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Dissertations / Theses on the topic 'Multibas'
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1
Larsson, Frida, and Matilda Svensson. "Multibas i matematikundervisningen : En empirisk undersökning ur ett elevperspektiv om det laborativa materialet multibas i matematikundervisningen." Thesis, Linnéuniversitetet, Institutionen för matematik (MA), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-64969.
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Syftet med denna studie är att undersöka på vilka grunder elever använder det laborativa materialet multibas i matematikundervisningen. Studien fokuserar på området positionssystemet och analyserar vilka tänkbara orsaker det finns till att eleverna väljer att använda eller inte använda multibas. Studien bygger på en tidigare systematisk litteraturstudie med fokus på laborativt material. John Deweys inriktning i pragmatismen är utgångspunkten för denna studies analys. Studien har en kvalitativ metod med intervjuer och observationer av 19 elever i årskurs 3 på en skola i Sverige. Resultatet visade att multibas endast används av vissa elever och att många elever saknar förståelse kring användandet av materialet och dess syfte. Detta har i sin tur bidragit till att elevernas egna uppfattningar om materialet blivit negativa. Resultatet stämde överens med författarnas tidigare studie som visade att laborativt material bör användas i undervisningen men kräver att användaren har kunskapar om materialet för att det ska främja elevens lärande.
2
Yngvesson, Johanna, and Josefine Jönsson. "Matematik ska engagera : Kommunikation i laboration." Thesis, Växjö University, School of Mathematics and Systems Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:vxu:diva-5488.
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Sandoval, Gomez Maria Del Rosario. "Conception et réalisation du système de gestion de multibases de données MUSE : architecture de schéma multibase et gestion du catalogue des données." Paris 6, 1989. http://www.theses.fr/1989PA066657.
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Durant ces dernieres annees, une nouvelle demarche a ete proposee pour faire face aux problemes poses par l'integration de bases de donnees existantes. C'est la demarche consistant a faire cooperer plusieurs bases sans obligation d'avoir un schema conceptuel global. Elle est connue sous le nom de multibases de donnees. Le systeme que nous presentons, muse, est base sur cette nouvelle demarche. Des questions relatives a l'autonomie des sites et a l'architecture du systeme sont discutees. Dans muse, une multibase se presente comme une collection de base de donnees autonomes et des schemas exportes/importes. Ces schemas sont stockes dans des catalogues d'exportation/importation. Les utilisateurs manipulent les donnees et adressent leurs requetes par moyen du langage d-sql
4
Cheuk, Kin-Wai. "Island multicast : the combination of IP-multicast with application-level multicast /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?COMP%202004%20CHEUK.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 34-37). Also available in electronic version. Access restricted to campus users.
5
Boissière, Guillaume 1974. "Personalized multicast." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/61100.
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Zeroual, Abdelmalek. "SESAME, un système multibase pour les stations de travail." [Le Chesnay] : [Institut national de recherche en informatique et en automatique], 1988. http://catalogue.bnf.fr/ark:/12148/cb349559811.
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Zeroual, Abdelmalek. "Sesame : un système multibase pour les stations de travail." Paris 11, 1988. http://www.theses.fr/1988PA112197.
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Cette thèse présente l'architecture générale du système multibase appelé SESAME conçu pour des stations de travail reliées au travers d'un réseau local. Cette architecture est orientée vers l'implémentation du système en tant qu'interface de composantes opérationnelles courantes. Sur le plan matériel, celle-ci concerne les stations de travail les plus répandues (IBM PC/AT, PS et SUN), les réseaux locaux (Ethernet) et les réseaux publics (Transpac). Sur la plan logiciel, SESAME est basé sur un SGBD relationnel classique et interface plusieurs SGBD relationnels (XDB, SYBASE, ORACLE, INGRES etc. . . ). Il utilise un langage multibase appelé MSQL. Ce langage est une extension du standard SQL adaptée à l'environnement multibase. Au niveau langage, nous avons proposé un nouveau type de requêtes que nous avons appelées requêtes interbases. Une requête interbase permet l'interaction entre deux ensembles de bases de données. Elle permet la mise à jour du premier ensemble, appelé cible, à partir du second, appelé source. Plusieurs opérations sont effectuées sur la source et sur la cible ce qui offre aux utilisateurs un outil de manipulation interbase facilitant la décentralisation des bases volumineuses et/ou l'enrichissement des bases personnelles à partir des bases publiques. Ce concept a d'abord été implémenté sur le prototype multibase MRDSM. Pour implémenter SESAME sur des stations de travail reliées par Ethernet, nous avons proposé des fonctions d'administration et de traitement des données multibases. Ces fonctions résolvent les problèmes de nommage de collections de bases de données, de structure de catalogue et de décomposition de requêtes. Dans cette architecture chaque machine préserve son autonomie locale mais nécessite la présence de la couche SESAME pour la coopération multibase.
8
Persson, Erold. "Multicast Time Distribution." Thesis, Linköping University, Department of Electrical Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2274.
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The Swedish National Testing and Research Institute is maintaining the Swedish realization of the world time scale UTC, called UTC(SP). One area of research and development for The Swedish National Laboratory of Time and Frequency is time synchronization and how UTC(SP) can be distributed in Sweden. Dissemination of time information by SP is in Sweden mainly performed via Internet using the Network Time Protocol (NTP) as well as via a modem dial up service and a speaking clock (Fröken Ur). In addition to these services, time information from the Global Positioning System (GPS) and from the long-wave transmitter DCF77 in Germany, is also available in Sweden.
This master’s thesis considers how different available commercial communication systems could be used for multicast time distribution. DECT, Bluetooth, Mobile Telecommunication and Radio Broadcasting are different techniques that are investigated. One application of Radio Broadcasting, DARC, was found to be interesting for a more detailed study. A theoretical description of how DARC could be used for national time distribution is accomplished and a practical implementation of a test system is developed to evaluate the possibilities to use DARC for multicast time distribution.
The tests of DARC and the radio broadcast system showed that these could be interesting techniques to distribute time with an accuracy of a couple of milliseconds. This quality level is not obtained today but would be possible with some alterations of the system.
9
Yiu, Wai-Pun. "Secure overlay multicast /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?COMP%202004%20YIU.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 71-77). Also available in electronic version. Access restricted to campus users.
10
Marques, Anselmo Miguel Magalhães. "Frustrated multiband superconductors." Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/12174.
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Mestrado em FísicaMotivada pela recente descoberta de supercondutores baseados em ferro, com altas temperaturas críticas e possibilidade de coexistência de múltiplas bandas no nível de Fermi, esta dissertação pretende estudar as condições sob as quais se podem manifestar configurações frustradas nas fases supercondutoras, em função das variáveis temperatura e campo magnético externo aplicado. A Acão reciproca entre as interações atrativas/repulsivas interbandas e intrabandas e analisada, sendo apresentado o diagrama de fases de campo magnético vs. temperatura para um regime de acoplamento entre bandas fraco.
Motivated by the recent discovery of iron-based superconductors, having high critical temperatures and multiple bands crossing the Fermi level, this dissertation aims to study the conditions under which frustrated con gurations in the superconducting phases can be present, as a function of the variables temperature and externally applied magnetic eld. The interplay between interband and intraband attractive/ repulsive interactions is analysed, with the magnetic eld vs. temperature phase diagram being presented for the weakly interband coupling regime.
11
Cai, Qingbo. "Layered Multicast Scheduling." Case Western Reserve University School of Graduate Studies / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=case1205436479.
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羅征桂 and Ching-quei Lo. "Study of multibay and multistorey infilled frames." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1988. http://hub.hku.hk/bib/B31231640.
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Lo, Ching-quei. "Study of multibay and multistorey infilled frames /." [Hong Kong] : University of Hong Kong, 1988. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12428620.
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ANAND, KUMAR. "A SCALABLE EXPLICIT MULTICAST PROTOCOL FOR MOBILE AD HOC NETWORKS." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1099354888.
