265 research outputs found
A cluster based communication architecture for distributed applications in mobile ad hoc networks
Thesis (Master)--Izmir Institute of Technology, Computer Engineering, Izmir, 2006Includes bibliographical references (leaves: 63-69)Text in English; Abstract: Turkish and Englishx, 85 leavesIn this thesis, we aim to design and implement three protocols on a hierarchical architecture to solve the balanced clustering, backbone formation and distributed mutual exclusion problems for mobile ad hoc network(MANET)s. Our ¯rst goal is to cluster the MANET into balanced partitions. Clustering is a widely used approach to ease implemen-tation of various problems such as routing and resource management in MANETs. We propose the Merging Clustering Algorithm(MCA) for clustering in MANETs that merges clusters to form higher level of clusters by increasing their levels. Secondly, we aim to con-struct a directed ring topology across clusterheads which were selected by MCA. Lastly, we implement the distributed mutual exclusion algorithm based on Ricart-Agrawala algo-rithm for MANETs(Mobile RA). Each cluster is represented by a coordinator node on the ring which implements distributed mutual exclusion algorithm on behalf of any member in the cluster it represents. We show the operations of the algorithms, analyze their time and message complexities and provide results in the simulation environment of ns2
Mobile Ad-Hoc Networks
Being infrastructure-less and without central administration control, wireless ad-hoc networking is playing a more and more important role in extending the coverage of traditional wireless infrastructure (cellular networks, wireless LAN, etc). This book includes state-of the-art techniques and solutions for wireless ad-hoc networks. It focuses on the following topics in ad-hoc networks: vehicular ad-hoc networks, security and caching, TCP in ad-hoc networks and emerging applications. It is targeted to provide network engineers and researchers with design guidelines for large scale wireless ad hoc networks
Session Management in Multicast
As a new network technique to efficiently distribute information from a small number of senders to large numbers of receivers, multicast encounters many problems in scalability, membership management, security, etc. These problems hinder the deployment of multicast technology in commercial applications. To overcome these problems, a more general solution for multicast technology is needed. In this paper, after studying current multicast technologies, we summarized the technical requirements for multicast, including data delivery, scalability, security, group management, reliability, and deployment. In order to understand and meet the requirements, we define a life cycle model that most multicast sessions should follow. According to the requirements and the life cycle model, we propose and design a general solution that can control each phase of a session and satisfy most requirements for multicast technology. This general solution has three parts: hierarchical topology auto-configuration algorithm, Session Management Mechanism, and techniques supporting different multicast protocols. To verify the feasibility of our solution and compare its performance with other multicast techniques, we simulate our solution and compare it with PIM-SM and ESM
Self-organizing Network Optimization via Placement of Additional Nodes
Das Hauptforschungsgebiet des Graduiertenkollegs "International Graduate
School on Mobile Communication" (GS Mobicom) der Technischen Universität
Ilmenau ist die Kommunikation in Katastrophenszenarien. Wegen eines
Desasters oder einer Katastrophe können die terrestrischen Elementen der
Infrastruktur eines Kommunikationsnetzwerks beschädigt oder komplett
zerstört werden. Dennoch spielen verfügbare Kommunikationsnetze eine sehr
wichtige Rolle während der Rettungsmaßnahmen, besonders für die
Koordinierung der Rettungstruppen und für die Kommunikation zwischen ihren
Mitgliedern. Ein solcher Service kann durch ein mobiles Ad-Hoc-Netzwerk
(MANET) zur Verfügung gestellt werden. Ein typisches Problem der MANETs
ist Netzwerkpartitionierung, welche zur Isolation von verschiedenen
Knotengruppen führt. Eine mögliche Lösung dieses Problems ist die
Positionierung von zusätzlichen Knoten, welche die Verbindung zwischen den
isolierten Partitionen wiederherstellen können. Hauptziele dieser Arbeit
sind die Recherche und die Entwicklung von Algorithmen und Methoden zur
Positionierung der zusätzlichen Knoten. Der Fokus der Recherche liegt auf
Untersuchung der verteilten Algorithmen zur Bestimmung der Positionen für
die zusätzlichen Knoten. Die verteilten Algorithmen benutzen nur die
Information, welche in einer lokalen Umgebung eines Knotens verfügbar ist,
und dadurch entsteht ein selbstorganisierendes System. Jedoch wird das
gesamte Netzwerk hier vor allem innerhalb eines ganz speziellen Szenarios -
Katastrophenszenario - betrachtet. In einer solchen Situation kann die
Information über die Topologie des zu reparierenden Netzwerks im Voraus
erfasst werden und soll, natürlich, für die Wiederherstellung mitbenutzt
werden. Dank der eventuell verfügbaren zusätzlichen Information können
die Positionen für die zusätzlichen Knoten genauer ermittelt werden. Die
Arbeit umfasst eine Beschreibung, Implementierungsdetails und eine
Evaluierung eines selbstorganisierendes Systems, welche die
Netzwerkwiederherstellung in beiden Szenarien ermöglicht.The main research area of the International Graduate School on Mobile
Communication (GS Mobicom) at Ilmenau University of Technology is
communication in disaster scenarios. Due to a disaster or an accident, the
network infrastructure can be damaged or even completely destroyed.
