10 research outputs found
Ătude de stratĂ©gies de diagnostic embarquĂ© des rĂ©seaux filaires complexes
Cette Ă©tude sâinscrit dans le cadre du diagnostic embarquĂ© des rĂ©seaux filaires complexes. Elle vise Ă dĂ©tecter et localiser les dĂ©fauts Ă©lectriques avec prĂ©cision. En effet, lâintĂ©gration du diagnostic par rĂ©flectomĂ©trie dans un systĂšme embarquĂ© fait apparaĂźtre des problĂšmes dâinterfĂ©rence qui sâaggravent dans le cas dâun rĂ©seau complexe oĂč plusieurs rĂ©flectomĂštres sont placĂ©s en diffĂ©rents points du rĂ©seau. Lâobjectif est de dĂ©velopper de nouvelles stratĂ©gies de diagnostic embarquĂ© des rĂ©seaux filaires complexes pour rĂ©soudre les problĂšmes dâinterfĂ©rence dâune part et lâambiguĂŻtĂ© de localisation du dĂ©faut dâautre part. La premiĂšre contribution concerne le dĂ©veloppement dâune nouvelle mĂ©thode de rĂ©flectomĂ©trie baptisĂ©e OMTDR (Orthogonal Multi-tone Time Domain Reflectometry). Elle utilise des signaux numĂ©riques modulĂ©s et orthogonaux pour Ă©liminer les interfĂ©rences. Pour davantage de couverture, la deuxiĂšme contribution propose dâintĂ©grer la communication entre les rĂ©flectomĂštres. Elle vise Ă fusionner les donnĂ©es afin de faciliter la prise de dĂ©cision. La troisiĂšme contribution adresse la problĂ©matique de la stratĂ©gie de diagnostic, câest-Ă -dire, de lâoptimisation des performances du diagnostic dâun rĂ©seau complexe sous contraintes opĂ©rationnelles dâutilisation. Lâutilisation des RĂ©seaux BayĂ©siens permet dâĂ©tudier lâimpact des diffĂ©rents facteurs et dâobtenir une estimation de la confiance et donc, de la fiabilitĂ© du rĂ©sultat du diagnostic. ABSTRACT : This study addresses embedded diagnosis of complex wired networks. Based on the reflectometry method, it aims at detecting and locating accurately electrical faults. Increasing demand for on-line diagnosis has imposed serious challenges on interference mitigation. It aims at making diagnosis while the target system is running. The interference becomes more critical in the case of complex networks where several reflectometers are injecting their test signals simultaneously. The objective is to develop new embedded diagnosis strategies in complex wired networks that would resolve interference problems and eliminate ambiguity related to the fault location. The first contribution is the development of a new method called OMTDR (Orthogonal Multi-tone Time Domain Reflectometry). It uses orthogonal modulated digital signals for interference mitigation and thereby on-line diagnosis. For better coverage of the network, the second contribution proposes to integrate communication between reflectometers. It uses sensors data fusion to facilitate decision making. The third contribution addresses the problem of the diagnosis strategy, i.e. the optimization of diagnosis performance of a complex network under operational constraints. The use of Bayesian Networks allows us to study the impact of different factors and estimate the confidence level and thereby the reliability of the diagnosis results
Applications of graph-based codes in networks: analysis of capacity and design of improved algorithms
The conception of turbo codes by Berrou et al. has created a renewed interest in modern graph-based codes. Several encouraging results that have come to light since then have fortified the role these codes shall play as potential solutions for present and future communication problems.
This work focuses on both practical and theoretical aspects of graph-based codes. The
thesis can be broadly categorized into three parts. The first part of the thesis focuses on
the design of practical graph-based codes of short lengths. While both low-density parity-check
codes and rateless codes have been shown to be asymptotically optimal under the message-passing (MP) decoder, the performance of short-length codes from these families under MP decoding is starkly sub-optimal. This work first addresses the
structural characterization of stopping sets to understand this sub-optimality. Using this
characterization, a novel improved decoder that offers several orders of magnitude improvement in bit-error rates is introduced. Next, a novel scheme for the design of a good rate-compatible family of punctured codes is proposed.