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Schier, Thomas. "IP-Multicast im Campusnetz." Universitätsbibliothek Chemnitz, 2000. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200000359.
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Gemeinsamer Workshop von Universitaetsrechenzentrum und
Professur Rechnernetze und verteilte Systeme (Fakultaet fuer
Informatik) der TU Chemnitz.
Workshop-Thema: Infrastruktur der ¨Digitalen Universitaet¨
Der Vortrag gibt einen Überblick über den aktuellen Stand (April 2000)
von IP-Multicast im Campusnetz und die MBONE-Anbindung der TU Chemnitz.
16
Shrinivas, V. Prasanna. "Pricing Multicast Network Services." Thesis, Indian Institute of Science, 2001. http://hdl.handle.net/2005/270.
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Multicast has long been considered an attractive service for the Internet for the provision of multiparty applications. For over a decade now multicast has been a proposed IETF standard. Though there is a strong industry push towards deploying multicast, there has been little multicast deployment by commercial Internet Service Providers (ISPs) and more importantly most end-users still lack multicast capabilities. Depending on the underlying network infrastructure, the ISP has several options of implementing his multicast capabilities. With significantly faster and more sophisticated protocols being designed and prototyped, it is expected that a whole new gamut of applications that are delay sensitive will come into being. However, the incentives to resolve the conflicting interests of the ISPs and the end-users have to be provided for successful implementation of these protocols. Thus we arrive at the following economic questions: What is the strategy that will enable the ISP recover his costs ? How can the end-user be made aware of the cost of his actions ? Naturally, the strategies of the ISP and the end-user depend on each other and form an economic game. The research problems addressed in this thesis are:
A pricing model that is independent of the underlying transmission protocols is prefered. We have proposed such a pricing scheme for multicast independent of the underlying protocols, by introducing the concept of pricing points* These pricing points provide a range of prices that the users can expect during a particular time period and tune their usage accordingly. Our pricing scheme makes both the sender and receiver accountable. Our scheme also provides for catering to heterogeneous users and gives incentive for differential pricing.
We explore a number of formulations of resource allocation problems arising in communication networks as optimization models. Optimization-based methods were only employed for unicast congestion control. We have extended this method for single rate multicast. We have also devised an optimization-based approach for multicast congestion control that finds an allocation rate to maximize the social welfare. Finally we also show that the session-splitting problem can also be cast as an optimization problem.
The commonly used "max-min" fairness criteria suffers from serious limitations like discriminating sessions that traverse large number of links and poor network utilization. We provide an allocation scheme that reduces discrimination towards multicast sessions that traverse many links and also improves network utilization.
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Onal, Kerem. "Internet Multicast Congestion Control." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12604726/index.pdf.
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Congestion control is among the fundamental problems of Internet multicast. It is an active research area with many challenges. In this study, an introduction to Internet congestion control and a brief literature survey of current multicast congestion control protocols is presented. Then two recently proposed &ldquosingle-rate, end-to-end, rate based&rdquo
class of protocols, namely LESBCC and TFMCC are evaluated with respect to their intersession fairness (TCP-friendliness), smoothness and responsiveness criteria. Throughout the experiments, which are conducted using a widely accepted network simulation tool &lsquo
ns&rsquo
, different topologies have been employed.
18
Roumani, Ali Mohamad. "QoS-based multicast routing." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0034/MQ52943.pdf.
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Kullberg, Elis, and Hannes Junnila. "IPv6 multicast home proxy." Thesis, KTH, Kommunikationssystem, CoS, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-91104.
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The Internet is becoming increasingly fragmented, leading to a more heterogeneous end-user experience depending on the user's network location (i.e., point of attachment to the network). This is a consequence of several ongoing changes of the Internet. Different regions of the world are in different phases of their rollout of IPv6, making intercommunication increasingly challenging. Copyright legislation has caught up with ICT technology, but differences in licensing agreements may very from nation to nation which often hinders content being accessed beyond borders. Finally, several high-profile government attempts have been made to enforce stringent censorship of data. Therefore, we believe that a demand exists for simple consumer-oriented technologies for proxying and tunneling data between separate regions of the Internet. Furthermore, we believe that this demand will increase dramatically during the coming years. A key success factor for this next generation of proxies will be the ability to handle multicast IPv6 packets, as these packets represent the most probable distribution method for IPTV in the future. This thesis examines the challenges presented by IPv6 multicast-routing in the context of constructing a proxy. It also presents a best-practice solution to the problem of designing, implementing, and utilizing such a proxy. The thesis also contains a review of current IPv6 multicast routing technology. Several implementations are benchmarked against each other, with the goal of building a prototype for a consumer-oriented IPv6 multicast proxy. The prototype is presented and was tested. These tests demonstrate the functionality of the prototype proxy and reveal areas where the prototype could be improved. Finally a possible capitalization strategy is suggested.Internet utvecklas mot att bli mer fragmenterat. Detta leder till en heterogen användarupplevelse beroende på uppkopplingspunkt. Utvecklingen är en konsekvens av flera pågående trender. Världens olika regioner ligger i ofas i utbyggnaden av IPv6 vilket medför nya tekniska utmaningar. Samtidigt har upphovsrättslagstiftningen hunnit ikapp teknikutvecklingen, så att länder med olika licensieringsmodeller inte kan dela innehåll. Slutligen försöker flera länder aktivt censurera datatrafik. Som konsekvens av detta ökar behovet för enkla konsumentorienterade metoder för att knyta ihop olika delar av Internet, så att åtkomst till data garanteras oavsett uppkopplingspunkt. Därmed förutspår vi att efterfrågan på produkter baserade på sofistikerad tunnelteknik kommer öka under de kommande åren. Denna rapport undersöker de utmaningar IPv6 multicast routing medför i samband med byggandet av en IPv6 multicast proxy. Rapporten presenterar en grundlig teoretisk genomgång av tekniken bakom IPv6 multicast routing. Vidare föreslås ett optimalt tillvägagångssätt för att designa, bygga och använda en sådan proxy. Flera existerande tekniker för multicast forwarding utvärderas och jämförs. Utifrån utvärderingen byggdes tre implementeringar av en IPv6 multicast proxy. Därefter analyseras dessa, tillsammans med förslag för fortsatta studier. Slutligen presenteras en möjlig kapitaliseringsstrategi för tekniken.
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Moulierac, Joanna Rubino Gerardo. "Agrégation des communications multicast." [S.l.] : [s.n.], 2006. ftp://ftp.irisa.fr/techreports/theses/2006/moulierac.pdf.
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Blaschke, Volker. "Multiband Cognitive Radio-Systeme." [S.l. : s.n.], 2008. http://digbib.ubka.uni-karlsruhe.de/volltexte/1000009926.
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Jawhar, Shadi. "Multicast over optical networks." Rennes 1, 2011. http://www.theses.fr/2011REN1S051.
