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1
Swenson, Markus. "A Distributed Approach to Context-Aware Networks : Prototype System Design, Implementation, and Evaluation." Thesis, KTH, Kommunikationssystem, CoS, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-92028.
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Utilizing context information and in networks, enabling network services to act upon context information, and exchanging context information with applications, constitutes an important new approach to designing communication systems and central to the research project named Ambient Networks. The Ambient Networks project is a part of the 6th Framework Project cofunded by the European Commission and carried out by industry and academia. A system is said to be context-aware when it reacts to changes in context i.e., information which describes an entity’s current situation. This new approach enables developments of systems that are more adaptive to user needs and behavior. As a result systems can provide a homogenous appearance which is important as more and more different network access technologies arise. This thesis investigates, models, implements, and evaluates a distributed context-aware architecture for Ambient Networks, the Distributed Context eXchange Protocol (DCXP). The solution is a proof-of-concept that shows how a context-aware ambient network can benefit from a distributed approach. The current design is based on a peer-to-peer architecture that forms an overlay to distribute context information among the participating units. This distributed approach was chosen in order to balance the load and also enable a device to easily locate and fetch desired context information. The evaluation of the proposed context-aware architecture addresses the issues of how such a system ties in with the ideas of Ambient Networks. The main result of this report is a prototype enabling nodes in an ambient network to exchange context information. Moreover, the results show that the prototype needs to be refined in order to work in larger scale networks.<br>Användning av miljö-beskrivande information, så kallad context information, i olika nätverk är en ny infallsvinkel i designen av kommunikationssystem och är av stor vikt i forskningsprojektet Ambient Networks. Målet är att context information ska kunna utnyttjas i nätverken av olika tjänster samt även dela informationen med applikationer. Ambient Networks projektet är en del av det sjätte EU finansierade ramprogrammet där industrin och den akademiska världen deltar. Ett nätverk eller system klassificeras som context medvetet, context-aware, när det tar hänsyn till förändringar i sk. context information. Context information eller miljö-beskrivande information beskriver en enhets nuvarande situation. Detta möjliggör utveckling av system som ”lyssnar” på användaren och anpassar sig efter dess behov och beteende. Ett praktiskt exempel skulle kunna vara att användare upplever det som ett homogent system trots att det finns flera underliggande access teknologier. Den här uppsatsen undersöker, designar, implementerar och utvärderar en distribuerad context-aware arkitektur för Ambient Networks, Distributed Context eXchange Protocol (DCXP). Lösningen visar hur ett ambient network kan nyttja en distribuerad lösning för att hantera context information. Designen bygger på att de deltagande noderna skapar ett virtuellt nät, overlay, för att mellan sig dela på context informationen. Den här lösningen valdes för att balansera belastningen jämt mellan de deltagande noderna samt att på ett enkelt sätt för varje enskild node kunna lokalisera och hämta önskad context information. Utvärdering av den föreslagna lösningen visar på hur den kan integreras med den övriga utvecklingen som skett inom Ambient Networks projektet. Det huvudsakliga resultatet av arbetet är en prototyp som möjliggör för noder i ett ambient nätverk att utbyta context information. Vidare visar även resultatet att prototypen bör vidareutvecklas för att fungera i större sammanhang.
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Matos, Ricardo Jorge Magalhães de. "Context-based wireless mesh networks." Doctoral thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/12450.
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Doutoramento em Engenharia Electrotécnica<br>In the modern society, new devices, applications and technologies, with sophisticated
capabilities, are converging in the same network infrastructure.
Users are also increasingly demanding in personal preferences and expectations,
desiring Internet connectivity anytime and everywhere. These aspects
have triggered many research efforts, since the current Internet is reaching
a breaking point trying to provide enough flexibility for users and profits for
operators, while dealing with the complex requirements raised by the recent
evolution.
Fully aligned with the future Internet research, many solutions have been
proposed to enhance the current Internet-based architectures and protocols,
in order to become context-aware, that is, to be dynamically adapted to
the change of the information characterizing any network entity. In this
sense, the presented Thesis proposes a new architecture that allows to create
several networks with different characteristics according to their context, on
the top of a single Wireless Mesh Network (WMN), which infrastructure
and protocols are very flexible and self-adaptable.
More specifically, this Thesis models the context of users, which can span
from their security, cost and mobility preferences, devices’ capabilities or
services’ quality requirements, in order to turn a WMN into a set of logical
networks. Each logical network is configured to meet a set of user context
needs (for instance, support of high mobility and low security). To
implement this user-centric architecture, this Thesis uses the network virtualization,
which has often been advocated as a mean to deploy independent
network architectures and services towards the future Internet, while allowing
a dynamic resource management. This way, network virtualization can
allow a flexible and programmable configuration of a WMN, in order to be
shared by multiple logical networks (or virtual networks - VNs). Moreover,
the high level of isolation introduced by network virtualization can be used
to differentiate the protocols and mechanisms of each context-aware VN.
This architecture raises several challenges to control and manage the VNs
on-demand, in response to user and WMN dynamics. In this context, we
target the mechanisms to: (i) discover and select the VN to assign to an
user; (ii) create, adapt and remove the VN topologies and routes. We
also explore how the rate of variation of the user context requirements can
be considered to improve the performance and reduce the complexity of
the VN control and management. Finally, due to the scalability limitations
of centralized control solutions, we propose a mechanism to distribute the
control functionalities along the architectural entities, which can cooperate
to control and manage the VNs in a distributed way.<br>Na sociedade actual, novos dispositivos, aplicações e tecnologias, com capacidades
sofisticadas, estão a convergir na mesma infra-estrutura de rede.
Os utilizadores são também cada vez mais exigentes nas suas preferências e
expectativas pessoais, desejando conetividade `a Internet em qualquer hora
e lugar. Estes aspectos têm desencadeado muitos esforços de investigação,
dado que a Internet atual está a atingir um ponto de rutura ao tentar promover
flexibilidade para os utilizadores e lucros para os operadores, enquanto
lida com as exigências complexas associadas `a recente evolução.
Em sintonia com a linha de investigação para a Internet do futuro, muitas
soluções têm sido propostas para melhorar as arquiteturas e protocolos da
Internet atual, de forma a torná-los sensíveis ao contexto, isto é, adaptá-los
dinamicamente `a alteração da informação que caracteriza qualquer entidade
de rede. Neste sentido, a presente Tese propõe uma nova arquitetura que
permite criar várias redes com diferentes características de acordo com o
contexto das mesmas, sobre uma única rede em malha sem fios (WMN),
cuja infra-estructura e protocolos são muito flexíveis e auto-adaptáveis.
Mais especificamente, esta Tese modela o contexto dos utilizadores, que
pode abranger as suas preferências de segurança, custo e mobilidade, capacidades
dos seus dispositivos ou requisitos de qualidade dos seus serviços,
de forma a transformar uma WMN num conjunto de redes lógicas. Cada
rede lógica ´e configurada para satisfazer um conjunto de necessidades de
contexto do utilizador (como exemplo, suporte de mobilidade elevada e
de baixa seguran¸ca). Para implementar esta arquitetura centrada no utilizador,
esta Tese utiliza a virtualização de redes, que tem muitas vezes
sido defendida como um meio para implementar arquiteturas e serviços de
rede de uma forma independente, enquanto permite uma gestão dinâmica
dos recursos. Desta forma, a virtualização de redes pode permitir uma
configuração flexível e programável de uma WMN, a fim de ser partilhada
por várias redes lógicas (ou redes virtuais - VNs). Além disso, o grau de
isolamento introduzido pela virtualização de redes pode ser utilizado para
diferenciar os protocolos e mecanismos de cada VN baseada em contexto.
Esta arquitetura levanta vários desafios para controlar e gerir as VNs em
tempo real, e em resposta `a dinâmica dos utilizadores e da WMN. Neste
contexto, abordamos os mecanismos para: (i) descobrir e selecionar a VN
a atribuir a um utilizador; (ii) criar, adaptar e remover as topologias e
rotas das VNs. Também exploramos a possibilidade de considerar a taxa
de variação dos requisitos de contexto dos utilizadores de forma a melhorar
o desempenho e reduzir a complexidade do controlo e gestão das VNs.
Finalmente, devido ´as limitações de escalabilidade das soluções de controlo
centralizadas, propomos um mecanismo para distribuir as funcionalidades
de controlo ao longo das entidades da arquitectura, que podem cooperar
para controlar e gerir as VNs de uma forma distribuída.
3
Condeixa, Tiago Silvestre. "Decentralizing IP mobility management in future networks." Doctoral thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/14853.
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Doutoramento em Engenharia Electrotécnica<br>The massive adoption of sophisticated mobile devices and applications led to the increase
of mobile data in the last decade, which it is expected to continue. This increase of mobile
data negatively impacts the network planning and dimension, since core networks are
heavy centralized. Mobile operators are investigating
atten network architectures that
distribute the responsibility of providing connectivity and mobility, in order to improve the
network scalability and performance. Moreover, service providers are moving the content
servers closer to the user, in order to ensure high availability and performance of content
delivery. Besides the e orts to overcome the explosion of mobile data, current mobility
management models are heavy centralized to ensure reachability and session continuity
to the users connected to the network. Nowadays, deployed architectures have a small
number of centralized mobility anchors managing the mobile data and the mobility context
of millions of users, which introduces issues related to performance and scalability
that require costly network mechanisms.
The mobility management needs to be rethought out-of-the box to cope with
atten network
architectures and distributed content servers closer to the user, which is the purpose
of the work developed in this Thesis. The Thesis starts with a characterization of mobility
management into well-de ned functional blocks, their interaction and potential grouping.
The decentralized mobility management is studied through analytical models and simulations,
in which di erent mobility approaches distinctly distribute the mobility management
functionalities through the network. The outcome of this study showed that decentralized
mobility management brings advantages. Hence, it was proposed a novel distributed
and dynamic mobility management approach, which is exhaustively evaluated through
analytical models, simulations and testbed experiments. The proposed approach is also
integrated with seamless horizontal handover mechanisms, as well as evaluated in vehicular
environments. The mobility mechanisms are also speci ed for multihomed scenarios,
in order to provide data o oading with IP mobility from cellular to other access networks.
In the pursuing of the optimized mobile routing path, a novel network-based strategy
for localized mobility is addressed, in which a replication binding system is deployed in
the mobility anchors distributed through the access routers and gateways. Finally, we go
further in the mobility anchoring subject, presenting a context-aware adaptive IP mobility
anchoring model that dynamically assigns the mobility anchors that provide the optimized
routing path to a session, based on the user and network context.
