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Magister Scientiae - MSc / This thesis shows that mobility management protocols for infrastructure Internet may be used in a wireless mesh network environment. In this research Mobile IPv6 and Fast Handover for Hierarchical Mobile IPv6 are successfully implemented in a wireless mesh network environment. Two experiments were carried out: vertical and horizontal handover simulations. Vertical handover simulation involved a heterogeneous wireless environment comprising both wireless local area and wireless mesh networks. An OPNET Mobile IPv6 model was used to simulate the vertical handover experiment. Horizontal handover simulation involved Mobile IPv6 and Fast Handover for Hierarchical Mobile IPv6 applied in ns2 wireless mesh network. The vertical handover results show that MIPv6 is able to manage vertical handover between wireless local area and wireless mesh network. The horizontal handover results illustrate that in mesh networks, Fast Handover for Hierarchical Mobile IPv6's performance is superior to Mobile IPv6. Fast Handover for Hierarchical Mobile IPv6 generates more throughput and less delay than Mobile IPv6. Furthermore, Fast Handover for Hierarchical Mobile IPv6 drops less data packets than Mobile IPv6. The simulations indicate that even though there are multi-hop communications in wireless mesh networks, the performance of the multi-hop routing may not play a big role in the handover performance. This is so because the mesh routers are mostly static and the multi-hop routes are readily available. Thus, the total handover delay is not affected too much by the WMN hops in the paths for signaling message transmission. / South Africa

abstract: As networks are playing an increasingly prominent role in different aspects of our lives, there is a growing awareness that improving their performance is of significant importance. In order to enhance performance of networks, it is essential that scarce networking resources be allocated smartly to match the continuously changing network environment. This dissertation focuses on two different kinds of networks - communication and social, and studies resource allocation problems in these networks. The study on communication networks is further divided into different networking technologies - wired and wireless, optical and mobile, airborne and terrestrial. Since nodes in an airborne network (AN) are heterogeneous and mobile, the design of a reliable and robust AN is highly complex. The dissertation studies connectivity and fault-tolerance issues in ANs and proposes algorithms to compute the critical transmission range in fault free, faulty and delay tolerant scenarios. Just as in the case of ANs, power optimization and fault tolerance are important issues in wireless sensor networks (WSN). In a WSN, a tree structure is often used to deliver sensor data to a sink node. In a tree, failure of a node may disconnect the tree. The dissertation investigates the problem of enhancing the fault tolerance capability of data gathering trees in WSN. The advent of OFDM technology provides an opportunity for efficient resource utilization in optical networks and also introduces a set of novel problems, such as routing and spectrum allocation (RSA) problem. This dissertation proves that RSA problem is NP-complete even when the network topology is a chain, and proposes approximation algorithms. In the domain of social networks, the focus of this dissertation is study of influence propagation in presence of active adversaries. In a social network multiple vendors may attempt to influence the nodes in a competitive fashion. This dissertation investigates the scenario where the first vendor has already chosen a set of nodes and the second vendor, with the knowledge of the choice of the first, attempts to identify a smallest set of nodes so that after the influence propagation, the second vendor's market share is larger than the first. / Dissertation/Thesis / Ph.D. Computer Science 2014

Physical constrains of integrated circuits (commonly called chip) in regards to size and finite number of wires, has made the design of System-on-Chip (SoC) more interesting to study in terms of finding better solutions for the complexity of the chip-interconnections. The SoC has hundreds of Processing Elements (PEs), and a single shared bus can no longer be acceptable due to poor scalability with the system size. Networks on Chip (NoC) have been proposed as a solution to mitigate complex on-chip communication problems for complex SoCs. They consists of computational resources in the form of PE cores and switching nodes which allow PEs to communicate with each other. In the design and development of Networks on Chip, performance modelling and analysis has great theoretical and practical importance. This research is devoted to developing efficient and cost-effective analytical tools for the performance analysis and enhancement of NoCs with m-port n-tree topology under bursty traffic. Recent measurement studies have strongly verified that the traffic generated by many real-world applications in communication networks exhibits bursty and self-similar properties in nature and the message destinations are uniformly distributed. NoC's performance is generally affected by different traffic patterns generated by the processing elements. As the first step in the research, a new analytical model is developed to capture the burstiness and self-similarity characteristics of the traffic within NoCs through the use of Markov Modulated Poisson Process. The performance results of the developed model highlight the importance of accurate traffic modelling in the study and performance evaluation of NoCs. Having developed an efficient analytical tool to capture the traffic behaviour with a higher accuracy, in the next step, the research focuses on the effect of topology on the performance of NoCs. Many important challenges still remain as vulnerabilities within the design of NoCs with topology being the most important. Therefore a new analytical model is developed to investigate the performance of NoCs with the m-port n-tree topology under bursty traffic. Even though it is broadly proved in practice that fat-tree topology and its varieties result in lower latency, higher throughput and bandwidth, still most studies on NoCs adopt Mesh, Torus and Spidergon topologies. The results gained from the developed model and advanced simulation experiments significantly show the effect of fat-tree topology in reducing latency and increasing the throughput of NoCs. In order to obtain deeper understanding of NoCs performance attributes and for further improvement, in the final stage of the research, the developed analytical model was extended to consider the use of virtual channels within the architecture of NoCs. Extensive simulation experiments were carried out which show satisfactory improvements in the throughput of NoCs with fat-tree topology and VCs under bursty traffic. The analytical results and those obtained from extensive simulation experiments have shown a good degree of accuracy for predicting the network performance under different design alternatives and various traffic conditions.

