Download or read book Techniques d mission multi antennes pour les syst mes de radio communication duplex temporel written by Guillaume Andrieux and published by . This book was released on 2004 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: Le travail présenté consiste à développer et appliquer des techniques d'émission multi-antennes afin d'améliorer les performances sur la liaison descendante de l'UMTS-TDD. Les méthodes étudiées reposent sur la connaissance a priori des canaux de propagation. Leurs performances ont été évaluées en utilisant des canaux simulés à l'aide de modèles proposés pour l'UMTS et des canaux réels obtenus lors d'une campagne de mesures.Les méthodes de formation de voies classiques ne prenant pas en compte l'interférence inter-symboles, leurs performances sont limitées. Nous avons alors proposé une méthode originale réduisant conjointement l'interférence multi-utilisateurs et l'interférence inter-symboles. Les performances des méthodes d'émission ont ensuite été analysées dans des conditions réalistes et le gain de capacité apporté par le traitement d'antenne a également été étudié.
Download or read book Radiowave propagation and antennas for high data rate mobile communications in the 60 GHz band written by Sylvain Ranvier and published by . This book was released on 2009 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: La bande de fréquence millimétrique autour de 60 GHz est considérée comme l’une des meilleures options pour l’implémentation des réseaux sans fils à très hauts débits de type WPAN (wireless personal area network). De plus, les systèmes multi-antennes de type MIMO (multiple-input multiple-output) sont très prometteurs. Ils peuvent augmenter de manière significative l’efficacité spectrale ou la fiabilité des communications sans fil. De ce fait, l’utilisation de systèmes multi-antennes à 60 GHz est, théoriquement, très prometteuse. Bien que les performances des systèmes MIMO aient été étudiées de manière approfondie à la fois théoriquement et expérimentalement à basses fréquences (2 et 5 GHz), il y a clairement un manque d’évaluation expérimentale de ces systèmes à 60 GHz. De plus, la conception et l’évaluation d’antennes millimétriques compactes à bas coûts pour des applications de type WPAN sont des sujets sur lesquels beaucoup de recherches doivent être encore faites. Dans la première partie de la thèse, le premier sondeur de canal MIMO à 60 GHz est présenté. Ce système, construit à partir d’un sondeur existant pour 2 et 5 GHz, utilise des réseaux d’antennes virtuelles. Afin d’améliorer la résolution temporelle, deux autres systèmes de mesure ont été développés. Le premier est construit à partir d’un sondeur ultra large bande et le second à partir d’un analyseur vectoriel de réseau. Ces systèmes permettent la caractérisation totale du canal MIMO dans les domaines temporel et angulaire. Dans la seconde partie, les performances de techniques pour systèmes multi-antennes sont analysées grâce aux mesures obtenues dans la première partie de la thèse. Les trois techniques étudiées sont: MIMO, MIMO avec sélection d’antennes et dépointage de faisceau. Les résultats indiquent que la capacité du canal MIMO mesuré est relativement proche de celle d’un canal idéal. Dans des conditions réalistes, la capacité obtenue grâce à la technique MIMO avec sélection d’antennes est souvent inférieure à celle obtenue avec la technique MIMO. Par ailleurs, lorsque l’on considère un réseau à déphasage avec des pertes réalistes, il apparait que la capacité obtenue avec la technique MIMO est presque toujours supérieure à celle obtenue avec la technique du dépointage du faisceau. Dans la dernière partie de la thèse, une antenne omnidirectionnelle est présentée. Cette antenne convient parfaitement aux applications de types WPAN car elle est plane et n’utilise qu’une seule couche de métallisation, ce qui la rend facile à réaliser et peut coûteuse. De plus, un banc de mesure quasi-3D de diagrammes de rayonnement d’antennes à 60 GHz à été développé. Ce système a une très bonne répétabilité. Le rayonnement de la pointe elle-même a été mesuré et les résultats indiquent que c’est la principale limitation de la dynamique d’amplitude de ce système.
