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Improving TCP Handover Performance in Wireless NetworksHuang, Chun-che 03 August 2010 (has links)
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Modelo para transparência de handover vertical em redes de quarta geraçãode Oliveira Nóbrega, Obionor 31 January 2011 (has links)
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Previous issue date: 2011 / Universidade Federal de Pernambuco / Atualmente diversas pesquisas têm sido elaboradas para melhorar o uso da tecnologia
móvel pelo usuário final. O desenvolvimento da quarta geração de sistemas de comunicação
móveis (4G) possui grandes desafios para a Internet do Futuro (FI). Dentre estes desafios está a
transparências de handover vertical, pois esta ação influencia diretamente na percepção do
usuário quanto à qualidade de experiência (QoE) e qualidade de serviço (QoS).
Este trabalho propõe um modelo para transparência de handover vertical centrado nas
preferências do usuário, nos requisitos de suas aplicações e nas características das redes. O
modelo proposto possibilita a predição de caminhos de um usuário com perfil de mobilidade e a
busca antecipada de informações das futuras redes candidatas de forma colaborativa. Para
selecionar previamente a rede candidata, utiliza-se o método AKAIKE em conjunto com a
técnica de regressção linear múltipla para estimar a melhor rede, considerando até nove
parâmetros, como características da rede, requisitos da aplicação e preferências do usuário. Este
modelo apresenta como diferencial a integração entre estas funções, por meio da utilização de
mensagens de sinalização MIH (Media Independent Handover), tornando-o compatível com o
padrão IEEE 802.21.
Como metodologia de avaliação de desempenho utilizou-se a modelagem com rede de
Petri e matemática, assim como simulações com a ferramenta estatísitca R, a ferramenta de
simulação Network Simulator e a ferramenta de avaliação de vídeos Evalvid. Como resultado, a
transparência de handover é obtida com a diminuição da percepção visual do usuário de
aplicações de vídeo em tempo real, durante o processo de handover vertical em redes
heterogêneas de quarta geração
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Integriertes, adaptives Dienstgüte- und Mobilitätsmanagement in MPLS-basierten Funkzugangsnetzen /Horvath, Oliver. January 2007 (has links)
Zugl.: Frankfurt (Main), Universiẗat, Diss., 2007.
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Handover among multidisciplines in obstetrics / Handover among multidisciplines in obstetrics: a mixed methods study of content and communication processPace, Julie 11 1900 (has links)
Background: Communication failures during handover has long been noted as a threat to patient safety.1 Breakdown in communication among health professionals is reported to account for up to 85% of hospital sentinel events.1 Lack of formal structure and training in handover methods 53 as well as modes of communication including nonverbal behaviors 59 have been reported to affect the quality of information exchange in handovers. 59 The objective of this mixed methods study is to conduct a detailed analysis of handover content among physicians and among nurses on a Birthing Unit and to examine communication processes within these groups in order to identify gaps in the process. This may provide a basis for future development of standardized approaches and training efforts.
Methods: A convergent, parallel mixed methodology was used. The sample in this study comprises the nurses and medical obstetrical team in a hospital Birthing Unit in Hamilton Ontario. Phase one of the study involved initial observations of handover, performing a Delphi to gain consensus on handover content and creating a handover assessment tool. Phase two involved reliability testing of the tool and in phase three, twenty five paired nurse to nurse compared to medical handovers were video recorded, scored and correlated to participant questionnaires.
