithms significantly improve the video quality when transmitted over channels prone to impulse noise
Astier, Florence. "Le canal du PBPI : une analyse théorique et empirique d'un canal de transmission particulier de la politique monétaire au Japon." Lyon 2, 2000. http://www.theses.fr/2000LYO22008.
The aim of this study is to analyze how monetary policy impulses are propagating through the FILP system and to show that the Japanese Fiscal Investment and Loan Program (FILP) system allows the existence of a new monetary policy channel : the FILP channel. .
Visoz, Raphaël. "Traitements itératif et conjoint pour les systèmes radio-mobiles." Paris, ENST, 2002. https://pastel.archives-ouvertes.fr/pastel-00001292.
Ghaith, Alaa. "Méthodes pour l'estimation de canal, égalisation et codage pour le traitement itératif en présence d'interférences." Paris, ENST, 2006. http://www.theses.fr/2006ENST0051.
This thesis report presents some new methods to improve the channel estimation, equalization, and coding for inter symbol interference channels. We begin by a new iterative procedure for channel estimation and detection, named Observation Separation, in a turbo equalization scheme for systems using high level modulation. We extend this technique to the mapping iterative detection. We suggest a binary mapping optimized of 16-QAM constellation to increase the coding gain. Then, we present a decoding algorithm for non binary codes which is accelerated by using the Fast Hadamard Transformer, and with reduced complexity thanks to the duel code. We suggest a new adaptive LDPC code which can be simply applied to the OFDM system and decoded by the rule designed beforehand. Finally, we improve the performance of turbo equalization, by combining all the techniques defined beforehand: non binary LDPC code, interference cancellation equalizer, separation observation and non binary LDPC decoding
Zheng, Shuo. "Prise en compte des contraintes de canal dans les schémas de codage vidéo conjoint du source-canal." Electronic Thesis or Diss., Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLT005.
SoftCast based Linear Video Coding (LVC) schemes have been emerged in the last decade as a quasi analog joint-source-channel alternative to classical video coding schemes. Theoretical analyses have shown that analog coding is better than digital coding in a multicast scenario when the channel signal-to-noise ratios (C-SNR) differ among receivers. LVC schemes provide in such context a decoded video quality at different receivers proportional to their C-SNR.This thesis considers first the channel precoding and decoding matrix design problem for LVC schemes under a per-subchannel power constraint. Such constraint is found, e.g., on Power Line Telecommunication (PLT) channels and is similar to per-antenna power constraints in multi-antenna transmission system. An optimal design approach is proposed, involving a multi-level water filling algorithm and the solution of a structured Hermitian Inverse Eigenvalue problem. Three lower-complexity alternative suboptimal algorithms are also proposed. Extensive experiments show that the suboptimal algorithms perform closely to the optimal one and can reduce significantly the complexity. The precoding matrix design in multicast situations also has been considered.A second main contribution consists in an impulse noise mitigation approach for LVC schemes. Impulse noise identification and correction can be formulated as a sparse vector recovery problem. A Fast Bayesian Matching Pursuit (FBMP) algorithm is adapted to LVC schemes. Subchannels provisioning for impulse noise mitigation is necessary, leading to a nominal video quality decrease in absence of impulse noise. A phenomenological model (PM) is proposed to describe the impulse noise correction residual. Using the PM model, an algorithm to evaluate the optimal number of subchannels to provision is proposed. Simulation results show that the proposed algorithms significantly improve the video quality when transmitted over channels prone to impulse noise
Jégou, Hervé. "Codes robustes et codes joints source-canal pour transmission multimédia sur canaux mobiles." Rennes 1, 2005. https://tel.archives-ouvertes.fr/tel-01171129.
Nzengue, Pegnet Christian. "Le canal du capital bancaire, voie de transmission des chocs réels et financiers." Thesis, Bordeaux 4, 2012. http://www.theses.fr/2012BOR40011/document.