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Optical networks had been an important area of improvement in terms of its deployment as a core of the backbone of the international communication network. Fiber optics show a big evolution in terms of link capacity and speed compared to any other type of cables. Moreover, multicasting over IP networks had matured in the past years and this was because of the reduction in traffic which resulted when multiple clients requested to receive the same information from the same source. To support multicasting in optical networks, optical nodes have to branch one incoming light wave to more than one output port. Optical nodes must be equipped with light splitters that split one light wave to more than one output. Due to its complex design, a light splitter is very expensive equipment, thus, equipping all optical nodes with splitters will increase the cost of the optical network setup. This leads to a consensus that not all optical nodes on the network will possess this splitting capability. This document is divided into three main parts. In the first part, a brief description of multicast routing and optical networks is given respectively. Then an introduction of multicasting over optical networks is given. The main issue is that not all nodes in the network are multicast capable. The second part provides propositions to resolve network design faces of this main issue. This part studies the optimal density, placement and capabilities of those splitters in the network. Each of these propositions is simulated to evaluate its performance and criticize its efficiency. The last part of this document, describes a new signaling mechanism that modify the process of generating the multicast trees because of the light splitting limitation. This rerouting signaling mechanism depends on the number of the light splitters compared to the size of the network. At the end, conclusions for all the work done in the three parts are summarized, and a prospective is given. Next steps are identified to benefit of work done in real network design and developmentLes réseaux optiques sont un domaine important de développement en termes de déploiement comme coeur de la dorsale du réseau de communication international. Les fibres optiques montrent une rapide évolution en termes de capacité et de vitesse de lien comparées à n'importe quel autre type de supports. Par ailleurs, le multicast sur réseaux IP a mûri ces dernières années. Il en résulte une grande réduction de trafic lorsque plusieurs clients demandent de recevoir la même information de la même source. Pour permettre le multicast dans les réseaux optiques, les noeuds optiques doivent diviser une onde lumineuse entrante et la commuter vers plusieurs ports de sortie. Les noeuds optiques doivent être équipés des répartiteurs de lumière ("light splitters") qui splitent une onde lumineuse vers plus d'une sortie. En raison de sa conception complexe, un répartiteur de lumière est un équipement très coûteux, de ce fait, équiper tous les noeuds optiques de répartiteurs peut augmenter inconsidérément le coût d'installation du réseau optique. Ceci mène à un consensus : tous les noeuds optiques du réseau ne sont pas capables de spliter la lumière. Le document est divisé en trois parties principales. Dans la première partie, une description du routage multicast et des réseaux optiques sont données successivement. Ensuite, nous introduisons le multicast sur les réseaux optiques. Le problème général est que tous les noeuds optiques dans le réseau ne sont pas capables de spliter. La deuxième partie propose plusieurs solutions pour résoudre ce problème général. Cette partie étudie la densité, le placement et les capacités de ces répartiteurs optiques dans le réseau. Chacune de ces solutions est simulée pour évaluer ses performances et pour analyser son efficacité. La dernière partie décrit un nouveau mécanisme de signalisation qui modifie le processus de construction d'un arbre multicast en raison de l'absence (ou la présence) d'un répartiteur optique dans les noeuds du réseau optique chargés de supporter l'arbre optique. Ce mécanisme de signalisation par reroutage dépend du nombre de répartiteurs de lumière comparé à la taille du réseau. En conclusion, le travail effectué dans les trois parties est récapitulé et une prospective est donnée. De prochaines étapes sont identifiées pour pleinement bénéficier de notre travail fait dans la conception et développement des futurs réseaux optiques
23
Moulierac, Joanna. "Agrégation des communications multicast." Rennes 1, 2006. http://www.theses.fr/2006REN1S151.
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L'agrégation d'arbres multicast est une proposition qui permet d'envisager le passage à l'échelle des communications de groupes sur l'Internet dites communications multicast. Cette proposition permet pour plusieurs groupes d'utiliser un seul arbre de communication, alors qu'en multicast traditionnel, pour chaque groupe, un arbre est maintenu. Ainsi, le nombre total d'arbres dans le réseau est réduit et avec lui le nombre d'entrées de routage multicast. Dans un premier temps, nous proposons un protocole d'agrégation STA qui réalise une agrégation très rapide en évaluant peu d'arbres pour chaque nouveau groupe. Ensuite, le protocole QSTA agrège des groupes sous contraintes de bande-passante. Le protocole DMTA est un protocole d'agrégation distribuée avec un nombre réduit de messages de contrôle entre les entités d'agrégation. Finalement, le protocole TALD réalise l'agrégation des groupes dans des domaines de très grande taille où les protocoles actuels d'agrégation ne sont pas efficaces.
24
Malayattil, Sarosh Aravind. "Design of a Multibus Data-Flow Processor Architecture." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/31379.
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General purpose microcontrollers have been used as computational elements in various spheres
of technology. Because of the distinct requirements of specific application areas, however, general purpose microcontrollers are not always the best solution. There is a need for specialized processor architectures for specific application areas. This thesis discusses the design of such a specialized processor architecture targeted towards event driven sensor applications. This thesis presents an augmented multibus dataflow processor architecture and an automation framework suitable for executing a range of event driven applications in an energy efficient manner. The energy efficiency of the multibus processor architecture is demonstrated by
comparing the energy usage of the architecture with that of a PIC12F675 microcontroller.Master of Science
25
Shah, Saurin Bipin. "Improvements in distribution of meteorological data using application layer multicast." Texas A&M University, 2006. http://hdl.handle.net/1969.1/4798.
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The Unidata Program Center is an organization working with the University
Center for Atmospheric Research (UCAR), in Colorado. It provides a broad variety
of meteorological data, which is used by researchers in many real-world applications.
This data is obtained from observation stations and distributed to various universities
worldwide, using UnidataâÂÂs own Internet Data Distribution (IDD) system, and
software called the Local Data Manager (LDM).
The existing solution for data distribution has many limitations, like high end-toend
latency of data delivery, increased bandwidth usage at some nodes, poor scalability
for future needs and manual intervention for adjusting to changes or faults in the
network topology. Since the data is used in so many applications, the impact of these
limitations is often substantial. This thesis removes these limitations by suggesting
improvements in the IDD system and the LDM. We present new algorithms for constructing
an application-layer data distribution network. This distribution network
will form the basis of the improved LDM and the IDD system, and will remove most
of the limitations given above.
Finally, we perform simulations and show that our algorithms achieve better
average end-to-end latency as compared to that of the existing solution. We also
compare the performance of our algorithms with a randomized solution. We find
that for smaller topologies (where the number of nodes in the system are less than
38) the randomized solution constructs efficient distribution networks. However, if the number of nodes in the system increases (more than 38), our solution constructs
efficient distribution networks than the randomized solution. We also evaluate the
performance of our algorithms as the number of nodes in the system increases and
as the number of faults in the system increases. We find that even if the number of
faults in the system increases, the average end-to-end latency decreases, thus showing
that the distribution topology does not become inefficient.
26
Sellami, Maher. "SMARD un système multibase d'aide à la recherche documentaire /." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb376185226.
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Sellami, Maher. "Smard : un système multibase d'aide à la recherche documentaire." Montpellier 2, 1988. http://www.theses.fr/1988MON20151.
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Presentation d'un systeme intermediaire pour la recherche documentaire. Il met a la disposition des utilisateurs un outil d'interrogation des bases de donnees documentaires reparties sur differents sites a l'aide d'un langage de commande unique et une communication homme-machine adaptee
28
Joroughi, Vahid. "Next generation multibeam satellite systems." Doctoral thesis, Universitat Politècnica de Catalunya, 2015. http://hdl.handle.net/10803/334988.
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Satellite communication will play a central role towards fulfilling next generation 5G communication requirements. As a matter of fact, anytime-anywhere connectivity cannot be conceived without the presence of the satellite segment. Indeed, satellite communication industry is not only targeting popular markets but also to high dense populated areas where the satellite will become an essential element to decongest the terrestrial wireless network.
In order to deliver broadband interactive data traffic, satellite payloads are currently implementing a multibeam radiation pattern. The use of a multibeam architecture brings several advantages in front of a single global beam transmission. First, as an array fed reflector is employed, the antenna gain to noise ratio can be increased leading to high gain in the achievable throughput. Second, different symbols can be simultaneously sent to geographically separated areas, allowing a spatially multiplexed communication. Last but not least, the available bandwidth can be reused in sufficiently separated beams, increasing the spectrum reuse in the overall coverage area. Whenever the system designers target the terabit satellite system the aforementioned multibeam architecture shall be reconsidered. Indeed, the achievable rates can be extremely increased in case a more aggressive frequency reuse is deployed and interference mitigation techniques are implemented either at the user terminal (multiuser detection) or in the transmitter (precoding).
Our study deals with the problem of precoding and linear filtering receiving methods for multibeam satellite systems when full frequency reuse is considered.
Concretely, we consider the particular restrictions of satellite communications which, in contrast to terrestrial communication systems, suffer from additional drawbacks.