The integration of dynamic and distributed concepts in the mobility management, such
as context-aware adaptive mobility anchoring and dynamic mobility support, allow the
optimization of network resources and the improvement of user experience. The overall
outcome demonstrates that decentralized mobility management is a promising direction,
hence, its ideas should be taken into account by mobile operators in the deployment of
future networks.<br>Na última década verificou-se uma massificação dos dispositivos móveis e das suas aplicações, o que tem vindo a aumentar o consumo de dados móveis. Este aumento dificulta o planeamento e dimensionamento das redes devido principalmente aos modelos
extremamente centralizados adoptados por estas. Os operadores móveis têm vindo a estudar
modelos mais até para as redes, os quais distribuem a responsabilidade de fornecer
conectividade e mobilidade, no sentido de melhorar a escalabilidade e desempenho da
rede. Além disso, de forma a garantir um desempenho elevado na entrega dos conteúdos,
os fornecedores de serviço têm vindo a mover os servidores de conteúdos para locais
mais próximos do utilizador. Apesar do esforço na procura de soluções para o crescente
consumo de dados móveis, os modelos atuais de gestão de mobilidade são demasiado
centralizados para conseguir assegurar a continuidade de sessão aos utilizadores conectados
à rede. As arquiteturas implementadas têm um número muito reduzido de âncoras
móveis centralizadas que gerem todos os dados móveis e a informação de contexto da
mobilidade, o que leva a uma diminuição de desempenho e escalabilidade, solucionadas
através de mecanismos de rede dispendiosos.
A gestão da mobilidade precisa de ser repensada de forma a poder lidar com arquiteturas
de rede até com a distribuição dos servidores de conteúdos para nós mais próximos dos
utilizadores, que é o objectivo principal da Tese apresentada. Primeiro, é apresentada a
caracterização da gestão de mobilidade em blocos funcionais, a interação entre eles e potenciais agrupamentos dos mesmos. A gestão da mobilidade descentralizada é estudada
através de modelos analíticos e simulações, em que diferentes abordagens distribuem
as funcionalidades da mobilidade pela rede. Como resultado deste estudo verificou-se
que a descentralização da mobilidade traz vantagens claras. Com base nestes resultados
foi proposta uma nova abordagem de gestão de mobilidade distribuída e dinâmica,
que é exaustivamente avaliada através de modelos analíticos, simulações e experiências
numa bancada de testes. A abordagem proposta é também integrada com mecanismos
de handovers horizontais transparentes, assim como é avaliada em ambientes veiculares.
Os mecanismos de mobilidade da abordagem proposta são também especificados para
cenários de multihoming, de forma a proporcionar o offloading de dados com suporte de
mobilidade das redes celulares para outras redes de acesso. Com o objectivo de optimizar
o encaminhamento de dados móveis, foi criada uma nova estratégia para o suporte
da mobilidade localizada, em que um sistema de replicação de bindings é integrado nas
âncoras de mobilidade distribuídas através dos routers de acesso e dos gateways. Finalmente
apresenta-se um modelo de ancoramento adaptativo para a mobilidade com base
em contexto, o qual dinamicamente determina as âncoras de mobilidade que oferecem a
melhor rota para uma dada sessão, baseado na informação do utilizador e da rede.
A integração de conceitos de dinamismo e de distribuição na gestão da mobilidade, como o
ancoramento adaptativo e o suporte dinâmico da mobilidade, permitem a optimização dos
recursos da rede e uma melhor experiência por parte do utilizador. Os resultados demonstram,
de uma forma geral, que a gestão descentralizada da mobilidade é um caminho
promissor, logo este deve ser tomado em consideração pelas operadoras móveis aquando
do desenvolvimento das redes do futuro.
4
Decarli, Nicolò <1985>. "Context-aware wireless networks." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5613/.
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This thesis investigates context-aware wireless networks, capable to adapt their behavior to the context and the application, thanks to the ability of combining communication, sensing and localization. Problems of signals demodulation, parameters estimation and localization are addressed exploiting analytical methods, simulations and experimentation, for the derivation of the fundamental limits, the performance characterization of the proposed schemes and the experimental validation.
Ultrawide-bandwidth (UWB) signals are in certain cases considered and non-coherent receivers, allowing the exploitation of the multipath channel diversity without adopting complex architectures, investigated. Closed-form expressions for the achievable bit error probability of novel proposed architectures are derived.
The problem of time delay estimation (TDE), enabling network localization thanks to ranging measurement, is addressed from a theoretical point of view. New fundamental bounds on TDE are derived in the case the received signal is partially known or unknown at receiver side, as often occurs due to propagation or due to the adoption of low-complexity estimators. Practical estimators, such as energy-based estimators, are revised and their performance compared with the new bounds.
The localization issue is addressed with experimentation for the characterization of cooperative networks. Practical algorithms able to improve the accuracy in non-line-of-sight (NLOS) channel conditions are evaluated on measured data. With the purpose of enhancing the localization coverage in NLOS conditions, non-regenerative relaying techniques for localization are introduced and ad hoc position estimators are devised.
An example of context-aware network is given with the study of the UWB-RFID system for detecting and locating semi-passive tags. In particular a deep investigation involving low-complexity receivers capable to deal with problems of multi-tag interference, synchronization mismatches and clock drift is presented. Finally, theoretical bounds on the localization accuracy of this and others passive localization networks (e.g., radar) are derived, also accounting for different configurations such as in monostatic and multistatic networks.
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Heaney, Séan F. "Context aware body area networks." Thesis, Queen's University Belfast, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680115.
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Body Area Networks (BAN) are unique in that the large-scale mobility of users alongside the complexity of body movements allows the network itself to travel across a diverse range of operating domains or even to enter new and unknown environments. These body movements along with the diversity of these unknown environments can create unique transmission channels. This network mobility is unlike node mobility in that sensed changes in inter-network interference level may be used to identify opportunities for intelligent inter-networking, for example, by merging or splitting from other networks, thus providing an extra degree of freedom. As the BAN network travels it will cause and be subject to inter-network interference but it also has the opportunity to sense and interact with a range of other networks. Using a series of carefully controlled measurements of the mesh interconnectivity both within and between ambulatory BANs as well as a stationary desk-based network, this thesis presents an investigation of context aware body area network (CABAN) interference detection at the physical layer. This thesis, also gives consideration to the co-existence of multiple co-located BAN users and the complex interaction of body-shadowing, user movement as well as the multi:"path environment itself and its impact on channel conditions. The final aspect of the thesis investigates the interaction between physical layer characteristics and packet error rate (PER) at the data link layer as two independent BANs operating in CSMA networks as they could merge and split
6
Houyou, Amine Mohamed. "Context-aware mobility : a distributed approach to context management /." kostenfrei, 2009. http://www.opus-bayern.de/uni-passau/volltexte/2010/1797/.
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Simons, Christof. "Context aware applications in mobile distributed systems." Aachen Shaker, 2007. http://d-nb.info/987900757/04.
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Simons, Christof. "Context aware applications in mobile distributed systems /." Aachen : Shaker, 2008. http://d-nb.info/987900757/04.
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Shi, Hong-Ling. "Development of an energy efficient, robust and modular multicore wireless sensor network." Phd thesis, Université Blaise Pascal - Clermont-Ferrand II, 2014. http://tel.archives-ouvertes.fr/tel-00968069.
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The wireless sensor network is a key technology in the 21st century because it has multitude applications and it becomes the new way of interaction between physical environment and computer system. Moreover, the wireless sensor network is a high resource constraint system. Consequently, the techniques used for the development of traditional embedded systems cannot be directly applied. Today wireless sensor nodes were implemented by using only one single processor architecture. This approach does not achieve a robust and efficient energy wireless sensor network for applications such as precision agriculture (outdoor) and telemedicine. The aim of this thesis is to develop a new approach for the realization of a wireless sensor network node using multicore architecture to enable to increase both its robustness and lifetime (reduce energy consumption).
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Bhatia, Nupur. "Policy Management in Context-Aware Networks." Thesis, KTH, Kommunikationssystem, CoS, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-92015.
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The Ambient Network (AN) Project is part of the European Commission’s 6th Framework Programme and aims to enable cooperation between heterogeneous networks, using current and future wireless technologies, minimising the effort of mobile users to gain access to the services that they are interested in - irrespective of their location or the network they are currently using. Because of the highly mobile nature of users and a demand for instant and dynamic access to services, these networks have to be composed ‘on the fly’ without any pre-configurations. The use of context information in AN can remove the need for pre-configuration of networks, hence making them autonomic. However, a concern exists that the free and uncontrolled dissemination of context information could breech the privacy of the participants. It is extremely important to address these privacy issues in order to control who has access to what context information. This control can be achieved through the use of well defined policies. This creates a requirement for a framework in the ContextWare architecture for protecting context information. This masters thesis project is part of an effort to create a policy based infrastructure for authorisation of access to network context information within the AN. The thesis investigates, models, and designs an architecture for a policy management system based on OASIS XACML, that creates an extension to the architecture for management of context information in the AN. In addition to a policy management architecture within an AN, a policy management architecture for composing ANs is also created. To facilitate the transfer of requests and policies, the thesis creates a Policy Management Protocol. The designed architecture was then implemented to create a proof of concept. The designed architecture and protocol were evaluated by running tests on the prototype. The measurements from the tests are analysed and presented in this thesis. The analysis of the experimental data indicates that a policy management system is both feasible and practical. The results show that the delay overhead caused by introducing policy management in a distributed context provisioning system, ranges from 1.7% in a system without load to 6% in a worst case scenario. The throughput of the policy management system is 15 requests per second under load.<br>Ambient Network är ett EU-finansierat project inom det 6:e ramprogrammet.Projektets mål är att möjliggöra samarbete mellan heterogena nätverk, som använderbåde dagens men även framtidens trådlösa teknologier, för att minimeraslutanvändarens insats för att nå den tjänst de är intresserade av – oberoende av platseller vilket nätverk de använder. På grund av den stora delen av mobila användaresom kräver omedelbar och dynamisk tillgång till tjänster måste dessa nätverk gåsamman ’on the fly’ utan tidigare konfigurering.Användningen av context information i Ambient Networks kan elmininera behovet avförkonfigurering av nätverk, följaktligen blir de då autonoma. Dock, ett problem somuppkommer med detta är att den fria och okontrollerade spridningen av contextinformation bryter integriteten för deltagarna. Det är väldigt viktigt att ta itu med dettaproblem för att kunna kontrollera vilka som har tillgång till vilken contextinformation. Den här kontrollen kan uppnås genom väldefinierade policies. Dettaskapar ett behov av ett ramverk inom ContextWare arkitekturen för att skydda dentillgängliga context informationen. Den här uppsatsen är en del i ansträngningen att skapa en policy baserad infrastrukturför attestering av tillgång till context information inom Ambient Networks. Uppsatsenundersöker och designar en arkitektur för ett policy handhavande system som ärbaserat på OASIS XACML, den bygger vidare på arkitekturen för handhavande avcontext information i Ambient Networks. Utöver policy hantering inom ett ambientnetwork skapas också policy hantering mellan ambient networks när de förenas. Denframtagna arkitekturen är därefter implementerad för att visa på konceptets hållbarhet. En sammanslagning av två policy handhavande system när två nätverk slås ihop ärbehandlat endast i teorin, det är inte implementerat. Designen utvärderas genom att köra test på den implementerade versionen ochdärefter analysera och visa resultaten i rapporten. Dessa test innehåller mätningar avfördröjningen av en enda begäran samt flera, responstiden i ett system med policyhanteringjämfört med utan samt prestandan i ett policy-hanteringssystem med en litenmängd policies jämfört med en större mängd policies.
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Panidis, Panteleimon. "Middleware for Context-Aware Opportunistic Networks." Thesis, KTH, Kommunikationssystem, CoS, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-92261.