In this thesis, we study the transmission of real and financial shocks in Europe focusing on the bank capital channel. In our approach, we consider both theoretical and empirical issues. The ai mis to empirically emphasize the heteregeneity in the transmission of shocks at a European level and the extent of the bank capital channel. In Chapter 1, we do a survey on the structure of bank capital and balance sheet to analyse their impact at micro and macro levels. Considering the existing literature on bank capital and transmission channel, the transmission process seems to be influenced by banks’ specificities and by their level of regulatory capital. Regulatory constraint on bank capital determines the magnitude of the transmission of shocks. In Chapter 2, we study the determinants of banks’ reaction to a shock. Or results show that, the ex ante level of capital and the various components of regulatory capital significantly impact banks’ behaviour. In Chapter 3, we focus on the impact of Basel I and II regulatory frameworks on the transmission of shocks from a general equilibrium model. The simulation results point out that considering simultaneously the bank capital channel and the financial accelerator mechanism increases the propagation of monetary shocks through the liquidity premium effect. In Chapter 4, we examine a singular aspect of the prudential regulation : the resolution of failing financial institutions. We focus on the systemic importance banks. Current policy statements have not reduced moral hazard behaviour of such financial institutions. Thus, to prevent the catastrophic consequences of their failure, bankruptcy laws have been adopted. Considering a theoretical model, we conclude that monetary sanctions, strengthen by stronger monitoring pressures may limit banks’ incentives to take excessive risks. This thesis provides new results to the existing literature. It emphasizes the role of the several components of bank balance sheet structure in both short and long runs, resulting from an estimated VECM
Jégou, Hervé Guillemot Christine. "Codes robustes et codes joints source-canal pour transmission multimédia sur canaux mobiles." [S.l.] : [s.n.], 2005. ftp://ftp.irisa.fr/techreports/theses/2005/jegou.pdf.
Jourdain, Dominique. "Caractérisation expérimentale du canal sous-marin petit fond pour la transmission acoustique horizontale." Grenoble INPG, 1996. http://www.theses.fr/1996INPG0074.
Mariotte, Hubert. "Caractérisation d'un canal non stationnaire et sélectif : Application aux communications numériques acoustiques sous-marines." Brest, 1995. http://www.theses.fr/1995BRES2018.
Liu, Yang. "Estimation de canal et détection conjointes dans les récepteurs itératifs." Paris, ENST, 2009. http://www.theses.fr/2009ENST0047.
This thesis is devoted to developing iterative joint channel estimation and decoding algorithms with the turbo principle. We focus on two main iterative algorithms: expectation-maximization (EM) algorithm and belief propagation (BP) algorithm. In this thesis, the BP and EM algorithms are optimized and compared. Orthogonal frequency-division multiplexing (OFDM) is a multi-carrier modulation scheme that provides efficient bandwidth utilization and robustness against time dispersive channels. In this thesis, we propose channel estimation techniques for a coded OFDM system using the expectation-maximization (EM) algorithm. By introducing different complete date, we derive two types of EM channel estimation algorithms. A derivation of the rate of convergence is also proposed to compare the two algorithms. The comparison reveals that one EM algorithm has a lower complexity for the same performance in a coded OFDM system. Factor graphs provide insightful and systematic ways to develop flexible iterative receivers, being able to switch from one system to another by running belief propagation algorithm on different factor graphs. In order to deal with continuous variables over factor graphs, instead of relying on quantization, in this thesis, we propose to model probability distributions as mixtures of Gaussian distributions. It allows for estimation improvement and complexity reduction simultaneously. With this Gaussian approximation method, we propose the BP algorithms for different systems and compare them to the EM algorithm. Based on the studies of EM and BP algorithms, some conclusions are drawn in the last part. Finally, some future works are proposed
Duroselle, Raphaël. "Robustesse au canal des systèmes de reconnaissance de la langue." Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0250.
Language recognition is the task of predicting the language used in a test speech utterance. Since 2017, the best performing systems have been based on a deep neural network which is trained to predict language labels for the whole utterance. These systems suffer from a drop in performance when they are exposed to a change of the transmission channel between train and test data. The goal of this thesis is to investigate approaches to limit this performance drop, for these new systems.An increase in the invariance, with respect to the transmission channel, of the representations used by the neural network can increase the robustness of the system. We show that the regularization of the loss function used to train the neural network is an efficient approach to increase invariance. Two kinds of regularization functions are analysed. Divergence measures between domains reduce effectively the variability between known domains, they can also be used to incorporate unlabeled data into the training set in a semi-supervised learning framework. Metric learning cost functions are able to reduce unknown variabilities within the training set. We show how this regularization method can be enforced for three practical learning settings: unsupervised domain adaptation, multi-domain learning and domain generalization.During this work, we have designed methods for analyzing the quality of the representations. They aim at evaluating the variability of the representations induced by the transmission channel and to compare it to the variability that caused the language. Two tools are proposed: ratio between inter class and intra class covariance matrices and divergence measures between groups of representations. With these tools, we quantitatively evaluate the robustness to a change of transmission channel of the representations and analyse the effect of the regularization functions over the space of representations. We understand that an increase in invariance between channels can lead to more discriminative representations between languages and consequently to an increase in performance over each transmission channel.Finally, we contribute to the improvement of the training recipe of another module of the system, the bottleneck feature extractor. We replace it with a multilingual end-to-end automatic speech recognition neural network. It achieves a simiar performance as a traditional bottleneck feature extractor with a simplified training recipe. The use of data augmentation and regularization methods improves further this module. Moreover we show that a performance gain can be achieved with a joint training of the bottleneck feature extractor along with the language identification neural network. This paves the way to the application of the proposed regularization loss functions to the two modules jointly
GHAHREMANI, TARANEH. "Modelisation d'un canal de transmission en diversite d'espace pendant les periodes de trajets multiples." Paris 7, 1989. http://www.theses.fr/1989PA077252.
