Dissertations / Theses on the topic 'Vertical handoffs'
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Mola, Guilo. "Interactions of Vertical Handoffs with 802.11b wireless LANs : Handoff Policy." Thesis, KTH, Mikroelektronik och Informationsteknik, IMIT, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-93067.
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Nomadic computing aims to be a leading short term revolution in the Internet, however to succeed in this the infrastructure, the protocols, the handoff mechanisms have to be designed and implemented to provide mobile computing with both reliability and transparency. A good deal of the work is addressed by mobile IP itself, but addressing wireless diversity is perhaps the most important next step. Many different wireless technologies are available; while one technology might provide wide coverage, another provides higher bandwidth, but can only be deployed locally, even uni-directional ad-hoc links can be used to carry IP traffic. To take full advantage of the potential infrastructure, a mobile device, with multiple network interfaces, should be able to dynamically switch from one link technology to another; hopefully totally transparently to the user. Moreover, having multiple interfaces allows the device to choose, each time a new connection is established, which interface to select to route the datagrams through, based on the type of service desired. In this thesis a possible solution is presented, involving both vertical handoff optimization and policy management. Our testing device is the the SmartBadge v4, provided with a GPRS link and a 802.11b WLAN interface.Nomadic Computing har för avsikt att revolutionera dagens Internet tillämpningar. För att lyckas måste dock infrastrukturen, IT protokollen och handoff procedurer utformas och implementeras med intentionen att förse mobilt dataöverföring med både driftsäkerhet och autonoma processer. En stor del av de nödvändiga förutsättningarna är tillgängliga tack vare Mobile IP, men mångfalden inom de befintliga Wireless teknologierna utgör fortfarande ett problem. Det stora antalet disponibla Wireless tekniker varierar från teknologierer som förser användaren med en stor täckningsgrad, till sådana som förser användaren med högre bandbredd, begränsad till lokala anv ändningområden. Även Uni-directional ad-hoc links kan läggas i denna lista av mångfald. För att förverkliga fördelarna med den tänkta infrastrukturen fullt ut måste den mobila enheten kunna utföra omkopplingar från den ena wireless teknologin till den andra, med syftet att vara osynlig för användaren. Utöver detta är det meningen att en apparat med många anslutningar ska kunna välja den anslutning som passar bäst, var gång en ny koppling ska göras, beroende på den tjänst som efterfrågas. Det här examensarbetet presenterar en möjlig lösning, som utnyttjar både Vertical Handoff optimering och Policy Management. Prototyp-enheten vi anv änder oss av för att genomföra undersökningen är Smart Badge v4, utrustad med GPRS och 802.11b Wireless LAN anslutningar.
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Sur, Abhijit Nettleton Ray W. "Technical and business aspects of vertical handoffs." Diss., Access abstract online. Then to access FREE full-text, click on "Order a copy.", 2004. http://proquest.umi.com/pqdweb?did=885648771&sid=1&Fmt=2&clientId=56281&RQT=309&VName=PQD.
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Benmimoune, Abderrahmane. "Handoff vertical entre réseau UMTS et WLAN." Mémoire, École de technologie supérieure, 2010. http://espace.etsmtl.ca/627/1/BENMIMOUNE_Abderrahmane.pdf.
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Un des principaux défis majeurs des prochaines générations des systèmes de communication
sans fil serait d'utiliser les ressources limitées des réseaux de communications d'une manière
efficace à l'effet d'obtenir une qualité et une capacité qui soient suffisantes pour faire face à
des demandes sans cesse croissante de services.
En effet, les besoins en bande passante des utilisateurs ont augmenté en raison des résultats
satisfaisants relevés des différentes applications telles que la vidéo et la navigation sur
Internet. Ceci a permit à plusieurs technologies de voir le jour et qui ne cessent de
s'améliorer afin de répondre aux besoins des utilisateurs. C'est notamment le cas des réseaux
hétérogènes qui servent à interconnecter les réseaux WIFI, GSM/UMTS et Satellitaires. Ce
progrès va permettre de répondre à la demande des utilisateurs en leurs offrants une très
grande mobilité dans le monde et une connexion n'importe où et n'importe quand.
L'objectif de ce présent mémoire de maîtrise est d'étudier la problématique de gestion de
mobilité entre les deux réseaux et de combiner ces techniques afin d'exploiter au mieux les
avantages inhérents à ces deux réseaux : cellulaire (UMTS) et local sans fil (WLAN) et de
pouvoir intégrer ces deux technologies de telle sorte que le changement de technologie soit
transparent.
Dans le cadre de la première partie de ce mémoire, nous avons traité particulièrement les
aspects de gestion de mobilité. Les deux différentes architectures d'interconnexion au
contexte des réseaux hétérogènes UMTS/WLAN sont relatées ainsi que différents algorithme
sont également mis en évidence principalement l'algorithme RSS, SNR et SINR
La plupart des contributions faites dans ce contexte prennent en considération juste la
maximisation du débit à travers les deux réseaux. Par contre la minimisation de nombre de
handoff durant un appel ou transfert de données joue un rôle très prépondérant, afin d'éviter
tout handoff inutile et d'éliminer par voie de conséquence l'effet ping-pong qui dégrade la
qualité de service.
C'est pourquoi, dans la seconde partie de notre mémoire, nous avons proposé une nouvelle
stratégie intégrant pour la réalisation d'un handoff vertical des utilisateurs mobiles entre les
deux réseaux tout en minimisant le nombre de handoff la probabilité de perdre des paquets
et d'atteindre un débit plus élevé avec meilleur prix conespondant. Dans ce cadre nous avons
présenté et nous avons testé plusieurs algorithmes de handoff et nous avons comparé ces
algorithmes avec notre solution proposée. Tous les algoritlmies entrepris ont été validés et
évalués par des simulations.
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Tsang, Cheuk-kan Ken, and 曾卓勤. "Vertical handoff in heterogeneous wireless networks with mSCTP." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B40687636.
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Tsang, Cheuk-kan Ken. "Vertical handoff in heterogeneous wireless networks with mSCTP." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B40687636.
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Sun, Chi. "A constrained MDP-based vertical handoff decision algorithm for wireless networks." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/1243.
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The 4th generation wireless communication systems aim to provide users with the convenience of seamless roaming among heterogeneous wireless access networks. To achieve this goal, the support of vertical handoff is important in mobility management. This thesis focuses on the vertical handoff decision algorithm, which determines the criteria under which vertical handoff should be performed. The problem is formulated as a constrained Markov decision process. The objective is to maximize the expected total reward of a connection subject to the expected total access cost constraint. In our model, a benefit function is used to assess the quality of the connection, and a penalty function is used to model the signaling incurred and call dropping. The user's velocity and location information are also considered when making the handoff decisions. The policy iteration and Q-learning algorithms are employed to determine the optimal policy. Structural results on the optimal vertical handoff policy are derived by using the concept of supermodularity. We show that the optimal policy is a threshold policy in bandwidth, delay, and velocity. Numerical results show that our proposed vertical handoff decision algorithm outperforms other decision schemes in a wide range of conditions such as variations on connection duration, user's velocity, user's budget, traffic type, signaling cost, and monetary access cost.
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Ylianttila, M. (Mika). "Vertical handoff and mobility — system architecture and transition analysis." Doctoral thesis, University of Oulu, 2005. http://urn.fi/urn:isbn:9514276922.
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Abstract
The contemporary information age is equipped with rich and affordable telecommunication services. In the future, people have even more flexibility when true wireless Internet and real-time multimedia are provided seamlessly over heterogeneous wireless networks. Optimally combining the capacity and services of the current and emerging networks requires a holistic view of mobility, resource and service management. This thesis contributes to the research and development of these hybrid systems with three main contributions.
Firstly, a system architecture for vertical handoff in location-aware heterogeneous wireless networks is proposed. The proposed architecture enables the mobile node to prepare for approaching vertical handoffs and wake-up a hotspot interface. The needed communication procedures are discussed, and inter-related issues of mobility and geolocation information are considered in proportion to usability, advantages and limitations.