Yes

Physical constrains of integrated circuits (commonly called chip) in regards to size and finite number of wires, has made the design of System-on-Chip (SoC) more interesting to study in terms of finding better solutions for the complexity of the chip-interconnections. The SoC has hundreds of Processing Elements (PEs), and a single shared bus can no longer be acceptable due to poor scalability with the system size. Networks on Chip (NoC) have been proposed as a solution to mitigate complex on-chip communication problems for complex SoCs. They consists of computational resources in the form of PE cores and switching nodes which allow PEs to communicate with each other. In the design and development of Networks on Chip, performance modelling and analysis has great theoretical and practical importance. This research is devoted to developing efficient and cost-effective analytical tools for the performance analysis and enhancement of NoCs with m-port n-tree topology under bursty traffic. Recent measurement studies have strongly verified that the traffic generated by many real-world applications in communication networks exhibits bursty and self-similar properties in nature and the message destinations are uniformly distributed. NoC's performance is generally affected by different traffic patterns generated by the processing elements. As the first step in the research, a new analytical model is developed to capture the burstiness and self-similarity characteristics of the traffic within NoCs through the use of Markov Modulated Poisson Process. The performance results of the developed model highlight the importance of accurate traffic modelling in the study and performance evaluation of NoCs. Having developed an efficient analytical tool to capture the traffic behaviour with a higher accuracy, in the next step, the research focuses on the effect of topology on the performance of NoCs. Many important challenges still remain as vulnerabilities within the design of NoCs with topology being the most important. Therefore a new analytical model is developed to investigate the performance of NoCs with the m-port n-tree topology under bursty traffic. Even though it is broadly proved in practice that fat-tree topology and its varieties result in lower latency, higher throughput and bandwidth, still most studies on NoCs adopt Mesh, Torus and Spidergon topologies. The results gained from the developed model and advanced simulation experiments significantly show the effect of fat-tree topology in reducing latency and increasing the throughput of NoCs. In order to obtain deeper understanding of NoCs performance attributes and for further improvement, in the final stage of the research, the developed analytical model was extended to consider the use of virtual channels within the architecture of NoCs. Extensive simulation experiments were carried out which show satisfactory improvements in the throughput of NoCs with fat-tree topology and VCs under bursty traffic. The analytical results and those obtained from extensive simulation experiments have shown a good degree of accuracy for predicting the network performance under different design alternatives and various traffic conditions. / Libyan Ministry of Higher Education

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No / Providing a guaranteed quality-of-service (QoS) is essential to many real-time applications. The existing distributed QoS routing algorithms are based on either shortest path or flooding and both tend to have high message overhead. A new distributed unicast QoS routing algorithm based on Fano¿s decoding method is studied. Fano¿s decoding method is a technique used in error control coding and it attempts to trace an optimal path probabilistically. The similarity of various aspects of Fano¿s decoding method to a QoS routing algorithm and the benefits it can provide encourages us to investigate the possibility of using it in QoS routing. This is the first known attempt to modify an error control technique using Fano¿s decoding method for the purpose of QoS routing in fixed wired networks. Simulation results demonstrate the effectiveness of the proposed algorithm in terms of message overhead and success ratio (% of paths obtained that satisfy the given QoS constraints). It is shown that the message overhead in the proposed algorithm is reduced compared to flooding based algorithms while maintaining a similar success ratio. Message overhead is also reduced compared to distance vector based algorithms for all but very sparsely connected networks, while success ratio is not compromised. Nodal storage is also considerably lower than for most other contemporary QoS routing algorithms.