- / -

- / -

Thesis (MScIng)--University of Stellenbosch, 2008. / ENGLISH ABSTRACT: The Applications of Superconductors in Cellular Network Base Stations R. Du Toit Department of Electronic Engineering University of Stellenbosch Private Bag X1, 7602 Matieland, South Africa Thesis: MScEng (E&E) March 2008 Wireless communications have increasingly become part of our world. The growth of radio frequency (RF) wireless communications has led to an increasing demand for frequency spectrum licenses, increased system capacity and larger user bandwidths. These demands lead to frequent improvements on the physical and higher layers of wireless communication protocols. Changes in the physical layer are frequently followed by the need for replacement of dedicated hardware components. The need therefore exists for a more general and programmable physical layer. A more general and programmable radio architecture implies increased radio front-end performance without losing programmability. The contribution of this thesis is the analysis of how superconductor electronics (SCE) using Rapid Single Flux Quantum (RSFQ) logic may advance wireless radio front-ends by providing a general-purpose programmable radio architecture. Superconductor analogue to digital converters (ADCs) are employed as high performance, programmable digitization structures. Once a received signal is digitized, SCE can be used to rapidly do recursive operations such as synchronization and multi-path delay estimation. These operations are based on correlation, and for evaluation of such operations with SCE the popular CDMA multiplexing method is studied along with the WCDMA protocol used in the 3G UMTS standard. Two delta-type oversampling superconductor ADC modulator designs are presented and evaluated along with a hybrid decimation filter design, using both the benefits of SCE and room temperature electronics. A fast RSFQ correlator design is also presented and evaluated for use in a multi-path estimation structure. A rapid multi-path delay estimation architecture based on fast RSFQ circular data buffers and correlators is presented. The architecture uses the fast speeds of RSFQ logic to obtain accurate path delay estimates in a rapidly changing wireless environment. It is concluded that RSFQ-based wireless receiver components offer promising new options for data conversion, correlation and multi-path delay estimation implementations. / AFRIKAANSE OPSOMMING: The Applications of Superconductors in Cellular Network Base Stations R. Du Toit Department of Electronic Engineering University of Stellenbosch Private Bag X1, 7602 Matieland, South Africa Thesis: MScEng (E&E) March 2008 Draadlose kommunikasie word al hoe meer deel van ons wêreld. Groei in radiofrekwensietipe kommunikasie het gelei tot ’n toenemende aanvraag na frekwensiespektrum lisensies, vergrote stelselkapasiteit en groter gebruikerbandwydtes. Hierdie aanvrae lei tot gereelde en spoedige verbeteringe op die fisiese en hoër lae van huidige draadlose kommunikasieprotokol. Veranderinge in die fisiese laag vereis gewoonlik dat toegewyde hardewarde komponente vervang word. Die behoefte bestaan dus vir ’n meer algemene, programmeerbare fisiese laag. Dit vereis dus ’n verbetering in die radio-ontvanger se komponente naaste aan die antenna sonder om programmeerbaarheid te verloor. Die bydrae van hierdie tesis is hoofsaaklik die analise van hoe supergeleierelektronika wat van Rapid Single Flux Quantum (RSFQ) logika gebruik maak, huidige draadlose sellulêre basisstasies se fisiese laag kan verbeter deur ’n meer algemene en programmeerbare radio-argitektuur op te lewer. Supergeleier analoog-na-syfer omsetters (ADCs) word bestudeer as moontlike programmeerbare versyferingstrukture wat steeds hoë werkverrigting lewer. Wanneer ’n ontvangde sein in digitale vorm omgesit is, kan supergeleierelektronika gebruik word om vinnig rekursiewe operasies uit te voer. Voorbeelde van sulke operasies is sinkronisasie en die waardebepaling van die vertraging van verskillende paaie wat ’n sein volg na die ontvanger. Hierdie spesifieke operasies se werking is gebaseer op korrelasie, en vir die evaluasie van sulke operasies met supergeleierelektronika is die gewilde wyeband-CDMA (WCDMA) protokol wat gebruik word in die 3G UMTS-standaard. Twee supergeleier-delta-tipe oorversyferings-ADC-moduleerderontwerpe word voorgelê en evaluasie word daarop gedoen saam met ’n hibriede desimasiefilterontwerp wat gebruik maak van beide die voordele van supergeleierelektronika en kamertemperatuurelektronika. ’n Vinnige RSFQ-korreleerder word ook voorgelê en evaluasie word daarop gedoen vir gebruik binne ’n multi-padvertraging-waardebepalerstruktuur. Hierdie struktuur wat gebaseer is op RSFQ sirkulêre buffers en korreleerders, word voorgelê. Die waardebepaler maak gebruik van die spoed van RSFQ-logika om akkurate multi-padvertragingswaardes te bepaal in ’n vinnig veranderende draadlose omgewing. Die gevolgtrekking word gemaak dat RSFQ-gebaseerde draadlose ontvangerkomponente groot voordele in versyfering-, korreleerder- en multi-padvertragingsbepaler-toepassings bied.