Secondly, a framework for the analysis of vertical handoff algorithm sensitivity to various mobility parameters including velocity, handoff delay and dwell time is introduced. Handoff smoothing with a dwell-timer is analyzed as one potential scheme for optimizing vertical handoff locally. It is compared to a power based algorithm to find out its sensitivity to the changes in effective data rates, velocity of the terminal and the amount of handoff delay. The analysis focuses on the transition region, having case studies on both moving-in and moving-out scenarios. An optimal value for dwell-timer is found through simulations, showing a performance gain over power based algorithm as a function of mean throughput. The analysis is extended also to a multiple network scenario.
Thirdly, experimental results on the behaviour of protocols used in wireless IP networks are presented. Prototype systems demonstrate results of using Mobile IP with a fuzzy logic algorithm for vertical handoff in a heterogeneous network environment and the role of IPv6 when using a voice application in a wireless LAN environment. Latest contributions include developing plug-and-play middleware functionalities for Symbian mobile devices, extending the use of the earlier results to state-of-the-art mobile devices.
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Zhu, Fang. "Optimizations for vertical handoff in next generation wireless networks." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0012983.
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Prado, Daniel. "Algoritmos de handoff vertical para sistemas de comunicação GPRS/ Satélite." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265118.
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Orientador: Rafael Santos MendesDissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Este projeto tem por objetivo estudar um problema de projeto para realizar o handoff vertical entre canais de comunicação GPRS e Satélite em um cenário que otimize o tempo e o custo através de equações probabilísticas. Através de um modelo de estados que descreve as diferentes possibilidades de comunicação entre sistemas GPRS e Satélite, o objetivo é determinar os tempos dos eventos controláveis que fazem a mudança entre os estados de modo a otimizar o tempo de comunicação num cenário probabilístico de handoff vertical entre canais de comunicação. Os resultados das simulações realizadas nesta dissertação em diferentes situações de qualidade dos sinais de transmissão GPRS e Satélite, mostram que através dos algoritmos de handoff desenvolvidos, a probabilidade estacionária de permanência nos estados de transmissão é aumentada
Abstract: This project aims to study a design problem to carry-out the handoff vertical of communication between communication channels GPRS and Satellite in a scenario that optimizes time and cost by probabilistic equations. Through a state model that describes the different possibilities of communication between GPRS and satellite systems, the goal is to set the times of the controllable events that do the changes between states in order to optimize the communication time in a probabilistic scenario of handoff vertical for communication channels. The results of the simulations in this work in different situations, quality of transmission signals GPRS and Satellite, show that through the handoff algorithms developed, the stationary probability of staying in the states of transmission is increased
Mestrado
Eletrônica
Mestre em Engenharia Automobilistica
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Nkansah-Gyekye, Yaw. "An intelligent vertical handoff decision algorithm in next generation wireless networks." Thesis, University of the Western Cape, 2010. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_2726_1307443785.
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The objective of the thesis research is to design such vertical handoff decision algorithms in order for mobile field workers and other mobile users equipped with contemporary multimode mobile devices to communicate seamlessly in the NGWN. In order to tackle this research objective, we used fuzzy logic and fuzzy inference systems to design a suitable handoff initiation algorithm that can handle imprecision and uncertainties in data and process multiple vertical handoff initiation parameters (criteria)
used the fuzzy multiple attributes decision making method and context awareness to design a suitable access network selection function that can handle a tradeoff among many handoff metrics including quality of service requirements (such as network conditions and system performance), mobile terminal conditions, power requirements, application types, user preferences, and a price model
used genetic algorithms and simulated annealing to optimise the access network selection function in order to dynamically select the optimal available access network for handoff
and we focused in particular on an interesting use case: vertical handoff decision between mobile WiMAX and UMTS access networks. The implementation of our handoff decision algorithm will provide a network selection mechanism to help mobile users select the best wireless access network among all available wireless access networks, that is, one that provides always best connected services to users.
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Puska, Alisson Andrey. "Decisão no handoff vertical ciente da confidencialidade das redes de acesso." reponame:Repositório Institucional da UFPR, 2015. http://hdl.handle.net/1884/41388.
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Orientador : Prof. Aldri Luiz dos SantosCo-orientadora : Profª. Michele Nogueira Lima
Dissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências Exatas, Programa de Pós-Graduação em Informática. Defesa: Curitiba, 31/08/2015
Inclui referências : f. 63-70
Resumo: A diversidade das tecnologias de comunicação sem fio existentes e o constante aumento do número de pontos de acessos resultaram em ambientes repletos de redes sem fio com diferentes características de desempenho e segurança. Estes avanços, em conjunto com o desenvolvimento de dispositivos móveis com mais de uma interface para comunicação sem fio e a proliferação do uso da comunicação no dia a dia das pessoas, instigaram o de-senvolvimento da interoperabilidade entre as diferentes tecnologias. A interoperabilidade tem como objetivo alcançar maiores áreas de cobertura, melhorar a qualidade dos serviços oferecidos para o usuário, bem como mantê-lo conectado em todo lugar e a todo momento, resultando no paradigma das redes heterogêneas. Este novo paradigma demanda o gerenciamento da mobilidade do usuário para manter a sua conectividade, transferindo a conexão do dispositivo móvel quando necessário e sem perdas nos serviços. Este processo e chamado de handoff em redes heterogêneas e depende da escolha automática de um ponto de acesso adequado as necessidades do usuário móvel. Com esta finalidade, vários métodos de decisão propostos na literatura avaliam as características de desempenho, qualidade de serviço e segurança das redes de acesso para classificá-las de acordo com estes conjuntos de propriedades. Entretanto, os métodos encontrados na literatura analisam a segurança de maneira genérica, ignorando os aspectos distintos de suas propriedades de confidencialidade, integridade e disponibilidade. Este problema pode gerar decisões inadequadas e que colocam o usuário em risco, como quando o dispositivo requer confidencialidade nas transmissões e o processo de decisão seleciona uma rede cuja à segurança se refere a disponibilidade das transmissões, conectando-o a uma rede inadequada. Alem disso, nenhum método considera a falta de informações a respeito dos critérios de comparação na escolha dos pontos de acesso, o que diminui a precisão das decisões, levando a escolhas inadequadas ou ate falhas do processo de transição. Portanto, este trabalho apresenta um método de decisão, chamado SDHet, que seleciona a rede de acesso com base no seu nível de confidencialidade. Ele e inspirado na teoria da prospecção, que modela a tomada de decisão por seres humanos quando em risco e falta de informações, para selecionar as redes quando nestas situações. O SDHet foi avaliado através de simulações e os resultados mostram a sua eficácia em escolher as redes considerando o nível de confidencialidade e a falta de informações dos critérios de comparação. Alem disso, a utilização do método não interfere de maneira significativa no desempenho do processo de transição. Palavras-chave: Redes Heterogeneas, handoff, método de decisão, teoria da prospecção, analise de risco, confidencialidade.
Abstract: The diversity of wireless communication technologies and the steady increase in the num-ber of access points resulted in full of wireless networks with different performance cha-racteristics and safety environments. This advances, together with the development of mobile devices with more than one interface for wireless communication and the proli-feration of the use of communication in day-to-day lives instigated the development of interoperability between different technologies. The interoperabolity aims to achieve gre-ater coverage areas, improve the quality of services offered to the user, as well as keep him connected everywhere and at all times resulting in the paradigm of heterogeneous networks. This new paradigm provides the mobility management for the user to maintain its connectivity, transferring the mobile connection when required and no with loss in service. This process is called vertical handoff and depends on the automated choice of a suitable access point for user needs. To this end, various decision methods proposed in the literature evaluate performance characteristics, quality of service and safety of access networks to classify them according to these sets of properties. However, the methods in the literature analyze the safety of the networks in a generic way, ignoring the different aspects of their confidentiality, integrity and availability properties. This problem can lead to inappropriate decisions and put the user at risk, such as when the device requires confidentiality in transmissions and the decision making process selects a network whose security criteria refers to the availability of transmissions. Furthermore, no method con-siders the absence of information about the comparison criteria in the choice of access points, which decreases the accuracy of the decisions, leading to inappropriate choices or to the transition faults. Therefore, this paper presents a decision method, called SDHet, which selects the access network based on their level of confidentiality. He is inspired by the prospect theory, modeling decision making by humans when at risk and lack of information, to select the networks on these situations. The SDHet method was evaluated through simulation and the results shows its effectiveness in choosing the networks consi-dering the level of confidentiality and the lack of information of the comparison criteria. Furthermore, the use of the method does not interfere significantly the performance of the transition. Keywords: Heterogeneous networks, handoff, decision method, prospect theory, risk analysis, confidentiality.
