Etude de l'optimisation d'un systeme DMT-ADSL. Application a la transmission video MPEG-2 en mode hierarchique PDF Download
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Author: Marie Zwingelstein
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Category :
Languages : fr
Pages : 0
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Author: Marie Zwingelstein
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Category :
Languages : fr
Pages : 0
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Author: Marie Colin
Publisher:
ISBN:
Category :
Languages : fr
Pages : 256
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Le travail présenté dans cette thèse se rapporte au système de transmission numérique ADSL (asymétrique digital suscrite line), dont le principe est d'exploiter les lignes téléphoniques d'abonnés existantes en paire torsadée cuivrée pour assurer une transmission de données à un débit de plusieurs mégabits par seconde. Un des éléments clés de l’ADSL est d'utiliser la modulation multi porteuse DMT (discrète multizone) qui permet d'adapter facilement le signal émis au canal de transmission par le biais du choix des répartitions fréquentielles du débit et de la puissance. Après avoir rappelé comment ces répartitions influencent le TEB (taux d'erreur par bit) atteint, nous développons dans une première partie deux méthodes originales qui optimisent ces répartitions, avec des compromis performance/complexité différents. Pour les deux méthodes, nous proposons un calcul simple de la répartition fréquentielle du débit, optimal au sens de la capacité du canal. En ce qui concerne la puissance, la première méthode, optimale, détermine la répartition qui minimise le TEB, et la seconde, plus simple, celle qui satisfait à l'hypothèse habituelle et légèrement sous-optimale d'un TES (taux d'erreur par symbole) identique sur toutes les fréquences. Les résultats de simulation sur un ensemble de lignes CSA caractéristiques ont montré que les deux méthodes proposées aboutissent à des performances plus élevées que les méthodes courantes, en particulier les méthodes de Hughes-Hartogs et de Peter Chow, avec une complexité de calcul généralement inférieure. Dans la deuxième partie du travail, nous nous intéressons à l'application d'une transmission de données vidéo, codées suivant la norme internationale MPEG-2, sur ADSL. L'originalité repose sur le choix d'un mode de codage et de transmission bi-résolution qui privilégie les données vidéo les plus importantes au détriment des autres données, dans le but d'améliorer la qualité de service. Dans ce cadre, nous avons proposé trois architectures ADSL bi-résolution, agissant soit au niveau de la modulation DMT, soit au niveau du codage FEC (foirard errer correction), en attribuant des codes Reed-Solomon différents aux données importantes et moins importantes. Les résultats ont démontré la validité de tels schémas, avec, compte tenu d'une proportion voisine de 30% pour les données importantes, une réduction du TEB des données importantes d'un facteur 100 par rapport au TEB mono-résolution, alors que le teb des données moins importantes n'est augmente que d'environ un facteur 2.
Author: William Shieh
Publisher: Academic Press
ISBN: 0080952062
Category : Technology & Engineering
Languages : en
Pages : 457
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- The first book on optical OFDM by the leading pioneers in the field - The only book to cover error correction codes for optical OFDM - Gives applications of OFDM to free-space communications, optical access networks, and metro and log haul transports show optical OFDM can be implemented - Contains introductions to signal processing for optical engineers and optical communication fundamentals for wireless engineers This book gives a coherent and comprehensive introduction to the fundamentals of OFDM signal processing, with a distinctive focus on its broad range of applications. It evaluates the architecture, design and performance of a number of OFDM variations, discusses coded OFDM, and gives a detailed study of error correction codes for access networks, 100 Gb/s Ethernet and future optical networks. The emerging applications of optical OFDM, including single-mode fiber transmission, multimode fiber transmission, free space optical systems, and optical access networks are examined, with particular attention paid to passive optical networks, radio-over-fiber, WiMAX and UWB communications. Written by two of the leading contributors to the field, this book will be a unique reference for optical communications engineers and scientists. Students, technical managers and telecom executives seeking to understand this new technology for future-generation optical networks will find the book invaluable. William Shieh is an associate professor and reader in the electrical and electronic engineering department, The University of Melbourne, Australia. He received his M.S. degree in electrical engineering and Ph.D. degree in physics both from University of Southern California. Ivan Djordjevic is an Assistant Professor of Electrical and Computer Engineering at the University of Arizona, Tucson, where he directs the Optical Communications Systems Laboratory (OCSL). His current research interests include optical networks, error control coding, constrained coding, coded modulation, turbo equalization, OFDM applications, and quantum error correction. "This wonderful book is the first one to address the rapidly emerging optical OFDM field. Written by two leading researchers in the field, the book is structured to comprehensively cover any optical OFDM aspect one could possibly think of, from the most fundamental to the most specialized. The book adopts a coherent line of presentation, while striking a thoughtful balance between the various topics, gradually developing the optical-physics and communication-theoretic concepts required for deep comprehension of the topic, eventually treating the multiple optical OFDM methods, variations and applications. In my view this book will remain relevant for many years to come, and will be increasingly accessed by graduate students, accomplished researchers as well as telecommunication engineers and managers keen to attain a perspective on the emerging role of OFDM in the evolution of photonic networks." -- Prof. Moshe Nazarathy, EE Dept., Technion, Israel Institute of Technology - The first book on optical OFDM by the leading pioneers in the field - The only book to cover error correction codes for optical OFDM - Applications of OFDM to free-space communications, optical access networks, and metro and log haul transports show optical OFDM can be implemented - An introduction to signal processing for optical communications - An introduction to optical communication fundamentals for the wireless engineer