Results: Gaps in handover content were identified; the nurses achieved a mean score of 10.24 items compared to physicians mean score of 9.02 (correlation 0.582, p <0.01). This showed statistically significant differences in the items mentioned among the two groups
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(t = 13.2, p < 0.001). Nonverbal behaviors noted during handover observations revealed inconsistencies in conveying information, within and between the two groups. The findings of this study contribute to a better understanding of handover gaps, has implications to other health team practices and highlights the need for standardized processes, training and policy development. / Thesis / Master of Science (MSc)
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CPMIPV6: uma abordagem intradomínio e interdomínio para redes IP móveisQUENTAL, Nivia Cruz 04 March 2016 (has links)
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Previous issue date: 2016-03-04 / A continuidade de sessões de comunicação entre sistemas finais, denominados nós, sobre
redes móveis heterogêneas mediante handover tem sido objeto de estudo de pesquisas
recentes. A ampla difusão de aplicativos multimídia para dispositivos móveis, permitindo
a interação entre usuários que se deslocam em uma rede móvel, tornam esse problema
ainda mais relevante e atual. No âmbito da mobilidade IP, alguns dos principais desafios
envolvem aliar interoperabilidade entre tecnologias de acesso e baixa latência de handover,
além de permitir a transição entre redes de domínios diferentes de forma transparente.
O protocolo Proxy MIP versão 6 (PMIPv6) torna locais as operações de gerenciamento
de mobilidade de modo a reduzir o overhead de comunicação em relação ao Mobile IP
(MIP). Entretanto, o consequente isolamento da gerência de mobilidade ao domínio local
impede que a transição entre diferentes domínios ocorra de forma transparente ao usuário.
A presente tese apresenta o Clustered PMIPv6 (CPMIPv6) como uma abordagem
intradomínio e interdomínio de baixo custo e latência para a camada de rede baseada
no Protocolo PMIPv6. Essa abordagem consiste em utilizar gerenciamento de mobilidade
distribuído como forma de compartilhar e antecipar informações de nós móveis à entidadeâncora
de cada domínio. Para tal, um cluster é formado por essas entidades-âncora e a
comunicação entre elas ocorre por meio de um protocolo P2P. Esse gerenciamento torna a
obtenção de informações dos nós móveis simplificada em handovers interdomínios futuros.
O caráter distribuído do CPMIPv6 associado ao mínimo de acréscimo de mensagens de
sinalização além daquelas existentes no PMIPv6 permite manter a infraestrutura da rede
original, sem introduzir entidades centralizadoras. Comparações entre soluções do Estado
da Arte e o CPMIPv6 são realizadas por meio de modelagem e simulação. Com auxílio do
simulador NS-3, um subconjunto dessas soluções são avaliadas em um cenário básico com
baixo número de usuários e de redes disponíveis. Os resultados de experimentos utilizando
modelagem executados em cenários com alta densidade de nós indicam que o CPMIPv6
obteve custo de sinalização ao menos 12% menor, latência no mínimo 16% inferior e
perda de pacotes ao menos 16% menor. Ademais, o CPMIPv6 obtém goodput superior às
demais abordagens. Ambos experimentos confirmam o CPMIPv6 como a abordagem intradomínio
e interdomínio com melhor desempenho nos cenários avaliados. O CPMIPv6
é um importante salto na evolução dos sistemas de comunicações móveis extrapolando
as fronteiras das tecnologias de enlace e limites de domínio sem perder as vantagens da
comunicação no âmbito local. / Communication sessions continuity among wireless devices during handover in heterogeneous
networks have been studied in recent research. The evolution and widespread
multimedia applications for mobile gadgets make that problem even more relevant. Some
of the main challenges in IP mobility include associating access technologies interoperability,
low handover latency, and seamless handover among different domains. Proxy MIP
version 6 (PMIPv6) protocol aims at reducing signaling overhead in comparison to Mobile
IP (MIP) making local the management operations. However, that local management
prevents the possibility of seamless interdomain handover. This thesis presents Clustered
PMIPv6 (CPMIPv6) as a low-cost and low-latency approach for intradomain and interdomain
handover in the network layer based on PMIPv6. That approach consists in using
distributed mobility management as a mean to share and anticipate mobile nodes information
to anchor entities in each domain. In order to achieve this, domain entities from each
domain forms a cluster and uses a P2P protocol for communication. That management
simplifies mobile nodes information gathering used in future interdomain handovers. CPMIPv6
distributed feature associated to a minimum set of additional signaling messages
to PMIPv6 allows to maintain the original networks infrastructure without introducing
centralized entities. Comparisons among state of the art approaches and CPMIPv6 are
made by means of analytical modeling and simulation. Simulations were run with the NS-
3 network simulator with a subset of the approaches in a small scenario with low number
of nodes and available networks. Modeling results in scenarios with high node densities
have shown that CPMIPv6 reduced cost in at least 12%, reduced latency at least in 16%,
and caused at least 16% reduction on packet loss. CPMIPv6 additionally obtained better
goodput values. Both experiments confirmed CPMIPv6 as the best interdomain approach
in the selected scenarios. Thus, CPMIPv6 is an important leap to the mobile communication
systems evolution going beyond link-layer technologies and domain frontiers without
losing the advantages of local signaling.