Download or read book Signal Level Relaying Strategies for Broadband MIMO ARQ Communications written by Hatim Chergui and published by . This book was released on 2015 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: Le relayage coopératif, multiple-input multiple-output (MIMO) et hybrid-ARQ sont des techniques primordiales pour améliorer le débit et la qualité des transmissions sans-fil sur les canaux large-bande. L'analyse de performance permet d'en évaluer les gains conséquents, mais également dévoile les compromis qu'elles impliquent: la diversité spatiale des relais est obtenue aux dépens de la capacité suite à la contrainte half-duplex; la déficience de rang du canal multi-antennes aux bordures de la cellule, où les relais sont généralement déployés, entrave l'activation du multiplexage spatio-temporel; la diversité temporelle du hybrid-ARQ se trouve rapidement dégradée par la nature quasi-statique et long-terme des environnements à évanouissement lent. Cette thèse essaie de surmonter ces enjeux inhérents en proposant une conception conjointe des trois techniques pour les communications sur les canaux MIMO-ARQ limités par les interférences entre symboles (IES). Dans une approche niveau-signal, nous exploitons la déficience de rang du canal source-relai--découlant de la distribution des réflecteurs et/ou du nombre d'antennes--en s'appuyant sur un relayage de type project-and-forward (PF). Le concept de projection est premièrement validé à travers l'analyse de sa performance sur un canal mixte MIMO-pinhole/Rayleigh à évanouissement plat, et ce en utilisant des fonctions mathématiques généralisées. En invoquant la théorie des résidus, nous étudions le comportement asymptotique du système, ce qui mène à des recommandations sur la conception des schémas de relayage basés sur PF. Nous appliquons ensuite le concept de projection orthogonale aux canaux MIMO à IES pour alléger la contrainte half-duplex. Ainsi, nous introduisons une architecture de multiplexage spatial coopératif à base de PF pour réduire la durée de la phase de relayage, sans toutefois recourir à la détection ou la remodulation au niveau du relais. Le modèle de communication mis en place permet d'assimiler le système de relayage à une transmission point à point MIMO, ce qui permet d'adopter les techniques de détection et de combinaison conjointes côté destination. Finalement, nous introduisons une conception inter-couches, où la projection est effectuée conjointement sur des transmissions MIMO-ARQ multiples, augmentant ainsi le gain de diversité et l'efficacité spectrale.
Download or read book Telecommunication Journal written by and published by . This book was released on 1979 with total page 676 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Space Systems as Contributors to the NATO Defence Mission written by North Atlantic Treaty Organization. Advisory Group for Aerospace Research and Development. Mission Systems Panel. Symposium and published by . This book was released on 1997 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Ultra Wide Band Antennas written by Xavier Begaud and published by John Wiley & Sons. This book was released on 2013-03-04 with total page 217 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ultra Wide Band Technology (UWB) has reached a level of maturity that allows us to offer wireless links with either high or low data rates. These wireless links are frequently associated with a location capability for which ultimate accuracy varies with the inverse of the frequency bandwidth. Using time or frequency domain waveforms, they are currently the subject of international standards facilitating their commercial implementation. Drawing up a complete state of the art, Ultra Wide Band Antennas is aimed at students, engineers and researchers and presents a summary of internationally recognized studies.
Download or read book MIMO written by Alain Sibille and published by Academic Press. This book was released on 2010-12-03 with total page 385 pages. Available in PDF, EPUB and Kindle. Book excerpt: Foreword from Arogyaswami Paulraj, Professor (Emeritus), Stanford University (USA) - The first book to show how MIMO principles can be implemented in today's mobile broadband networks and components - Explains and solves some of the practical difficulties that arise in designing and implementing MIMO systems - Both theory and implementation sections are written in the context of the most recent standards: IEEE 802.11n (WiFi); IEEE 802.16 (WIMAX); 4G networks (3GPP/3GPP2, LTE)
Download or read book Quantum Communications and Cryptography written by Alexander V. Sergienko and published by CRC Press. This book was released on 2018-10-03 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Pervasive Mobile and Ambient Wireless Communications written by Roberto Verdone and published by Springer Science & Business Media. This book was released on 2012-01-02 with total page 696 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reporting the findings of COST 2100, a major European intergovernmental project, this volume offers system designers a good source of guidelines based on channel characterization and measurement-based modeling, as well as worthwhile ideas for future research.