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Kaleem, Faisal. "VHITS: Vertical Handoff Initiation and Target Selection in a Heterogeneous Wireless Network." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/602.
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Global connectivity, for anyone, at anyplace, at anytime, to provide high-speed, high-quality, and reliable communication channels for mobile devices, is now becoming a reality. The credit mainly goes to the recent technological advances in wireless communications comprised of a wide range of technologies, services, and applications to fulfill the particular needs of end-users in different deployment scenarios (Wi-Fi, WiMAX, and 3G/4G cellular systems). In such a heterogeneous wireless environment, one of the key ingredients to provide efficient ubiquitous computing with guaranteed quality and continuity of service is the design of intelligent handoff algorithms.
Traditional single-metric handoff decision algorithms, such as Received Signal Strength (RSS) based, are not efficient and intelligent enough to minimize the number of unnecessary handoffs, decision delays, and call-dropping and/or blocking probabilities.
This research presented a novel approach for the design and implementation of a multi-criteria vertical handoff algorithm for heterogeneous wireless networks. Several parallel Fuzzy Logic Controllers were utilized in combination with different types of ranking algorithms and metric weighting schemes to implement two major modules: the first module estimated the necessity of handoff, and the other module was developed to select the best network as the target of handoff.
Simulations based on different traffic classes, utilizing various types of wireless networks were carried out by implementing a wireless test-bed inspired by the concept of Rudimentary Network Emulator (RUNE).
Simulation results indicated that the proposed scheme provided better performance in terms of minimizing the unnecessary handoffs, call dropping, and call blocking and handoff blocking probabilities. When subjected to Conversational traffic and compared against the RSS-based reference algorithm, the proposed scheme, utilizing the FTOPSIS ranking algorithm, was able to reduce the average outage probability of MSs moving with high speeds by 17%, new call blocking probability by 22%, the handoff blocking probability by 16%, and the average handoff rate by 40%. The significant reduction in the resulted handoff rate provides MS with efficient power consumption, and more available battery life. These percentages indicated a higher probability of guaranteed session continuity and quality of the currently utilized service, resulting in higher user satisfaction levels.
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Ramalingam, Mukesh. "Vertical Handoff Target Selection in a Heterogeneous Wireless Network Using Fuzzy ELECTRE." FIU Digital Commons, 2015. http://digitalcommons.fiu.edu/etd/2014.
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Global connectivity is on the verge of becoming a reality to provide high-speed, high-quality, and reliable communication channels for mobile devices at anytime, anywhere in the world. In a heterogeneous wireless environment, one of the key ingredients to provide efficient and ubiquitous computing with guaranteed quality and continuity of service is the design of intelligent handoff algorithms. Traditional single-metric handoff decision algorithms, such as Received Signal Strength (RSS), are not efficient and intelligent enough to minimize the number of unnecessary handoffs, decision delays, call-dropping and blocking probabilities.
This research presents a novel approach for of a Multi Attribute Decision Making (MADM) model based on an integrated fuzzy approach for target network selection.
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Narisetti, Mary. "Implementation of Vertical Handoff Algorithm between IEEE802.11 WLAN and CDMA Cellular Network." Digital Archive @ GSU, 2006. http://digitalarchive.gsu.edu/cs_theses/24.
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Today’s wireless users expect great things from tomorrow’s wireless networks. These expectations have been fueled by hype about what the next generations of wireless networks will offer. The rapid increase of wireless subscribers increases the quality of services anytime, anywhere, and by any-media becoming indispensable. Integration of various networks such as CDMA2000 and wireless LAN into IP-based networks is required in these kinds of services, which further requires a seamless vertical handoff to 4th generation wireless networks. The proposed handoff algorithm between WLAN and CDMA2000 cellular network is implemented. The results of the simulation shows the behavior of the handoff and the time spent in WLAN or CDMA. The number of weak signal beacons determines whether a handoff is required or not. In this algorithm, traffic is classified into real-time and non real-time services.
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Rastogi, Nidhi. "A Novel Security Scheme during Vertical Handoff in Integrated Heterogeneous Wireless Networks." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1259071990.
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Narisetti, Mary. "Implementation of vertical handoff algorithm between IEEE 802.11 WLAN and CDMA cellular network." unrestricted, 2005. http://etd.gsu.edu/theses/available/etd-07202006-181806/.
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Thesis (M.S.)--Georgia State University, 2005.Title from title screen. Yi Pan, committee chair; Anu G. Bourgeois, A. P. Preethy, committee members. Electronic text (84 p. : i;;. (some col.)) : digital, PDF file. Description based on contents viewed July 2, 2007. Includes bibliographical references (p. 67-68).
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Hatzikonstantinou, Antonios C. "A unified architecture for adaption of mobile system behaviour : implementation of the vertical handoff paradigm." Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/17982/.
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Independent attempts from the computing and telecommunications worlds to provide wireless access resulted in networks with very different characteristics. This has given rise to a number of issues, such as the management of user mobility, power consumption, contingency when a communication session is interrupted etc. The result is significant Quality of Service fluctuation. A particular issue arises in an environment where more than one wireless networks offer coverage over the same area making the decision about which network to connect to, rather complex. The thesis offers the hypothesis that a unified architecture can meet the current QoS demands of qos-sentitive applications. It provides the framework that can effectively include, activate, configure and orchestrate disparate communication enhancement tools. The architecture must be extensible, flexible, and provide means for the incorporated modules to interoperate. Finally, it must allow the QoS requirements to be specified in platform independent ways and QoS adaptation to be effected under application, application manager, or user control in a continuous and dynamic way. The Vertical Handoff paradigm is studied as an illustration of a communication enhancement module of this architecture. Consider a two layer wireless network. Layer one offers high bandwidth but short-range coverage, while layer two offers low bandwidth but wide range coverage. A mobile host moving fast will experience high bandwidth with frequent handovers when connected to layer one or low bandwidth with fewer handover interruptions if connected to the bigger cells of layer two. This and other scenarios are studied in this research in order to test the hypothesis that the use of local and/or network cache can result in significant performance enhancement in terms of frequency of interruptions due to handovers and overall quality of the communication’s service depending on factors such as the host’s mobility, the population density, etc.
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Márquez, Barja Johann Marcelo. "SCALABLE AND EFFICIENT VERTICAL HANDOVER DECISION ALGORITHMS IN VEHICULAR NETWORK CONTEXTS." Doctoral thesis, Universitat Politècnica de València, 2012. http://hdl.handle.net/10251/17869.
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A finales de los años noventa, y al comienzo del nuevo milenio, las redes inalámbricas han evolucionado bastante, pasando de ser sólo una tecnología prometedora para convertirse en un requisito para las actividades cotidianas en las sociedades desarrolladas. La infraestructura de transporte también ha evolucionado, ofreciendo comunicación a bordo para mejorar la seguridad vial y el acceso a contenidos de información y entretenimiento.
Los requisitos de los usuarios finales se han hecho dependientes de la tecnología, lo que significa que sus necesidades de conectividad han aumentado debido a los diversos requisitos de las aplicaciones que se ejecutan en sus dispositivos móviles, tales como tabletas, teléfonos inteligentes, ordenadores portátiles o incluso ordenadores de abordo (On-Board Units (OBUs)) dentro de los vehículos. Para cumplir con dichos requisitos de conectividad, y teniendo en cuenta las diferentes redes inalámbricas disponibles, es necesario adoptar técnicas de Vertical Handover (VHO) para cambiar de red de forma transparente y sin necesidad de intervención del usuario.
