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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.
1

To investigate and evaluate a prototype for a remote database access protocol

Haughton, Howard January 1990 (has links)
In the past, techniques for specifying, verifying and implementing protocols have taken on a somewhat ad hoc (non -uniform) and informal nature. This lack of uniformity has resulted in an abundance of techniques and methodologies for analysing protocols, most of which are applicable to protocols having a small degree of complexity. Typically, different techniques are applied to various stages of a protocol development without an underlying formal basis for their integrated application. As a result, there may be no way to guarantee that subsequent stages of a development represent correct realisations of earlier ones. This thesis aims to address the problem of protocol development stated above by describing unified frameworks within which: 1) A formal theoretical foundation is laid for specifying, verifying and implementing protocols. 2) A knowledge based system is used for the formal development of a certain class of protocols. A number of limitations have been identified in the approach taken for developing the frameworks: a) The lack of 'compositional' expressiveness of the algebraic specification language. This makes it difficult to effectively analyse concurrently executing processes of protocols. b) The lack of support provided for addressing performance related issues. This makes it difficult to compare different protocols to assess their effect with respect to how long they take to achieve some data processing task. c) The protocol derivation algorithm can prove cumbersome in its application and may require a significant amount of domain knowledge (about types of 'primitives') in order to be machine automated. d) The knowledge based framework is currently limited to supporting the development of end-to-end protocols. This however is not a serious problem as the ideas and principles applied in developing these protocols form the basis for work in analysing other types. The above limitations form the basis for future work which will aim to address the problems stated. The thesis is in 5 main parts:- I) A description of various formalisms used in the past, to specify protocols. From this analysis, criteria are developed for assessing the relative merits of these formalisms, with a view towards choosing one such technique to be employed in specifying protocols. ii) A formal development of the protocol which includes a discussion of automatic theorem proving via a syntactic measure known as a trace. iii) A description of a notation with operational semantics developed for specifying and verifying protocols and services. In addition, a method utilising the notation is described whereby a service can be derived from a protocol. iv) A description of a framework within which a protocol may be verified in respect of the service it provides. v) A description of an interactive program (environment) allowing the formal development of a certain class of distributed protocols, such as the ECMA application layer protocol. The originality of this work lies in the: I) development of a methodology for automatically deriving and proving invariant properties of a specification. ii) development of a notation with operational semantics, capable of specifying and verifying distributed protocols and services. iii) identification of a means by which the correspondence between a specification and its implementation may be used as rewrite rules (not necessarily preserving all semantic information) in developing communication protocols. v) numerous algorithms described for addressing safety, liveness and conformity issues, as part of the interactive environment.
2

General queueing networks with blocking

Xenios, Nicholas P. January 1989 (has links)
No description available.
3

Stability and performance of contention resolution protocols

Al-Ammal, Hesham M. January 2000 (has links)
No description available.
4

Synchronisation services for digital continuous media

Sreenan, Cormac John January 1992 (has links)
No description available.
5

Monitoring and management of OSI networks

Modiri, Nasser January 1989 (has links)
No description available.
6

ICT applications as e-health solutions in rural healthcare in the Eastern Cape Province of South Africa

Ruxwana, NL, Herselman, ME, Conradie, DP 26 February 2010 (has links)
Abstract Information and Communication Technology (ICT) solutions (e.g. e-health, telemedicine, e-education) are often viewed as vehicles to bridge the digital divide between rural and urban healthcare centres and to resolve shortcomings in the rural health sector. This study focused on factors perceived to infl uence the uptake and use of ICTs as e-health solutions in selected rural Eastern Cape healthcare centres, and on structural variables relating to these facilities and processes. Attention was also given to two psychological variables that may underlie an individual’s acceptance and use of ICTs: usefulness and ease of use. Recommendations are made with regard to how ICTs can be used more effectively to improve health systems at fi ve rural healthcare centres where questionnaire and interview data were collected: St. Lucy’s Hospital, Nessie Knight Hospital, the Tsilitwa Clinic, the Madzikane Ka-Zulu Memorial Hospital and the Nelson Mandela General Hospital.
7

Hybrid RFID Sensors: Design, Implementation and Application

Martin, Jarred 01 January 2014 (has links)
The fields of Wireless sensor networks and RFID technology are two examples of the current move to ubiquitous computing. Wireless sensor networks has emerged as a tool for long term remote monitoring for applications ranging from agriculture to military. While in RFID we have already seen it being used in everyday life from access control to asset tracking. The integration of these two fields allows for a whole range of new applications, the focus of this dissertation is to present a wireless sensor network platform which incorporates a hybrid RFID sensor mote for the detection of environmental conditions and the locating of objects or personnel within an environment. The solution that is proposed comprises of both hardware and software but focuses on the design of the platforms’ prototype wireless sensor mote which provides object detection through the use of an RFID reader and environmental conditions by using low cost slave sensors. The solution was then applied to solving the problem of locating mining personnel and detecting hazardous levels of methane gas for use in underground mines.
8

Ubiquitous Mesh Networking: application to mobile communication and information dissemination in a rural context