However, available communication networks play a vital role during the
rescue activities especially for the coordination of the rescue teams and
for the communication between their members. Such a communication service
can be provided by a Mobile Ad-Hoc Network (MANET). One of the typical
problems of a MANET is network partitioning, when separate groups of nodes
become isolated from each other. One possible solution for this problem is
the placement of additional nodes in order to reconstruct the communication
links between isolated network partitions. The primary goal of this work is
the research and development of algorithms and methods for the placement of
additional nodes. The focus of this research lies on the investigation of
distributed algorithms for the placement of additional nodes, which use
only the information from the nodes’ local environment and thus form a
self-organizing system. However, during the usage specifics of the system
in a disaster scenario, global information about the topology of the
network to be recovered can be known or collected in advance. In this case,
it is of course reasonable to use this information in order to calculate
the placement positions more precisely. The work provides the description,
the implementation details and the evaluation of a self-organizing system
which is able to recover from network partitioning in both situations
Desempenho de QoS e mobilidade de sessões multicast em redes dinâmicasMes
Mestrado em Engenharia Electrónica e TelecomunicaçõesThe increasing demand in multimedia group services, contextawareness
and seamless mobility implies strict requirements that
cannot be satisfactorily addressed by the traditional transport control
architectures for session content delivery. Moreover, context-aware
networks introduce personalized concepts: any change in context
can change the overall services and network environments, requiring
the network and multicast sessions to be completely restructured in a
very dynamic way.
Regarding the complexity of maintaining scalability in context-aware
networks, this Thesis has as main goal the development of an
intelligent module, included in C-CAST architecture, capable of
managing the entire network scheme. This mechanism depending on
the scenario and the context of users and sources, and in
cooperation with other network entities, must decide the most
suitable network transport path in order to provide the best multiparty
content delivery to the users, and manage the dynamicity of the
network whenever changes occur. To perform its implementation, it
was used an approach based in the interaction of different network
components, exchanging context information between them. The
intelligent module, using the updated network information, decides
the better network connection to serve each user.
In order to simulate the network behaviour in various situations,
several scenarios were tested to evaluate its performance. The
network is evaluated according to the several configured parameters,
evaluating the improvements achieved in the network performance
concerning different metrics, e.g. delay, lost packets ratio, overhead
introduced by the architecture signalling. Through the implemented
simulation setup, it is possible to conclude that the deployment of the
solution proposed effectively provides an enhanced service to the
users, distributing the multiparty content with QoS assurance using
context information.O aumento da exigência em serviços de grupo, redes baseadas em
contexto e mobilidade transparente implicam requisitos rígidos que
não podem ser satisfeitos pelas arquitecturas tradicionais de controlo
de transporte para entrega de conteúdos de sessão. Não obstante,
redes baseadas em contexto introduzem conceitos personalizados:
qualquer mudança no contexto pode mudar completamente os
serviços e a própria rede, sendo necessário que a rede e as sessões
multicast sejam completamente reestruturadas de uma forma
dinâmica.
