An adaptive approach for optimized opportunistic routing over Delay Tolerant Mobile Ad hoc Networks
- Authors: Zhao, Xiaogeng
- Date: 2008
- Subjects: Ad hoc networks (Computer networks) Computer network architectures Computer networks Routing protocols (Computer network protocols)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4588 , http://hdl.handle.net/10962/d1004822
- Description: This thesis presents a framework for investigating opportunistic routing in Delay Tolerant Mobile Ad hoc Networks (DTMANETs), and introduces the concept of an Opportunistic Confidence Index (OCI). The OCI enables multiple opportunistic routing protocols to be applied as an adaptive group to improve DTMANET routing reliability, performance, and efficiency. The DTMANET is a recently acknowledged networkarchitecture, which is designed to address the challenging and marginal environments created by adaptive, mobile, and unreliable network node presence. Because of its ad hoc and autonomic nature, routing in a DTMANET is a very challenging problem. The design of routing protocols in such environments, which ensure a high percentage delivery rate (reliability), achieve a reasonable delivery time (performance), and at the same time maintain an acceptable communication overhead (efficiency), is of fundamental consequence to the usefulness of DTMANETs. In recent years, a number of investigations into DTMANET routing have been conducted, resulting in the emergence of a class of routing known as opportunistic routing protocols. Current research into opportunistic routing has exposed opportunities for positive impacts on DTMANET routing. To date, most investigations have concentrated upon one or other of the quality metrics of reliability, performance, or efficiency, while some approaches have pursued a balance of these metrics through assumptions of a high level of global knowledge and/or uniform mobile device behaviours. No prior research that we are aware of has studied the connection between multiple opportunistic elements and their influences upon one another, and none has demonstrated the possibility of modelling and using multiple different opportunistic elements as an adaptive group to aid the routing process in a DTMANET. This thesis investigates OCI opportunities and their viability through the design of an extensible simulation environment, which makes use of methods and techniques such as abstract modelling, opportunistic element simplification and isolation, random attribute generation and assignment, localized knowledge sharing, automated scenario generation, intelligent weight assignment and/or opportunistic element permutation. These methods and techniques are incorporated at both data acquisition and analysis phases. Our results show a significant improvement in all three metric categories. In one of the most applicable scenarios tested, OCI yielded a 31.05% message delivery increase (reliability improvement), 22.18% message delivery time reduction (performance improvement), and 73.64% routing depth decrement (efficiency improvement). We are able to conclude that the OCI approach is feasible across a range of scenarios, and that the use of multiple opportunistic elements to aid decision-making processes in DTMANET environments has value.
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- Date Issued: 2008
Computers and African languages in education: an ICT tool for the promotion of multilingualism at a South African university: conversations
- Authors: Dalvit, Lorenzo , Murray, Sarah , Mini, Buyiswa , Terzoli, Alfredo , Zhao, Xiaogeng
- Date: 2005
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/428911 , vital:72545 , https://hdl.handle.net/10520/EJC87340
- Description: This article describes a web-based application designed to provide meaningful access to the study of Computer Science to speakers of an African language who have limited experience of using English for ac-ademic purposes. Our research is focused upon students of Computer Skills in the Extended Studies Programme at Rhodes University who have studied English as a second language for the matriculation exam-ination. The intervention involves the cooperative production and shar-ing of multilingual support material in both English and the students' home languages. The article illustrates how the use of computers has the potential to solve some of the problems traditionally associated with the use of African languages as additional media of instruction in ter-tiary education (i.e. lack of terminology and resources in the African languages, stigma attached to their use, etc.). We maintain that learning about computers partly in their stronger language (i.e. their home lan-guage) could give students increased and more meaningful access to an educationally and economically empowering field of study.
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- Date Issued: 2005
Producing and sharing ICT-based knowledge through English and African languages at a South African university
- Authors: Terzoli, Alfredo , Dalvit, Lorenzo , Murray, Sarah , Mini, Buyiswa , Zhao, Xiaogeng
- Date: 2005
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/428531 , vital:72518 , https://hdl.handle.net/10520/EJC37193
- Description: This article describes an intervention aimed at providing increased ac-cess to the study of information and communication technology (ICT) and computer literacy in Higher Education in South Africa. Our focus group is speakers of an African language from a previously disadvan-taged background in the extended studies programme at Rhodes Uni-versity. Preliminary investigation suggests that such students have dif-ficulties becoming computer literate partly because of their lack of Eng-lish proficiency. This might prevent them from furthering their studies of Computer Science (CS) up to the postgraduate level. Shifting away from the dominant approach to academic support in extended studies programmes in South Africa, in our research we focus primarily on the lexical rather than the discourse level. With the help of a web-based application, students collaboratively produce and share additional mate-rial in both English and the African languages. This allows them to inte-grate new concepts and knowledge about computers into their existing knowledge structures. With our intervention, we hope to improve the students' participation in the production and sharing of knowledge in the field of ICT.
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- Date Issued: 2005
A comparative analysis of Java and .NET mobile development environments for supporting mobile services
- Authors: Zhao, Xiaogeng
- Date: 2003 , 2013-05-23
- Subjects: Microsoft .NET , Java (Computer program language) , Mobile computing , Wireless communication systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4578 , http://hdl.handle.net/10962/d1003064 , Microsoft .NET , Java (Computer program language) , Mobile computing , Wireless communication systems
- Description: With the rapid development of wireless technologies, traditional mobile devices, such as pagers and cellular phones, have evolved from a purely communications and messaging-oriented medium to one that supports mobile data communication in general and acts as an application platform. As shown in a recent survey conducted by MDA, easy access to the present-day wireless Internet has resulted in mobile devices gaining more and more attention and popularity. The growth of and demand for mobile Web applications is expected to increase rapidly in the near future, as a range of software companies and mobile device manufacturers release increasingly accessible tools for creating mobile Web application and services. From a variety of possible development environments of this kind, the author has selected and examined two leading contenders, the J2ME and the Microsoft .NET mobile Web application development environments. This document reports the product life cycle of pilot mobile web applications, designed and implemented in each host environment in tum. A feature-by-feature investigation and comparison of the J2ME and .NET environments was carried out, covering the range of issues necessary for a complete mobile Web application development life cycle. The resulting analysis addresses features and efficiencies of the application development environment and the target deployment environment, the degree to which the resultant services are compatible on a variety of platforms, and the ease with which applications can be designed to be extensible. The thesis offers an objective evaluation of the J2ME and the .NET mobile development environments, which highlights their strengths and weaknesses, and suggests guidelines for designing, creating, and deploying high quality mobile Web applications. The research uncovers no clear winner across all categories assessed. J2ME currently favours situations in which bandwidth is limited and client side processing power is relatively sufficient, it exerts the processing power of mobile devices over distributed network environments. .NET requires a less constrained network throughput, but performs adequately on clients with more limited processing power, supports a more diverse target platform range, and offers a more efficient, in terms of development time, development environment. Both technologies are likely to receive significant user support for some time. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
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- Date Issued: 2003