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Using Anycast Concept to Improve QoS of Session-Oriented Mobile ServicesYang, Kai-ting 28 August 2006 (has links)
In response to the presence of portable devices and the change in usage patterns, mobility support for computer networking has received increasing attentions in recent years. There has been wide variety of established works focusing on the shortening of the handover delay. Most of them had tried their best in maintaining the connections to their peer nodes as mobile nodes moving across different network domains. This might not be a best policy in certain applications, such as homogeneous content distribution systems.
A new handover scheme incorporating anycasting and service migration is developed and presented in this thesis. In the proposed approach, anycast is used to locate a new nearest server as a mobile node entering a new domain, and an ongoing service will be dynamically migrated from a distant server to a new server with shorter weighted network distance to the client. As a result, the individual service connection, as well as the global network environment, will benefit from the service migration, in terms of improved service quality and bandwidth utilization.
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Handover im mobile broadcastMay, Gunther January 2009 (has links)
Zugl.: Braunschweig, Techn. Univ., Diss., 2009
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Ποιότητα υπηρεσιών, κινητικότητα και ενεργειακή κατανάλωση σε ασύρματα τοπικά δίκτυα (WiFi)Μανωλόπουλος, Τιμολέων 26 August 2009 (has links)
Αντικείμενο της παρούσας διπλωματικής εργασίας είναι η μελέτη της κινητικότητας,
της ποιότητας των υπηρεσιών (QoS) και η ενεργειακή κατανάλωση σε ασύρματα τοπικά
δίκτυα, όταν αυτά διασυνεργάζονται με άλλης κατηγορίας δίκτυα ασύρματων
επικοινωνιών. Στο σύγχρονο αυτό ετερογενών τεχνολογιών περιβάλλον, προτείνουμε ένα
σύστημα διαχείρισης της κινητικότητας ελεγχόμενο από τον κινητό τερματικό κόμβο και
έναν αλγόριθμο επιλογής πρόσβασης με σκοπό την διαρκώς βέλτιστη ανάθεση των
υπηρεσιών, έτσι ώστε να ικανοποιείται παντού και πάντα η συνθήκη της βέλτιστης
σύνδεσης. / The objective of this diploma thesis is the study of mobility management, quality of service and energy consumption of Wireless Local Access Networks (WLAN) when they interact with other wireless networks. In this heterogeneous wireless enviroment we propose a management system of mobility controlled by the terminal node and an algorithm of access interface selection, which satisfies the requirements of the concept ABC (Always Best Connected).
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Theoretische und experimentelle Untersuchung des IEEE 802.11 (WLAN) Handover-Verfahren im Rahmen eines Voice-over-IP Projektes der Firma SIEMENSDonner, Sandra, January 2005 (has links)
Chemnitz, Techn. Univ., Diplomarb., 2005.
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The Nursing Handover: The Role Of The Electronic Health Record In Facilitating The Transfer Of CareMcIntire, Anne January 2016 (has links)
No description available.
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