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Mobile devices such as palmtops and cell phones are continuously increasing in capabilities and popularity. At the same time, due to their decreasing price they are becoming more and more attractive and available to the average customer. This has lead to the development of many new applications for such portable electronic devices. Mobile devices tend to have increasing local resources in terms of memory/storage and CPU [2]. Despite these improvements in hardware attributes, there are still limitations that characterize these portable devices and which have not improved as quickly as the increase of the local computational power. These limitations mostly concern the network resources and battery power that are both still rather poor. Thus the main barriers for mobile nodes are network resources and limiting the power consumption of the device itself. Today, wireless networks provide limited reliability and less bandwidth than fixed networks. Moreover, all mobile nodes are highly energy dependent as they use batteries with a limited capacity. Additionally, roaming is a feature that increasingly must be supported for such wireless devices, as their physical portability leads to users to use them even as they move about. This may require the utilization of different wireless networks while the node is on the move. Therefore, for all the above reasons there is a demand for the development of intelligent mechanisms and techniques for optimizing the management of these limited resources, while exploiting the local resources, thus providing users with the best possible performance within the available resources. At the present, there are operating systems, such as the Symbian OS [22], specially designed for supporting advanced features in mobile computing. However, there is still development to be done. Moreover, although there are many new applications for mobile computing, they are not yet sophisticated enough to cope with changes in the wireless environment, these changes occur due to the node’s change in context. This creates a gap that should be filled by software between the applications and the operating system; this is frequently called middleware. This middleware provides a collaborative partnership between the operating system and the applications, assisting and making both more sophisticated, in terms of scheduling and managing traffic in a wireless environment. The focus of this project is how to utilize such middleware to best serve the needs of the mobile user.<br>Mobila enheter som handdatorer och mobiltelefoner har kontinuerligt utökat sina användningsområden och popularitet. Samtidigt har de i och med det fallande priset blivit mer och mer attraktiva och tillgängliga för den allmänna marknaden. Detta har lett till utveckling av nya tillämpningar för sådana portabla elektriska enheter. Mobila enheter tenderar att få ökade lokala resurser som exempelvis större minne och CPU [2]. Fastän en förbättring av dessa hårdvaror har gjorts så karaktäriseras enheterna av begränsningar som inte har utvecklats i lika rask takt som de lokala resurserna. Dessa begränsningar handlar till större delen om nätverks resurser och tillförsel av energi via batteri, som båda fortfarande är relativt dåliga. De huvudsakliga barriärerna för de mobila noderna är alltså nätverks resurser och enheternas energikonsumtion. I dagens läge förser de trådlösa närverken en begränsad pålitlighet och lägre bandbredd än de fasta nätverken. Alla mobila noder är även väldigt energiberoende eftersom de använder sig av ett energibegränsat batteri. Förutom detta så är roaming en aspekt som måste öka för sådana trådlösa enheter eftersom deras transportabla egenskaper medför att användaren kan använda sig av enhetens funktioner även vid mobilitet. Detta leder till att det behövs tillgång till olika trådlösa nätverk i och med att enheten omplaceras. På grund av alla dessa orsaker som beskrivits ovan finns det en efterfrågan på utveckling av intelligenta mekanismer och tekniker för användningsoptimering av dessa begränsande faktorer, samtidigt som man maximerar de lokala resurserna och på detta sätt ger användaren bästa möjliga prestanda inom det tillgängliga området. I dagens läge finns det operativ system, som Symbian OS [22], speciellt designade för att stödja avancerade drag inom mobile computing. Det finns däremot utrymme för utveckling av dessa och fastän det finns många nya tillämpningar för mobile computing så är de inte tillräckligt sofistikerade för att klara av ett smidigt byte mellan trådlösa nätverk när noderna omplaceras. Detta medför ett glapp som borde åtgärdas med mjukvara kallad mellanvara, ett program som förmedlar arbetsuppgifter mellan användarnas tillämpningar och datornätets resurser. Mellanvaran gör att operativ systemet samarbetar med användarens tillämpningar och gör att hela systemet blir mer sofistikerat i termer av trafik hantering i den trådlösa miljön. Tyngdpunkten i detta projekt ligger i hur man ska utnyttja sådan mellanvara för att optimera systemet i de mobila enheterna utifrån användarens behov.
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Ergüt, Salih. "Context-aware computing for wireless networks." Diss., [La Jolla] : University of California, San Diego, 2010. http://wwwlib.umi.com/cr/ucsd/fullcit?p3402341.
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Thesis (Ph. D.)--University of California, San Diego, 2010.<br>Title from first page of PDF file (viewed May 14, 2010). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
13
Simons, Christof [Verfasser]. "Context-Aware Applications in Mobile Distributed Systems / Christof Simons." Aachen : Shaker, 2008. http://d-nb.info/116279027X/34.
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Liu, Bin. "Channel aware distributed detection in wireless sensor networks." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2006. http://proquest.umi.com/login?COPT=REJTPTU0NWQmSU5UPTAmVkVSPTI=&clientId=3739.
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Wennlund, Andreas. "Context-aware Wearable Device for Reconfigurable Application Networks." Thesis, KTH, Mikroelektronik och Informationsteknik, IMIT, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-93116.
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Context information available in wearable devices is believed to be useful in many ways. It allows for hiding much of the complexity from the user, thus enabling simpler user interfaces and less user interaction when carrying out tasks on behalf of a user, as well as enabling network operators to provide a better interface to thirdparty service providers who will provide and deliver wireless services. Using the available context information from the wearable device, optimization of service delivery in wireless networks, such as setting up optimal delivery paths between two wearable devices, may be possible without using a third party to do negotiations. In order to fully enable context-awareness, a clear model for how to sense, manage, derive, store, and exchange context information must be defined. This will then provide the platform needed to enable development of context-aware applications that can exploit the possibilities of context-aware computing. The model must take into consideration parameters such as memory usage and power and bandwidth consumption, in order to be efficient on all types of platforms and in all types of networks. It must also be modular enough to survive replacing and upgrading of internal parts. Today little research is available about sensing context information, sensor management, APIs towards other applications, and how and how often to present context information to applications. Since context aware computing relies heavily on the ability to obtain and represent context information, sensing strategies greatly affect efficiency and performance. It is therefore of great interest to develop and evaluate models for carrying out these tasks in order to exploit the results of context awareness research. This thesis will identify and design several components of such a model, as well as test and evaluate the design, in order to be able to make conclusions to whether is lives up to the expectations stated. In order to make the proper design decisions, a full understanding of the context-awareness research area and the goals and purposes of context-aware computing are required. To understand the entire picture is crucial to find a suitable solution. Therefore, determining an efficient sensor input and management strategy, along with a powerful and flexible API for applications, which are the goals of this thesis, fully qualifies as a significant master thesis assignment.<br>Information om bärbara enheters omgivning som kan göras tillgänglig i enheten, tros kunna vara användbart på många sätt. Det kan möjliggöra gömmande av komplexitet från användaren, vilket ger enklare användargränssnitt och mindre användarinteraktivitet, när utförandet av uppdrag från användaren sker, eller underlätta för en nätverksoperatör som tillhandahåller ett bättre gränssnitt gentemot en tredje part, som tillhandahåller och levererar trådlösa tjänster. Genom att utnyttja tillgänglig information om omgivningen från en bärbar enhet, kan man optimera leverans av tjänster i trådlösa nätverk, så som att hitta en optimal kommunikationsväg mellan två bärbara enheter, utan att använda sig av förhandlingar med en tredje part. För att till fullo möjliggöra ett sådant omgivningsmedvetande, krävs en tydlig modell för att uppfatta, förfina, lagra och utbyta det data som beskriver omgivningen. Denna modell kan då utgöra en plattform som möjliggör utveckling av omgivningsmedvetande applikationer, som kan utnyttja och reagera på de data som beskriver omgivningen. Modellen måste ta hänsyn till parametrar så som minneskonsumtion och batteri- och bandbreddsförbrukning, för att vara effektiv på alla typer av plattformar och i alla typer av nätverk. Den måste också bestå av tillräckligt väl separerade moduler för att klara av byten och uppgraderingar av dess beståndsdelar. Idag finns endast lite tillgänglig forskning om insamlandet av omgivningsdata, hanteringen av sensorer, gränssnitt gentemot mot applikationer och hur och hur ofta omgivningsdata skall presenteras för applikationer. Eftersom omgivningsmedvetenhet beror av möjligheten att införskaffa och representera omgivningsdata, påverkar strategier för att uppfatta omgivningen både effektivitet och prestanda. Det finns därför ett stort intresse i att utveckla och utvärdera modeller för utförandet av dessa uppdrag och för att utforska forskningsresultat om omgivningsmedvetande. Denna rapport identifierar och konstruerar flera komponenter till en sådan modell, samt testar och utvärderar denna för att kunna dra slutsatser om huruvida den lever upp till de förväntningar som finns. För att kunna göra en fullgod konstruktion, krävs en ingående förståelse i forskningsområdet omgivningsmedvetande och syften och mål med densamma. Att förstå den övergripande bilden är nyckeln till en passande lösning. Konstruktion av effektiva strategier för att uppfatta omgivningen, tillsammans med ett kraftfullt och flexibelt API gentemot applikationer, vilket är målen med denna rapport, kvalificerar sig därför som ett examensarbete.
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Mokhesi, Lekometsa. "Context-Aware Handoff Support for Wireless Access Networks." Thesis, University of Cape Town, 2010. http://pubs.cs.uct.ac.za/archive/00000678/.
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The phenomenal emergence of several heterogeneous wireless networks and technologies has allowed users to have access IP services anywhere at anytime from any network with whatever terminal they use. This computing platform has also been driven by the rapid evolution of mobile devices that are equipped with multiple network interfaces and the development of IP based applications. One of the challenging tasks with this Next-Generation Networks (NGN) computing platform is service continuity when users roam around different wireless networks e.g. Wi-Fi, Bluetooth and Cellular networks. This challenge is elevated more when dealing with applications that distribute time continuous data with stringent Quality of Service (QoS) requirements. One of the adaptation methods to ensure service continuity by minimizing flow interruptions when users are mobile is session handoff.
The main contribution of the thesis is to present a handoff support system which implements a handoff decision engine using a Multi-Criteria Decision Making (MCDM) method based on a Bayesian Belief Network (BBN) and a handoff execution procedure based on buffering and doublecasting techniques. The handoff support system is built around the following features: 1) It utilises a proxy-based middleware architecture, 2) It uses a BBN based MCDM for handoff decision, 3) It is able to represent the full context information which represents the execution environment, 4) It is able to perform decision making under both certainty and uncertainty, 5) It is able to decide correctly on the target network under dynamic context, 6) It performs decision making in the midst of conflicting, interdependent and constraint criteria, and 7) It uses a profile-based handoff decision to offer personalisation to users.
The experimental results showed that when compared with Analytical Hierarchy Process (AHP), the handoff decision method based on BBN performs better on: 1) Modelling of the handoff decision problem and the full representation of the context information, 2) Decision making under uncertainty, 3) Modelling of constraints and interdependent criteria and 4) Support for user preferences. When evaluating the handoff execution, further results revealed that the underlying handoff management strategies provide service continuity by minimising handoff latency and packet losses.
