Thesis--M. Phil., University of Hong Kong, 1986.

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Masters Research - Masters of Engineering / Mobile telephony, wireless networks and wireless telemetry systems have gone from simple single-input single-output wireless architectures with low data transmission rates to complex systems employing multiple antennas and forward error correction algorithms capable of high data transmission rates over wireless channels. Claude Shannon provided the fundamental capacity limits for a communications system and it can be shown that the capacity for a single-input single-output systems is limited in it’s capability to provide for modern wireless applications. The introduction of multiple-input multiple-output systems employing multiple antenna elements and orthogonal coding structures proved beneficial and could provide the capacities required for modern wireless applications. This thesis begins with an introduction and overview of space-time coding and the codes of Tarokh, Jafarkhani and Alamouti. Further, this thesis provides an introduction and overview to the family of forward error correction codes known as low-density parity-check (LDPC) codes. LDPC codes, when employed over Gaussian channels, provide near-Shannon limit performance and the question is posed as to their suitability for a wireless multiple-input multiple-output system employing multiple antennas and space-time coding. This question is answered by the use and demonstration of LDPC codes as outer codes to a MIMO system employing space-time block codes and a modified maximum-likelihood decoder. By modifying the space-time block-code decoder to provide a soft-information output, iterative decoders such as the sum-product algorithm can be employed to provide significant performance gains over a Rayleigh flat-fading channel. Further the use of design tools such as EXIT charts can then be used to design codes. The key to allowing the use of EXIT charts is the observation that a MIMO system employing orthogonal transmissions in a Rayleigh flat-fading channel is the equivalent to a SISO channel employing Nakagami-m fading coefficients. The seemingly complex MIMO system can now be analyzed in the form of a simpler SISO equivalent allowing the use of techniques such as EXIT charts to be employed in order to design codes with known and predictable performance haracteristics. This thesis demonstrates this technique and shows by example the performance gains that can be achieved for MIMO systems and opens some further questions for future research.

Masters Research - Masters of Engineering / Mobile telephony, wireless networks and wireless telemetry systems have gone from simple single-input single-output wireless architectures with low data transmission rates to complex systems employing multiple antennas and forward error correction algorithms capable of high data transmission rates over wireless channels. Claude Shannon provided the fundamental capacity limits for a communications system and it can be shown that the capacity for a single-input single-output systems is limited in it’s capability to provide for modern wireless applications. The introduction of multiple-input multiple-output systems employing multiple antenna elements and orthogonal coding structures proved beneficial and could provide the capacities required for modern wireless applications. This thesis begins with an introduction and overview of space-time coding and the codes of Tarokh, Jafarkhani and Alamouti. Further, this thesis provides an introduction and overview to the family of forward error correction codes known as low-density parity-check (LDPC) codes. LDPC codes, when employed over Gaussian channels, provide near-Shannon limit performance and the question is posed as to their suitability for a wireless multiple-input multiple-output system employing multiple antennas and space-time coding. This question is answered by the use and demonstration of LDPC codes as outer codes to a MIMO system employing space-time block codes and a modified maximum-likelihood decoder. By modifying the space-time block-code decoder to provide a soft-information output, iterative decoders such as the sum-product algorithm can be employed to provide significant performance gains over a Rayleigh flat-fading channel. Further the use of design tools such as EXIT charts can then be used to design codes. The key to allowing the use of EXIT charts is the observation that a MIMO system employing orthogonal transmissions in a Rayleigh flat-fading channel is the equivalent to a SISO channel employing Nakagami-m fading coefficients. The seemingly complex MIMO system can now be analyzed in the form of a simpler SISO equivalent allowing the use of techniques such as EXIT charts to be employed in order to design codes with known and predictable performance haracteristics. This thesis demonstrates this technique and shows by example the performance gains that can be achieved for MIMO systems and opens some further questions for future research.

Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2006. / Committee Chair: A. Rahmen M. Zaghloul ; Committee Members: W. Russell Callen and P. Douglas Yoder. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (M.S.)--University of Wisconsin--Madison, 1970. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Orientador: Leandro Eugenio da Silva Cerri / Banca: Oswaldo Augusto Filho / Banca: Fábio Augusto Gomes Vieira Reis / Resumo: As cartas geotécnicas são ferramentas importantes para os profissionais ligados ao planejamento e gestão do meio físico. Elas mostram como um fenômeno está se comportando espacialmente para que o usuário possa buscar a informação desejada que dá suporte a uma decisão. Muitas cartas elaboradas hoje apresentam algumas incoerências na representação de dados devido a grande quantidade de informações que essas cartas deveriam apresentar. Por isso é importante que essas cartas tenham uma representação do meio físico de forma adequada para que a linguagem cartográfica seja legível aos seus usuários. Assim, o objetivo dessa pesquisa foi a realização de uma proposta de representação cartográfica para as cartas geotécnicas a partir do estudo de uma análise de representação de duas metodologias de elaboração de cartas geotécnicas mais utilizadas no país: IPT (Instituto de Pesquisas Tecnológicas de São Paulo) e EESC (Escola de Engenharia de São Carlos - USP). / Abstract: The geotechnical charts are important tools for professionals that deal with planning and management of physical environment. They show how a particular phenomenon behaves spatially so the user can search the information desired that provides him support to take a decision. Actually many charts present some incoherencies on the representation of data due the great amount of information that charts would have to present. Therefore it is important that these charts have a adequate representation of the physical environment in order to have a legible cartographic language for its users. Thus, the aim of this research was the accomplishment of a cartographic representation proposal for geotechnical charts from the study of representation analysis of two distinct geotechnical chart methodologies most used in Brazil: IPT - São Paulo Institute of Technological Research and EESC/USP - São Carlos Engineering School/São Paulo University. / Mestre