Bergeron, Cyril. "Optimisation conjointe source/canal d'une transmission vidéo H. 264/AVC sur lien sans fil." Paris, ENST, 2007. https://pastel.hal.science/pastel-00004234.
Traverso, Sylvain Fijalkow Inbar. "Transposition de fréquence et compensation du déséquilibre IQ pour des systèmes multiporteuses sur canal sélectif en fréquence." [S.l.] : [s.n.], 2008. http://biblioweb.u-cergy.fr/theses/07CERG0343.pdf.
Jeanne, Marion. "Etude de systèmes robustes de décodage conjoint source-canal pour la transmission sans fil de vidéo." Rennes, INSA, 2003. http://www.theses.fr/2003ISAR0018.
Guillaud, Maxime. "Techniques de transmission et de modélisation de canal pour les systèmes de communications multi-antennes." Phd thesis, Télécom ParisTech, 2005. http://pastel.archives-ouvertes.fr/pastel-00001353.
Van, Roy Stéphane. "Modélisation spatio-temporelle ultra-large bande du canal de transmission pour réseaux corporels sans fil." Doctoral thesis, Universite Libre de Bruxelles, 2010. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210003.
L’objectif de cette Thèse vise la réduction de la consommation énergétique au niveau des senseurs de sorte à leur garantir une autonomie de quelques mois, voire de quelques années. En réponse à cette contrainte énergétique, une association innovante de deux technologies émergentes est proposée, à savoir une combinaison des transmissions à ultra-large bande aux systèmes à multiples antennes. Une nouvelle architecture pour les réseaux corporels sans fil est donc envisagée pour laquelle les performances doivent être évaluées. Notre principale contribution à cet objectif consiste en la proposition d'une modélisation spatio-temporelle complète du canal de transmission dans le cadre de senseurs répartis autour du corps. Cette modélisation fait appel à la définition de nouveaux modèles, l'élaboration d'outils spécifiques d'extraction de paramètres et une compréhension fine des mécanismes de propagation liés à la proximité du corps humain. Ce manuscrit présente les résultats majeurs de nos recherches en cette matière.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
Chiang, Jui-Chiu. "Codage source-canal conjoint pour la transmission robuste de vidéo sur des canaux radio-mobiles." Paris 11, 2004. http://www.theses.fr/2004PA112267.
With the rapid advance of internet, wireless communication and digital technologies, multi-media and wireless communication are widely recognized as another industrial revolution that has profound impact on future human civilization. Due to the limited bandwidth, the video signal has to be highly compressed by efficient coding techniques. However, such schemes suffer from error propagation problem under the error-phone environment because of the use of entropy coding and motion prediction. Thus, the demand for efficient compression algorithms as well as reliable coding techniques is always a particular challenge in wireless transmission. In this thesis, a joint source channel coding for robust still image and video transmission is proposed. This coding scheme is based on oversampled filterbanks(ofbs) where an overcomplete representation of the input signals is provided. First, after the parity-check matrix and syndrome of an ofb are derived, we show how ofbs can be seen as channel codes using the redundancy between the subband signals. Then two algorithms referred to error detection and error correction are developed using this syndrome. In still image application, a reliable transmission is built implemented by ofbs and quantizations. Then, an extension of these techniques to video application is presented, where a motion-compensated 2d+t video coding scheme is proposed. As demonstrated in the simulation results, the error correction ability of ofbs in both applications is achieved even in the transmission environment with high bit error rates
Gabriel, Chadi. "Caractérisation du canal pour un système de transmission optique sous-marine et analyse des performances." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4311.