First, the feeder link shall aggregate the overall data traffic leading to a very large rate requirement. This required data rate is even increased whenever linear filtering at the return link and precoding in the forward link are deployed. This is because the feed signals, which are larger than the number of beams, shall be computed on ground. In order to solve this problem, we propose a hybrid architecture where the satellite payload is equipped with a fixed processing. This on-board processing linearly transforms the received and transmitted data in order to keep the feeder link rate requirement low. The on-board processing results to be the same for both return and forward links, leading to a large reduction of the payload complexity, mass and cost.
Second, as the data traffic can be generated by different gateways, the precoding method shall be designed accordingly. In contrast to previous works, this work studies the case where the collaboration between different gateways is limited. In addition to the aforementioned contribution, in this work some unexplored aspects of multi-gateway multibeam precoding are also investigated.
Finally, we consider an important phenomena that currently needs to be treated in multibeam systems: the fact that a single codeword is embedded the information of multiple users in each beam. This leads to the difficult so-called multigroup multicast model, whose optimization requires computationally complex operations. In order to solve this problem: i) we propose a two-stage precoding design in order to both limit the multibeam interference and to enhance the intra-beam minimum user signal power, ii) a robust version of the proposed precoder based on a first perturbation model is presented. This mechanism behaves well when the channel state information is corrupted, iii) we propose a per beam user grouping mechanism so as its robust version in order to increase the precoding gain. Forth, a method for dealing with the multiple gateway architecture is presented that offers high throughputs with a low inter-gateway communication.La comunicación por satélite desempeñará un papel central en el cumplimiento de los requisitos de comunicación 5G de próxima generación. Como cuestión de hecho, la conectividad cualquier momento y lugar no se puede concebir sin la presencia del segmento satelital. De hecho, la industria de la comunicación por satélite no sólo se dirige a los mercados populares, sino también a la alta densas zonas pobladas donde el satélite se convertirá en un elemento esencial para descongestionar la red inalámbrica terrestre. Para entregar el tráfico de datos interactiva de banda ancha, las cargas útiles de satélites están implementando un diagrama de radiación de haces múltiples. El uso de una arquitectura multihaz aporta varias ventajas frente a un único haz de transmisión global. En primer lugar, como se emplea un reflector alimentado matriz, la ganancia de antena a ruido puede aumentar dando lugar a una alta ganancia en el rendimiento alcanzable. En segundo lugar, diferentes símbolos pueden ser enviados simultáneamente a las áreas separadas geográficamente, lo que permite una comunicación multiplexada espacialmente. Por último, pero no menos importante, el ancho de banda disponible puede ser reutilizado en las vigas suficientemente separadas, el aumento de la reutilización del espectro en el área de cobertura global. Cada vez que los diseñadores de sistemas se dirigen el sistema de satélites terabit se reconsideró la arquitectura multihaz mencionado. De hecho, las tasas alcanzables pueden ser extremadamente aumentaron en caso de reutilización de frecuencias más agresiva está desplegado y las técnicas de reducción de interferencias se implementan ya sea en el terminal de usuario (detección multiusuario) o en el transmisor (precodificación). Nuestros estudio aborda el problema de precodificación y filtrado lineal recibir métodos para sistemas de satélites multihaz cuando se considera la reutilización de frecuencias completa. Concretamente, consideramos las restricciones particulares de comunicaciones por satélite que, en contraste con los sistemas de comunicación terrestres, sufren de desventajas adicionales. En primer lugar, el enlace de conexión deberá agregar el tráfico global de datos que conduce a un requisito tasa muy grande. Esta velocidad de datos requerida es incluso aumentó cada vez filtrado lineal en el enlace de retorno y precodificación en el enlace directo se despliegan. Esto se debe a que las señales de alimentación, que son más grandes que el número de haces, se computarán en el suelo. Con el fin de resolver este problema, se propone una arquitectura híbrida, donde la carga útil del satélite está equipado con un procesamiento fijo. Este procesamiento a bordo transforma linealmente los datos recibidos y transmitidos con el fin de mantener el requisito de baja tasa de enlace de conexión. Los resultados del procesamiento de a bordo para ser el mismo para ambos enlaces directo y de retorno, dando lugar a una gran reducción de la complejidad de carga útil, la masa y el coste. En segundo lugar, como el tráfico de datos puede ser generada por diferentes puertas de enlace, el método de precodificación deberá ser diseñado en consecuencia. A diferencia de los trabajos anteriores, este trabajo estudia el caso en que la colaboración entre las diferentes pasarelas es limitado. Además de la contribución anterior, en este trabajo también se investigan algunos aspectos inexplorados de multi-gateway multihaz precodificación. Finalmente, consideramos un fenómeno importante que necesita actualmente para ser tratados en sistemas multihaz: el hecho de que una sola palabra de código se incrusta la información de múltiples usuarios en cada viga. Esto conduce a la denominada modelo de multidifusión multigrupo difícil, cuya optimización requiere operaciones computacionalmente complejos. En tal escenario, el diseño de precodificación en el enlace directo será dirigido.
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Boinpalli, Vamshi Krishna. "A Robust Wireless Multicast Protocol." Ohio University / OhioLINK, 2005. http://www.ohiolink.edu/etd/view.cgi?ohiou1121356426.
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Wagh, Prasad J. "DiffServ overlay multicast for videoconferencing." Diss., Columbia, Mo. : University of Missouri-Columbia, 2005. http://hdl.handle.net/10355/4301.
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Thesis (M.S.)--University of Missouri-Columbia, 2005.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (January 10 , 2007) Includes bibliographical references.
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Sauvé, Pierre-Paul. "Multibit decoding of turbo codes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0004/MQ40947.pdf.
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Saucier, Scott. "Multiband Analog-to-Digital Conversion." Fogler Library, University of Maine, 2002. http://www.library.umaine.edu/theses/pdf/SaucierS2002.pdf.
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Blundell, Nick. "Voice over application-level multicast." Thesis, Lancaster University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435872.
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Abutarboush, Hattan F. "Fixed and reconfigurable multiband antennas." Thesis, Brunel University, 2011. http://bura.brunel.ac.uk/handle/2438/9037.
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With the current scenario of development of antennas in the wireless communication field, the need of compact multiband, multifunctional and cost effective antenna is on the rise. The objective of this thesis is to present fixed and reconfigurable techniques and methods for small and slim multiband antennas, which are applicable to serve modern small and slime wireless, mobile and cognitive radio applications. In the fixed designs, independent control of the operating frequencies is investigated to enhance the antennas capabilities and to give the designer an additional level of freedom to design the antenna for other bands easily without altering the shape or the size of the antenna. In addition, for mobile phone antenna, the effect of user’s hand and mobile phone housing are studied to be with minimum effect. Although fixed multiband antennas can widely be used in many different systems or devices, they lack flexibility to accommodate new services compared with reconfigurable antennas. A reconfigurable antenna can be considered as one of the key advances for future wireless communication transceivers. The advantage of using a reconfigurable antenna is to operate in multiband where the total antenna volume can be reused and therefore the overall size can be reduced. Moreover, the future of cell phones and other personal mobile devices require compact multiband antennas and smart antennas with reconfigurable features. Two different types of frequency reconfigurability are investigated in this thesis: switchable and tunable. In the switchable reconfigurability, PIN diodes have been used so the antenna’s operating frequencies can hop between different services whereas varactor diode with variable capacitance allow the antenna’s operating frequencies to be fine-tuned over the operating bands. With this in mind, firstly, a switchable compact and slim antenna with two patch elements is presented for cognitive radio applications where the antenna is capable of operating in wideband and narrow bands depending on the states of the switches. In addition to this, a switchable design is proposed to switch between single, dual and tri bands applications (using a single varactor diode to act as a switch at lower capacitance values) with some fine tuning capabilities for the first and third bands when the capacitance of the diode is further increased. Secondly, the earlier designed fixed antennas are modified to be reconfigurable with fine-tuning so that they can be used for more applications in both wireless and mobile applications with the ability to control the bands simultaneously or independently over a wide range. Both analytical and numerical methods are used to implement a realistic and functional design. Parametric analyses using simulation tools are performed to study critical parameters that may affect the designs. Finally, the simulated designs are fabricated, and measured results are presented that validate the design approaches.