Distribution-free (nonparametric) control charts can be useful to the quality practitioner when the underlying distribution is not known. The term nonparametric is not intended to imply that there are no parameters involved, in fact, quite the contrary. While the term distribution-free seems to be a better description of what we expect from these charts, that is, they remain valid for a large class of distributions, nonparametric is perhaps the term more often used. In the statistics literature there is now a rather vast collection of nonparametric tests and confidence intervals and these methods have been shown to perform well compared to their normal theory counterparts. Remarkably, even when the underlying distribution is normal, the efficiency of some nonparametric tests relative to the corresponding (optimal) normal theory methods can be as high as 0.955 (see e.g. Gibbons and Chakraborti (2010) page 218). For some other heavy-tailed and skewed distributions, the efficiency can be 1.0 or even higher. It may be argued that nonparametric methods will be ‘less efficient’ than their parametric counterparts when one has a complete knowledge of the process distribution for which that parametric method was specifically designed. However, the reality is that such information is seldom, if ever, available in practice. Thus it seems natural to develop and use nonparametric methods in statistical process control (SPC) and the quality practitioners will be well advised to have these techniques in their toolkits. In this thesis we only propose univariate nonparametric control charts designed to track the location of a continuous process since very few charts are available for monitoring the scale and simultaneously monitoring the location and scale of a process. Chapter 1 gives a brief introduction to SPC and provides background information regarding the research conducted in this thesis. This will aid in familiarizing the reader with concepts and terminology that are helpful to the following chapters. Details are given regarding the three main classes of control charts, namely the Shewhart chart, the cumulative sum (CUSUM) chart and the exponentially weighted moving average (EWMA) chart. We begin Chapter 2 with a literature overview of Shewhart-type Phase I control charts followed by the design and implementation of these charts. A nonparametric Shewhart-type Phase I control chart for monitoring the location of a continuous variable is proposed. The chart is based on the pooled median of the available Phase I samples and the charting statistics are the counts (number of observations) in each sample that are less than the pooled median. The derivations recognize that in Phase I the signalling events are dependent and that more than one comparison is © University of Pretoria v made against the same estimated limits simultaneously; this leads to working with the joint distribution of a set of dependant random variables. An exact expression for the false alarm probability is given in terms of the multivariate hypergeometric distribution and this is used to provide tables for the control limits. Some approximations are discussed in terms of the univariate hypergeometric and the normal distributions. In Chapter 3 Phase II control charts are introduced and considered for the case when the underlying parameters of the process distribution are known or specified. This is referred to as the ‘standard(s) known’ case and is denoted Case K. Two nonparametric Phase II control charts are considered in this chapter, with the first one being a nonparametric exponentially weighted moving average (NPEWMA)-type control chart based on the sign (SN) statistic. A Markov chain approach (see e.g. Fu and Lou (2003)) is used to determine the run-length distribution of the chart and some associated performance characteristics (such as the average, standard deviation, median and other percentiles). In order to aid practical implementation, tables are provided for the chart’s design parameters. An extensive simulation study shows that on the basis of minimal required assumptions, robustness of the in-control run-length distribution and out-of-control performance, the proposed NPEWMA-SN chart can be a strong contender in many applications where traditional parametric charts are currently used. Secondly, we consider the NPEWMA chart that was introduced by Amin and Searcy (1991) using the Wilcoxon signed-rank statistic (see e.g. Gibbons and Chakraborti (2010) page 195). This is called the nonparametric exponentially weighted moving average signed-rank (NPEWMA-SR) chart. In their article important questions remained unanswered regarding the practical implementation as well as the performance of this chart. In this thesis we address these issues with a more in-depth study of the NPEWMA-SR chart. A Markov chain approach is used to compute the run-length distribution and the associated performance characteristics. Detailed guidelines and recommendations for selecting the chart’s design parameters for practical implementation are provided along with illustrative examples. An extensive simulation study is done on the performance of the chart including a detailed comparison with a number of existing control charts. Results show that the NPEWMA-SR chart performs just as well as and in some cases better than the competitors. In Chapter 4 Phase II control charts are introduced and considered for the case when the underlying parameters of the process distribution are unknown and need to be estimated. This is referred to as the ‘standard(s) unknown’ case and is denoted Case U. Two nonparametric Phase II control charts are proposed in this chapter. They are a Phase II NPEWMA-type control chart and a nonparametric cumulative sum (NPCUSUM)-type control chart, based on the exceedance statistics, © University of Pretoria vi respectively, for detecting a shift in the location parameter of a continuous distribution. The exceedance statistics can be more efficient than rank-based methods when the underlying distribution is heavy-tailed and / or right-skewed, which may be the case in some applications, particularly with certain lifetime data. Moreover, exceedance statistics can save testing time and resources as they can be applied as soon as a certain order statistic of the reference sample is available. We also investigate the choice of the order statistics (percentile), from the reference (Phase I) sample that defines the exceedance statistic. It is observed that other choices, such as the third quartile, can play an important role in improving the performance of these exceedance charts. It is seen that these exceedance charts perform as well as and, in many cases, better than its competitors and thus can be a useful alternative chart in practice. Chapter 5 wraps up this thesis with a summary of the research carried out and offers concluding remarks concerning unanswered questions and / or future research opportunities. © University / Thesis (PhD)--University of Pretoria, 2013. / gm2013 / Statistics / restricted

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