In this thesis, we consider optical wireless communication as a promising solution for high rate data transmission in power restricted underwater wireless sensor networks. A propagating light beam in seawater is subject to absorption and scattering due to the interaction with the particles within water. This practically limits the transmission range to a few tens of meters. In view of characterizing the underwater optical channel, we first study the inherent optical properties of the seawater and provide a model for underwater optical beam propagation. Concerning angle scattering, we propose to use the two-term Henyey-Greenstein model and show that it is more accurate than the commonly used Henyey-Greenstein model, especially in pure sea waters. Then, based on Monte Carlo simulations, we obtain the channel impulse response and quantify the channel time dispersion for different transmitter/receiver parameters and link distances. Through the numerical results that we present, we show that, except for highly turbid waters, the channel time dispersion can be neglected when working over moderate distances. Next, as a practical limitation, we focus on transmitter-receiver misalignment and evaluate its effect, in particular, by taking into account the limited receiver's field-of-view. Afterwards, we investigate the choice of the photo-detector, and furthermore contrast the performance of different intensity modulation techniques and discuss their suitability for use in the underwater optical communication system. Lastly, we provide a series of experimental measurement results that we have conducted inside a pool in order to validate a part of our theoretical studies
Guillaud, Maxime. "Techniques de transmission et de modélisation de canal pour les systèmes de communications multi-antennes /." Paris : École nationale supérieure des télécommunications, 2005. http://catalogue.bnf.fr/ark:/12148/cb40082865d.
Bibliogr. p. 129-139. Résumé en anglais et en français.
Francisco, Martín Rubén de. "Optimisation de la performance des systèmes MIMO avec connaissance partielle du canal." Paris, ENST, 2008. http://pastel.archives-ouvertes.fr/pastel-00003718.
Multiple-input multiple-output (MIMO) wireless communication systems have the potential to offer high data rates as well as link reliability. The feasibility of these systems in future mobile communication standards depends on the ability to provide high rates with a reduced amount of channel state information at the transmitter (CSIT), due to limited resource availability on the feedback link. This thesis addresses the problem of optimizing MIMO systems with partial CSIT. On the one hand, we provide methods for obtaining CSIT. On the other hand, we propose techniques to exploit the available sources of CSIT to optimize the system performance. In the first part, point-to-point MIMO channels are considered for the purpose of error rate minimization. Linear precoding techniques are proposed to enhance the performance of space-time coded (STC) MIMO systems, by appropriately combining information on the channel mean and covariance. In the second part of this thesis, we focus on sum-rate performance optimization in MIMO broadcast channels with limited feedback. Low-complexity cross-layer approaches are proposed for systems with joint linear beamforming and multiuser scheduling, optimizing the following parts in the MIMO communications system: linear beamforming techniques, scheduling algorithms, feedback strategies and feedback quantization techniques. A design framework for channel quality information (CQI) feedback design is proposed, based on an estimate on each user's signal-to-interference-plus-noise ratio (SINR). As we show, the system performance can be enhanced by using simple channel quantization strategies combined with optimized linear beamforming techniques
Le, Pemp Gaël. "Capacité de poursuite des algorithmes adaptatifs dans un canal de transmission sous-marin à trajets multiples." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq25651.pdf.
Cornejo, Bautista Joaquim Alfonso Alejandro. "Etude de la sécurisation du canal de transmission optique par la technique de brouillage de phase." Télécom Bretagne, 2009. http://www.theses.fr/2008TELB0095.
Mamfoumbi-Ocloo, Jean-Marcel. "Estimation de canaux de transmission respectant un modèle d'évolution temps/fréquence." Paris 11, 2006. http://www.theses.fr/2006PA112072.
The aim of this work is to propose channel estimation methods in the context of wireless transmission for the IEEE802. 11a standard. Multicareers technics (OFDM) have already been accepted in such standards. Our approach is in the framework of multicareers systems and takes advatange of these techniques. We propose, in a first time, a new channel model which is piecewise constant. This model permits to increase the observations being used to estimate a given parameter and also to reduce the number of channel coefficients which must be estimated. The introduction of this model in the EM (Expectation-Maximization) algorithm procedure provides an algorithm which maximizes the likelihood and the arithmetical complexity is turned from exponential to linear. The performances of this new algorithm are satisfactory. Then, we propose a Maximum a posteriori (MAP) version which takes into account the output of an autoregressive filter as a channel evolution model. The resulting algorithm improves performances significantly but its complexity becomes important. The last part of this work consists in proposing a method maximizing the a posteriori probability with a linear arithmetical complexity. The proposed method has the same fixed points than the original MAP algorithm and the convergence of these algorithms is established
Hénaff, Françoise. "Réception optimale en présence de trajets multiples et d'effet doppler : Application aux transmissions sur canal acoustique sous-marin." Brest, 1993. http://www.theses.fr/1993BRES2017.
Katto, Junji. "Análise da dinâmica da transmissão da política monetária através do canal de crédito utilizando modelagem baseada em agentes." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/100/100132/tde-23012015-113905/.