Download or read book Routledge International Handbook of Ignorance Studies written by Matthias Gross and published by Routledge. This book was released on 2015-05-15 with total page 427 pages. Available in PDF, EPUB and Kindle. Book excerpt: Once treated as the absence of knowledge, ignorance today has become a highly influential topic in its own right, commanding growing attention across the natural and social sciences where a wide range of scholars have begun to explore the social life and political issues involved in the distribution and strategic use of not knowing. The field is growing fast and this handbook reflects this interdisciplinary field of study by drawing contributions from economics, sociology, history, philosophy, cultural studies, anthropology, feminist studies, and related fields in order to serve as a seminal guide to the political, legal and social uses of ignorance in social and political life. Chapter 33 of this book is freely available as a downloadable Open Access PDF under a Creative Commons Attribution-Non Commercial-No Derivatives 4.0 license available here: https://tandfbis.s3-us-west-2.amazonaws.com/rt-files/docs/Open+Access+Chapters/9780415718967_oachapter33.pdf
Download or read book Outside Innovation written by Patricia B. Seybold and published by Harper Collins. This book was released on 2009-10-06 with total page 430 pages. Available in PDF, EPUB and Kindle. Book excerpt: How dynamic businesses of every size can unleash innovation by inviting customers to co–design what they do and make. Reading line: The 8 Roles Customers Play in Trend–Setting Companies The refrain is familiar for Patricia Seybold in her journeys as a top technology and management strategist: "I want our company to be acknowledged as the most admired and most customer–valued in our industry and to be recognized as the company that has forever changed the way things are done." "How can we become the Google of banking?" "How can we be the eBay of software?" "I want to be the JetBlue of manufacturing." "How can we become the undisputed trend–setter in our industry–with a competitive bar no one can topple?" In Outside Innovation, bestselling author Seybold taps her close relationship with dozens of high–innovation companies to reveal the untold strategy behind the trendsetters and the next HUGE leap forward in customer strategy. Seybold shows that companies that are dominating their category and staying ahead of the pack are collaborating at every level of their business with their customers.
Download or read book Building Wireless Community Networks written by Rob Flickenger and published by "O'Reilly Media, Inc.". This book was released on 2003 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: Building Wireless Community Networks is about getting people online using wireless network technology. The 802.11b standard (also known as WiFi) makes it possible to network towns, schools, neighborhoods, small business, and almost any kind of organization. All that's required is a willingness to cooperate and share resources. The first edition of this book helped thousands of people engage in community networking activities. At the time, it was impossible to predict how quickly and thoroughly WiFi would penetrate the marketplace. Today, with WiFi-enabled computers almost as common as Ethernet, it makes even more sense to take the next step and network your community using nothing but freely available radio spectrum. This book has showed many people how to make their network available, even from the park bench, how to extend high-speed Internet access into the many areas not served by DSL and cable providers, and how to build working communities and a shared though intangible network. All that's required to create an access point for high-speed Internet connection is a gateway or base station. Once that is set up, any computer with a wireless card can log onto the network and share its resources. Rob Flickenger built such a network in northern California, and continues to participate in network-building efforts. His nuts-and-bolts guide covers: Selecting the appropriate equipment Finding antenna sites, and building and installing antennas Protecting your network from inappropriate access New network monitoring tools and techniques (new) Regulations affecting wireless deployment (new) IP network administration, including DNS and IP Tunneling (new) His expertise, as well as his sense of humor and enthusiasm for the topic, makes Building Wireless Community Networks a very useful and readable book for anyone interested in wireless connectivity.
Download or read book Biological Effects of Radiofrequency Radiation written by Joe Allen Elder and published by . This book was released on 1984 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Governance Regulation and Powers on the Internet written by Eric Brousseau and published by Cambridge University Press. This book was released on 2012-04-23 with total page 463 pages. Available in PDF, EPUB and Kindle. Book excerpt: An interdisciplinary survey of the issues surrounding the governance of the Internet.
Download or read book Decisions of the Commissioner of Patents written by and published by . This book was released on 1871 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Engineering Acoustics written by Michael Möser and published by Springer Science & Business Media. This book was released on 2009-09-01 with total page 540 pages. Available in PDF, EPUB and Kindle. Book excerpt: Suitable for both individual and group learning, Engineering Acoustics focuses on basic concepts and methods to make our environments quieter, both in buildings and in the open air. The author’s tutorial style derives from the conviction that understanding is enhanced when the necessity behind the particular teaching approach is made clear. He also combines mathematical derivations and formulas with extensive explanations and examples to deepen comprehension. Fundamental chapters on the physics and perception of sound precede those on noise reduction (elastic isolation) methods. The last chapter deals with microphones and loudspeakers. Moeser includes major discoveries by Lothar Cremer, including the optimum impedance for mufflers and the coincidence effect behind structural acoustic transmission. The appendix gives a short introduction on the use of complex amplitudes in acoustics.
Download or read book Wireless Hacks written by Rob Flickenger and published by "O'Reilly Media, Inc.". This book was released on 2003 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt: Continuing with the successful Hack Series, this title provides real-world working examples of how to make useful things happen with wireless equipment.