El objetivo de esta tesis es desarrollar algoritmos de decisión (Vertical Handover Decision Algorithms (VHDAs)) eficientes y escalables, optimizados para el contexto de las redes vehiculares. En ese sentido se ha propuesto, desarrollado y probado diferentes algoritmos de decisión basados en la infraestructura disponible en las actuales, y probablemente en las futuras, redes inalámbricas y redes vehiculares. Para ello se han combinado diferentes técnicas, métodos computacionales y modelos matemáticos, con el fin de garantizar una conectividad apropiada, y realizando el handover hacia las redes más adecuadas de manera a cumplir tanto con los requisitos de los usuarios como los requisitos de las aplicaciones.
Con el fin de evaluar el contexto, se han utilizado diferentes herramientas para obtener información variada, como la disponibilidad de la red, el estado de la red, la geolocalizaciónMárquez Barja, JM. (2012). SCALABLE AND EFFICIENT VERTICAL HANDOVER DECISION ALGORITHMS IN VEHICULAR NETWORK CONTEXTS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/17869
Palancia
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Sethom, Kaouthar. "Gestion de la mobilité dans les réseaux sans fil de nouvelle génération." Paris 6, 2006. http://www.theses.fr/2006PA066410.
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Yarkan, Serhan. "Environment, channel, and interference awareness for next generation wireless networks." [Tampa, Fla] : University of South Florida, 2009. http://purl.fcla.edu/usf/dc/et/SFE0003269.
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Monteiro, Alex Fernando Duarte. "Seleção de interfaces de acesso baseada em análise de contexto." Universidade Federal do Amazonas, 2015. http://tede.ufam.edu.br/handle/tede/4070.
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The demand for different applications and services on the Internet has grown dramatically in recent years. To meet this demand, various wireless communication technologies with different characteristics have been used to provide access these services. However, not always technology wireless access used is the most appropriate to the requirements of the applications and services or even the user's interest in issues such as access speed, financial cost and power consumption. The main issue is how to identify the best network and access interface that offers the best value for money, meeting user expectations and operating autonomously. In order to propose a solution to address this issue, this paper describes a new interface selection mechanism based on analysis of contextual information obtained from the user and the device. This mechanism, called CANS (Context-Aware Network Selection), is composed of an acquisition module of context information and selection strategies and management interfaces specific to each type of access technology. The CANS is designed to operate on computers that support the Linux operating system. The evaluation of the proposed mechanism is held in the real environment. The results show that the adoption of the proposed selection strategies enables the user to better exploit the advantages of access technologies in an environment, achieving a reduction in device power consumption and financial cost.
A demanda por diferentes aplicações e serviços na Internet tem crescido drasticamente nos últimos anos. Para atender esta demanda, diversas tecnologias de comunicação sem fio com diferentes características têm sido utilizadas para fornecer acesso estes serviços. Contudo, nem sempre a tecnologia de acesso sem fio utilizada é a mais adequada aos requisitos exigidos pelas aplicações e serviços ou mesmo a questões de interesse do usuário como velocidade de acesso, custo financeiro e consumo de energia. A questão principal é como identificar a melhor rede e interface de acesso que ofereça a melhor relação custo benefício, atendendo as expectativas do usuário e que opere de forma autônoma. Com o intuito de propor uma solução para tratar essa questão, este trabalho descreve um novo mecanismo de seleção de interfaces baseado em análise de informações contextuais obtidas a partir do usuário e do dispositivo. Este mecanismo, denominado CANS (Context-Aware Network Selection), é composto por um módulo de aquisição de informações de contexto e por estratégias de seleção e gerenciamento de interfaces específicas a cada tipo de tecnologia de acesso. O CANS é projetado para operar em computadores que suportem o sistema operacional Linux. A avaliação do mecanismo proposto é realizada em ambiente real. Os resultados mostram que a adoção das estratégias de seleção propostas possibilita ao usuário explorar melhor as vantagens das tecnologias de acesso em um ambiente, obtendo uma redução no consumo de energia do dispositivo e do custo financeiro.
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Wu, Shao-feng, and 吳韶峰. "Synchronization of Media Streaming Services during Vertical Handoffs in Heterogeneous Wireless Networks." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/51311136425415322713.
Full textAbstract:
碩士國立中央大學
資訊工程研究所
93
With the rapid development of wireless network technologies, there are more and more heterogeneous wireless networks. High bandwidth of wireless heterogeneous networks make possible more and more media streaming services provided in heterogeneous wireless networks, such as the Voice over IP (VoIP), the video conference and the Video on Demand (VoD) and so on. But, media streaming services are fragile and affected easily by varied network qualities. And the following are the major problems to be solved. First, there are very different end-to-end delays in different wireless networks; it causes the offset of frame arrival times when a mobile node roams in heterogeneous wireless networks. Users will be conscious of frame dropped if the offset is too large. Second, the vertical handoff delay is too long and the mobile node may lose many packets in the duration. Users would feel the media streaming services suspended during vertical handoffs. The thesis proposes a Media Streaming Synchronization System (MSSS) which adopts a synchronization estimating algorithm (SEA) to estimate the sequence number of media frame which mobile node should request the media streaming server in different access networks. In other words, the MSSS can synchronize the media streams and then reduce the offset of frame arrival interval. In order to reduce packet loss during vertical handoff, the MSSS receives media streams from another interface before vertical handoff. Because of receiving media streams from multiple interfaces during vertical handoff, there are redundant frames received. The MSSS also reduce the redundant frames during vertical handoff effectively by SEA. In the thesis, the simulations show that the proposed MSSS could reduce 97.12% the offset of frame arrival time. At the part of packet loss during vertical handoffs, the MSSS can reduce approximately 72.69% packet loss and 78.18% redundant frames in average. Hence, the proposed MSSS could reduce the effect of varied network qualities on media streaming services.
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Kang, Rong-Jyh, and 康容致. "Seamless Vertical Handoff in Overlay Networks." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/95006831456846164217.
Full textAbstract:
碩士國立交通大學
資訊科學系
90
In the last decade, many new wireless communication systems have been developed. Those communication systems have different extents of network coverage, thus formed a hierarchical overlay networks. When moving between those networks, a vertical handoff mechanism is needed to handle the handover between different hierarchies of networks. The problem of current vertical handoff approaches is that the network infrastructures needed to be modified, which is almost impossible. In this thesis, we propose a seamless vertical handoff approach that can integrate the overlay networks to achieve high service availability. Our approach only modifies the two end nodes of a communication path so that we can keep the network infrastructure unmodified. It performs vertical handoff through TCP migration. To verify the feasibility of our approach, we implement a prototype system on Linux. The experiment results show that the time for vertical handoff performed by the system is short and acceptable for most of the applications.
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Larosa, Yanuarius Teofilus, and 雷提歐. "Cooperative Vertical Handoff Strategy inHeterogeneous Wireless Networks." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/m9qsc6.
Full textAbstract:
碩士國立臺灣科技大學
資訊工程系
98
Pursuing best vertical hando performance in e cient and seamless manner on heterogeneous wireless networks (HWN) is important and a multidimensional issue. Perceiving toward those problems, a mechanism that exploiting collaborative and opportunistic behaviors of mobile nodes is purposed in this thesis. Initially, analyzing network information dispersion on heterogeneous wireless network gives us knowledge about how optimally gather scattered and distinguished network information in HWN. Later, we can convince that the best connectivity and network selection mechanism incurred if mobile nodes are behaving based on our cooperative arranged scheme, called temporary cooperative network (TCN). Eventually, through comprehensive arranged simulations we exhibit that our TCN schemes give better overall performance than two other network selection strategies.
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Chuang, Sen Chu, and 莊森駒. "A vertical handoff mechanism in heterogeneous wireless network." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/25354378772400718666.
Full textAbstract:
碩士國立政治大學
資訊科學學系
97
In this paper, we propose a terminal –control scheme to avoid unnecessary vertical handovers between 3G cellular and WLAN hotspots. The proposed algorithm is a fuzzy logic based algorithm that can adapt itself to the dynamic conditions of the hybrid networks. The scheme can reduce the access delay, unnecessary handoff probability and aid the handoff decision for better connectivity. This handoff algorithm has much better performance than conventional algorithms and can be extended to other heterogeneous networks.