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RODRIGUES, VAGNER JOSE DO SACRAMENTO. "PRIVACY TO CONTEXT-AWARE APPLICATIONS IN MOBILE NETWORKS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2006. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=9347@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>A difusão das redes sem fio IEEE 802.11 e o avanço das
técnicas de posicionamento baseadas na força de sinal de
rádio frequência (RF) (e.g.,
sensores, algoritmos de triangulação, etc.) têm motivado o
desenvolvimento
de aplicações e serviços sensíveis ao contexto e sua
localização (Location Based Services). Essas aplicações
oferecem vários benefícios para os usuários
finais, por exemplo, adaptação às limitações dos
dispositivos e da rede sem fio, acesso às informações de
localização, ou a capacidade de enviar notificações
baseadas na localização ou na proximidade entre os
usuários (e.g.,
Geocaching). Entretanto, há dois desafios principais
relacionados ao desenvolvimento e uso de aplicações
sensíveis ao contexto: a complexidade em
desenvolver os serviços de provisão de contexto e a
necessidade de manter a privacidade da informação de
contexto (e.g., localização) do usuário.
Para auxiliar o desenvolvimento de aplicações sensíveis ao
contexto, projetamos e implementamos alguns serviços que
constituem o núcleo de uma
arquitetura de provisão de contexto, chamada MoCA (Mobile
Collaboration
Architecture). Esses serviços implementam a coleta, o
processamento e a
difusão da informação de contexto através de interfaces de
comunicação
síncronas e baseadas em eventos. A MoCA serviu de base
para o desenvolvimento da nossa pesquisa sobre privacidade
na qual projetamos um serviço
que auxilia o usuário no controle de privacidade das suas
informações de
contexto, em especial, da sua informação de localização.
Como parte do
nosso trabalho, definimos um modelo conceitual que serviu
de base para
o desenvolvimento do serviço de privacidade proposto (a
ser utilizado por
uma comunidade de usuários) e discutimos alguns requisitos
que devem ser
levados em conta no projeto de um serviço deste gênero. A
maioria destes requisitos delinearam o projeto e
implementação do Context Privacy Service
(CoPS). Este serviço foi integrado aos serviços de
provisão de contexto da
arquitetura MoCA.<br>The widespread dissemination of IEEE 802.11 networks and
the enhancement of positioning techniques based on RF
signal strength (e.g., sensors,
positioning triangulation algorithms, etc) have fostered
the development of
location-based and context-aware services and
applications. These applications offer several benefits to
the end-users, e.g. adaptation to the device
and wireless network limitations, access to location-
specific information, or
the ability to send location-specific notifications to
other users (e.g., Geocaching). However, there are two
main challenges concerning the development
and use of context-aware applications: the complexity in
developing context
provisioning services and the need to guarantee the
privacy of the users'
context information (e.g., their location). In order to
support the development of context-aware applications, we
have designed and implemented
some services that constitute the core of a context
provisioning architecture
called MoCA (Mobile Collaboration Architecture). These
services implement the gathering, processing and diffusion
of context information through
synchronous and event-based communication interfaces. MoCA
architecture
has been used as a basis to the development of our
research about privacy in which we have designed a service
that aids the end-user in defining
the privacy level for his/her contextual information, and
in particular for
his/her location information. As part of our work, we
define the conceptual
model underlying our privacy control service (targeted at
a community of
users) and discuss the most important requirements that
should be conside-
red in the design of such a service. Most of these
requirements have guided
the design and implementation of the Context Privacy
Service (CoPS). This
service has been integrated to the context provisioning
services of the MoCA
middleware.
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Hager, Creighton Tsuan-Ren. "Context Aware and Adaptive Security for Wireless Networks." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/29875.
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This research investigated methods to determine appropriate security protocols for specific wireless network applications. The specific problem being addressed was that there are tradeoffs between security, performance, and efficiency among current and proposed security protocols. Performance and efficiency issues are particularly important in wireless networks which tend to have constrained network capacity and connect to resource-limited nodes. Existing security protocols address problems such as authentication, availability, confidentiality, integrity, and non-repudiation. However, these protocols use resources and limit the efficient use of node resources. Thus, the overall objective of this research is to improve the efficiency of security mechanisms for wireless networks.
<P>
A methodology was constructed to satisfy this objective and is an important contribution of this research. The methodology can be used to define the relevant operational parameters of different wireless network applications, classify wireless networks into distinct categories, incorporate appropriate security protocols to a category, and analyze the security protocols through metrics. Three groups of operational parameters were created to classify wireless networks; these are equipment, network topology, and communication characteristics. The wireless network categories include, but are not limited to, fixed broadband wireless networks, wireless local area networks, mobile ad hoc networks, and small device sensor networks. The metrics in the methodology are used to measure end-to-end data throughput and delay, efficiency and overhead, power and energy consumption, and energy consumed per packet transferred.
<P>
The main advantage of this methodology is the flexibility of how constraints are considered and suitability is analyzed. This approach can identify problems from manageable categories of networks and find or create solutions for each of them. Another advantage of this methodology is that after suitable security protocols are found or created for each category, any new wireless network application that falls into an existing category may be able to use the security protocols from that category and find that they are the most suitable.
<P>
Another key contribution of this research was the implementation and evaluation of a context aware and adaptive security manager (CASM) that selects appropriate protocols in real-time. CASM was developed using the methodology as a guide. Results from a resource analysis of four encryption algorithms were utilized for the design of CASM. A feasibility study of CASM was then completed. Three different experimental scenarios were used to evaluate CASM's operation. The results and analysis of the experiments indicate that the security manager functions properly and security is provided efficiently with different user settings and environments. Three schemes were deemed the best to use for the decision module of CASM.<br>Ph. D.
19
Liaquat, Saad. "Federated broker model for context provisioning in large-scale distributed context-aware systems." Thesis, University of the West of England, Bristol, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.572893.
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Context-awareness is a computer science concept that aims to enhance the usability of computing systems for users by unobtrusively providing services based on user and environmental context. Experimental context- aware systems typically constitute the functions of data acquisition, reasoning, context representation, context storage and context dissemination. Due to the mobile and spatial nature of the computational actors context-aware systems are usually designed with distributed software components. This distribution presents challenges in context provisioning, that is. the coordination and communication of contextual information between distributed components of the system. One of the main challenges is the diversity of settings in which context-awareness functions take place, highlighted by the heterogeneity of devices and the fluid pattern of human behaviour. Moreover, as mobile devices increasingly become the primary tool of user interaction with the environment, the complexity to adequately support awareness for diverse context applications, poses a crucial challenge in development of a large-scale context provisioning systems .. Many prototype context-aware systems have been developed that showcase context-awareness in one application domain or other but large- scale context provisioning, which also facilitates the emerging cognitive role of mobile devices, has proved elusive so far due to multi-faceted challenges in this area. Most of the research in the domain of context-aware computing focuses on context creation, prototyping context-aware applications and context use, while the challenges posed by large-scale context provisioning in such systems have not been adequately addressed. The common theme in existing efforts into developing context-aware systems has been the centralisation of the context management component that acquires, processes and distributes context information. In order to seamlessly coordinate and disseminate contextual information in a large-scale ubiquitous computing environment, a context provisioning approach is required that can overcome scalability, heterogeneity and coordination related challenges. These challenges are addressed in this work and a distributed context provisioning model is presented that can 1) disseminate multi-domain context over a large (geographic or network) scale, 2) provide coordination of context between distributed con- text producing and consuming components, 3) scale well with the increase in the system load due to context related traffic and 4) facilitate user and device mobility within the distributed system. The large-scale context provisioning model proposed by this work, entitled the Context Provisioning Architecture, is based on a federation of context brokers and uses a publish/subscribe based context coordination and communication mechanism. This thesis presents the theoretical modelling and practical implementation of the inter-broker routing of context subscriptions and notifications, management of component mobility, context modelling and context caching. Our proposed federated broker model is the first practical demonstration of federated context brokers for large-scale context provisioning. The load scalability aspect of our proposed model is experimentally evaluated against that of a centralised broker based model and the results demonstrate the improved scalability of the federated broker model. This work also proposes and demonstrates the concept of a context brokering component to manage and facilitate the evolving role of mobile devices towards cognitive context-aware devices.. The novel Mobile Context Broker component reduces the functional burden on mobile device based context consuming/providing applications. Our empirical evaluation shows a significant reduction in average energy consumption on mobile devices during the execution of context-awareness related functions in presence of the Mobile Context Broker. A minor contribution of this thesis is the use and comparison of cache replacement policies that can be utilised in a context caching component of the system. Our experiments reveal that caching is a viable strategy for improving the scalability of a context provisioning system and different cache replacement policies can be utilised within this strategy. Furthermore, this work also demonstrates a unified context model that is used not only for context representation but also for context coordination across distributed context brokers and context consuming/providing applications. Collectively, these contributions provide a holistic architectural level support and conceptual foundation that can serve as a guideline for designing large-scale context provisioning systems.
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Shzu-Juraschek, Felix. "Distributed channel assignment for interference-aware wireless mesh networks." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2014. http://dx.doi.org/10.18452/16957.
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Die Besonderheit der drahtlosen Kommunikation gegenüber den drahtgebundenen Netzwerken liegt im drahtlosen Übertragungsmedium. Aufgrund der Broadcast-Eigenschaft des Übertragungsmediums werden Nachrichten potentiell von allen Netzwerkstationen empfangen, welche sich in der Übertragungsreichweite des Senders aufhalten. Als Konsequenz können bei einem unsynchronisierten Medienzugriff mehrere Nachrichten beim Empfänger kollidieren und nicht korrekt empfangen werden. Dieses Phänomen wird auch als Interferenz bezeichnet. Um solche Interferenzen zu vermeiden, wurden spezielle Protokolle für den Medienzugriff in drahtlosen Netzen entwickelt. Ein solcher Ansatz für drahtlose Maschennetze ist die verteilte Kanalzuweisung. Bei der verteilten Kanalzuweisung werden sich nicht-überlappende Kanäle im verfügbaren Frequenzspektrum für Übertragungen verwendet, die auf dem gleichen Kanal Interferenzen erzeugen würden. Dieser Ansatz ist möglich, da die verwendeten Funktechnologien, wie zum Beispiel IEEE 802.11 (WLAN), mehrere nicht-überlappende Kanäle bereitstellen. Aufgrund der großen Verbreitung von IEEE 802.11, ist eine hohe Dichte von privaten wie kommerziellen Netzen im urbanen Raum die Norm. Diese räumlich überlappenden Netze konkurrieren um den Medienzugriff. Daher ist es für die Leistung von Kanalzuweisungsalgorithmen von großer Bedeutung, die Aktivität der externen Netze mit einzubeziehen. Die Leistung der vorgelegten Arbeit umfasst das Design, die Implementierung und Validierung von Modellen und Algorithmen zur Reduzierung von Interferenzen in drahtlosen Maschennetzen. Die Arbeit beinhaltet die Entwicklung eines Messungs-basierten Interferenzmodells, mit dem Interferenzabhängigkeiten der Maschenrouter untereinander effizient bestimmt werden können. Weiterhin wurde ein Algorithmus für die verteilte Kanalzuweisung entwickelt, der die Aktivität von externen Netzen berücksichtigt. Die Gesamtlösung wurde in einem großen drahtlosen Maschennetz experimentell validiert.<br>Due to the broadcast nature of the shared medium, wireless transmissions are potentially received by all network stations in the communication range of the sender. With an unsynchronized medium access, multiple transmissions may be active at the same time and thus interfere with each other. In consequence, multiple transmissions may collide at the receiver side and cannot be properly decoded. For this reason, protocols have been developed on the MAC layer to synchronize the medium access and thus reduce interference effects. One of these approaches in wireless mesh networks is channel assignment. The idea of channel assignment is to minimize the network-wide interference by utilizing non-overlapping channels for otherwise interfering wireless transmissions. This is feasible, since wireless mesh routers are usually equipped with multiple radios and commonly used wireless network technologies, such as IEEE 802.11, provide multiple non-overlapping channels. Since IEEE 802.11 operates in the unlicensed frequency spectrum, the dense distribution of private and commercial network deployments of WLANs in urban areas poses a new challenge. Co-located networks compete for the wireless medium, thus decreasing the achievable network performance in terms of throughput and latency. Therefore, an important issue for efficient channel assignment is to also address external interference The contributions of this dissertation comprise the design, implementation, and validation of models and algorithms to enable wireless multi-hop networks to become interference-aware. This includes a measurement-based interference model suitable for large-scale network deployments. A distributed channel assignment algorithm has been developed that considers external sources of interference. The overall solution has been experimentally validated in a large-scale wireless multi-hop multi-radio testbed and has significantly increased the network performance with regard to the network capacity.