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Hughes, Frank Lawrence Kingsman. "Multicast communications in distributed systems." Thesis, University of Newcastle Upon Tyne, 1986. http://hdl.handle.net/10443/2007.
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One of the numerous results of recent developments in communication networks and distributed systems has been an increased interest in the study of applications and protocolsfor communications between multiple, as opposed to single, entities such as processes and computers. For example, in replicated file storage, a process attempts to store a file on several file servers, rather than one. MUltiple entity communications, which allow one-to-many and many-to-one communications, are known as multicast communications. This thesis examines some of the ways in which the architectures of computer networks and distributed systems can affect the design and development of multicast communication applications and protocols. To assist in this examination, the thesis presents three contributions. First, a set of classification schemes are developed for use in the description and analysis of various multicast communication strategies. Second, a general set of multicast communication primitives are presented, unrelated to any specific network or distributed system, yet efficiently implementable on a variety of networks. Third, the primitives are used to obtain experimental results for a study ofintranetwork and internetwork multicast communications.
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Asfour, Taghrid. "Protocoles de communication multicast fiables." Paris : École nationale supérieure des télécommunications, 2001. http://catalogue.bnf.fr/ark:/12148/cb388211552.
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Miao, Jun. "Load balance in overlay multicast /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?COMP%202004%20MIAO.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 59-62). Also available in electronic version. Access restricted to campus users.
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Li, Fulu 1970. "Cooperative multicast in wireless networks." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32507.
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Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2005.Includes bibliographical references (p. 102-106).
Wireless communication has fundamental impairments due to multi-path fading, attenuation, reflections, obstructions, and noise. More importantly, it has historically been designed to mimic a physical wire; in concept other communicators in the same region are viewed as crossed wires. Many systems overcome these limitations by either speaking more loudly, or subdividing the space to mimic the effect of a separate wire between each pair. This thesis will construct and test the value of a cooperative system where the routing and transmission are done together by using several of the radios in the space to help, rather than interfere. The novel element is wireless, cooperative multicast that could be the basis for a new broadcast distribution paradigm. In the first part of the thesis,. we investigate efficient ways to construct multicast trees by exploring cooperation among local radio nodes to increase throughput and conserve energy (or battery power), whereby we assume single transmitting node is engaged in a one-to-one or one-to-many transmission. In the second part of the thesis, we further investigate transmit diversity in the general context of cooperative routing, whereby multiple nodes are allowed for cooperative transmissions. Essentially, the techniques presented in the second part of the thesis can be further incorporated in the construction of multicast trees presented in the first part.
by Fulu Li.
S.M.
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Cardoso, João Batista Freitas. "Cenário televisivo: linguagens multiplas fragmentadas." Pontifícia Universidade Católica de São Paulo, 2006. https://tede2.pucsp.br/handle/handle/4723.
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Previous issue date: 2006-03-20Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
This study considers a semiotic system as something constituted by different codifications that act simultaneously; a television program is a text which involves some systems, among them scenography; and the scene is one of its elements. The general objective of the present work is to verify how the scene can participate of the televising text as a signification element. Analyzing the specificities of different types of televising scenes, this thesis has as a specific objective: to verify how the scene intervenes with texts of different types of programs, and how it relates to the context, and the other elements of the scene; to identify, in the analyzed programs, how the scene acts with bigger communicative intensity, objectifying to cause definitive interpreters; to indicate, in the television, the characteristics of the scene, how it relates to its structure and to its style, in some of its main genres; to suggest forms of use of the scene as significant element inside of some types of television programs. In order to reach the objectives, a bibliographical research was made, focusing scenography in the theater, television genres, scenographic topologies in the television, as well as a bibliographical survey of the instruments supplied by the peircean semiotics and the theories of gestalt. The observation of scene s space configurations, in the different television genres, was carried through a collection of national videographic material
Tendo em mente que um sistema semiótico é constituído por diversas codificações que atuam simultaneamente; que um programa de televisão é um texto que se constitui de vários sistemas, entre eles a cenografia; que o cenário é um dos elementos da cenografia, o objetivo geral do presente trabalho é verificar de que forma o cenário pode participar do texto televisivo como elemento de significação. A partir da observação das especificidades de diferentes tipos de cenários televisivos, a tese tem como objetivos específicos: verificar como o cenário interfere no texto de diferentes tipos de programas e de que forma dialoga com o contexto e com os outros elementos da cena; identificar, entre os gêneros analisados, aqueles em que o cenário deve atuar com maior intensidade comunicacional, visando ocasionar interpretantes determinados; indicar, na televisão, as características do cenário, tanto no que se refere à estrutura como ao estilo, em alguns de seus principais gêneros; sugerir formas de utilização do cenário como elemento significativo dentro de determinados tipos de programas televisivos. Para se alcançarem os objetivos, foi realizada pesquisa bibliográfica referente a cenografia no teatro, gêneros televisivos e topologias cenográficas na televisão. Para análise dos objetos, fez-se levantamento bibliográfico dos instrumentais fornecidos pela semiótica peirceana e das teorias da gestalt. A observação das configurações espaciais do cenário, nos diferentes gêneros televisivos, foi elaborada a partir da coleta de material videográfico nacional
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Andrade, Romerito Campos de. "Multicast packing problem: abordagem multiobjetivo." Universidade Federal do Rio Grande do Norte, 2013. http://repositorio.ufrn.br:8080/jspui/handle/123456789/18078.
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Previous issue date: 2013-02-01Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
This work presents a algorithmic study of Multicast Packing Problem considering a multiobjective approach. The first step realized was an extensive review about the problem. This review serverd as a reference point for the definition of the multiobjective mathematical model. Then, the instances used in the experimentation process were defined, this instances were created based on the main caracteristics from literature. Since both mathematical model and the instances were definined, then several algoritms were created. The algorithms were based on the classical approaches to multiobjective optimization: NSGA2 (3 versions), SPEA2 (3 versions). In addition, the GRASP procedures were adapted to work with multiples objectives, two vesions were created. These algorithms were composed by three recombination operators(C1, C2 e C3), two operator for build solution, a mutation operator and a local search procedure. Finally, a long experimentation process was performed. This process has three stages: the first consisted of adjusting the parameters; the second was perfomed to indentify the best version for each algorithm. After, the best versions for each algorithm were compared in order to identify the best algorithm among all. The algorithms were evaluated based on quality indicators and Hypervolume Multiplicative Epsilon
O presente trabalho apresenta um estudo algor?tmico do Multicast Packing Problem levando em considera??o uma abordagem multiobjetivo. Para tal, faz-se uma extensa revis?o sobre o problema em quest?o. Esta revis?o serviu como ponto de refer?ncia para defini??o de um modelo matem?tico multiobjetivo, tendo em vista que n?o h? na literatura nenhum trabalho que tenha tratado o tema neste aspecto. Em seguida, define-se os casos de teste utilizados no processo de experimenta??o dos algoritmos. Uma vez que tanto modelo matem?tico multiobjetivo quanto os casos de teste foram criados, ent?o desenvolve-se v?rios algoritmos com base nas abordagens cl?ssicas para problemas de otimiza??o multiobjetivo: NSGA2 (3 vers?es) e SPEA2 (3 vers?es). Al?m disso, adaptou-se a metaheur?stica GRASP (2 vers?es) para aplica??o considerando o modelo proposto. Estes algoritmos foram compostos por tr?s operadores de recombina??o (C1, C2, C3), dois operadores de constru??o de solu??o, um operador de muta??o e um operador de busca local. Por fim, um extenso processo de experimenta??o dos algoritmos ? realizado. Este processo possui tr?s etapas: a primeira etapa consistiu de ajustar os par?metros que cada algoritmo necessita, neste caso o ajuste de par?metro foi realizado para todas as vers?es do SPEA2, NSGA2 e GRASP; A segunda etapa consistiu de verificar, para cada algoritmo, qual a melhor vers?o. Por fim, as melhores vers?es de cada algoritmo, no total 3 vers?es, foram comparadas entre si visando identificar qual o melhor algoritmo dentre todos. Os algoritmos foram avaliados com base nos indicadores de qualidade Hypervolume e Epsilon Multiplicativo. Os resultados dos experimentos foram avaliados atrav?s de testes estat?sticos n?o-param?tricos (teste de Mann-Whitney e teste de Friedman). A avalia??o dos resultados foi favor?ravel ao NSGA2-C2 segundo a metodologia de avalia??o utilizada
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Amaral, António Manuel Nunes Carvalho. "Encaminhamento multicast em redes IP." Master's thesis, Universidade de Aveiro, 2006. http://hdl.handle.net/10773/1888.
