A reliable totally-ordered group multicast protocol for mobile Internet

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Self-Configuration and Self-Optimization Process in Heterogeneous Wireless Networks

Self-organization in Wireless Mesh Networks (WMN) is an emergent research area, which is becoming important due to the increasing number of nodes in a network. Consequently, the manual configuration of nodes is either impossible or highly costly. So it is desirable for the nodes to be able to configure themselves. In this paper, we propose an alternative architecture for self-organization of WMN based on Optimized Link State Routing Protocol (OLSR) and the ad hoc on demand distance vector (AODV) routing protocols as well as using the technology of software agents. We argue that the proposed self-optimization and self-configuration modules increase the throughput of network, reduces delay transmission and network load, decreases the traffic of HELLO messages according to network’s scalability. By simulation analysis, we conclude that the self-optimization and self-configuration mechanisms can significantly improve the performance of OLSR and AODV protocols in comparison to the baseline protocols analyzed

RGB: a scalable and reliable group membership protocol in mobile Internet

We propose a membership protocol for group commu-nications in mobile Internet. The protocol is called RGB, which is the acronym of “a Ring-based hierarchy of ac-cess proxies, access Gateways, and Border routers”. RGB runs in a parallel and distributed way in the sense that each network entity in the ring-based hierarchy maintains local information about its possible leader, previous, next, par-ent and child neighbors, and that each network entity inde-pendently collects/generates membership change informa-tion, which is propagated by the one-round membership al-gorithm concurrently running in all the logical rings. We prove that the proposed protocol is scalable in the sense that the scalability of a ring-based hierarchy is as good as that of a tree-based hierarchy. We also prove that the proposed protocol is reliable, in the sense that, with high probability of 99.500%, a ring-based hierarchy with up to 1000 access proxies attached by a large number of mobile hosts will not partition when node faulty probability is bounded by 0.1%; if at most 3 partitions are allowed, then the Function-Well probability of the hierarchy is 99.999 % accordingly. 1

Self-organization and management of wireless sensor networks

Wireless sensor networks (WSNs) are a newly deployed networking technology consisting of multifunctional sensor nodes that are small in size and communicate over short distances. These sensor nodes are mainly in large numbers and are densely deployed either inside the phenomenon or very close to it. They can be used for various application areas (e.g. health, military, home). WSNs provide several advantages over traditional networks, such as large-scale deployment, highresolution sensed data, and application adaptive mechanisms. However, due to their unique characteristics (having dynamic topology, ad-hoc and unattended deployment, huge amount of data generation and traffic flow, limited bandwidth and energy), WSNs pose considerable challenges for network management and make application development nontrivial. Management of wireless sensor networks is extremely important in order to keep the whole network and application work properly and continuously. Despite the importance of sensor network management, there is no generalize solution available for managing and controlling these resource constrained WSNs. In network management of WSNs, energy-efficient network selforganization is one of the main challenging issues. Self-organization is the property which the sensor nodes must have to organize themselves to form the network. Selforganization of WSNs is challenging because of the tight constraints on the bandwidth and energy resources available in these networks. A self organized sensor network can be clustered or grouped into an easily manageable network. However, existing clustering schemes offer various limitations. For example, existing clustering schemes consume too much energy in cluster formation and re-formation. This thesis presents a novel cellular self-organizing hierarchical architecture for wireless sensor networks. The cellular architecture extends the network life time by efficiently utilizing nodes energy and support the scalability of the system. We have analyzed the performance of the architecture analytically and by simulations. The results obtained from simulation have shown that our cellular architecture is more energy efficient and achieves better energy consumption distribution. The cellular architecture is then mapped into a management framework to support the network management system for resource constraints WSNs. The management framework is self-managing and robust to changes in the network. It is application-co-operative and optimizes itself to support the unique requirements of each application. The management framework consists of three core functional areas i.e., configuration management, fault management, and mobility management. For configuration management, we have developed a re-configuration algorithm to support sensor networks to energy-efficiently re-form the network topology due to network dynamics i.e. node dying, node power on and off, new node joining the network and cells merging. In the area of fault management we have developed a new fault management mechanism to detect failing nodes and recover the connectivity in WSNs. For mobility management, we have developed a two phase sensor relocation solution: redundant mobile sensors are first identified and then relocated to the target location to deal with coverage holes. All the three functional areas have been evaluated and compared against existing solutions. Evaluation results show a significant improvement in terms of re-configuration, failure detection and recovery, and sensors relocation