Maliwatu, Richard 01 January 2014 (has links)
ICT has furthered the social and economic development of societies but, rural African communities have lagged behind due to issues such as sparse population, low household income, a lack of electricity and other basic infrastructure that make it unattractive for telecommunication service providers to extend service provision. Where the service is available, ubiquitous service coverage has not translated into ubiquitous access for individuals because of the associated costs. A community-wide WMN offering VoIP using fixed telephone handsets has been deployed as a viable alternative to the cellular service provider. The effectiveness of this WMN VoIP service springs from the mobile phone usage statistics which showed that the majority of calls made are intra-community. This dissertation has been an effort towards improved communication and access to information for the under-served communities. Key contributions include, mobile VoIP support, translation gateway deployment to make textual information accessible in voice form via the phone, IP-based radio for community information dissemination. The lack of electricity has been mitigated by the use of low-power devices. In order to circumvent the computational challenges posed by the processing and storage limitations of these devices, a decentralised system architecture whereby the processing and storage load are distributed across the mesh nodes has been proposed. High-performance equipment can be stationed at the closest possible place with electricity in the area and connectivity extended to the non-electrified areas using low-power mesh networking devices. Implementation techniques were investigated and performance parameters measured. The quality of service experienced by the user was assessed using objective methods and QoS correlation models. A MOS value of 4.29, i.e. very good, was achieved for the mobile VoIP call quality, with the underlying hardware supporting up to 15 point-to-point simultaneous calls using SIP and the G.711 based codec. Using the PEAQ algorithm to evaluate the IP-based radio, a PEAQ value of 4.15, i.e. good, was achieved. Streaming audio across the network reduces the available bandwidth by 8Kbps per client due to the unicast nature of streaming. Therefore, a multicast approach has been proposed for efficient bandwidth utilization. The quality of the text-to-voice service rendered by the translation gateway had a PESQ score of 1.6 i.e. poor. The poor performance can be attributed to the TTS engine implementation and also to the lack of robustness in the time-alignment module of the PESQ algorithm. The dissertation also proposes the use of the WMN infrastructure as a back-haul to isles of WSNs deployed in areas of interest to provide access to information about environmental variables useful in decision making.
9

Internet of Things: Least Interference Beaconing Algorithms

Tuyishimire, Emmanuel 01 January 2014 (has links)
The emerging sensor networking applications are predicting the deployment of sensor devices in thousands of computing elements into multi-technology and multi-protocol platforms. Access to information will be available not only anytime and anywhere, but also using anything in a first-mile of the Internet referred to as the internet-of-things (IoT). The management of such a large-scale and heterogeneous network, would benefit from some of the traditional IP-based network management techniques such as load and energy balancing, which can be re-factored to achieve efficient routing of sensor network traffic. Research has shown that minimizing the path interference on nodes was necessary to improve traffic engineering in connection oriented networks. The same principle has been applied in past research in the context of the IoT to reveal that the least interference beaconing protocol (LIBP); a protocol derived from the least interference beaconing algorithm (LIBA) outperforms the Collection Tree Protocol (CTP) and Tiny OS Beaconing (ToB) protocol, in terms of energy efficiency and lifetime of the sensor network. However for the purpose of efficiency and accuracy, it is relevant, useful and critical to revisit or re-examine the LIBA algorithm in terms of correctness and investigate potential avenues for improvement. The main contributions of this research work are threefold. Firstly, we build upon formal methods to verify the correctness of the main principles underlying the LIBA, in terms of energy efficiency and interference minimization. The interference is here defined at each node by the number of routing paths carrying the sensor readings from the motes to the sink of the network that traverse the node. Our findings reveal the limitations in LIBA. Secondly, building upon these limitations, we propose two improvements to the algorithm: an algorithm called LIBA+ that improves the algorithm performance by keeping track of the energy usage of the sensor nodes, and a multi-sink version of the algorithm called LIBAMN that extends the algorithm to account for multiple sinks or gateways. These enhancements present preventive mechanisms to include in IoT platforms in order to improve traffic engineering, the security of network protocols and network stability. Lastly, we present analytical results, which reveal that the LIBA algorithm can be improved by more than 84% in terms of energy balancing. These results reveal that formal methods remain essential in the evaluation and performance improvement of wireless sensor network algorithms and protocols.
10

Multi-Layered Security in the Internet of the Things

Ngqakaza, Lutando 01 January 2014 (has links)
It is well discussed and understood that there is still a need for suitable security for the Internet of Things. It is however still not clear how existing or emerging security paradigms can be effectively applied to a network of constrained nodes in a lossy communications environment. This thesis provides a survey into what routing protocols can be used with network security in mind. What will also be discussed, is an implementation, that in conjunction which a robust routing protocol, can provide security for a network of constrained devices with a certain level of confidence. The implementation and design involves including communications encryption and centralized non-cryptographic methods for securing the network. This thesis basically explores the use of multiple security mechanisms in an Internet of Things environment by using Contiki OS as the platform of choice for simulations and testing.

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