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MILLER, TAMARA GUERRA. "DISTRIBUTED SPARSITY-AWARE SIGNAL PROCESSING ALGORITHMS FOR SENSOR NETWORKS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2016. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=27190@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>PROGRAMA DE EXCELENCIA ACADEMICA<br>Neste trabalho de dissertação são propostos algoritmos adaptativos que
exploram a esparsidade em redes distribuídas de sensores para estimação de
parâmetros e estimação espectral. São desenvolvidos algoritmos gradiente conjugado
(CG) distribuído para os protocolos consenso e difusão em versão
convencional e modificada (MCG). Esses algoritmos são desenvolvidos com
exploração de esparsidade usando as funções penalidades l1 e log-sum. Os
métodos propostos apresentam um melhor desempenho en termos de velocidade
de convergência e desvio médio quadratico (MSD) que as já conhecidas
variantes distribuídas do algoritmo least mean square (LMS) e muito próximo
ao desempenho do algoritmo recursive least square (RLS). Além disso, propõe-se
um algoritmo distribuído de optimização alternada de variáveis discretas e
contínuas (DAMDC) baseado no LMS. O algoritmo DAMDC-LMS apresenta
um desempenho muito próximo ao algoritmo oráculo e tem maior velocidade
de convergência que os algoritmos estudados com exploração de esparsidade.
Os resultados numéricos mostram que o algoritmo DAMDC-LMS pode ser
aplicado em vários cenários.<br>This dissertation proposes distributed adaptive algorithms exploiting
sparsity for parameter and spectrum estimation over sensor networks. Conventional
and modified conjugate gradient (CG and MCG) algorithms using
consensus and diffusion strategies are presented. Sparsity-aware versions of CG
an MCG algorithms using l1 and log-sum penalty functions are developed. The
proposed sparsity-aware and non-sparse CG and MCG methods outperform
the equivalent variants of the least-mean square (LMS) algorithms in terms of
convergence rate and mean square deviation (MSD) at steady state, and have a
close performance to the recursive least square (RLS) algorithm. The diffusion
CG strategies have shown the best performance, specifically the adapt then
combine (ATC) version. Furthermore a distributed alternating mixed discretecontinuous
(DAMDC) algorithm to approach the oracle algorithm based on the
diffusion strategy for parameter and spectrum estimation over sensor networks
is proposed. An LMS type algorithm with the DAMDC proposed technique obtains
the oracle matrix in an adaptive way and compare it with the existing
sparsity-aware as well as the classical algorithms. The proposed algorithm has
an improved performance in terms of MSD. Numerical results show that the
DAMDC-LMS algorithm is reliable and can be applied in several scenarios.
22
Kalousek, Jiří. "Context-Aware P2P Network Construction." Thesis, Linnéuniversitetet, Institutionen för datavetenskap (DV), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-65460.
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With growing number of devices connected to the network, there is a greater need for use of Peer-to-Peer (P2P) networks and distributed P2P protocols.Devices participating in the P2P network do not usually need to use any central server that links up connections. It has many advantages but it needs to use so-called overlay network that consists of protocols used for traffic routing and decision making. Protocols used in today’s P2P networks are mostly not considerate of particular participating nodes and all the nodes in the network are usually equal. This can have negative impacts on network performance. In order to avoid or reduce some unwanted negative impacts, it would be advantageous if the overlay network could route traffic and make decisions according to context information like battery levels or connection speeds. This work reviews a few popular P2P overlay networks and based on that it introduces an improvement of one of them – Chord. The structure of the improved version of the Chord protocol called Context-Aware Chord is described. Then results of the evaluation are presented. With a use of the improved protocol, nodes can participate longer in the network and throughput of lookup messages is improved.
23
Gartrell, Charles M. "SocialAware: Context-aware multimedia presentation via mobile social networks." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1460857.
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Mendonca, Costa Javier. "Context-Aware Machine to Machine Communications in Cellular Networks." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-143180.
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Cellular network based Machine-to-Machine (M2M) communications have been growing rapidly in recent years, being used in a wide range of services such as security, metering, health, remote control, tracking and so on. A critical issue that needs to be considered in M2M communications is the energy efficiency, typically the machines are powered by batteries of low capacity and it is important to optimize the way the power is consumed. In search of better M2M systems, we propose a context-aware framework for M2M communications so the machine type communication (MTC) devices dynamically adapt their settings depending on a series of characteristics such as data reporting mode and quality of service (QoS) features so higher energy efficient is achieved, extending the operating lifetime of the M2M network. Simulations were performed with four commonly used M2M applications:home security, telehealth, climate and smart metering, achieving considerable energy savings and operating lifetime extension on the network. Thus, it is shown that contexts play an important role on the energy efficiency of a M2M system.
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Nilsson, Joackim. "Dynamic Personal Networks for Location-Based Applications : Within MediaSense." Thesis, Mid Sweden University, Department of Information Technology and Media, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-11782.
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<p>As the development of context aware applications has evolved, there has been a corresponding increase in need for more sophisticated system. The aim for this thesis is the development of a dynamical P2P network system which is based on locations. The P2P network is self organizing and in a lightweight format. Modern technical solutions including AGPS have facilitated the work associated with the ability to position users and modern mathematical solutions such as spherical trigonometry provides the P2P system with the necessary accuracy even for short distances. The P2P system works on different Java platforms including JSE, JME and Android. Unfortunately the 3G network distributor has not yet solved a NAT traversal problem, which means that the P2P network self organization and architecture has only been proved by means of simulations. Another problem is that certain mathematical formulas are required for the spherical trigonometry and the limitation for JME is that it is unable to handle inverse trigonometry. However, the Android and JSE versions can form a correct P2P network, under the condition that the Android device uses a WIFI connection point outside the 3G distributor network system. This thesis reports the successful testing of the locations-based P2P network.</p><br>MediaSense
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Kocurova, Anna. "Distributed collaborative context-aware content-centric workflow management for mobile devices." Thesis, University of West London, 2013. https://repository.uwl.ac.uk/id/eprint/745/.
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Ubiquitous mobile devices have become a necessity in today’s society, opening new opportunities for interaction and collaboration between geographically distributed people. With the increased use of mobile phones, people can collaborate while on the move. Collaborators expect technologies that would enhance their teamwork and respond to their individual needs. Workflow is a widely used technology that supports collaboration and can be adapted for a variety of collaborative scenarios. Although the originally computer-based workflow technology has expanded also on mobile devices, there are still research challenges in the development of user-focused device-oriented collaborative workflows. As opposed to desktop computers, mobile devices provide a different, more personalised user experience and are carried by their owners everywhere. Mobile devices can capture user context and behave as digitalised user complements. By integrating context awareness into the workflow technology, workflow decisions can be based on local, context information and therefore, be more adapted to individual collaborators’ circumstances and expectations. Knowing the current context of collaborators and their mobile devices is useful, especially in mobile peer-topeer collaboration where the workflow process execution can be driven by devices according to the situation. In mobile collaboration, team workers share pictures, videos, or other content. Monitoring and exchanging the information on the current state of the content processed on devices can enhance the overall workflow execution. As mobile devices in peer-to-peer collaboration are not aware of a global workflow state, the content state information can be used to communicate progress among collaborators. However, there is still a lack of integrating content lifecycles in process-oriented workflows. The aim of this research was therefore to investigate how workflow technology can be adapted for mobile peer-to-peer collaboration, in particular, how the level of context awareness in mobile collaborative workflows can be increased and how the extra content lifecycle management support can be integrated. The collaborative workflow technology has been adapted for mobile peerto- peer collaboration by integrating context and content awareness. In the first place, a workflow-specific context management approach has been developed that allows defining workflow-specific context models and supports the integration of context models with collaborative workflows. Workflow process has been adapted to make decisions based on context information. Secondly, extra content management support has been added to the workflow technology. A representation for content lifecycles has been designed, and content lifecycles have been integrated with the workflow process. In this thesis, the MobWEL workflow approach is introduced. The Mob- WEL workflow approach allows defining, managing and executing mobile context-aware content-centric workflows. MobWEL is a workflow execution language that extends BPEL, using constructs from existing workflow approaches, Context4BPEL and BPELlight, and adopting elements from the BALSA workflow model. The MobWEL workflow management approach is a technology-based solution that has been designed to provide workflow management support to a specific class of mobile applications.
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Ferner, Ulric John. "Distributed belief propagation and its generalizations for location-aware networks." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/57690.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2010.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 77-80).<br>This thesis investigates the use of generalized belief propagation (GBP) and belief propagation (BP) algorithms for distributed inference. The concept of a network region graph is introduced, along with several approximation structures that can be distributed across a network. In this formulation, clustered region graphs are introduced to create a network "backbone" across which the computation for inference is distributed. This thesis shows that clustered region graphs have good structural properties for GBP algorithms. We propose the use of network region graphs and GBP for location-aware networks. In particular, a method for representing GBP messages non-parametrically is developed. As an special case, we apply BP algorithms to mobile networks without infrastructure, and we propose heuristics to optimize degree of network cooperation. Numerical results show a five times performance increase in terms of outage probability, when compared to conventional algorithms.<br>by Ulric John Ferner.<br>S.M.
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Kafle, Sijan. "Securing Distributed Context Exchange Networks in Mobile Environments." Thesis, Mittuniversitetet, Avdelningen för informations- och kommunikationssystem, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-20036.