Information and Communication Technologies for Integrated Operations of Ships

Over the past three decades, information and communication technologies have filled our daily life with great comfort and convenience. As the technology keeps evolving, user expectations for more challenging cases that can benefit from advanced information and communication technologies are increasing, e.g., the scenario of Integrated Operations (IO) for ships in the maritime domain. However, to realize integrated operations for ships is a complex task that involves addressing problems such as interoperability among heterogeneous operation applications and connectivity within harsh maritime communication environments. The common approach was to tackle these challenges separately by service integration and communication integration, respectively: each utilizes optimized and independent implementations. Separate solutions work fine within their own contexts, whereas conflicts and inconsistencies can be identified by integrating them together for specific maritime scenarios. Therefore, connection between separate solutions needs to be studied. In this dissertation, we first take a look at complex systems to obtain useful methodologies applied to integrated operations for ships. Then we study IO of ships from different perspectives and divide the complex task into sub-tasks. We explore separate approaches to these sub-tasks, examine the connection in between, resolve inconsistencies if there are any, and continue the exploration process till a compatible and integrated solution can be accomplished. In general, this journey represents our argument for an integration-oriented complex system development approach. In concrete, it shows the way on how to achieve IO of ships by both providing connectivity in harsh communication environments and allowing interoperability among heterogeneous operation applications, and most importantly by ensuring the synergy in between. This synergy also gives hints on the evolution towards a next generation network architecture for the future Internet

P2P and SOA architecture for digital libraries

Doutoramento em Engenharia InformáticaIn an information-driven society where the volume and value of produced and consumed data assumes a growing importance, the role of digital libraries gains particular importance. This work analyzes the limitations in current digital library management systems and the opportunities brought by recent distributed computing models. The result of this work is the implementation of the University of Aveiro integrated system for digital libraries and archives. It concludes by analyzing the system in production and proposing a new service oriented digital library architecture supported in a peer-to-peer infrastructureNuma sociedade em que o volume e o valor da informação produzida e disseminada tem um peso cada vez maior, o papel das bibliotecas digitais assume especial relevo. O presente trabalho analisa as limitações dos actuais sistemas de gestão de bibliotecas digitais e as oportunidades criadas pelos mais recentes modelos de computação distribuída. Deste trabalho resultou a implementação do sistema integrado para bibliotecas e arquivos digitais da Universidade de Aveiro. Este trabalho finaliza debruçando-se sobre o sistema em produção e propondo uma nova arquitectura de biblioteca digital sustentada numa infrastrutura peer-to-peer e orientada a serviços

Semantic search and composition in unstructured peer-to-peer networks

This dissertation focuses on several research questions in the area of semantic search and composition in unstructured peer-to-peer (P2P) networks. Going beyond the state of the art, the proposed semantic-based search strategy S2P2P offers a novel path-suggestion based query routing mechanism, providing a reasonable tradeoff between search performance and network traffic overhead. In addition, the first semantic-based data replication scheme DSDR is proposed. It enables peers to use semantic information to select replica numbers and target peers to address predicted future demands. With DSDR, k-random search can achieve better precision and recall than it can with a near-optimal non-semantic replication strategy. Further, this thesis introduces a functional automatic semantic service composition method, SPSC. Distinctively, it enables peers to jointly compose complex workflows with high cumulative recall but low network traffic overhead, using heuristic-based bidirectional haining and service memorization mechanisms. Its query branching method helps to handle dead-ends in a pruned search space. SPSC is proved to be sound and a lower bound of is completeness is given. Finally, this thesis presents iRep3D for semantic-index based 3D scene selection in P2P search. Its efficient retrieval scales to answer hybrid queries involving conceptual, functional and geometric aspects. iRep3D outperforms previous representative efforts in terms of search precision and efficiency.Diese Dissertation bearbeitet Forschungsfragen zur semantischen Suche und Komposition in unstrukturierten Peer-to-Peer Netzen(P2P). Die semantische Suchstrategie S2P2P verwendet eine neuartige Methode zur Anfrageweiterleitung basierend auf Pfadvorschlägen, welche den Stand der Wissenschaft übertrifft. Sie bietet angemessene Balance zwischen Suchleistung und Kommunikationsbelastung im Netzwerk. Außerdem wird das erste semantische System zur Datenreplikation genannt DSDR vorgestellt, welche semantische Informationen berücksichtigt vorhergesagten zukünftigen Bedarf optimal im P2P zu decken. Hierdurch erzielt k-random-Suche bessere Präzision und Ausbeute als mit nahezu optimaler nicht-semantischer Replikation. SPSC, ein automatisches Verfahren zur funktional korrekten Komposition semantischer Dienste, ermöglicht es Peers, gemeinsam komplexe Ablaufpläne zu komponieren. Mechanismen zur heuristischen bidirektionalen Verkettung und Rückstellung von Diensten ermöglichen hohe Ausbeute bei geringer Belastung des Netzes. Eine Methode zur Anfrageverzweigung vermeidet das Feststecken in Sackgassen im beschnittenen Suchraum. Beweise zur Korrektheit und unteren Schranke der Vollständigkeit von SPSC sind gegeben. iRep3D ist ein neuer semantischer Selektionsmechanismus für 3D-Modelle in P2P. iRep3D beantwortet effizient hybride Anfragen unter Berücksichtigung konzeptioneller, funktionaler und geometrischer Aspekte. Der Ansatz übertrifft vorherige Arbeiten bezüglich Präzision und Effizienz