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Mestrado em Engenharia Electrónica e TelecomunicaçõesActualmente a maioria das aplicações que usam Internet baseiam-se no modelo de comunicação ponto-a-ponto. No entanto, os recentes avanços tecnológicos e o aparecimento de aplicações cada vez mais sofisticadas fizeram surgir a necessidade de transmitir informações para grupos de participantes (comunicações ponto-multiponto e multiponto-multiponto), como por exemplo, áudio e vídeo conferência para encontros remotos, programas de entretenimento, entre muitos outros. Por outro lado, a evolução da Internet, actualmente baseada no protocolo IPv4, para o protocolo IPv6, deverá ser feita de uma forma progressiva recorrendo a mecanismos de transição e as comunicações multicast terão que ter em consideração este factor. O IETF (Internet Engineering Task Force) definiu dois modelos de transmissão multicast. Inicialmente foi definido o modelo ASM (Any Source Multicast) e mais recentemente, o modelo SSM (Source Specific Multicast). Actualmente existem soluções protocolares que permitem garantir as comunicações multicast em redes IPv4 e em redes IPv6, usando os dois modelos, mas poucas soluções existem que permitam garantir as comunicações multicast em redes mistas IPv4/IPv6. Do ponto de vista de gestão do encaminhamento, a Internet encontra-se dividida em Sistemas Autónomos (SAs). De entre os vários protocolos de encaminhamento multicast, a família de protocolos PIM (Protocol Independent Multicast) é, actualmente, a mais utilizada pois permite resolver as questões do encaminhamento multicast dentro de um Sistema Autónomo (encaminhamento intra-domínio) e, em alguns casos, entre diferentes Sistemas Autónomos (encaminhamento inter-domínio). Esta dissertação aborda o problema de como providenciar comunicações multicast em redes IPv4, em redes IPv6 e em redes mistas IPv4/IPv6. Na primeira parte, é abordado o endereçamento IP multicast bem como o problema da atribuição e divulgação de endereços. Na segunda parte, são descritos os protocolos IGMP e MLD de adesão a sessões multicast e apresentados cenários práticos que validam os protocolos estudados. Na terceira parte, é abordado o funcionamento dos protocolos de encaminhamento multicast da família de protocolos PIM e apresentados cenários práticos de encaminhamento multicast intra-domínio. Na última parte, são descritos mecanismos de transição e apresentados cenários práticos que permitem comunicações multicast em redes mistas IPv4/IPv6 e finalmente, são estudados os problemas e soluções existentes para o encaminhamento multicast inter-domínio. ABSTRACT: Presently most applications used in the Internet, are based on point-to-point communications. However, the recent technological advances and new sophisticated applications are causing an increasing need to transmit information to groups of participants (multicast communications), such us audio and video conferences used for remote meetings, entertainment programs, etc… Moreover, it is known that the evolution of the current Internet, based on IPv4 protocol, to the future IPv6 Internet will be based on transition scenarios, and multicast should consider this fact. Two models have been proposed by the IETF (Internet Engineering Task Force) for multicast communications. The first one is ASM (Any Source Multicast) model and second one, more recently proposed, is the SSM (Source Specific Model) model. Presently, many solutions exist to support multicast on IPv4 only networks and IPv6 only networks using each of the two models. However, there are not many solutions to support multicast on mix IPv4/IPv6 networks. In the point of view of routing management, the Internet is composed by different Autonomous Systems, each one administrated by an individual network operator. From all available multicast routing protocols, the PIM family of protocols is by far the most used one since it solves the multicast routing problems inside an Autonomous System (intra-domain multicast routing) and also in some cases between different Autonomous System (inter-domain multicast routing). This dissertation addresses the issue of how to provide the support of multicast communications in IPv4 networks, IPv6 networks and mixing IPv4/IPv6 scenarios. First, it analyses multicast IP addressing issues like types and formats, how they are assigned and how they are announced. Next, the IGMP and MLD protocols are described together with a set of laboratory experiments validating how they work. Then, the PIM family of multicast routing protocols is described together with a set of intra-domain laboratory experiments used to validate these protocols. In the last part, a study of available IETF transition mechanisms and a set laboratory scenarios is presented to validate solutions that allows multicast communications in mix IPv4/IPv6 networks and, finally, a study of multicast inter-domain routing issues and available solutions finishes this work.
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Videira, António Germano Paiva. "Difusão e multicast em UMTS." Master's thesis, Universidade de Aveiro, 2008. http://hdl.handle.net/10773/1936.
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Mestrado em Engenharia Electrónica e TelecomunicaçõesDesde os primórdios da existência humana que existe a necessidade de comunicar. O ser humano desde então tem procurado meios de comunicação mais rápidos e eficientes. A eficácia da comunicação bem como a partilha de conteúdos quando vários clientes requerem a mesma informação no mesmo instante de tempo constituem o tema central deste trabalho, permitindo utilizar os recursos de rede dos operadores móveis de uma forma muito mais optimizada. Actualmente as redes UMTS usam a transmissão em modo unicast que não é uma solução escalável para a distribuição de conteúdos em tempo real, distribuídos em massa, como é o caso da Mobile TV. A release 6 da norma UMTS introduziu pela primeira vez capacidades de difusão e multicast nas redes móveis através do serviço MBMS. Com isto podemos ter aplicações que permitem às redes móveis disponibilizar serviços do tipo multicast e broadcast nos telemóveis que são considerados por muitos como as killer applications que há muito se procura, podendo contribuir para o aumento da receita por utilizador dos operadores. Este trabalho começa com a apresentação do estado da arte das comunicações móveis seguido da apresentação de uma plataforma de distribuição de conteúdos que vai ser evoluída na sua arquitectura e funcionalidades. O principal objectivo é a especificação de um BM-SC e fazer um estudo aprofundado do MBMS. Com vista à validação e avaliação dos conhecimentos foi contruido um demostrador com especial enfoque para o protocolo entre o BM-SC e os distribuidores de conteúdos. No final, como conclusão, são apontadas as direcções possíveis para a evolução do BM-SC. ABSTRACT: Right from the beginnings of human existence, there has always been a human need to communicate. Since then, humans have found the means of communicating more directly and efficiently. Nowadays, clients also make much better use of the resources at their disposal by being able to share the same information at the same time and this is the focus of this research project. At the moment, UMTS networks transmit via the Unicast mode which is not a viable solution to send contents in real time, as is the case with Mobile TV. For the first time, the UTMS release 6 makes it possible to broadcast and multicast in mobile networks through the MBMS service. MBMS provides us with an application that allows mobile networks to get multicast services via their mobile phones. Many consider these to be the so-called ‘killer applications’ that have been long awaited because they are able to increase the operator’s average revenue per user. This work begins with a presentation of state-of-the-art mobile telecommunications followed by a brief introduction to a platform of content distribution which is going to be further developed and enhanced both in terms of its structure and its functions. The main objective of this work is first to specify and then build a BM-SC and then to carry out some more profound research into MBMS. With the aim of validating and evaluating this knowledge, a demonstration model has been built in order to highlight the specifications of the BM-SC and the content distributors. At the end and to conclude this study, we will provide some pointers to show how we believe the BM-SC will develop and in which directions it will progress.
