As video applications become more diverse, video must be adapted in different ways to meet the requirements of different applications when there are insufficient resources. In this dissertation, we address two sorts of requirements that cannot be addressed by existing video adaptation technologies: (i) accommodating large variations in resolution and (ii) collecting video effectively in a multi-hop sensor network. In addition, we also address requirements for implementing video adaptation in a sensor network. Accommodating large variation in resolution is required by the existence of display devices with widely disparate screen sizes. Existing resolution adaptation technologies usually aim at adapting video between two resolutions. We examine the limitations of these technologies that prevent them from supporting a large number of resolutions efficiently. We propose several hybrid schemes and study their performance. Among these hybrid schemes, Bonneville, a framework that combines multiple encodings with limited scalability, can make good trade-offs when organizing compressed video to support a wide range of resolutions. Video collection in a sensor network requires adapting video in a multi-hop storeand- forward network and with multiple video sources. This task cannot be supported effectively by existing adaptation technologies, which are designed for real-time streaming applications from a single source over IP-style end-to-end connections. We propose to adapt video in the network instead of at the network edge. We also propose a framework, Steens, to compose adaptation mechanisms on multiple nodes. We design two signaling protocols in Steens to coordinate multiple nodes. Our simulations show that in-network adaptation can use buffer space on intermediate nodes for adaptation and achieve better video quality than conventional network-edge adaptation. Our simulations also show that explicit collaboration among multiple nodes through signaling can improve video quality, waste less bandwidth, and maintain bandwidth-sharing fairness. The implementation of video adaptation in a sensor network requires system support for programmability, retaskability, and high performance. We propose Cascades, a component-based framework, to provide the required support. A prototype implementation of Steens in this framework shows that the performance overhead is less than 5% compared to a hard-coded C implementation.

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A form of data transmission which is increasing in popularity is satellite communication. In order to insure that data is received correctly, certain error control strategies are employed. In packetized transmission, automatic-repeat-request (ARQ) schemes and error correcting codes have been employed. Currently a combination of both is not employed by the AX.25 protocol. The purpose of this project is to determine which error correcting code should be combined with ARQ to provide the optimum performance. This project investigates the performance of the (7,4) Hamming code, (23,12) Golay code, Reed-Solomon, RS , codes over the Galois fields of 16, GF(16), and 256, GF(256), elements, and common rate convolutional codes of various constraint lengths. The codes are evaluated on three primary criteria, which include: throughput vs. input bit error rate, coding complexity, and burst error performance. The class of Reed-Solomon codes over GF(256) was chosen to be superior due to the throughput and burst error performance. The encoding complexity is small, but the decoding is more complicated. The conclusion is that error correcting codes should be employed in ARQ satellite systems. However, the error correcting strength of the code must be determined by observing the channel characteristics. / Master of Science

Intercomputer communications involves the transfer of information between intelligent hosts. Since communication costs are almost proportional to the amount of data transferred, the processing capability of the respective hosts might advantageously be applied through pre-processing and post-processing of data to reduce redundancy. The major emphasis of this research is development of the Substitution Method which minimizes data transfer between hosts required to reconstruct user JCL files, Fortran source files, and data files. The technique requires that a set of user files for each category of files be examined to determine the frequency distribution of symbols, fixed strings, and repeated symbol strings to determine symbol and structural redundancy. Information gathered during the examination of these files when combined with the user created Source Language Syntax Table generate Encoding/Decoding Tables which are used to reduce both symbol and structural redundancy. The Encoding/Decoding Tables allow frequently encountered strings to be represented by only one or two symbols through the utilization of table shift symbols. The table shift symbols allow less frequently encountered symbols of the original alphabet to be represented as an entry in a Secondary Encoding/Decoding Table. A technique is described which enables a programmer to easily modify his Fortran program such that he can take advantage of the Substitution Method's ability to compress data files by removing both informational and structural redundancy. Each user file requested to be transferred is preprocessed at cost, C[prep], to reduce data (both symbol and structural redundancy) which need not be transferred for faithful reproduction of the file. The file is transferred over a noiseless channel at cost, C[ptran]. The channel consists of presently available or proposed services of the common-carriers and specialized common-carriers. The received file is post-processed to reconstruct the original source file at cost, C[post]. The costs associated with pre-processing, transferring, and post-processing are compared with the cost, C[otran], of transferring the entire file in its original form. / Ph. D.