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The use of the internet has exploded with many more context aware applications for different services, simplifying the use and access for human requirements. The present situation shows an increasing number of devices from computers to sensors and actuators that are connected to the internet. MediaSense[1] is a growing framework that provides a platform for applications to connect these devices (smart-phones, sensors, actuators etc.) and provide services using the internet. Applications based on the MediaSense[1] framework access globally available sensors to provide contextual information with regards to a situation and provide better services. However, information flowing between the devices or sensors are open to the internet without any security. Thus, the focus of this thesis is on the development of a security mechanism for the MediaSense framework which is a fully distributed network. The task involves analyzing the security measures with and without centralized authority as well as the advantages and disadvantages of both scenarios regarding the MediaSense framework and proposing appropriate solutions to achieve the maximum possible security on the framework. The first challenge of this thesis is to identify different properties required for a security mechanism which is capable of secure key distribution and secure peer to peer communication among MediaSense instances without having any centralized authority. Therefore, this thesis proposes a resilient solution, namely, a security architecture for MediaSense which is capable of performing in a distributed environment with the ability of key distribution and management and thus securing the communication using different encryption techniques. The next challenge to the security architecture is to store the keys securely and prevent any unauthorized access from a third party. The thesis proposes the use of built in Java Application Programming Interface(API), “KeyStore” to store valuable keys locally. Thus, by addressing these challenges and other related issues, this thesis forms a security architecture or mechanism that is adaptive to a distributed system and utilizes encryption algorithms, key distribution and secure storage of the keys. To support these proposals, this thesis has developed a proof of concept application and prototypes to verify the approach. In addition, the thesis has implemented security features from the security architecture as an extension to the MediaSense framework. Hence, in conclusion, this thesis proposal regarding a security architecture for MediaSense has the ability to provide the necessary security together with the required key distribution mechanism to the framework without any centralized authority.
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Ahmed, Tansir [Verfasser]. "Context-Aware Vertical Handover in Heterogeneous Wireless Networks / Tansir Ahmed." Aachen : Shaker, 2007. http://d-nb.info/1164339540/34.
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Rondini, E. "Bandwidth-aware distributed ad-hoc grids in deployed wireless sensor networks." Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/146986/.
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Nowadays, cost effective sensor networks can be deployed as a result of a plethora of recent engineering advances in wireless technology, storage miniaturisation, consolidated microprocessor design, and sensing technologies. Whilst sensor systems are becoming relatively cheap to deploy, two issues arise in their typical realisations: (i) the types of low-cost sensors often employed are capable of limited resolution and tend to produce noisy data; (ii) network bandwidths are relatively low and the energetic costs of using the radio to communicate are relatively high. To reduce the transmission of unnecessary data, there is a strong argument for performing local computation. However, this can require greater computational capacity than is available on a single low-power processor. Traditionally, such a problem has been addressed by using load balancing: fragmenting processes into tasks and distributing them amongst the least loaded nodes. However, the act of distributing tasks, and any subsequent communication between them, imposes a geographically defined load on the network. Because of the shared broadcast nature of the radio channels and MAC layers in common use, any communication within an area will be slowed by additional traffic, delaying the computation and reporting that relied on the availability of the network. In this dissertation, we explore the tradeoff between the distribution of computation, needed to enhance the computational abilities of networks of resource-constrained nodes, and the creation of network traffic that results from that distribution. We devise an application-independent distribution paradigm and a set of load distribution algorithms to allow computationally intensive applications to be collaboratively computed on resource-constrained devices. Then, we empirically investigate the effects of network traffic information on the distribution performance. We thus devise bandwidth-aware task offload mechanisms that, combining both nodes computational capabilities and local network conditions, investigate the impacts of making informed offload decisions on system performance. The highly deployment-specific nature of radio communication means that simulations that are capable of producing validated, high-quality, results are extremely hard to construct. Consequently, to produce meaningful results, our experiments have used empirical analysis based on a network of motes located at UCL, running a variety of I/O-bound, CPU-bound and mixed tasks. Using this setup, we have established that even relatively simple load sharing algorithms can improve performance over a range of different artificially generated scenarios, with more or less timely contextual information. In addition, we have taken a realistic application, based on location estimation, and implemented that across the same network with results that support the conclusions drawn from the artificially generated traffic.
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Gligorijevic, Jelena. "Context-aware Learning from Partial Observations." Diss., Temple University Libraries, 2018. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/484799.
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Computer and Information Science<br>Ph.D.<br>The Big Data revolution brought an increasing availability of data sets of unprecedented scales, enabling researchers in machine learning and data mining communities to escalate in learning from such data and providing data-driven insights, decisions, and predictions. However, on their journey, they are faced with numerous challenges, including dealing with missing observations while learning from such data or making predictions on previously unobserved or rare (“tail”) examples, which are present in a large span of domains including climate, medical, social networks, consumer, or computational advertising domains. In this thesis, we address this important problem and propose tools for handling partially observed or completely unobserved data by exploiting information from its context. Here, we assume that the context is available in the form of a network or sequence structure, or as additional information to point-informative data examples. First, we propose two structured regression methods for dealing with missing values in partially observed temporal attributed graphs, based on the Gaussian Conditional Random Fields (GCRF) model, which draw power from the network/graph structure (context) of the unobserved instances. Marginalized Gaussian Conditional Random Fields (m-GCRF) model is designed for dealing with missing response variable value (labels) in graph nodes, whereas Deep Feature Learning GCRF is able to deal with missing values in explanatory variables while learning feature representation jointly with learning complex interactions of nodes in a graph and together with the overall GCRF objective. Next, we consider unsupervised and supervised shallow and deep neural models for monetizing web search. We focus on two sponsored search tasks here: (i) query-to-ad matching, where we propose novel shallow neural embedding model worLd2vec with improved local query context (location) utilization and (ii) click-through-rate prediction for ads and queries, where Deeply Supervised Semantic Match model is introduced for dealing with unobserved and tail queries click-through-rate prediction problem, while jointly learning the semantic embeddings of a query and an ad, as well as their corresponding click-through-rate. Finally, we propose a deep learning approach for ranking investigators based on their expected enrollment performance on new clinical trials, that learns from both, investigator and trial-related heterogeneous (structured and free-text) data sources, and is applicable to matching investigators to new trials from partial observations, and for recruitment of experienced investigators, as well as new investigators with no previous experience in enrolling patients in clinical trials. Experimental evaluation of the proposed methods on a number of synthetic and diverse real-world data sets shows surpassing performance over their alternatives.<br>Temple University--Theses
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Li, Herman Hon Yu. "The Impress Context Store: A Coordination Framework for Context-Aware Systems." Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/1091.
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The dream of weaving technology into our everyday fabric of life is recently being made possible by advances in ubiquitous computing and sensor technologies. Countless sensors of various sizes have made their way into everyday commercial applications. Many projects aim to explore new ways to utilize these new technologies to aid and interact with the general population. Context-aware systems use available context information to assist users automatically, without explicit user input. By inferring user intent and configuring the system proactively for each user, context-aware systems are an integral part of achieving user-friendly ubiquitous computing environments. <br /><br /> A common issue with building a distributed context-aware system is the need to develop a supporting infrastructure providing features such as storage, distributed messaging, and security, before the real work on processing context information can be done. This thesis proposes a coordination framework that provides an effective common foundation for context-aware systems. The separation between the context-processing logic component and the underlying supporting foundation allows researchers to focus their energy at the context-processing part of the system, instead of spending their time re-inventing the supporting infrastructure. <br /><br /> As part of an ongoing project, Impress, the framework uses the open standard, Jabber, as its communication protocol. The Publish-Subscribe (pubsub) extension to Jabber provides interesting features that match those needed by a context-aware system. The main contribution of this thesis is the design and implementation of a coordination framework, called the Impress Context Store, that provides an effective common foundation for context-aware systems. The separation between the context-processing logic and the underlying supporting foundation allows researchers to focus their energy at the context-processing part of the system, instead of spending their time re-inventing the supporting infrastructure.
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Dargie, Waltenegus. "A Distributed Architecture for Computing Context in Mobile Devices." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2006. http://nbn-resolving.de/urn:nbn:de:swb:14-1151308912028-83795.
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Context-aware computing aims at making mobile devices sensitive to the social and physical settings in which they are used. A necessary requirement to achieve this goal is to enable those devices to establish a shared understanding of the desired settings. Establishing a shared understanding entails the need to manipulate sensed data in order to capture a real world situation wholly, conceptually, and meaningfully. Quite often, however, the data acquired from sensors can be inexact, incomplete, and/or uncertain. Inexact sensing arises mostly due to the inherent limitation of sensors to capture a real world phenomenon precisely. Incompleteness is caused by the absence of a mechanism to capture certain real-world aspects; and uncertainty stems from the lack of knowledge about the reliability of the sensing sources, such as their sensing range, accuracy, and resolution. The thesis identifies a set of criteria for a context-aware system to capture dynamic real-world situations. On the basis of these criteria, a distributed architecture is designed, implemented and tested. The architecture consists of Primitive Context Servers, which abstract the acquisition of primitive contexts from physical sensors; Aggregators, to minimise error caused by inconsistent sensing, and to gather correlated primitive contexts pertaining to a particular entity or situation; a Knowledge Base and an Empirical Ambient Knowledge Component, to model dynamic properties of entities with facts and beliefs; and a Composer, to reason about dynamic real-world situations on the basis of sensed data. Two additional components, namely, the Event Handler and the Rule Organiser, are responsible for dynamically generating context rules by associating decision events ? signifying a user?s activity ? with the context in which those decision events are produced. Context-rules are essential elements with which the behaviour of mobile devices can be controlled and useful services can be provided. Four estimation and recognition schemes, namely, Fuzzy Logic, Hidden Markov Models, Dempster-Schafer Theory of Evidence, and Bayesian Networks, are investigated, and their suitability for the implementation of the components of the architecture of the thesis is studied. Subsequently, fuzzy sets are chosen to model dynamic properties of entities. Dempster-Schafer?s combination theory is chosen for aggregating primitive contexts; and Bayesian Networks are chosen to reason about a higher-level context, which is an abstraction of a real-world situation. A Bayesian Composer is implemented to demonstrate the capability of the architecture in dealing with uncertainty, in revising the belief of the Empirical Ambient Knowledge Component, in dealing with the dynamics of primitive contexts and in dynamically defining contextual states. The Composer could be able to reason about the whereabouts of a person in the absence of any localisation sensor. Thermal, relative humidity, light intensity properties of a place as well as time information were employed to model and reason about a place. Consequently, depending on the variety and reliability of the sensors employed, the Composer could be able to discriminate between rooms, corridors, a building, or an outdoor place with different degrees of uncertainty. The Context-Aware E-Pad (CAEP) application is designed and implemented to demonstrate how applications can employ a higher-level context without the need to directly deal with its composition, and how a context rule can be generated by associating the activities (decision events) of a mobile user with the context in which the decision events are produced.
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Espinosa, Carlin Juan Miguel [Verfasser]. "Context-Aware Service Provisioning in Converging Networks / Juan Miguel Espinosa Carlin." Aachen : Shaker, 2010. http://d-nb.info/1081886854/34.
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Loi, Yew-Cheng. "The use of Bayesian networks to support context aware mobile devices." Thesis, University of Surrey, 2006. http://epubs.surrey.ac.uk/844596/.