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Chen, Qi-Jin, and 陳奇進. "A Seamless Vertical Handoff Scheme over Heterogeneous Network." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/65597379436412076360.
Full textAbstract:
碩士國立中興大學
資訊科學研究所
94
During the past few years, with the dramatic improvement of networking technology, many new networking systems, for example IEEE 802.3 Ethernet network, IEEE 802.11 Wireless LAN and GPRS network, are proposed and deployed accordingly. However, no single network system can simultaneously provide low latency, high bandwidth and wide coverage area to users. Nevertheless, with the increasingly popularity of portable devices, how to efficiently select a suitable network system and seamless transfer connections from a network system to another network system is an important research topic. In this thesis, we thus proposed an end-to-end mobility management scheme that enables users to handoff between heterogeneous networks with short delay time. There are three components in our system: handoff decision, connection manager, and CWND Freeze. The proposed handoff decision can detect different network conditions and triggers a vertical handoff if necessary. Connection manager takes charge of the connection management and simultaneously support TCP and UDP. Furthermore, by connection manager, the performs connection migration is transparent to applications. Finally, a CWND freeze scheme is proposed to enhance TCP performance during a vertical handoff and in the wireless environment.
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Bai, Liping. "Adaptive Vertical Handoff for Integrated UMTS and WLAN Networks." Thesis, 2007. http://hdl.handle.net/10012/3414.
Full textAbstract:
Next-generation wireless networks have been envisioned to be an integration of heterogeneous wireless access networks such as UMTS (Universal Mobile Telecommunication Networks) and the IEEE 802.11 based
WLAN (Wireless Local Area Networks). It is an
important and challenging issue to support seamless vertical handoff management in such an integrated architecture that provides the mobile users uninterrupted service continuity anywhere, any time.
In such a networking environment, the signaling delay of the vertical handoff is not fixed due to the traffic load in the backbone Internet, wireless channel quality and the distance between a mobile node and its home network. However, the currently handoff solutions implicitly considers the signaling delay as a constant value.
In this thesis, we study a typical link layer assisted handoff, identifying its deficiency due to the considerably large handoff delay. We propose an adaptive vertical handoff management scheme for integrated UMTS and WLAN networks. The proposed scheme incorporates the idea of pre-handoff with adaptive handoff threshold. We estimate the handoff signaling delay in advance, therefore, providing the delay information required for making an adaptive handoff decision. Instead of setting a fixed threshold, an adaptive handoff threshold value is determined for every single MN based on the estimated handoff signaling delay. The RSS and the RSS's rate of change are used to determine the estimated handoff time instant. Extensive simulation has been conducted to verify the performance of the proposed handoff scheme.
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Zhang, Yongqiang. "Vertical Handoff between 802.11 and 802.16 Wireless Access Networks." Thesis, 2008. http://hdl.handle.net/10012/3725.
Full textAbstract:
Heterogeneous wireless networks will be dominant in the next-generation wireless networks with the integration of various wireless access networks. Wireless mesh networks will become to a key technology as an economically viable solution for wide deployment of high speed, scalable and ubiquitous wireless Internet services. In this thesis, we consider an interworking architecture of wireless mesh backbone and propose an effective vertical handoff scheme between 802.11 and 802.16 wireless access networks. The proposed vertical handoff scheme aims at reducing handoff signaling overhead on the wireless backbone and providing a low handoff delay to mobile nodes. The handoff signaling procedure in different scenarios is discussed. Together with call admission control, the vertical handoff scheme directs a new call request in the 802.11 network to the 802.16 network, if the admission of the new call in the 802.11 network can degrade quality-of-service (QoS) of the existing real-time traffic flows. Simulation results demonstrate the performance of the handoff scheme with respect to signaling cost, handoff delay, and QoS support.
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Hsiao, Shang-Feng, and 蕭尚峰. "Resource Management：Integrated Vertical Handoff Mechanism for Heterogeneous Wireless Networks." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/39970210105092586373.
Full textAbstract:
碩士中原大學
電機工程研究所
98
ABSTRACT The handoff of mobile wireless users among different heterogeneous networks is influenced heavily by radio signals. Actually, the real handoff also depends upon remaining resources of the network, various management of networks, and different grades of customers. Consequently, the handoff among heterogeneous networks should not be judged and decided only by the radio signal strength. The resource-allocation-based handoff strategy (RAHS) mechanism proposed in this paper can cope with the handoff management according to the perspective of the resource allocation. The handoff algorithm can be divided into three types, surpassing the range of the wireless coverage, erasing the overloading condition, and the active handoff of mobile users, respectively. The different scheduling and judging process is carried out according to the specific handoff. As a result, the fairness and objectiveness of the handoff scheduling can be guaranteed. The network performance hence can be improved further. The results of this thesis are beneficial to both theoreticians and engineers and promote the use of handoff scheme in the further mobile communications systems.
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Shu, Yen-Yuan, and 徐延源. "Active Application Oriented Vertical Handoff in Next-Generation Wireless Networks." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/14677398728454197093.
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Lin, Shu-yu, and 林書宇. "Mobile IPv6-based Efficient Vertical Handoff Approach for HeterogeneousWireless Networks." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/k8vcss.
Full textAbstract:
碩士朝陽科技大學
資訊工程系碩士班
93
The demand and amount of data transfer in heterogeneous wireless network increases as the techniques of the third/fourth generation mobile communications (3G/4G) are progressed significantly. Vertical handoff provides continuous and seamless transfer between various wireless mobile networks, which have different data transmission techniques and standards such as GPRS, UMTS, cdma2000 and IEEE 802.11 family WLANs. In contrast to the horizontal handoff, the vertical handoff should consider not only the strength of signal power but also QoS classes, network bandwidth and service types, etc. Most of the previous works proposed the Received Signal Strength (RSS) based methods to set thresholds for making the decision of performing vertical handoff or not. The RSS-based approach yields serious ping-pong effect when the mobile node moves around the overlay area of two heterogeneous wireless networks, which causes unnecessary handoff and increases the handoff overhead. Although the RSS-based approach with the hysteresis technique decreases the number of unnecessary handoffs, it remains large overhead of handoff, which causes some drawbacks, including low network throughput, long handoff delay and high dropping probability. Therefore, an efficient cost-based vertical handoff algorithm is proposed herein to reduce unnecessary handoffs while increasing network throughput, decreasing handoff delay and avoiding connection dropping. Two primary motivations of this paper include the prediction of node mobility from RSS and the adaptive cost-based competitive on-line (COL) method to determine the optimal network for handoff from several available wireless networks. Furthermore, message flows of vertical handoff between 3G/UMTS and WLAN with mobile IPv6 protocol are investigated in detail. Numerical results demonstrate that the proposed cost-based approach outperforms other approaches in the number of vertical handoffs and connection dropping while yielding competitive throughput.
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Juang, Ming-Jong, and 莊銘忠. "The Discussion on Vertical Handoff Mechanisms in Heterogeneous Wireless Networks." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/kp2z77.
Full textAbstract:
碩士國立東華大學
資訊工程學系
96
Due to the development of various wireless communication technology different communication have diversify characteristics in coverage, bandwidth and mobility. For example, the WLAN（Wireless Local Area Network）provides a relatively higher bandwidth with smaller coverage and less mobility while WWAN（Wireless Wide A rea Network） and WMAN（Wireless Metropolitan Area Network） maintain greater coverage and enhanced mobility with relatively narrower bandwidth. Therefore, it is important to take advantage of these wireless communication technology, combining associated techniques to form Heterogeneous Wireless Network in an effort to furnish the users with borderless network environment with the capability to retrieve internet resources by using the function of roaming. At the present, the portable equipments are generally supplied with multiple networks interfaces which ensure the users with roaming capability between various network systems. Among the variety of topics under roaming, there are two critical issues. The first one is the Mobile Management, with the emphasis on discussing how two different networks find each other, exchange information and the associated action after handoff. In terms of handoff management, the main consideration is about network system condition and the decision process on selecting the appropriate network. The issues involve the methodology making the users roaming under different network systems, switch with well timing to usable network without loss of data during the process. Hence, the handoff decision under the handoff management mechanism becomes crucial. This report focuses on Vertical Handoff decision between networks of differing character and seeks to compare and analyze various handoff decisions. The result of this discussion will become the references of future research.