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Pinho, Luís André Silva Cruz. "Next generation multimedia multicast services." Master's thesis, Universidade de Aveiro, 2011. http://hdl.handle.net/10773/8813.
Full textAbstract:
Mestrado em Engenharia Electrónica e TelecomunicaçõesUma das mais recentes conquistas na evolução móvel foi o 3G, permitindo o acesso a serviços multimédia com qualidade de serviço assegurada. No entanto, a tecnologia UMTS, tal como definida na sua Release ’99, é apenas capaz de transmitir em modo unicast, sendo manifestamente ineficiente para comunicações multimédia almejando grupos de utilizadores. A tecnologia IMS surge na Release 5 do 3GPP que começou a responder já a algumas necessidades, permitindo comunicações sobre IP oferecendo serviços Internet a qualquer momento e em qualquer lugar sobre tecnologias de comunicação móveis fornecendo pela primeira vez sessões multimédia satisfatórias. A Release 6 por sua vez trouxe a tecnologia MBMS que permite transmissões em broadcast e multicast para redes móveis. O MBMS fornece os serviços de aplicações multimédia que todos estavam à espera, tanto para os utilizadores como para os prestadores de serviços. O operador pode agora fazer uso da tecnologia existente aumentando todo o tipo de benefícios no serviço prestado ao cliente. Com a possível integração destas duas tecnologias passa a ser possível desenvolver serviços assentes em redes convergentes em que os conteúdos são entregues usando tecnologias unicast, multicast ou broadcast. Neste contexto, o principal motivo deste trabalho consiste essencialmente em fazer uso dos recursos da rede terminando com o desperdício dos mesmos e aumentando a eficiência dos serviços através da integração das tecnologias IMS e MBMS. O trabalho realizado começa com o estudo do estado da arte das telecomunicações móveis com referência às tecnologias referidas, seguindo-se a apresentação da possível integração IMS-MBMS e terminando com o projecto de uma plataforma de demonstração que no futuro possa ser uma implementação de serviço multimédia multicast. O objectivo principal é mostrar os benefícios de um serviço que era normalmente executado em unicast relativamente ao modo multicast, fazendo uso da nova convergência de tecnologias IMS e MBMS. Na conclusão do trabalho são referidas as vantagens do uso de portadoras multicast e broadcast, tendo como perspectiva de que este trabalho possa ser um ponto de partida para um novo conjunto de serviços poupando recursos de rede e permitindo uma eficiência considerável em serviços inovadores.
3G is bang up to date in the mobile phone industry. It allows access to multimedia services and gives a guarantee of quality of service. The UMTS technology, defined in 3GPP Release ’99, provides an unicast transmission, but it is completely inefficient when it comes to multimedia group communications. The IMS technology first appeared in Release 5 that has already started to consider the interests of the clients. It provides communications over IP, offering Internet services anytime, anywhere on mobile communication technologies. Also, it offers for the first time satisfactory multimedia sessions. On the other hand, Release 6 gave rise to the MBMS technology that provides broadcast and multicast transmissions for mobile networks. The MBMS provides multimedia applications services that everyone was waiting, including users and service providers. Now the operator makes use of existing technology in order to provide better costumer services. The possible integration of these two technologies will contribute to develop services based on converged networks in which contents are delivered through the unicast, multicast or broadcast technologies. Therefore, the objective of this work is basically to make use of network resources avoiding wastes and improving customer services through the integration of the IMS and the MBMS technologies. The executed work starts with the mobile telecommunications state of the art with reference to the referred technologies, followed by the IMS-MBMS convergence presentation and finishing with the proposal for implementation of a service platform that can be used for a multimedia multicast service. The main point is to show the benefits of a service that has been normally executed in unicast mode over the multicast mode, making use of the new IMS and MBMS technologies integration. To closure the work it is referred the advantages to use multicast and broadcast bearers, with the perspective that this work could be a starting point to a new set of services, saving network resources and allowing for innovate services a considerable efficency.
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Maxwell, Michael. "Multiband observations of recurrent novae." Thesis, University of Central Lancashire, 2014. http://clok.uclan.ac.uk/10719/.
Full textAbstract:
Recurrent novae are binary systems which undergo outbursts due to a thermonuclear runaway on a timescale of decades. Two systems, U Scorpii and RS Ophiuchi, are the main focus of this thesis having gone into outburst in 2010 and 2006 respectively. Optical and near-IR spectroscopy of U Sco obtained with facilities including the Liverpool Telescope, the Very Large Telescope, and the Southern African Large Telescope, as well as ultra-violet and optical spectroscopy of RS Oph obtained with the Ultra-Violet and Optical Telescope, are presented here. Observations of U Sco obtained in outburst are used to determine the helium abundance of the ejecta, with observations in quiescence used to constrain the nature of the companion star and the accretion disc. Observations of RS Oph are used to produce lightcurves of the decline from maximum to the post-outburst minimum. Analysis of optical and near-IR spectra following the 2010 outburst of U Sco leads to the determination of the reddening and the helium abundance. The reddening is found to be E(B-V) = 0.17 ± 0.14, consistent with previous estimates. The helium abundance, N(He)/N(H), is determined to be 0.122 ± 0.018, lower than previous estimates and suggesting that the companion is not helium rich. The fitting of model stellar atmospheres to observations of U Sco in quiescence, obtained ∼18-30 months after the 2010 outburst, constrains the effective temperature of the companion and indicates that it is a cool F or hot G star. The accretion disc is found to be still in a state of development until at least ∼18 months after outburst, contrary to previous studies. The strength of the Heii 4686 ̊A line in quiescence is found to be consistent with a high mass white dwarf accreting solar-abundance material at a high rate. The He line strengths do not require an overabundance of helium, as has been previously suggested, consistent with the solar abundance of helium found in the ejecta of the 2010 outburst. UVOT observations of RS Oph following the 2006 outburst are used to produce B and u′ lightcurves of the decline to minimum. These lightcurves are used in con- junction with published V and B lightcurves to show the change in the colour of the system throughout the outburst. Spectra of RS Oph show the spectroscopic evolution during the initial decline, plateau, final decline, and post-outburst minimum phases. SALT spectra obtained during the late decline phase of the 2011 outburst of a third recurrent nova, T Pyxidis, are used to derive a helium abundance of N(He)/N(H)= 0.161 ± 0.013, approximately twice the solar value. Very strong [O iii] lines are also detected.
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Abunjaileh, Alaa Ibrahim. "Multimode and multiband microstrip antennas." Thesis, University of Leeds, 2007. http://etheses.whiterose.ac.uk/759/.
Full textAbstract:
This thesis describes original work on the broadband and multiband matching of microstrip patch antennas. Microstrip patch antennas suffer from many constraints on their performance. One major restriction is their narrow impedance bandwidth. An effective method to resolve this is adding more resonators to the antenna structure to achieve multi-resonance and hence wider bandwidth. Structures such as circular, square and triangular patch antennas may support two orthogonal resonant modes or polarisations. This allows excitation of an additional resonance beside the fundamental. With the correct coupling between the resonant modes, the impedance bandwidth can be significantly increased. The equivalent circuit of such structures is similar to those used in microwave filter design. Using techniques normally employed in filter synthesis, the equivalent circuits can be generated, and aid in finding the couplings and dimensions of the specified antenna requirement. The bandwidth of circular microstrip patch antennas is significantly increased by exciting two modes on a single circular microstrip antenna, and four modes using two stacked circular microstrip patches. In this work, the designs are also extended into multimode antennas achieving multi-frequency operation.
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Fernandes, Ana Margarida Xavier Ferreira. "Comunicação em grupo: Multicast Aplicacional versus Multicast IP." Master's thesis, 2015. http://hdl.handle.net/1822/41875.