Serial or parallel data links have been the primary tools of data transfer across physical layer boundaries for point-to-point communication systems. However there exists a tradeoff between these two kinds of data transfer mechanisms based on their cost-effectiveness and complexity. A recent technological advancement has altered this trade-off considerations. A new chip-set from Advanced Micro Devices offers a high performance integrated alternative to traditional serial/parallel data transfer techniques. The Transparent Asynchronous Transmitter Receiver Interface chipset offers a new means to establish a transparent high speed serial link between two high performance parallel buses. The current TAXlchip set has a maximum effective data rate throughput of 140Mbps which is ten times faster than the RS-422 drivers and receivers. The TAXIchip set can be used in conjunction with the optical components and optical fiber to form a simple fiber optic communication link. The inherent advantages of optical communications can be combined with the versatility of the TAXIchip set to establish TAXI links using optical fiber to cover distances up to several kilometers. This thesis will systematically develop on the TAXI communication system Focus of the effort will be on understanding the functionality of the building blocks of the TAXIchip set and the encoding and decoding schemes of the chip set. On obtaining a complete understanding of the communication system fundamentals the communication system will be interfaced to the optical media with a specific reference to the development of the Optical Slip Ring. / Master of Science

Telecommunication includes voice, video and internet communication services. Thus, mobile telecommunication services involve voice communication, video streaming, graphics and television services at high speed. Technology development in mobile telecommunication has enabled users to exchange data using cell phones, laptops and other telecommunication devices. More so, understanding the concept of user experience is very important in the context of provision of mobile telecommunication services. This research will evaluate the effectiveness of mobile telecommunication services in Durban, South Africa and Lagos, Nigeria amongst first-year IT students of the University of KwaZulu-Natal and Lagos State University. The research is focused on the actual experience and perceptions of first-year IT students. The study will examine the factors that influence first-year IT students' judgment of the quality of mobile telecommunication services. It will also access the impact of quality of mobile telecommunication services on the loyalty of first-year IT students towards their network operator. However, Technology Acceptance Model (TAM) is the theory adopted for this research, which explains how attitude of users determine the intention to use technology and the intention eventually influences the overall use of such technology. The objectives of this research highlight opportunities associated with understanding first-year IT students' experiences and perceptions of mobile telecommunication services in UKZN, Durban and LASU, Lagos. Other opportunities include giving an insight into the operations of network providers, determine the quality of mobile telecommunication services and understanding the impact of mobile telecommunication services on students in UKZN and LASU. Another significance of this study allows network providers to understand students' behaviour and to respond to their preferences. / Thesis (M.Com.)-University of KwaZulu-Natal, Westville, 2011.

Thesis (MScEng (Electrial and Electronic Engineering.))--University of Stellenbosch, 2006. / This thesis covers the design and development of a radio telemetry system to assist in management of the Grumeti reserves. This was accomplished through the integration of a digital data transmission system into the existing analog voice radio network, while minimizing any possible interference. The primary application of the system is vehicle tracking, but it is also capable of supporting other telemetry data in the future. The system relies on a server based at the reserve headquarters and various client telemetry units installed in the vehicles. A vehicle’s location is requested via the server application. The results are displayed on a digital map and stored into a database. Various methods are used to reduce radio interference and support reliable transmission of data. The system is also designed to be affordable, maintainable and robust. Two prototypes were implemented to perform various tests and establish the feasibility of the sysem. It proved to be capable of meeting the main objectives and implementation will commence in the future.