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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Models for QoS mapping of IP flows over ATM cell streams

Basu, Kashinath January 2006 (has links)
No description available.
32

Access control scheme for delay/disruption tolerant networks (DTNs)

Johnson, Enyenihi Henry January 2012 (has links)
DelaylDisruption tolerant networks (DTNs) are wireless networks where a complete path from source to destination is not in existence most of the time, and even when it does exist, it is highly unstable and unpredicted. This together with limited computing and storage capacity, heterogeneity and high error rate amongst others violate most of the internet assumptions. This necessitated the design of DTN architecture to relax some of the Internet assumptions and provide interoperabilijy across heterogeneous networks with different network characteristics. The identified security threats in these networks this work is designed to address are masquerading, modification, replay and unauthorized access/use of resources. This work proposes a novel access control scheme that is based on both secret-key and public-key cryptography. The scheme is designed to be independent of server availability and recipient network connectivity during post trust establishment communication. The main contributions in this thesis are: Propose and implement a lightweight asymmetric based Authorization Pass (APass) as an alternative to digital certificate; Design and implement a PKI-based trust management scheme that facilitates secure exchange of public keys without binding it to credential, access control implementation and flexible trust termination process; Propose and implement a trust based authentication scheme that employs Hash-based Message Authentication Code (HMAC) for message authentication and integrity, and APass for source authentication; Investigate and establish the applicability of the push messaging sequence of the generic AAA (Authentication, Authorization and Accounting) architecture with modification, and extend the proposed authentication scheme to implement policy; Propose and implement generic AAA architecture concepts based access control decision making process using DTN Bundle Node. The proposed solutions are extensively discussed with their efficiency and effectiveness as well as comparative advantage demonstrated through simulations.
33

Hierarchical wireless framework for real-time collaborative generation and distribution of telemetry data

Kucukdurgut, I. January 2010 (has links)
This project introduces a novel multidisciplinary approach combining Vehicular Ad Hoc Networks and Granular Computing, to the data processing and information generation problem in large urban traffic systems. It addresses the challenge of realtime information generation and dissemination in such systems by designing and investigating a hierarchical real-time information framework. The research work is complemented by designing and developing a simulator for such a system, which provides a simulation environment for the model developed. The proposed multidisciplinary hierarchical real-time information processing and dissemination system framework utilises results from two different areas of study, which are Vehicular Ad Hoc Networks (VANETS) and Granular Computing concepts. Furthermore, a new geographically constrained VANET topology for information generation is proposed, simulated and investigated. The simulator is developed to model the proposed system and to help with the proof of concept investigation of the system. Its components have been designed and implemented to demonstrate how such multidisciplinary architectures can be simulated. Simulations using the hierarchical information framework have been run, and the results reported in the thesis suggest the feasibility of the concept. The system model and the simulator demonstrate that building future large and complex systems in terms of scalability and real-time information induction based on distributed nodes environment algorithms is possible. Both the system architecture and the simulator model are novel and they provide an important step towards achieving a solution to building infinitely scalable real-time information processing urban traffic systems.
34

Design models for service-based software application

Anjum, Maria January 2013 (has links)
Context: The use of a Service Oriented Architecture (SOA) offers a new and distinct approach to creating software based applications (SBAs) around the idea of integrating distributed autonomous computing resources. A widely available realisation of an SOA exists in the form of web services. However, to date no standard techniques have emerged for developing SBAs. There is also a lack of consistency in describing the concept itself, and the published literature offers little evidence derived from the experience of developing `real world examples. Aims: The objective of the work described in this thesis was to conduct a series of studies to explore systematically the concept of what constitutes an SOA by using the published literature, to employ this to construct a proof of concept SOA design model based on a real world problem, and in doing so, to investigate how well existing design notations are able to support this architectural style. Method: The research described in this thesis has been conducted in an evolutionary manner by employing a range of empirical methods. A mapping study was performed to investigate how the concept of SOA is interpreted by the research community. Based upon this model of SOA, a participant-observer case study was employed to construct an SOA design model and a use case model for an energy engineering application to demonstrate use for a real world problem. Finally, expert knowledge was employed for evaluation of the case study through the use of walkthroughs. Results: From the mapping study we created an integrated model of what constitutes an SOA for the use with the case study. The case study outcomes include a design for a renewable energy control system together with codified experience of constructing and recording the SOA design model. The experience of employing the walkthrough method for evaluation, and the outcomes of the evaluation are also discussed. Conclusion: From this research we conclude that the SOA research community needs to develop a clearer shared understanding and agreement on the model of what constitutes an SOA and the vocabulary used to describe the SOA concept. This will aid designers to communicate their mental models more effectively and will provide the semantics needed for devising the new notations that this study implies are needed for SBA design. Further, some lessons about SBA design have been derived from the case study experiences.
35