Tendo em conta a complexidade de manter a escalabilidade em
redes baseadas em contexto, esta Tese tem como principal objectivo
o desenvolvimento de um módulo inteligente, que faz parte da
arquitectura do projecto C-CAST, capaz de gerir toda a rede. Este
mecanismo, dependendo do cenário da rede e do contexto dos
utilizadores e das fontes, e em cooperação com outras entidades da
rede, deve seleccionar a o caminho mais apropriado da rede de
modo a fornecer da melhor forma o conteúdo aos utilizadores, e gerir
a dinâmicidade da rede sempre que ocorrem mudanças. Para o
implementar foi usada um método baseado na interacção de vários
componentes, que trocam informação sobre contextos entre eles. O
componente inteligente, usando informação actualizada da rede
decide qual a melhor conexão da rede para servir cada utilizador.
De forma a simular o comportamento da rede em várias situações,
foram testados diversos cenários para avaliar a sua performance. A
rede é avaliada de acordo com os vários parâmetros configurados,
avaliando as melhorias conseguidas na performance da rede, por
exemplo em termos de atrasos, rácio de pacotes perdidos e a carga
imposta pelas mensagens de controlo da arquitectura. Através das
simulações efectuadas é possível concluir que aplicando a
arquitectura proposta, é fornecido de forma eficiente um serviço
melhorado aos utilizadores, distribuindo o serviço de grupo com
garantias de Qualidade de Serviço e usando informação de contexto
Mobile Ad-Hoc Networks
Being infrastructure-less and without central administration control, wireless ad-hoc networking is playing a more and more important role in extending the coverage of traditional wireless infrastructure (cellular networks, wireless LAN, etc). This book includes state-of-the-art techniques and solutions for wireless ad-hoc networks. It focuses on the following topics in ad-hoc networks: quality-of-service and video communication, routing protocol and cross-layer design. A few interesting problems about security and delay-tolerant networks are also discussed. This book is targeted to provide network engineers and researchers with design guidelines for large scale wireless ad hoc networks
A survey on Bluetooth multi-hop networks
Bluetooth was firstly announced in 1998. Originally designed as cable replacement connecting devices in a point-to-point fashion its high penetration arouses interest in its ad-hoc networking potential. This ad-hoc networking potential of Bluetooth is advertised for years - but until recently no actual products were available and less than a handful of real Bluetooth multi-hop network deployments were reported. The turnaround was triggered by the release of the Bluetooth Low Energy Mesh Profile which is unquestionable a great achievement but not well suited for all use cases of multi-hop networks. This paper surveys the tremendous work done on Bluetooth multi-hop networks during the last 20 years. All aspects are discussed with demands for a real world Bluetooth multi-hop operation in mind. Relationships and side effects of different topics for a real world implementation are explained. This unique focus distinguishes this survey from existing ones. Furthermore, to the best of the authors’ knowledge this is the first survey consolidating the work on Bluetooth multi-hop networks for classic Bluetooth technology as well as for Bluetooth Low Energy. Another individual characteristic of this survey is a synopsis of real world Bluetooth multi-hop network deployment efforts. In fact, there are only four reports of a successful establishment of a Bluetooth multi-hop network with more than 30 nodes and only one of them was integrated in a real world application - namely a photovoltaic power plant. © 2019 The Author
A reinforcement learning-based link quality estimation strategy for RPL and its impact on topology management
Over the last few years, standardisation efforts are consolidating the role of the Routing Protocol for Low-Power and Lossy Networks (RPL) as the standard routing protocol for IPv6-based Wireless Sensor Networks (WSNs). Although many core functionalities are well defined, others are left implementation dependent. Among them, the definition of an efficient link-quality estimation (LQE) strategy is of paramount importance, as it influences significantly both the quality of the selected network routes and nodesâ\u80\u99 energy consumption. In this paper, we present RL-Probe, a novel strategy for link quality monitoring in RPL, which accurately measures link quality with minimal overhead and energy waste. To achieve this goal, RL-Probe leverages both synchronous and asynchronous monitoring schemes to maintain up-to-date information on link quality and to promptly react to sudden topology changes, e.g. due to mobility. Our solution relies on a reinforcement learning model to drive the monitoring procedures in order to minimise the overhead caused by active probing operations. The performance of the proposed solution is assessed by means of simulations and real experiments. Results demonstrated that RL-Probe helps in effectively improving packet loss rates, allowing nodes to promptly react to link quality variations as well as to link failures due to node mobility
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