Semantic search and composition in unstructured peer-to-peer networks

This dissertation focuses on several research questions in the area of semantic search and composition in unstructured peer-to-peer (P2P) networks. Going beyond the state of the art, the proposed semantic-based search strategy S2P2P offers a novel path-suggestion based query routing mechanism, providing a reasonable tradeoff between search performance and network traffic overhead. In addition, the first semantic-based data replication scheme DSDR is proposed. It enables peers to use semantic information to select replica numbers and target peers to address predicted future demands. With DSDR, k-random search can achieve better precision and recall than it can with a near-optimal non-semantic replication strategy. Further, this thesis introduces a functional automatic semantic service composition method, SPSC. Distinctively, it enables peers to jointly compose complex workflows with high cumulative recall but low network traffic overhead, using heuristic-based bidirectional haining and service memorization mechanisms. Its query branching method helps to handle dead-ends in a pruned search space. SPSC is proved to be sound and a lower bound of is completeness is given. Finally, this thesis presents iRep3D for semantic-index based 3D scene selection in P2P search. Its efficient retrieval scales to answer hybrid queries involving conceptual, functional and geometric aspects. iRep3D outperforms previous representative efforts in terms of search precision and efficiency.Diese Dissertation bearbeitet Forschungsfragen zur semantischen Suche und Komposition in unstrukturierten Peer-to-Peer Netzen(P2P). Die semantische Suchstrategie S2P2P verwendet eine neuartige Methode zur Anfrageweiterleitung basierend auf Pfadvorschlägen, welche den Stand der Wissenschaft übertrifft. Sie bietet angemessene Balance zwischen Suchleistung und Kommunikationsbelastung im Netzwerk. Außerdem wird das erste semantische System zur Datenreplikation genannt DSDR vorgestellt, welche semantische Informationen berücksichtigt vorhergesagten zukünftigen Bedarf optimal im P2P zu decken. Hierdurch erzielt k-random-Suche bessere Präzision und Ausbeute als mit nahezu optimaler nicht-semantischer Replikation. SPSC, ein automatisches Verfahren zur funktional korrekten Komposition semantischer Dienste, ermöglicht es Peers, gemeinsam komplexe Ablaufpläne zu komponieren. Mechanismen zur heuristischen bidirektionalen Verkettung und Rückstellung von Diensten ermöglichen hohe Ausbeute bei geringer Belastung des Netzes. Eine Methode zur Anfrageverzweigung vermeidet das Feststecken in Sackgassen im beschnittenen Suchraum. Beweise zur Korrektheit und unteren Schranke der Vollständigkeit von SPSC sind gegeben. iRep3D ist ein neuer semantischer Selektionsmechanismus für 3D-Modelle in P2P. iRep3D beantwortet effizient hybride Anfragen unter Berücksichtigung konzeptioneller, funktionaler und geometrischer Aspekte. Der Ansatz übertrifft vorherige Arbeiten bezüglich Präzision und Effizienz