The second part of the thesis aims at establishing these codes as a good tool to develop
reliable, energy-efficient and low-latency data dissemination schemes in networks. The problems of broadcasting in wireless multihop networks and that of unicast in delay-tolerant networks are investigated. In both cases, rateless coding is seen to offer an elegant means of achieving the goals of the chosen communication protocols. It was noticed that the ratelessness and the randomness in encoding process make this scheme
specifically suited to such network applications.
The final part of the thesis investigates an application of a specific class of codes called
network codes to finite-buffer wired networks. This part of the work aims at establishing a framework for the theoretical study and understanding of finite-buffer networks. The
proposed Markov chain-based method extends existing results to develop an iterative
Markov chain-based technique for general acyclic wired networks. The framework not only estimates the capacity of such networks, but also provides a means to monitor network traffic and packet drop rates on various links of the network.Ph.D.Committee Chair: Fekri, Faramarz; Committee Member: Li, Ye; Committee Member: McLaughlin, Steven; Committee Member: Sivakumar, Raghupathy; Committee Member: Tetali, Prasa
Management, Technology and Learning for Individuals, Organisations and Society in Turbulent Environments
This book presents the collection of fifty papers which were presented in the Second International Conference on BUSINESS SUSTAINABILITY 2011 - Management, Technology and Learning for Individuals, Organisations and Society in Turbulent Environments , held in PĂłvoa de Varzim, Portugal, from 22ndto 24thof June, 2011.The main motive of the meeting was growing awareness of the importance of the sustainability issue. This importance had emerged from the growing uncertainty of the market behaviour that leads to the characterization of the market, i.e.
environment, as turbulent. Actually, the characterization of the environment as uncertain and turbulent reflects the fact that the traditional technocratic and/or socio-technical approaches cannot effectively and efficiently lead with the present situation. In other words, the rise of the sustainability issue means the quest for new instruments to deal with uncertainty and/or turbulence.
The sustainability issue has a complex nature and solutions are sought in a wide range of domains and instruments to achieve and manage it. The domains range from environmental sustainability (referring to natural environment) through organisational and business sustainability towards social sustainability. Concerning the instruments for sustainability, they range from traditional engineering and management methodologies towards âsoftâ instruments such as knowledge, learning, and creativity. The papers in this book address virtually whole sustainability problems space in a greater or lesser extent. However, although the uncertainty and/or turbulence, or in other words the dynamic properties, come from coupling of management, technology, learning, individuals, organisations and society, meaning that everything is at the same time effect and cause, we wanted to put the emphasis on business with the intention to address primarily companies and their businesses.
Due to this reason, the main title of the book is âBusiness Sustainability 2.0â but with the approach of coupling Management, Technology and Learning for individuals, organisations and society in Turbulent Environments. Also, the notationâ2.0â is to promote the publication as a step further from our previous publication â âBusiness Sustainability Iâ â as would be for a new version of software.
Concerning the Second International Conference on BUSINESS SUSTAINABILITY, its particularity was that it had served primarily as a learning environment in which the papers published in this book were the ground for further individual and collective growth in understanding and perception of sustainability and capacity for building new instruments for business sustainability.
In that respect, the methodology of the conference work was basically dialogical, meaning promoting dialog on the papers, but also including formal paper presentations. In this way, the conference presented a rich space for satisfying different authorsâ and participantsâ needs.
Additionally, promoting the widest and global learning environment and participation, in accordance with the Conference's assumed mission to promote Proactive Generative Collaborative Learning, the Conference Organisation shares/puts open to the community the papers presented in this book, as well as the papers presented on the previous Conference(s). These papers can be accessed from the conference webpage (http://labve.dps.uminho.pt/bs11).
In these terms, this book could also be understood as a complementary instrument to the Conference authorsâ and participantsâ, but also to the wider readershipsâ interested in the sustainability issues.
The book brought together 107 authors from 11 countries, namely from Australia, Belgium, Brazil, Canada, France, Germany, Italy, Portugal, Serbia, Switzerland, and United States of America. The authors ârangedâ from senior and renowned scientists to young researchers providing a rich and learning environment.
At the end, the editors hope, and would like, that this book to be useful, meeting the expectation of the authors and wider readership and serving for enhancing the individual and collective learning, and to incentive further scientific development and creation of new papers.
Also, the editors would use this opportunity to announce the intention to continue with new editions of the conference and subsequent editions of accompanying books on the subject of BUSINESS SUSTAINABILITY, the third of which is planned for year 2013.info:eu-repo/semantics/publishedVersio