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Chen, Chien-Ta, and 陳建達. "MDP-based CAC and Vertical Handoff in Heterogeneous Wireless Networks." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/86465069739132201680.
Full textAbstract:
碩士朝陽科技大學
資訊工程系碩士班
96
Call Admission Control (CAC) and Vertical Handoff (VH) are two important mechanisms for a heterogeneous wireless network (HWN) that consists of various wireless networks (e.g., WiMAX and WiFi) and cellular communications (e.g., 3G, 3.5G and 4G). First, an adaptive CAC has the capability to achieve high network reward while guaranteeing QoS transmission. Second, an efficient vertical handoff enables mobile nodes achieving seamless, fast, QoS-aware mobility in HWN. In CAC, most researches proposed several mechanisms: the static/dynamic resource reservation-based, bandwidth borrow-based, and Markov chain model-based approaches. They suffer from moderate Grade of Service (GoS), Fractional Reward Loss (FRL), and transmission quality. In VH, VH considers not only the received signal strength (RSS), but also service-class mapping between the serving and target networks. Most studies have adopted the RSS-based method and the method integrating the RSS-based method with a hysteresis to minimize unnecessary handoff. High handoff dropping and low network utilization limit the contribution. This paper thus proposes a Markov decision process (MDP) CAC and a cross layer (CL) predictive RSS for vertical handoff in a loosely-coupled heterogeneous wireless network. First, the MDP CAC models the available resource of each wireless network in HWN as a Markov decision process, and then forms a cost-reward mechanism for maximizing network reward. Second, the CL VH scheme adopts: (1) a predictive RSS to predict the moving trend of each mobile node and (2) a cross layer mechanism for a TCP receiver to reply to the sender with the information of currently serving wireless network’s protocol-type. Numerical results indicate that the proposed approach outperforms other approaches in GoS, FRL, and number of vertical handoffs while yielding competitive utilization. Additionally, the cross layer scheme cooperates with existing TCP algorithms for increasing goodput up to 28%.
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Huang, Xie-Kuan, and 黃劦寬. "An Adaptive Scheme for Vertical Handoff in Wireless Overlay Networks." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/24768896495403082228.
Full textAbstract:
碩士國立清華大學
資訊工程學系
91
The next-generation communication system will combine several different wireless access technologies with different coverage, bandwidth, cost and power consumption, such as IEEE802.11, GPRS/EDGA and WCDMA. Vertical handoff is the switching process between base stations with different wireless technologies. Discovering the reachable wireless networks is the first step for vertical handoff. The mobile terminal must discover the reachable wireless networks before performing vertical handoff. After discovering the reachable wireless networks, the mobile terminal decides whether to perform handoff or not relying on the demands of the running application, the resources of the reachable wireless networks and the moving speed. In this thesis, we proposed an ideal coverage concept and the adaptive interface activating method for the mobile terminal to discovery the reachable wireless network effectively. Moreover, we present two adaptive handoff decision methods for the mobile terminal to determine the handoff timing. The simulation results show that the proposed system discovery method can balance the power consumption and the system discovery time. Furthermore, the proposed adaptive handoff decision methods help the mobile terminal to decide the appropriate handoff timing.
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Liu, Chang-Wei, and 劉昌瑋. "Study of Vertical Handoff for WiMAX and WiFi Heterogeneous Network." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/87416021813642814909.
Full textAbstract:
碩士清雲科技大學
電腦通訊與系統工程研究所
100
Following the wireless network to develop rapidly, many cities have deployed WiFi nodes. Users can connect to the Internet anytime and anywhere in the service ranges of these nodes. The service ranges of WiFi nodes are small, users often subject to the signal weakened or interrupted from the influence of terrain and building cannot connect. Therefore, this paper proposes an intelligent vertical handoff algorithm for the integration networks of WiMAX and WiFi. WiFi and WiMAX combined in the module, it make the mobile stations (MS) of signal weakened can handoff to light-load base stations (BS) and can maintain normal call continuity. Also, an ongoing-call user can hand-over from the original congested BS to others light-load BS, it will release the using channel resource to the just reached handoff-call or new-call on original congested BS. Through the simulation results prove that this algorithm can effectively enhance the quality of communications services.
36
Xiao, Wei-Cheng, and 蕭偉成. "An Intelligent Decision Model for Seamless Vertical Handoff across Heterogeneous Networks." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/98018503848075424647.
Full textAbstract:
碩士國立臺灣大學
資訊工程學研究所
94
In recent years, network technologies such as WLAN, GPRS, and 3G are getting more and more popular. There is high probability that signal coverage of these coexisting networks overlaps with each other. For a user roaming among these networks, it is desirable that his or her mobile device can have anytime connectivity, and therefore vertical handoff becomes an important issue. To achieve high performance, a user may want to choose the best network to connect to. However, properties such as signal coverage area, maximum data rate, monetary cost, and power consumption on end devices vary largely among these networks. Moreover, different types of services require various combinations of these properties. While most vertical handoff schemes are based on single optimization policy in which service difference is not taken into consideration, we propose a service-based handoff decision model. Through this decision model, weight of the parameters in the cost function is adjustable based on the type of service in use, and therefore we can make a more appropriate decision on network selecting. In recent research, mobile IP is a generally used handoff scheme. However, to facilitate vertical handoff, help from a home agent and a foreign agent is required in the mobile IP scheme, which induces overloading on the agents themselves. In our handoff scheme, only with mobile host itself can handoff be realized, hence the overall handoff scheme is simplified. Moreover, through our implementation, handoff latency can probably be even shorter than that in the mobile IP scheme.
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Chen, Li-Ming, and 陳力銘. "QoS-based Vertical Handoff between IEEE802.11 WLAN and GPRS Cellular Network." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/11963943884859601560.
Full textAbstract:
碩士國立臺灣大學
資訊工程學研究所
92
With the rising and flourishing development of mobile communication markets, many international organizations and research groups have promoted B3G (3G and Beyond) research and standard actively. The vision of B3G is expected to integrate all kinds of wireless technologies and create a heterogeneous multi-access network which provides wireless users with convenient global information access capabilities and multimedia wireless communication services. In the heterogeneous multi-access network, vertical handoff had been proposed to achieve seamless handoff between different kinds of wireless technologies. In addition to the mobility management, we propose that the vertical handoff is also a good way to avoid degrading QoS due to wireless channel interference or network overload. Instead of RSS, the proposed algorithm uses measured bandwidth as the criterion for handoff decision. In this paper, a QoS-based vertical handoff scheme is proposed. The vertical handoff process is divided into two phases. In the handoff trigger phase, access network selection and handoff time decision is made by the vertical handoff algorithm. In order to maintain the QoS, the handoff algorithm will guide mobile device to switch between IEEE802.11 WLAN and mobile cellular networks by comparing their transport capacity and the user service requirements. In the handoff execution phase, a smooth (seamless) vertical handoff procedure is involved. We design a loosely coupled WLAN and GPRS network with mobile IP. In order to reduce the registration latency, an enhancement of mobile IP is also proposed. In this paper, we will simulate the vertical handoff process in the NS2 to verify the design.
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Gyekye, Yaw Nkansah. "An intelligent vertical handoff decision algorithm in next generation wireless networks." Thesis, 2010. http://hdl.handle.net/11394/3449.