Full textAbstract:
Dissertação de Mestrado - Ciclo de Estudos Integrados Conducentes ao Grau de
Mestre em Engenharia de Telecomunicações e InformáticaNos últimos anos, o Internet Protocol Television (IPTv) tem vindo a aumentar a sua popularidade junto dos principais Internet Service Providers (ISPs), que o utilizam de forma a modernizar as suas redes de partilha de conteúdos audiovisuais. Este tipo de aplicações utilizam comunicação em grupo, sobre redes IP (Internet Protocol), que requerem muita largura de banda e por isso, a escolha da melhor tecnologia para as suportar é de extrema importância. O multicast é a principal tecnologia para permitir uma comunicação eficiente para este tipo de rede, devido ao facto de ter sido desenhado para comunicações de um-paramuitos. No multicast implementado ao nível da camada de rede, o multicast IP, os routers são responsáveis pela subscrição dos utilizadores nos diferentes grupos e de fazer chegar o tráfego para os nós interessados. Apesar da crença que o multicast IP é a arquitetura mais eficiente para distribuir informação para diferentes grupos, a sua lenta implementação levou a que alguns investigadores questionassem se a camada de rede é, necessariamente, a melhor camada para implementar a funcionalidade de multicast. Assim, surgiu o multicast na camada de aplicação (Application Layer Multicast - ALM), como uma técnica alternativa para o multicast. Nesta abordagem, a funcionalidade multicast é implementada nos sistemas finais, em vez de nos routers da rede. A presente dissertação começa por efetuar um levantamento dos principais protocolos do paradigma multicast, ao nível da camada de rede e da camada aplicacional. Depois estabelece plataformas de simulação para multicast aplicacional e de nível de rede. Por fim, analisa o desempenho de uma solução multicast de cada camada, num cenário de teste, com recurso à simulação, de modo a contribuir para a longa discussão sobre qual a solução mais adequada, para ser implementada em larga escala.
In the past few years, Internet Protocol Television (IPTv) popularity has been growing among the Internet Service Providers, in order to modernize its networks to deliver audiovisual content. This type of application use group communication over IP networks, that require high bandwidth and so, choosing the best technology to support them, is extremely important. Multicast is the main technology to allow an efficient communication for this type of network, due to being designed for communications one-to-many. In IP multicast (multicast implemented at the network level), routers are meant to make/remove subscription from users to different groups and replicate traffic to interested nodes. Despite the belief that IP multicast is the most efficient architecture for data distribution to multiple groups, their slow implementation led some researchers to question whether the network layer is necessarily the best layer for implementing multicast functionality. Therefore, application layer multicast (ALM) has emerged as an alternative technique for multicasting. In this approach, the multicast functionality is implemented at the end-systems instead of the network routers. This dissertation begins by presenting a survey of multicast protocols at the network level and application level. Then sets simulation platforms for application layer multicast and IP multicast. Finally, it analyzes the performance of a multicast solution on both layers, using the simulation of a test scenario, in order to contribute to the long discussion about the most appropriate solution to implement multicast on a large scale network.
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Rochman, Muhammad Iqbal Cholilur, and Muhammad Iqbal Cholilur Rochman. "CONMIQ Multicast: A Scalable Multicast Video Streaming in LTE Networks." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/31690980527017988550.
Full textAbstract:
碩士國立臺灣科技大學
資訊工程系
104
Multicast transmission is a recurrent problem in wireless networking as the system has to cater for a multiple number of users at the same time. Furthermore video payload adds more complexity to the problem, i.e. video needs to be delivered in timely and orderly manner. Using H.264/SVC standard for scalable video, scaling could be used to compromise the quality and the size of the video, yet it poses a complex dependency problem. We propose a multicast scheme named CONMIQ (Constrained Non-linear Model of Incremental Quality) that provides suboptimal video quality to all users, and still fulfill resource requirement. The solution will be applied to LTE-A (Long-Term Evolution-Advanced) network which provides robust user channel quality assessment and a better OFDMA channel. To find the maximum video quality, we model the video quality of each video block in a GOP (Group of Pictures) as a second-degree polynomial function, then solve the maximization problem on that function, along with the considerations of resource constraints, video block dependency, and the varying channel condition of subscribed users. The experimental results verify that our suboptimal solution outperforms naive approaches while still performing comparably well than the much slower optimal solution.
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吳松軒. "Multiband Planar Antennas." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/91172014680560215948.
Full textAbstract:
碩士明新科技大學
電機工程研究所
98
Recently,there are rapid developments in wireless Communications.The frequency range covers 2-6GHz for Radio Frequency Identification (RFID 2.4GHz) , Wireless LAN (2400–2484 MHz,and 5150–5350/5725–5875 MHz MHz), Worldwide Interoperability for Microwave Access(WiMAX 3.5GHz) and Bluetooth(2.4GHz) and so on. In order to satisfy the IEEE 802.11WLAN standards and wimax application, the triple band operations of the printed antennas are required.A compact modified unilateral fed coplanar Waveguide antenna (CPW) designed by IE3D software is presented. The antennas are implemented on planar printed circuit boards (PCBs). These antennas are low profile, easy to be constructed and easy to be integrated with microwave integrated circuits. The thickness of the FR-4 PCB is 1.6mm. The size of the antenna is . The small broadband antenna (2265MHz~5895MHz) was constructed with same technique, The size of the antenna is also . This antenna is suitable for notebook application.
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Guo, Ming-Huang, and 郭明煌. "Multicast ATM Switches." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/72912534671562330604.
Full textAbstract:
博士國立臺灣科技大學
資訊管理系
88
With the advances of technology and the decline in hardware prices, network usage is growing and propagating beyond the expectance while it was built. More and more network applications are developed and deployed to help people doing things quickly without the constraint in geography and space. For example, video-on-demand, distant learning, distant diagnosis, video-conferencing, and many others applications have popped up one after another in recent years. All the applications not only provide the convenience, but also improve the progression in human culture, technology, and history. However, these applications all need multicasting functionality to support. In traditional networks, this operation can not be handled easily and cheaply. When scaled up to high-speed ATM-based networks, the situation could be worse. Multiple streams of data travel around ATM networks. Each tries to send to many different destinations simultaneously. Therefore, designing economical ATM switches to support multicasting operations easily is very important in the future generation high-speed networks. In this thesis, three design issues for multicast ATM switches are introduced at first. Two pre-scheduling algorithms that can help improving the performance of multicast ATM switches are reviewed then. A simple multicast ATM switch based on broadcast buses is also proposed. Afterwards, a suggestion to deploy the multicast ATM switches with ATM UNI3.0/3.1 is given. Without easy and inexpensive multicasting, all the exciting services may become unaffordable. This will in turn lead to the diminishing of customer bases and finally will hinder the full-scale deployment of high-speed networks.
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Lee, Wei-Yuan, and 李維源. "Pivot Multicast Routing." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/48861557893736394311.
Full textAbstract:
碩士國立臺灣大學
資訊工程研究所
84
We provided a new multicast routing, called Pivot Multicast Routing, for central-computing multicast routing system. It considers the central nodes among all multicast members to find a smaller multicast/Steiner tree as given a network model and a multicast group. To avoid repetitive computing central nodes like ADH, we divided Pivot Multicast Routing into two steps. The first is to find any possible central nodes, and the second is to produce one multicast tree by the central nodes. We proposed pivot-tree concept to substitute central-node one, and two methods, Asynchronous Waves Algorithm (AWA) and Synchronous Waves Algorithm (SWA), to find any possible pivot trees are designed. We also proposed five algorithms, Pivot KMB, Pivot Covering, Switching, Pivot Try-All and Pivot SPH, to construct a multicast tree from those pivot trees. We justified by simulation that SPH has the best multicasting quality but with the longest time. Then we propounded Limited Grouping Waves Algorithm (LGWA) and Limited Combination Method (LCM) to improve Pivot SPH within two to three times of SPH-ZZ.