Architecture aware parallel programming in Glasgow parallel Haskell (GPH)

Aswad, Mustafa K. H. January 2012 (has links)
General purpose computing architectures are evolving quickly to become manycore and hierarchical: i.e. a core can communicate more quickly locally than globally. To be effective on such architectures, programming models must be aware of the communications hierarchy. This thesis investigates a programming model that aims to share the responsibility of task placement, load balance, thread creation, and synchronisation between the application developer and the runtime system. The main contribution of this thesis is the development of four new architectureaware constructs for Glasgow parallel Haskell that exploit information about task size and aim to reduce communication for small tasks, preserve data locality, or to distribute large units of work. We define a semantics for the constructs that specifies the sets of PEs that each construct identifies, and we check four properties of the semantics using QuickCheck. We report a preliminary investigation of architecture aware programming models that abstract over the new constructs. In particular, we propose architecture aware evaluation strategies and skeletons. We investigate three common paradigms, such as data parallelism, divide-and-conquer and nested parallelism, on hierarchical architectures with up to 224 cores. The results show that the architecture-aware programming model consistently delivers better speedup and scalability than existing constructs, together with a dramatic reduction in the execution time variability. We present a comparison of functional multicore technologies and it reports some of the first ever multicore results for the Feedback Directed Implicit Parallelism (FDIP) and the semi-explicit parallelism (GpH and Eden) languages. The comparison reflects the growing maturity of the field by systematically evaluating four parallel Haskell implementations on a common multicore architecture. The comparison contrasts the programming effort each language requires with the parallel performance delivered. We investigate the minimum thread granularity required to achieve satisfactory performance for three implementations parallel functional language on a multicore platform. The results show that GHC-GUM requires a larger thread granularity than Eden and GHC-SMP. The thread granularity rises as the number of cores rises.
36

The design and performance evaluation of a proactive multipath routing protocol for mobile ad hoc networks

Etorban, Ali Abdalla January 2012 (has links)
Due to unpredictable network topology changes, routing in Mobile Ad Hoc Networks (MANET) is an important and challenging research area. The routing protocol should detect and maintain a good route(s) between source and destination nodes in these dynamic networks. Many routing protocols have been proposed for mobile ad hoc networks, and none can be considered as the best under all conditions. This thesis presents the design and implementation of a new proactive multipath MANET routing protocol. The protocol, named Multipath Destination Sequenced Distance Vector (MDSDV), is based on the well known single path Destination Sequenced Distance Vector (DSDV). We show that the protocol finds node-disjoint paths, i.e., paths which do not have any nodes in common, except for the source and the destination. The thesis presents a systematic evaluation of MDSDV in comparison with three well known protocols: one proactive (DSDV), and two reactive (AODV) and (DSR). MDSDV behaves very well in terms of its packet delivery fraction and data dropped in both static and dynamic networks. It delivers nearly 100% of data in dense networks (networks with more than 20 nodes). The speed of the nodes and the number of sources have a low impact on its performance.
37

Activity awareness in context-aware systems using software sensors

Pathan, Kamran Taj January 2013 (has links)
Context-aware systems being a component of ubiquitous or pervasive computing environment sense the users’ physical and virtual surrounding to adapt their behaviour accordingly. To achieve activity context tracking devices are common practice. Service Oriented Architecture is based on collections of services that communicate with each other. The communication between users and services involves data that can be used to sense the activity context of the user. SOAP is a simple protocol to let applications exchange their information over the web. Semantic Web provides standards to express the relationship between data to allow machines to process data more intelligently. This work proposes an approach for supporting context-aware activity sensing using software sensors. The main challenges in the work are specifying context information in a machine processable form, developing a mechanism that can understand the data extracted from exchanges of services, utilising the data extracted from these services, and the architecture that supports sensing with software sensors. To address these issues, we have provided a bridge to combine the traditional web services with the semantic web technologies, a knowledge structure that supports the activity context information in the context-aware environments and mapping methods that extract the data out of exchanges occurring between user and services and map it into a context model. The Direct Match, the Synonym Match and the Hierarchical Match methods are developed to put the extracted data from services to the knowledge structure. This research will open doors to further develop automated and dynamic context-aware systems that can exploit the software sensors to sense the activity of the user in the context-aware environments.
38