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Mobile communications technology has increasingly become integrated into modern day life and the rate of this integration is growing rapidly. However, many mobile devices including personal digital assistants (PDA) and mobile phones are predominantly passive, lacking a facility for automated information handling. For example, a mobile phone cannot automatically detect a user's context and react to support that situation. In this thesis, we present a context aware system that automatically detects mobile users' activity context through information gathered from a mobile phone. The thesis contains two main contributions: the development of the context prediction model and the implementation of a context aware system. The development of the context prediction model involves the use of Bayesian networks to solve the uncertainty regarding a user current activity, along with the prediction of possible future activities. A Bayesian probabilistic network is a comprehensive probabilistic computational framework for reasoning under conditions of uncertainty. In this research, we utilise Bayesian networks as a modelling tool to support context reasoning and activity prediction within the context aware domain. A further contribution of this work is the development of a real world context aware system based upon our above theoretical contribution. A Sony Ericsson P910i mobile phone alongside a context aware engine server has been implemented to demonstrate the theoretical principles. The mobile phone is used to capture contextual information from a user and interact with the context engine server. Using a probabilistic approach and uncertainty metric, the Bayesian context prediction network (which is located on the context engine server) predicts a user's likely activity, and contextual information is provided to the user via their mobile phone. A dataset of real-life user activities has been collected to evaluate the accuracy of the predicted activities. The results of the evaluation demonstrated encouraging levels of accuracy for this approach.
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Edinger, Janick [Verfasser], and Christian [Akademischer Betreuer] Becker. "Context-aware task scheduling in distributed computing systems / Janick Edinger ; Betreuer: Christian Becker." Mannheim : Universitätsbibliothek Mannheim, 2019. http://d-nb.info/1191098680/34.
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Bagaria, Devang. "Topology-aware transmission scheduling for distributed highway traffic monitoring wireless sensor networks." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1193080027/.
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Arabo, Abdullahi. "User-centred and context-aware identity management in mobile ad-hoc networks." Thesis, Liverpool John Moores University, 2011. http://researchonline.ljmu.ac.uk/6103/.
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The emergent notion of ubiquitous computing makes it possible for mobile devices to communicate and provide services via networks connected in an ad-hoc manner. These have resulted in the proliferation of wireless technologies such as Mobile Ad-hoc Networks (MANets), which offer attractive solutions for services that need flexible setup as well as dynamic and low cost wireless connectivity. However, the growing trend outlined above also raises serious concerns over Identity Management (IM) due to a dramatic increase in identity theft. The problem is even greater in service-oriented architectures, where partial identities are sprinkled across many services and users have no control over such identities. In this thesis, we review some issues of contextual computing, its implications and usage within pervasive environments. To tackle the above problems, it is essential to allow users to have control over their own identities in MANet environments. So far, the development of such identity control remains a significant challenge for the research community. The main focus of this thesis is on the area of identity management in MANets and emergency situations by using context-awareness and user-centricity together with its security issues and implications. Context- awareness allows us to make use of partial identities as a way of user identity protection and node identification. User-centricity is aimed at putting users in control of their partial identities, policies and rules for privacy protection. These principles help us to propose an innovative, easy-to-use identity management framework for MANets. The framework makes the flow of partial identities explicit; gives users control over such identities based on their respective situations and contexts, and creates a balance between convenience and privacy. The thesis presents our proposed framework, its development and lab results/evaluations, and outlines possible future work to improve the framework.
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Vardalachos, Nikolaos. "Towards a novel framework for management of context-aware services and networks." Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/1446786/.
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There are very many different ways how context information could be used to make computer systems and applications more user-friendly, flexible, and adaptable. The use of context information is especially important in a mobile environment, where the environment of interaction, execution, and usage needs change rapidly. Areas where increased use of context information can bring added value and where research work is conducted include human computer interaction, adaptable user interfaces, virtual and augmented reality, mobile, ubiquitous, handheld, and wearable computing. The objectives of this thesis were to briefly clarify what context and context-awareness mean and to analyse the network context-awareness in networks through the use of policies. This was done through the development of a Context Policy Based Management Framework (Context Aware Policy Language and Policy Based Management Architecture), which was initially functionally tested at component level, and eventually successfully exercised by implementing two context aware services through the use of context aware policies.
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Yew, Alvin. "Policy-based management of context-aware services in 3rd Generation mobile networks." Thesis, University of Surrey, 2007. http://epubs.surrey.ac.uk/843082/.
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Current 3rd Generation (3G) mobile networks have the ability to deploy and offer context- aware services. 3G service frameworks such as the Open Service Access and the Location Service provide context-aware services easy access to the user's context. Service adaptation is fundamental to context-aware service provisioning and to the realisation of the Virtual Home Environment concept, which is now an integral part of the 3G service framework. The additional complexity in service adaptation inherent in context-aware services, however, requires a powerful and appropriate management framework to control service behaviour. Policy-based management, a proven solution in the network management field, is an appropriate framework to manage adaptable context-aware services as it reduces complexity through a rule-based approach of mapping events and conditions to management actions to achieve management goals. 3GPP has incorporated a policy management interface in the OSA specifications but has not provided any mappings or bindings to the underlying 3G network to achieve its realisation. This thesis proposes a framework that realizes the OSA policy management API while maintaining strict compliance to the plethora of 3G specifications regarding the underlying 3G network. It explores the various operating requirements for deploying the policy-based management framework including the various 3G business models, the VHE concept, and the context-aware service adaptation requirements. Solutions to managing and enforcing multi-dimensional context-aware service adaptation are also presented in this thesis. A policy information model to aid the creation of context-aware service adaptation policies was designed and developed with strict compliance to the various 3G specifications. A prototype of the framework was implemented as a proof of concept and its evaluation is provided with an empirical analysis of its performance.
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Stabellini, Luca. "Toward Reliable Wireless Sensor Networks : Energy-Aware Distributed interference Management for Unlicensed Bands." Doctoral thesis, KTH, Kommunikationssystem, CoS, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-26145.
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Wireless sensor networks have been proposed as a cost effective and easy to deploy alternative to traditional wired systems in a multitude of application scenarios ranging from industrial automation to healthcare monitoring. They are expected to enable an unparalleled number of new services that will bring countless benefits to society. However, low power communications of sensor nodes operating in unlicensed bands face several challenges and are easily corrupted by transmissions of other collocated wireless networks. This problem has recently raised reliability concerns which have been tremendously enhanced by the proliferation of wireless devices we have been witnessing during the last years in the few available regions of the spectrum. This dissertation studies how to achieve reliable communications by proposing different ways for the energy aware management of the radio interference problem. The use of wireless sensing technologies has been envisaged in a broad variety of settings: for this reason it is not possible to identify a unifying solution for the problem of interference, but rather it is necessary to tailor the design of communication schemes accounting for the specific communication paradigm adopted by sensors, the traffic pattern generated by the expected application, as well as for the channel conditions experienced by nodes. When packet transmissions are addressed to a single receiver, cognitive access schemes can be utilized and sensors can opportunistically select for their transmissions when to access a certain channel or which channel to access so as to avoid interference. We provide an energy aware design for communication schemes implementing these ideas and evaluate their energy performance by means of experiments using real hardware. Our results indicate that the first approach should be considered only for sporadic packet transmissions over channels presenting limited interfering activities; channel adaptation should instead be preferred for large bulks of data or when the risk of operating in heavily interfered frequency bands is high. We further propose and evaluate a novel adaptive frequency hopping algorithm: this algorithm has been shown to be very efficient in mitigating the negative effects of interference allowing at the same time to avoid the use of the energy costly spectrum sensing algorithms required by cognitive access schemes. However, none of these three approaches may be suitable for scenarios where packet transmissions are addressed to multiple receivers. To deal with the packet losses that nodes may experience over noisy or interfered channels we envisage the use of fountain codes and show how it is possible to engineer such a coding solution so as to reduce the complexity and overhead introduced by the encoding and decoding procedures. The resulting codes provide an efficient way for disseminating data over multi-hop wireless sensor networks. Results obtained in this dissertation can be of great utility for designers of sensor applications who can use them in order to select the most energy efficient way to achieve reliable interference-aware communications.<br>QC 20101124
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Sajid, Muhammad, and Imran Siddiqui. "A distributed, load-aware, power and frequency bargaining protocol for LTE-based networks." Thesis, Linköpings universitet, Kommunikations- och transportsystem, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-76893.
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In this thesis a distributed, dynamic, load aware, joint power and frequency allocation protocol for 4G networks along with system-level simulated results are presented. In all cellular networks, a key limiting factor for throughput is inter-cell interference, especially at the cell edges. Several methods have been proposed and adopted in each mobile network generation to cancel or suppress its effects, whereas each method has its drawbacks in terms of receiver complexity or additional control nodes. However, the proposed protocol presented here does not impose any architectural changes. In 4G networks such as LTE, the choice of OFDMA for the air interface has paved the way for selective frequency and power allocation in the available spectrum. Taking advantage of this opportunity, fractional frequency reuse (FFR) has been proposed in OFDMA based mobile networks in order to reduce the throughput loss at the cell edges due to inter-cell interference. In FFR, center users lose part of available spectrum that is dedicated to the edge users. Our protocol aims to minimize this loss of center users incurred by FFR, at the cost of minimal degradation at the edges. An eNodeB, only when overloaded, requests its neighbours’ edge band to be used for its center users at a reduced power level. This is done via small message exchange between the eNodeBs. The neighbors of the overloaded eNodeBs solve a small local knapsack problem to decide whether band lending is feasible or not. A distinguishing feature of this protocol is the power level adjustment for the borrowed band, which is mutually decided by the borrower and lender. The band is released when it is not needed or it is causing unacceptable loss to the lender. The implementation is done in a Matlab based LTE system level simulator. For the implementation of our protocol in the simulator, starting point was implementation of FFR-3 functionality, a prerequisite and a baseline for comparison with our protocol. Results are compared among three different setups of re-use1, FFR-3 and our protocol by varying number of overloaded eNodeBs for various numbers of scenarios and the comparison is made based on the center users’ throughput, edge users’ throughput. An estimation of time and protocol overhead is also presented. We have observed center users’ throughput gain up to 46%, at the cost of 9% edge users’ throughput loss, when compared to the classic FFR-3 scheme. The overall system throughput goes up to 26 % in heavily loaded scenario. The utility of the protocol for an LTE system is evident from the results, which is supported by the dynamic and decentralized nature of the protocol. This ensures better utilization of spectrum, by temporarily allocating more bandwidth where it is needed more.
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Li, Xiaoyun. "Distributed topology-aware algorithms & topology control probabilistic analysis for wireless sensor networks." Thesis, University of Essex, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.446490.
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Ho, Qirong. "Modeling Large Social Networks in Context." Research Showcase @ CMU, 2014. http://repository.cmu.edu/dissertations/543.
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Today’s social and internet networks contain millions or even billions of nodes, and copious amounts of side information (context) such as text, attribute, temporal, image and video data. A thorough analysis of a social network should consider both the graph and the associated side information, yet we also expect the algorithm to execute in a reasonable amount of time on even the largest networks. Towards the goal of rich analysis on societal-scale networks, this thesis provides (1) modeling and algorithmic techniques for incorporating network context into existing network analysis algorithms based on statistical models, and (2) strategies for network data representation, model design, algorithm design and distributed multi-machine programming that, together, ensure scalability to very large networks. The methods presented herein combine the flexibility of statistical models with key ideas and empirical observations from the data mining and social networks communities, and are supported by software libraries for cluster computing based on original distributed systems research. These efforts culminate in a novel mixed-membership triangle motif model that easily scales to large networks with over 100 million nodes on just a few cluster machines, and can be readily extended to accommodate network context using the other techniques presented in this thesis.