Full textAbstract:
Philosophiae Doctor - PhDSeamless mobility is the missing ingredient needed to address the inefficient communication problems faced by the field workforces of service companies that are using field workforce automation solutions to streamline and optimise the operations of their field workforces in an increasingly competitive market place. The key enabling function for achieving seamless mobility and seamless service continuity is seamless handoffs across heterogeneous wireless access networks. A challenging issue in the multi-service next generation wireless network (NGWN) is to design intelligent and optimal vertical handoff decision algorithms, beyond traditional ones that are based on only signal strength, to determine when to perform a handoff and to provide optimal choice of access network technology among all available access networks for users equipped with multimode mobile terminals. The objective of the thesis research is to design such vertical handoff decision algorithms in order for mobile field workers and other mobile users equipped with contemporary multimode mobile devices to communicate seamlessly in the NGWN. In order to tackle this research objective, we used fuzzy logic and fuzzy inference systems to design a suitable handoff initiation algorithm that can handle imprecision and uncertainties in data and process multiple vertical handoff initiation parameters (criteria); used the fuzzy multiple attributes decision making method and context awareness to design a suitable access network selection function that can handle a tradeoff among many handoff metrics including quality of service requirements (such as network conditions and system performance), mobile terminal conditions, power requirements, application types, user preferences, and a price model; used genetic algorithms and simulated annealing to optimise the access network selection function in order to dynamically select the optimal available access network for handoff; and we focused in particular on an interesting use case: vertical handoff decision between mobile WiMAX and UMTS access networks. The implementation of our handoff decision algorithm will provide a network selection mechanism to help mobile users select the best wireless access network among all available wireless access networks, that is, one that provides always best connected services to users
39
Wang, Ching-Hsiang, and 王慶祥. "A Dynamic Resource Allocation for Vertical Handoff on Heterogeneous Wireless Networks." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/53760987842179185024.
Full textAbstract:
碩士朝陽科技大學
資訊管理系碩士班
91
With technical advanced of video communication and application of wireless networks in recent years, the way that people communicate are dramatically changed. Many mobile handset devices are not only as a telephone but also able to browse web pages, transmit messages, inquire locations by GPS, subscribe video on demand and execute video conference with remote users. However, there are still some issues needed to be resolved. For instance, the mobile user does not stay at a fixed place, so the mobile device has to hand off between neighboring base stations to continue the ongoing connection. But the handoff operations will introduce significant delays and degrade the Quality of Service (QoS) on multimedia during the handoff period. In addition, there are many varieties of heterogeneous wireless networks coexisted in the same space simultaneously. Wireless cells of different networks have different capabilities, for example, the cells of wireless LAN can provide high data transmission rate and those of the wireless WAN can support high velocity of mobile nodes. It is necessary to design a scheme for selecting the candidate cells to satisfy the QoS requirements of mobile users from these heterogeneous networks. In this thesis, we propose a dynamic resource allocation model that is mainly suitable for the multimedia transmission on heterogeneous wireless networks. This model has two goals. First, it induces the resource map of the current cell using the beacon codes received from the neighboring cells. It then extracts the mobility pattern of the mobile nodes from past handoff records by the BPN neural network. With the mobility pattern, we can infer which cells would be possible target ones of the mobile node when it moves. Second, it uses rules of application layers, e.g., the communication cost, maximal moving velocity, maximal data rate, etc., to select candidate cells from the target ones chosen above. It then executes dynamic resource allocations on the candidate cells for supporting the mobile node with guaranteed QoS in advance. In this way, it decreases the handoff call dropping probability and new call blocking probability, and further, increases the resource utilization on the heterogeneous wireless networks.
40
Wang, Ying-Yuan, and 王穎淵. "Improving TCP Performance with Fast Adaptive Congestion Control during Soft Vertical Handoff." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/14695504995708108044.
Full textAbstract:
碩士朝陽科技大學
資訊工程系碩士班
94
With the extensive spread of the Internet and mobile terminals, Internet access from a mobile terminal becomes more important than ever before. In the Internet, the Transmission Control Protocol (TCP) is used as a standard data transport protocol; however, it is well known that TCP performance degrades in wired-wireless network environments. This is because TCP was designed originally for an exclusively wired network environment. In a near future, mobile users demand the diverse multimedia services with higher bandwidth over a larger area. There is usually a hot spot area like airports, hotels and large buildings since mobile users are not equally distributed in a service area. These needs justify a hierarchical mobile wireless network. In a hierarchical network, a larger mobile network supporting a lower bandwidth service overlays a smaller mobile network supporting a higher bandwidth service. Current trends show that a wireless wide area network (WWAN) and a wireless local area network (WLAN) will co-exist and complement to constitute a hierarchical network. To integrate these two technologies, there are many issues such as the network architecture, mobility management, and security which should be solved. During vertical handoff, some undesirable phenomenon may erroneously trigger TCP congestion control operations and thus degrade the TCP performance. In this thesis, we propose an approach that can fast estimate available bandwidth when the MN (Mobile Node) handoff occurs. Then the sender updates adaptive slow-start threshold (ssthresh) and congestion window size (cwnd) to improve TCP performance during soft vertical handoff in hybrid mobile networks. Base stations send advertisement messages to get bandwidth information to help the MN judge about what kind of handoff. When handoff is impending, receiver sends a handoff notification from another link during soft vertical handoff. The receiver uses Handoff Notification option field in TCP header to notify the sender while a handoff is impending. The receiver will send this kind of ACK from the new link. When the sender receives this ACK, it will halt some parameters about timeout timers and freeze the data transmission. TCP gets the value of Round Trip Time (RTT) when it receives this ACK in a new network environment. Base stations send advertisement messages at a regular interval to help the MN to detect link changes. Then, TCP readjusts proper ssthresh by exponential weight moving average (EWMA) for transmission congestion control. We examine a TCP performance during a soft vertical handoff between a WLAN and a WWAN and discuss some problems that the current TCP will experience during soft vertical handoff and propose a scheme to improve TCP performance. Our scheme requires only minor modifications on transport layer of the end hosts. Finally, simulation results show that our scheme can effectively improve the TCP performance.
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Yeh, Chi-Shuai, and 葉旗帥. "A SIP-Based Vertical Handoff Mechanism for Multimedia Streaming in Heterogeneous Networks." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/88979694274740412944.
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碩士國立成功大學
資訊工程學系碩博士班
95
The trend of next generation mobile networks is to embed more than one wireless connectivity, e.g., equipped with WLAN and 3G simultaneously. In a heterogeneous network environment, users may suffer horizontal handoffs or vertical handoffs during their movement. Most current handoff solutions are received signal strength (RSS) oriented, in which the RSS with threshold (RSS-T) and the RSS with hysteresis and threshold (RSS-HT) are most popular. However, the RSS-T approach would suffer many unnecessary handoffs at the edge of the wireless networks. Although the RSS-HT mechanism can reduce such unnecessary handoffs, it may still have several drawbacks, such as high handoff delay and low network throughput. This thesis proposes a vertical handoff mechanism for multimedia streaming services in heterogeneous networks. The proposed vertical handoff algorithm employs (1) adaptive hysteresis with threshold to determine which access technique is the better one and (2) a score function for subnet selection. In addition, we adopt the MPEG-4 layered streaming technology and a frame re-transmission mechanism to maintain the multimedia streaming quality during the handoff operation.
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Liu, Chun-Yi, and 劉俊毅. "Vertical Handoff and Load Balancing for Heterogeneous Wireless Networks using Combinatorial Fusion." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/dzhyqa.
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博士國立清華大學
資訊工程學系所
105
Network selection in Heterogeneous Wireless Networks (HWN) aims to select the best network for a variety of communication tasks at any time and anywhere. Due to its importance and necessity, it has been studied using various mathematical models including game theory, multiple attribute decision making (MADM), Markov chain, and fuzzy logic. Since these models have different features and functions to produce different results, it has been suggested to combine these models in order to harness the benefit of individual model. However, it remains a challenge to decide when and how to combine these models or systems. In this thesis, we propose a new approach to study the network selection problem in HWN using combinatorial fusion. More specifically, we investigate: (a) vertical handoff decision to fuse three metrics: received signal strength (RSS), data rate, and network latency using fuzzy logic and combinatorial fusion; and (b) load balancing using combinatorial fusion on three metrics: RSS, accumulated message queue length, and channel utilization. Experimental results demonstrated that our method can make network selection much simpler and more effective. Our work provides a novel way to fuse these metrics for network selection. It is also the first method to integrate fuzzy logic and combinatorial fusion in solving the network selection problem in heterogeneous wireless network.