Author: Alexander V. Sergienko
Publisher: CRC Press
ISBN: 1420026607
Category : Science
Languages : en
Pages : 248
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Book Description
All current methods of secure communication such as public-key cryptography can eventually be broken by faster computing. At the interface of physics and computer science lies a powerful solution for secure communications: quantum cryptography. Because eavesdropping changes the physical nature of the information, users in a quantum exchange can easily detect eavesdroppers. This allows for totally secure random key distribution, a central requirement for use of the one-time pad. Since the one-time pad is theoretically proven to be undecipherable, quantum cryptography is the key to perfect secrecy. Quantum Communications and Cryptography is the first comprehensive review of the past, present, and potential developments in this dynamic field. Leading expert contributors from around the world discuss the scientific foundations, experimental and theoretical developments, and cutting-edge technical and engineering advances in quantum communications and cryptography. The book describes the engineering principles and practical implementations in a real-world metropolitan network as well as physical principles and experimental results of such technologies as entanglement swapping and quantum teleportation. It also offers the first detailed treatment of quantum information processing with continuous variables. Technologies include both free-space and fiber-based communications systems along with the necessary protocols and information processing approaches. Bridging the gap between physics and engineering, Quantum Communications and Cryptography supplies a springboard for further developments and breakthroughs in this rapidly growing area.
Author:
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Category : Armor
Languages : en
Pages : 482
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Category : DDR
Languages : en
Pages : 214
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Author: Mustafa Ergen
Publisher: Springer Science & Business Media
ISBN: 0387681922
Category : Technology & Engineering
Languages : en
Pages : 518
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This book addresses the emerging technology for Orthogonal Frequency Division Multiple Access (OFDMA), covering OFDMA physical layer as well as network technology. The book also includes information on IEEE 802.16e and WiMAX networks and also offers a comparison with other OFDMA technologies. OFDMA is the fastest growing area in the wireless marketplace, and the backbone of systems used in WiMAX. WiMAX is the technology that enables wireless users to communicate at any time from any location without having to find a WiFi hotspot.
Author: Ivan Kaminow
Publisher: Elsevier
ISBN: 0080513182
Category : Science
Languages : en
Pages : 898
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Book Description
Volume IVA is devoted to progress in optical component research and development. Topics include design of optical fiber for a variety of applications, plus new materials for fiber amplifiers, modulators, optical switches, light wave devices, lasers, and high bit-rate electronics. This volume is an excellent companion to Optical Fiber Telecommunications IVB: Systems and Impairments (March 2002, ISBN: 0-12-3951739).- Fourth in a respected and comprehensive series- Authoritative authors from a range of organizations- Suitable for active lightwave R&D designers, developers, purchasers, operators, students, and analysts- Lightwave components reviewed in Volume A-Lightwave systems and impairments reviewed in Volume B- Up-to-the minute coverage
Author: David R. Collie
Publisher:
ISBN:
Category : Investments
Languages : en
Pages : 54
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Author: Wolfgang Hoeg
Publisher: John Wiley & Sons
ISBN: 0470871423
Category : Technology & Engineering
Languages : en
Pages : 362
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Now the standardisation work of DAB (Digital Audio Broadcasting)system is finished many broadcast organisations, network providersand receiver manufacturers in European countries and outside ofEurope (for example Canada and the Far East) will be installing DABbroadcast services as pilot projects or public services. Inaddition some value added services (data and video services) areunder development or have already started as pilot projects. The new digital broadcast system DAB distinguishes itself fromexisting conventional broadcast systems, and the various newinternational standards and related documents (from ITU-R, ISO/IEC,ETSI, EBU, EUREKA147, and others) are not readily available and aredifficult to read for users. Therefore it is essential that a wellstructured technical handbook should be available. The Second Edition of Digital Audio Broadcasting has beenfully updated with new sections and chapters added to reflect allthe latest developments and advances. Digital Audio Broadcasting: Provides a fully updated comprehensive overview of DAB Covers international standards, applications and othertechnical issues Combines the expertise of leading researchers in the field ofDAB Now covers such new areas as: IP-Tunneling via DAB; ElectronicProgramme Guide for DAB; and Metadata A comprehensive overview of DAB specifically written forplanning and system engineers, developers for professional anddomestic equipment manufacturers, service providers, as well aspostgraduate students and lecturers in communicationstechnology.