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Herborn, Stephen Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "PACMAN: a personal-network centric approach to context and mobility aware networking." Awarded by:University of New South Wales. Electrical Engineering and Telecommunications, 2006. http://handle.unsw.edu.au/1959.4/31217.
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Users (or software agents) are served by multiple networked terminal devices, each of which may in turn have multiple network interfaces. This multi-homing at both ???user??? and ???device??? level presents new opportunities for mobility handling. Mobility may be handled by switching ongoing application data streams between devices, by utilising intermediary adaptation or connectivity enhancement services, or both. However this requires middleware support that is not provided by current systems. This thesis presents a set of integrated solutions to enable this kind of mobility handling, based on concept of Personal Networks (PN). Personal Networks (PN) consist of dynamic conglomerations of terminal and service devices tasked to facilitate the delivery of information to and from a single focal point, which may be a human user or software agent. This concept creates the potential to view mobility handling as a path selection problem, since there may be multiple valid terminal device and service proxy configurations that can successfully carry a given communication session from one PN to another PN. Depending on context, it may be necessary to switch between paths. To this end, this thesis proposes and evaluates a set of inter-dependent mechanisms to facilitate the discovery and use of different candidate end-to-end paths. The proposal comprises mechanisms for secure inter-device mobility using delegated cryptographic identifiers, autonomous service proxy selection and composition, and distributed resolution of cryptographic identifiers to lower layer addresses.
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Synnes, Kåre. "On distributed real-time systems : the mStar environment, net-based learning and context-aware applications." Doctoral thesis, Luleå tekniska universitet, Datavetenskap, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17057.
Full textAbstract:
This doctoral thesis presents two frameworks for distributed real-time systems, the mStar environment for Computer Supported Collaborative Work (CSCW) and the Alipes architecture for context-aware applications, from the perspective of distributed teamwork and net-based learning. The mStar environment was designed to be symmetric and fully distributed, which allows all users equal access and thus full interactivity, as well as scalable through the use of IP multicast and a server-less design. The environment makes use of reliable multicast, network resource management and packet loss recovery techniques to increase robustness. Heterogeneous networks and terminals are supported through tunneling and transcoding of media. Asynchronous use of the environment is made possible through support for recording and replay of sessions. It is therefore well equipped to meet the requirements for net-based learning, as the inherent time- and location-independence allows students to follow distributed courses, when otherwise large geographical distances or time restrictions otherwise would limit where and when education could be offered. The student can be anything from a full-time student attending lectures physically at the university, to a part-time student following courses from his home during evenings and weekends. Students will thus have increased possibilities of taking part in education. The Alipes architecture for context-aware applications allows multiple positioning techniques to be seamlessly interchanged and combined, enabling applications to utilize a single interface, yet benefit from several advantages that single positioning techniques cannot offer alone. Add peer-to-peer interchange of position information using ad-hoc networks, and the platform offers a wide variety of techniques to be interchanged or combined, with obvious advantages such as increased coverage and accuracy. Privacy issues are central to managing a user?s context information, for example his position, as that information could cause serious violations of personal integrity if misused. The Alipes architecture handles privacy through general criteria and contracts between users and location servers. Information exchange is typically carried out on a peer-to-peer basis using ad-hoc networks. Integrated examples could be combining locating a nearby tutor with setting up a conference call to initiate a tutoring session, using context information to enhance the perceived feeling of presence within the mStar environment or to optimize network-usage depending on the user?s context. A final conclusion is that systems aiming at enhancing the social aspects of distributed applications by using context information might be important, if not vital, when creating new real-time services for mobile terminals.<br>Godkänd; 2002; 20060921 (ysko)
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SILVA, JORDAN JANEIRO LOPES DA. "A CONTEXT-AWARE PROTOCOL FOR COORDINATED ADAPTATION OF COMMUNICATION SERVICES IN WIRELESS NETWORKS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2008. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=12142@1.
Full textAbstract:
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>A pesquisa em redes móveis e computação pervasiva têm
demonstrado que adaptação dinâmica e sensibilidade ao
contexto são requisitos básicos para aplicações nestes
ambientes. Muitos dos trabalhos sobre adaptação dinâmica
sensível ao contexto encontrados na literatura se baseiam
nas informações de contexto de dispositivos para selecionar
e executar uma determinada adaptação, mas somente no
próprio dispositivo. Para aplicações distribuídas cientes do
contexto envolvendo um grupo de dispositivos portáteis,
executando em uma rede sem fio, por vezes faz-se necessária
uma adaptação conjunta e coordenada de todos os
dispositivos do grupo, adaptação essa que depende de um
contexto global do grupo. Este trabalho apresenta Moratus,
um protocolo para obter o contexto global de um grupo de
dispositivos e executar uma única adaptação de serviços de
comunicação em todos os dispositivos de forma coordenada.
Este protocolo também leva em conta e trata desconexões
involuntárias de membros do grupo durante o processo. O
Moratus é o elemento central de um middleware, o SACS,
que permite que tal adaptação coordenada ocorra de forma
transparente e sem interrupção para a aplicação distribuída
que usa o middleware.<br>Research in mobile networks and pervasive computing has
shown that dynamic adaptation and context-awareness are
basic requirements for applications executing in such
environments. Many of the works about context-awareness
dynamic adaptation found in the literature use the device's
context information to execute an adaptation only locally
at the device. For distributed, context-aware applications
composed of a group of portable devices (executing in a
wireless network) sometimes it is necessary to perform a
collective and coordinated adaptation at all the devices of
the group, and where this adaptation depends on the global
context of the group. This thesis presents Moratus, a
protocol that processes the global context of a group and
executes a unique adaptation of a communication service at
all devices in the group in a coordinated way. This
protocol also handles unplanned disconnections of group
members during the adaptation process. Moratus is the
central element of a middleware named SACS, which allows
that such coordinated adaptation is performed transparently
and without disruption for the distributed application
based on this middleware.
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Hu, Xiping. "A platform for building context-aware mobile crowdsensing applications in vehicular social networks." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/55236.
Full textAbstract:
In the past few years, many research works have demonstrated that mobile crowdsensing could be effectively applied in vehicular social networks (VSNs) to serve many purposes and bring huge economic benefits in transportation. In this thesis, we provide a crowdsensing platform which addresses the research challenges in the overall workflow of crowdsensing in VSNs in terms of task allocation and task execution. This platform supports the creation of different context-aware mobile crowdsensing applications and facilitates their real-world deployments in VSNs. First, because of the inherent nature of crowdsensing, usually a crowdsensing task needs a group of different participants to finish it collaboratively. Thus, for task allocation in crowdsensing, we propose an application-oriented service collaboration model (ASCM). This ASCM automatically allocates multiple participants with multiple crowdsensing tasks across different mobile devices and cloud platform in an efficient and effective manner in VSNs.
Second, for task exaction of mobile crowdsensing applications in VSNs, the dynamic network connectivity of the underlying vehicular ad-hoc networks (VANETs) may cause failures of such applications during their executions. We design S-Aframe, an agent-based multi-layer framework, which provides a programming model to support creation and deployment of robust and reliable crowdsensing applications that self-adapt to the dynamic nature of VANETs. Furthermore, due to the dynamism of VANETs and the opportunism of user connections in VSNs, the changing environments of the users involved in the VSNs may also result in users’ dynamic contexts. We propose a context-aware semantic service (CSS), and incorporate this service with S-Aframe to improve the self-adaptiveness of mobile crowdsensing applications to users’ dynamic contexts of VSNs. Finally, we design and develop SAfeDJ, a crowdsensing-based situation-aware music recommendation application for drivers. The development of SAfeDJ has further demonstrated how our platform supports the creation of a context-aware mobile crowdsensing application, and facilitates the realization of such an application in real-world deployment in VSNs.<br>Applied Science, Faculty of<br>Electrical and Computer Engineering, Department of<br>Graduate
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Bahceci, Oktay. "Deep Neural Networks for Context Aware Personalized Music Recommendation : A Vector of Curation." Thesis, KTH, Skolan för datavetenskap och kommunikation (CSC), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-210252.
Full textAbstract:
Information Filtering and Recommender Systems have been used and has been implemented in various ways from various entities since the dawn of the Internet, and state-of-the-art approaches rely on Machine Learning and Deep Learning in order to create accurate and personalized recommendations for users in a given context. These models require big amounts of data with a variety of features such as time, location and user data in order to find correlations and patterns that other classical models such as matrix factorization and collaborative filtering cannot. This thesis researches, implements and compares a variety of models with the primary focus of Machine Learning and Deep Learning for the task of music recommendation and do so successfully by representing the task of recommendation as a multi-class extreme classification task with 100 000 distinct labels. By comparing fourteen different experiments, all implemented models successfully learn features such as time, location, user features and previous listening history in order to create context-aware personalized music predictions, and solves the cold start problem by using user demographic information, where the best model being capable of capturing the intended label in its top 100 list of recommended items for more than 1/3 of the unseen data in an offine evaluation, when evaluating on randomly selected examples from the unseen following week.<br>Informationsfiltrering och rekommendationssystem har använts och implementeratspå flera olika sätt från olika enheter sedan gryningen avInternet, och moderna tillvägagångssätt beror påMaskininlärrning samtDjupinlärningför att kunna skapa precisa och personliga rekommendationerför användare i en given kontext. Dessa modeller kräver data i storamängder med en varians av kännetecken såsom tid, plats och användardataför att kunna hitta korrelationer samt mönster som klassiska modellersåsom matris faktorisering samt samverkande filtrering inte kan. Dettaexamensarbete forskar, implementerar och jämför en mängd av modellermed fokus påMaskininlärning samt Djupinlärning för musikrekommendationoch gör det med succé genom att representera rekommendationsproblemetsom ett extremt multi-klass klassifikationsproblem med 100000 unika klasser att välja utav. Genom att jämföra fjorton olika experiment,så lär alla modeller sig kännetäcken såsomtid, plats, användarkänneteckenoch lyssningshistorik för att kunna skapa kontextberoendepersonaliserade musikprediktioner, och löser kallstartsproblemet genomanvändning av användares demografiska kännetäcken, där den bästa modellenklarar av att fånga målklassen i sin rekommendationslista medlängd 100 för mer än 1/3 av det osedda datat under en offline evaluering,när slumpmässigt valda exempel från den osedda kommande veckanevalueras.
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Yildiz, Ali. "Resource-aware Load Balancing System With Artificial Neural Networks." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607613/index.pdf.
Full textAbstract:
As the distributed systems becomes popular, efficient load balancing systems taking
better decisions must be designed. The most important reasons that necessitate load
balancing in a distributed system are the heterogeneous hosts having different com-
puting powers, external loads and the tasks running on different hosts but communi-
cating with each other. In this thesis, a load balancing approach, called RALBANN,
developed using graph partitioning and artificial neural networks (ANNs) is de-
scribed. The aim of RALBANN is to integrate the successful load balancing deci-
sions of graph partitioning algorithms with the efficient decision making mechanism
of ANNs. The results showed that using ANNs to make efficient load balancing can
be very beneficial. If trained enough, ANNs may load the balance as good as graph
partitioning algorithms more efficiently.