published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

published_or_final_version / Electrical and Electronic Engineering / Master / Master of Philosophy

The effect of amplifier non-linearity on the performance of a CDMA communications system / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2009.

Small mobile devices which have an ability to access the world wide web (WWW) wirelessly are in demand of late. This demand is attributed to the fact that video and audio streaming are cost effectively accessible via the WWW through wireless fidelity (Wi-Fi). This high demand for cheap real-time multimedia access via Wi-Fi makes it imperative for researchers to develop a wireless local area network (WLAN) standard, such as IEEE (802.11n), that has high data throughput and/or link reliability. The current drawback with the IEEE (802.11n) standard is that it is not power efficient for battery powered small mobile devices because of the high complexity multiple-input-multiple-output (MIMO) scheme implemented within the standard. Spatial modulation (SM) is a recently proposed low complexity MIMO scheme that can achieve high data throughput with good link reliability whilst being power efficient for small mobile devices. This study is aimed at further improving data throughputs of SM and also determining the bit error rate (BER) performance of SM in a city centre environment. Conventional spatial modulation has been investigated in literature with most research efforts geared towards improving the BER performance and minimizing receiver complexity of the scheme over non-cascaded fading channels. We propose adaptive M-ary quadrature amplitude spatial modulation (A-QASM) as a scheme that will improve the average throughput in comparison to conventional spatial modulation given a target BER constraint. The analytical BER lower bound is derived for this proposed scheme and validated by the Monte Carlo simulation results. The simulation results also prove that the average throughput of the proposed scheme (A-QASM) outperforms that of conventional spatial modulation. The definition for the received SNR of the A-QASM scheme is also proposed. In research literature, conventional spatial modulation has been discussed in depth in non-cascaded wireless fading channels. The performance analysis derived in literature in non-cascaded wireless fading channels; does not apply in predicting the BER performance of a mobile device, using conventional spatial modulation, in an environment where there is signal diffraction (i.e city centre or a forest) which makes the signal susceptible to independent cascaded fading. This study contributes by developing an analytical framework for the BER lower bound of conventional spatial modulation over cascaded fading channels. Simulation results closely agree with the derived theoretical framework. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.

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The study investigated the preparedness of University of KwaZulu-Natal (UKZN) libraries to implement and use mobile phone technology in the provision of library and information services. This investigation included the factors which could influence and impact technology adoption. It is imperative that libraries respond to changes in technology in terms of the provision of their services. A recent development has been the emergence and proliferation of mobile phone technology and it is the adoption and implementation of this technology by academic libraries in the provision of services that concerned this study. The significance of this study lies in its adding value to the little knowledge out there by improving our understanding of the challenges and opportunities associated with mobile technology in an academic library context. In terms of the methodology, the study used a quantitative approach and survey design. Data was collected from a total of 30 staff members working in libraries on the UKZN Pietermaritzburg and Howard College campuses. A self-administered questionnaire that consisted of both open and closed questions was used to collect the data. The research questions which underpinned the study can be summarised as follows: what mobile phone technology is and what it comprised of in this research context, what skills the staff required to be able to provide library and information through mobile phone technology, and finally, what technological, organizational and environmental factors could influence the implementation of this technology in the libraries concerned. The Technology Organisation and Environment Framework (TOE) was used as the framework to guide the study. The data collected was analysed using SPSS and the findings were presented in the form of tables, bar graphs, pie charts and text. Interpretation of the findings revealed that the staff of the libraries were in the main positively predisposed to mobile technology, with many of them having Internet enabled mobile phones and the skills to do some of the tasks associated with the provision of library and information services via the technology. The technological, organizational and environmental factors identified and investigated were such that the libraries could be regarded as sufficiently prepared for the introduction of mobile phone technology in the provision of services. Funding or budgetary constraints, however, were identified as the main constraint. Recommendations were made based on the finding of the survey and the literature review and these relate to funding concerns and the implementation and usage of mobile phone technology to the advantage of the libraries. / Thesis (M.I.S.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

Huge amounts of data are being collected as a result of the increased use of mobile telecommunications. Insight into information and knowledge derived from these databases can give operators a competitive edge in terms of customer care and retention,<br /> marketing and fraud detection. One of the strategies for fraud detection checks for signs of questionable changes in user behavior. Although the intentions of the mobile phone users cannot be observed, their intentions are reflected in the call data which define usage patterns. Over a period of time, an individual phone generates a large pattern of use. While call data are recorded for subscribers for billing purposes, we are making no prior assumptions about the data indicative of fraudulent call patterns, i.e. the calls made for billing purpose are unlabeled. Further analysis is thus, required to be able to isolate fraudulent usage. An unsupervised learning algorithm can analyse and cluster call patterns for each subscriber in order to facilitate the fraud detection process.<br /> <br /> This research investigates the unsupervised learning potentials of two neural networks for the profiling of calls made by users over a period of time in a mobile telecommunication network. Our study provides a comparative analysis and application of Self-Organizing Maps (SOM) and Long Short-Term Memory (LSTM) recurrent neural networks algorithms to user call data records in order to conduct a descriptive data mining on users call patterns.<br /> <br /> Our investigation shows the learning ability of both techniques to discriminate user call patterns / the LSTM recurrent neural network algorithm providing a better discrimination than the SOM algorithm in terms of long time series modelling. LSTM discriminates different types of temporal sequences and groups them according to a variety of features. The ordered features can later be interpreted and labeled according to specific requirements of the mobile service provider. Thus, suspicious call behaviours are isolated within the mobile telecommunication network and can be used to to identify fraudulent call patterns. We give results using masked call data<br /> from a real mobile telecommunication network.

Thesis (PhD)--University of South Australia, 2008.