Prefetching and clustering techniques for network based storage

Thakker, Dhawal January 2009 (has links)
The usage of network-based applications is increasing, as network speeds increase, and the use of streaming applications, e.g BBC iPlayer, YouTube etc., running over network infrastructure is becoming commonplace. These applications access data sequentially. However, as processor speeds and the amount of memory available increase, the rate at which streaming applications access data is now faster than the rate at which the blocks can be fetched consecutively from network storage. In addition to sequential access, the system also needs to promptly satisfy demand misses in order for applications to continue their execution. This thesis proposes a design to provide Quality-Of-Service (QoS) for streaming applications (sequential accesses) and demand misses, such that, streaming applications can run without jitter (once they are started) and demand misses can be satisfied in reasonable time using network storage. To implement the proposed design in real time, the thesis presents an analytical model to estimate the average time taken to service a demand miss. Further, it defines and explores the operational space where the proposed QoS could be provided. Using database techniques, this region is then encapsulated into an autonomous algorithm which is verified using simulation. Finally, a prototype Experimental File System (EFS) is designed and implemented to test the algorithm on a real test-bed.
39

Reducing energy consumption in mobile ad-hoc sensor networks

Jambli, Mohamad Nazim January 2014 (has links)
Recent rapid development of wireless communication technologies and portable mobile devices such as tablets, smartphones and wireless sensors bring the best out of mobile computing, particularly Mobile Ad-hoc Sensor Networks (MASNETs). MASNETs are types of Mobile Ad-hoc Networks (MANETs) that are designed to consider energy in mind because they have severe resource constraints due to their lack of processing power, limited memory, and bandwidth as in Wireless Sensor Networks (WSNs). Hence, they have the characteristics, requirements, and limitations of both MANETs and WSNs. There are many potential applications of MASNETs such as a real-time target tracking and an ocean temperature monitoring. In these applications, mobility is the fundamental characteristic of the sensor nodes, and it poses many challenges to the routing algorithm. One of the greatest challenge is to provide a routing algorithm that is capable of dynamically changing its topology in the mobile environment with minimal consumption of energy. In MASNETs, the main reason of the topology change is because of the movement of mobile sensor nodes and not the node failure due to energy depletion. Since these sensor nodes are limited in power supply and have low radio frequency coverage, they easily lose their connection with neighbours, and face diffi culties in updating their routing tables. The switching process from one coverage area to another consumes more energy. This network must be able to adaptively alter the routing paths to minimize the effects of variable wireless link quality, topological changes, and transmission power levels on energy consumption of the network. Hence, nodes prefer to use as little transmission power as necessary and transmit control packets as infrequently as possible in energy constrained MASNETs. Therefore, in this thesis we propose a new dynamic energy-aware routing algorithm based on the trans- mission power control (TPC). This method effectively decreases the average percentage of packet loss and reduces the average total energy consumption which indirectly pro- long the network lifetime of MASNETs. To validate the proposed protocol, we ran the simulation on the Avrora simulator and varied speed, density, and route update interval of mobile nodes. Finally, the performance of the proposed routing algorithm was measured and compared against the basic Ad-hoc On-demand Distance Vector (AODV) routing algorithm in MASNETs.
40

VISrec! : visual-inertial sensor fusion for 3D scene reconstruction

Aufderheide, Dominik January 2014 (has links)
The self-acting generation of three-dimensional models, by analysing monocular image streams from standard cameras, is one fundamental problem in the field of computer vision. A prerequisite for the scene modelling is the computation of the camera pose for the different frames of the sequence. Several techniques and methodologies have been introduced during the last decade to solve this classical Structure from Motion (SfM) problem, which incorporates camera egomotion estimation and subsequent recovery of 3D scene structure. However the applicability of those approaches to real world devices and applications is still limited, due to non-satisfactorily properties in terms of computational costs, accuracy and robustness. Thus tactile systems and laser scanners are still the predominantly used methods in industry for 3D measurements. This thesis suggests a novel framework for 3D scene reconstruction based on visual-inertial measurements and a corresponding sensor fusion framework. The integration of additional modalities, such as inertial measurements, are useful to compensate for typical problems of systems which rely only on visual information. The complete system is implemented based on a generic framework for designing Multi-Sensor Data Fusion (MSDF) systems. It is demonstrated that the incorporation of inertial measurements into a visual-inertial sensor fusion scheme for scene reconstruction (VISrec!) outperforms classical methods in terms of robustness and accuracy. It can be shown that the combination of visual and inertial modalities for scene reconstruction allows a reduction of the mean reconstruction error of typical scenes by up to 30%. Furthermore, the number of 3D feature points, which can be successfully reconstructed can be nearly doubled. In addition range and RGB-D sensors have been successfully incorporated into the VISrec! scheme proving the general applicability of the framework. By this it is possible to increase the number of 3D points within the reconstructed point cloud by a factor of five hundred if compared to standard visual SfM. Finally the applicability of the VISrec!-sensor to a specific industrial problem, in corporation with a local company, for reverse engineering of tailor-made car racing components demonstrates the usefulness of the developed system.

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