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MING-HSIUNG, CHUANG, and 莊明雄. "Realization of Vertical Handoff of Mobile IP on Mobile Platforms Using SCTP." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/49awp5.
Full textAbstract:
碩士國立宜蘭大學
電機資訊學院碩士在職專班
107
In recent years, wireless communication has evolved and encompasses various types of wireless technologies which differ in many aspects, leading to a heterogeneous network environment. Users can switch to different network connections through vertical handoffs. In order to improve the performance in such a heterogeneous network environment, IETF proposed the stream control transmission protocol (SCTP) in 2000. SCTP combines the advantages of both TCP and UDP and offers features such as multi-homing, multi-streaming, and selective acknowledgment. In this thesis, we describe the basic operations of SCTP and how these features can improve throughput and reduce the receiver buffer size. Specifically, we use SCTP to achieve simultaneous transmissions of packets on multiple links and make the handoff process smooth with good transmission quality. The network environment of this research comprises 3G/4G and Wi-Fi. The multi-homing feature of SCTP combined with dynamic address reconfiguration and expansion of functions helps mobile devices achieve seamless vertical handoffs. The Mobile Node (MN) emulates endpoint device with an iOS mobile device, and the Correspondent Node (CN) emulates endpoint device with an Android mobile device. CBR packets are sent from the MN to the CN. In addition, another mobile device transmits FTP data on the same link starting at 10 seconds, 20 seconds, and 30 seconds, respectively, for three different scenarios: (1) Web Browsing in 3G and WiFi, (2) VoIP in WiFi and LTE, and (3) Video Streaming in 3G and LTE wireless network environment. The bandwidth contention between CBR and FTP traffic causes the RTT to go up. In the proposed QoS-based path switching scheme, bandwidth, RTT,and packet loss are used as the criteria for path switching. Simulation results demonstrate that the proposed method compares favorably against other handoff schemes.
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Huang, Kun-Shi, and 黃坤喜. "Implementation of Mobile-IP based Vertical Handoff in a Heterogeneous WiMAX and WLAN." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/bcmb2x.
Full textAbstract:
碩士國立中山大學
電機工程學系研究所
95
Many different wireless technologies have increased the demand of accessing Internet resources through wireless networks. One of the most popular applications is watching multimedia streaming over wireless. However, when a user is roaming in a heterogeneous network, he needs to acquire adequate bandwidth from different wireless access points. In this Thesis, we propose a Mobile-IP based vertical handoff scheme in a heterogeneous WiMAX and WLAN. When a mobile node is in the overlapped area of WiMAX and WLAN, it may have to execute the vertical handoff based on the received average signal strength, the transmitting queue length of network interface, and the available network bandwidth. Our goal is to reduce the influences of RTP-based video streaming when the network is congested and when a mobile node executes the vertical handoff in the heterogeneous network. We implement the Dynamic Mobile-IP based vertical handoff on Linux platform by modifying handoff decisions between WiMAX and WLAN. The above-mentioned performance parameters are implemented as modules on Linux platform. At last, we prove that our scheme can effectively improve packet loss ratio and system processing ratio. As a result, the frame mosaic phenomenon and frame slow-playing phenomenon in RTP-based video streaming can be significantly improved.
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Heng-TienWu and 吳姮瑱. "Efficient Load-Aware Vertical Handoff for HetNet with Poisson-Point-Process Distributed Traffics." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/07858804110232434057.
Full textAbstract:
碩士國立成功大學
電腦與通信工程研究所
103
Nowadays, the emerging hyper-dense heterogeneous network (HetNet) is an effective solution to building an easy-access wireless communication environment. In the hyper-dense HetNet, however, the inescapable handoff procedure is the key to its success. An effective handoff algorithm can not only achieve the goal of load-balancing but also enhance the overall system capacity. In this thesis, we proposed an efficient load-aware vertical handoff (VHO) algorithm for HetNets. With the aid of the system load information from the neighboring cells, the computational complexity during the VHO procedure can be significantly reduced. Moreover, by effectively multi-stage off-loading the cells with relatively light traffic loads, the dropping rate can be significantly reduced. Most importantly, the user and the overall system capacity can be greatly enhanced as well.
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Hsu, Chin-Wei, and 許晉維. "Performance of Adaptive Hysteresis Vertical Handoff in Heterogeneous Networks of WCDMA and WLAN Systems." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/37911205775919539928.
Full textAbstract:
碩士朝陽科技大學
資訊工程系碩士班
97
This thesis explores the performance of adaptive vertical handoff schemes for overlaid WCDMA and wireless LAN (WLAN) heterogeneous networks. We propose an adaptive hysteresis vertical handoff scheme to effectively adjust the hysteresis to compromise the handoff rate and bandwidth. Simulation results show that the proposed Adaptive hysteresis Vertical (AHYV) handoff scheme can increase lots of average data rate than the fixed hysteresis vertical handoff scheme. Furthermore, with quality of service (QoS), we model three service by video, talk and internet services. Moreover, for three type mobility users with0, 10 and 60(km/hr), we design QoS based AHYV (QAHYV) schemes to compromise the handoff rate and system bandwidth. Simulation results show that the proposed QAHYV can not only reduce the handoff rate but also maintain the demanded QoS bandwidth for different mobile users.
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Huang, Tin-Chun, and 黃鼎鈞. "Design and Implementation of TCP-Compatible SCTP Vertical Handoff Platform for All-IP Heterogeneous Networks." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/28881676338533788083.
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Chung-Wei, Li. "Design and Implementation of Seamless Vertical Handoff Algorithms for Voice Communications on Dual-Mode Mobile Devices." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2707200613505400.
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Li, Chung-Wei, and 李中崴. "Design and Implementation of Seamless Vertical Handoff Algorithms for Voice Communications on Dual-Mode Mobile Devices." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/69237965489868173267.
Full textAbstract:
碩士國立臺灣大學
電信工程學研究所
94
The objective of the thesis is to design and implement algorithms for seamless vertical handoff between GSM and VoWLAN on dual-mode mobile devices. Due to the low cost of WLAN chips, in the future everyone is expected to own one or more dual-mode handsets equipped with the GSM and WLAN modules. Although the users can access GSM and WLAN simultaneously, they still won''t feel convenient without the interoperability between GSM and WLAN. For example, people wish to use VoIP through WLAN access to save money but use GSM audio service to maintain session continuity. Currently, there are several research endeavors working toward solving the vertical handoff problems between GSM and VoWLAN access, including proprietary and standardized solutions. However, current proprietary solutions are designed for specific dual-mode clients and the users cannot enjoy the vertical handoff services without the specific handsets. Standardized solutions are designed for GSM telephony operators and hence vertical handoff services will fail if the users are not within the coverage of corresponding WLAN service. Therefore, we need to design a flexible vertical handoff solution to satisfy all situations, including all kinds of dual-mode clients, different WLAN operators, and different GSM operators. To design our intelligent vertical handoff algorithm, we conduct several experiments to figure out potential problems during the vertical handoff procedure. By way of the experimental results we understand that the problems of deciding handoff timing and synchronizing two different audio streams are the most critical issues. To perform seamless vertical handoff between VoWLAN and GSM accesses, we design the handoff decision mechanism to ensure that the GSM and VoWLAN coverage will overlap. By utilizing the audio time-scaling method, we design an audio mixing mechanism to ensure seamless audio switching between GSM and VoWLAN. To implement the algorithm on a dual-mode client, we make several modifications on related entities. At the remote client side, we let it respond to the handoff querying by using winsock programming. At the dual-node client side, we do the handoff triggering and modify the SIP softphone to perform audio waveform tapping for controlling and buffering the instant audio streams of GSM and VoWLAN. The results show that without audio mixing algorithm, there is audio block for more than three hundred milliseconds. With audio mixing mechanism, on the other hand, there is no audio gap during the vertical handoff procedure and the audio streams can be seamlessly migrated. Hence, the proposed vertical handoff algorithms with audio mixing can help the dual-mode client seamlessly switch the audio path and achieve seamless vertical handoffs between GSM and VoWLAN.