This study aims to analyze the dynamics of the monetary policy transmission through the credit channels (Bank Lending Channel and Balance Sheets Channel), using concepts and tools from the Complex Systems field to simulate an economy represented by different sectors in which agents are interconnected via credit relationships. This model is based on the work of Gatti et al. (2009) that used agent-based modeling. The novelty was to introduce a transmission mechanism of monetary policy through an interbank market and a primary interest rate, allowing the analysis of the impacts on the economy through the credit channels. The simulation results show that the impact of monetary policy on microeconomic level can be developed as a result of the complex interaction of these heterogeneous agents via credit relationships over time, and the variables in the macroeconomic context, such as the primary interest rate, affect the system through a feedback process.
Cheikh, M'hand Mohamed. "Etude du canal de propagation radio pour les systèmes embarqués sans fil automobile." Phd thesis, Toulouse, INPT, 2010. http://oatao.univ-toulouse.fr/17847/1/cheikh_mhand.pdf.
Long, Shihe. "Modélisation du canal intra-bâtiment et transmission haut-débit pour les communications optiques dans le spectre visible." Thesis, Ecole centrale de Marseille, 2016. http://www.theses.fr/2016ECDM0005.
Visible Light Communications (VLC) have attracted particular attention in the research community since a few years as a promising solution for high-speed indoor wireless networks. By exploiting the existing solid-state light-emitting diode (LED) lighting infrastructure, VLC offer numerous advantages such as a large unlicensed bandwidth, transmission security, and immunity to electro-magnetic interference compared to their radiofrequency counterparts. Within the context of indoor VLC, the multipath propagation channel and the non-ideal characteristics of the commercial white LEDs cause the main limitations for achieving high data-rate transmission. The objective of this thesis is to investigate the true impact of these limitations on the data transmission and to propose efficient signal processing solutions to mitigate their adverse effects. We start by the study of the indoor VLC channel impulse response by developing an efficient simulation tool. We then consider evaluating the channel frequency selectivity through different metrics. Next, given the potentially frequency-selective channel and the limited modulation bandwidth of the LEDs, we investigate the suitability of employing different signal transmission techniques including optical orthogonal frequency-division multiplexing (O-OFDM) in order to achieve high data-rate transmission. Given the high peak-to-average power ratio (PAPR) of O-OFDM signals and the limited dynamic range of the LEDs, we then propose a novel transmission scheme, which consists of using carrier-less amplitude and phase (CAP) modulation together with frequency domain equalization (FDE) at the receiver. We analyze the performance of the VLC link using this technique and compare it with the O-OFDM schemes, especially by taking the non-linear characteristics of the LED into account. Lastly, we demonstrate the merits of using the CAP-FDE transmission scheme via some experimental results
TANGUY, CHRISTOPHE. "Caracterisation du bruit dans le canal de transmission vlf/lf : application a la goniometrie des impulsions orageuses." Rennes 1, 1999. http://www.theses.fr/1999REN10066.
Fiévé, Sophie. "Caractérisation du bruit dans le canal de transmission VLF/LF : création d'un nouveau modèle de bruit : valerie." Rennes 1, 2005. http://www.theses.fr/2005REN1S060.
Geller, Benoît. "Transmission numérique pour radiomobiles par étalement de spectre et filtrage adapté dans un canal à trajets multiples." Grenoble INPG, 1992. http://www.theses.fr/1992INPG0090.
Milla, Peinado Manuel. "Modélisation et validation expérimentale du canal de transmission radio sol-projectile pour la conception d'un transceiver numérique." Thesis, Poitiers, 2018. http://www.theses.fr/2018POIT2326.
This thesis summarizes three years of work in the field of wideband characterization of the radio channel in projectile applications. The popularization of the miniaturized electronics has allowed the instrumentation of projectiles. The information gathered by the onboard sensors needs to be sent from the projectile to the base station as efficiently as possible by means of bi-directional communication links. In order to fulfill this requirement, it is fundamental to optimize every element in the communication chain. The channel, which is the medium where the radio wave propagation takes places, is one of the elements to be modeled. With the purpose of characterizing the radio channel in projectile applications, this thesis has been structured in five chapters: in chapter one and two, the general context of the thesis is presented, introducing the reader to this topic and giving the necessary elements to understand the rest of the manuscript. In chapter three, we address the problem of developing the necessary elements in order to characterize the propagation channel. The first contribution of this thesis is found here in the form of a set of procedures to perform channel modeling. In chapter four and five, we present our results. While chapter in chapter four a preliminary study of the channel is performed, in chapter five a complete characterization is given. The chapters ends with the presentation of the second contribution of this thesis, i.e.a channel model to be used in simulations in order to improve the projectile communication link. In a last stage, the conclusions and open questions are detailed