Manter e ampliar relacionamentos com clientes, na área de serviços, é estimular a retenção de clientes e, consequentemente, fazer com que as empresas passem a ser vistas de forma diferenciada pelo mercado. Entretanto, as empresas prestadoras de serviços devem compreender o processo que envolve os clientes nos encontros de serviços, investigando os construtos que implicam na captação e na retenção dos mesmos, para que sejam desenvolvidas estratégias adequadas. Sendo assim, esta pesquisa propôs a replicação e testagem de um Modelo Teórico, considerando os construtos Valor Percebido, Reputação do Provedor de Serviços, Confiança e Custos de Troca como determinantes da Retenção de Clientes. Desenvolveu-se, então, a construção teórica acerca da Retenção de Clientes e dos demais construtos contemplados nesta pesquisa, com a intenção de compreender e analisar a atuação dos mesmos no relacionamento entre clientes e prestadores de serviços, bem como suas relações com as estratégias competitivas das empresas. Dando sequência ao estudo, foi realizada a pesquisa quantitativa, por meio da aplicação de uma survey. Para a análise dos dados, foram utilizadas estatísticas multivariadas, incluindo a Modelagem de Equações Estruturais, para que fossem testadas e analisadas as hipóteses levantadas pelo estudo aqui proposto. Os resultados evidenciaram que: o valor percebido pelos clientes influencia positivamente a reputação do provedor de serviços; o valor percebido pelos clientes não influencia positivamente os custos de troca; a reputação do provedor de serviços influencia positivamente a confiança do cliente no provedor de serviços; a reputação do provedor de serviços não influencia positivamente os custos de troca; a confiança depositada pelo cliente em relação ao provedor de serviços influencia positivamente a retenção de clientes; os custos de troca não influenciam positivamente a retenção de clientes; e a reputação do provedor de serviços influencia positivamente a retenção de clientes. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2015-04-01T17:00:54Z No. of bitstreams: 1 Dissertacao Daniele Nespolo.pdf: 1700635 bytes, checksum: f523232449b286777b973826707eb6dd (MD5) / Made available in DSpace on 2015-04-01T17:00:54Z (GMT). No. of bitstreams: 1 Dissertacao Daniele Nespolo.pdf: 1700635 bytes, checksum: f523232449b286777b973826707eb6dd (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES. / Maintaining and expanding relationships with customers in the service area, is to encourage customer retention and thus cause the corporation to be viewed differently by the market. However, the service providers must understand the process involving customers in service encounters, investigating the constructs involving the capture and retention of the same, so that appropriate strategies can be developed. Thus, this research has proposed replication and testing a theoretical model, considering the constructs Perceived Value, Reputation of Service Provider, Reliability and Cost of Exchange as determinants of Customer Retention. Developed the theoretical construction about Customer Retention and others constructs included in this study, with the intent to understand and analyze the performance of the same in the relationship between clients and service providers, as well as its relations with the competitive strategies of firms. Giving sequence to the study, was realized a quantitative research by the application of a survey. For data analysis, multivariate statistics, including Structural Equation Modeling, to be tested and analyzed the hypotheses proposed by the study presented here. The results showed that: perceived value positively influences the reputation of the service provider; perceived value by customers not positively influences switching costs; the reputation of the service provider positively influences customer trust in the provider; the reputation of the service provider not positively influences the switching costs; the trust placed by the customer in relation to the provider positively influences customer retention; the switching costs not positively influences customer retention; and the reputation of the service provider positively influences customer retention.

The spatially distributed adaptive array is defined and analyzed. It is applied to both time division multiple access (TDMA) and code division multiple access (CDMA) cellular networks to improve the outage probability at either the base station or mobiles. In a TDMA network, the distributed array consists of three sub-arrays at alternate corners of a hexagonal cell. It is shown analytically that the SINR of combined beamforming of the distributed sub-arrays is greater than or equal to the SIR or independent beamforming of the sub-arrays. Closed form solutions are derived for estimating the BER performance of Rayleigh fading mobile signals received at a distributed adaptive array with combined beamforming of the sub-arrays. The simulated TDMA uplink outage probability of multiple same-cell co-channel users in a fading environment is compared between conventional, spatially distributed arrays with independent beamforming of the sub-arrays and combined beamforming of the sub-arrays. The effect of the antenna element spacing, number of elements and angular spread is also investigated. Spatially distributed arrays are formed in a CDMA network on the downlink with arrays in multi-way soft handoff with the mobiles. The outage probability performance of combined beamforming of the arrays in handoff is compared to independent beamforming of the arrays as well as to conventional sectorized antennas. The range between mobiles and distributed sub-arrays in the case of a spatially distribu-ted array can be larger than between conventional center cell arrays and mobiles. Therefore, the effect of interference on the range increase relative to an omni antenna of adaptive and phased arrays in a multipath environment for both narrowband and wideband spread spectrum systems is investigated. An analytical model for predicting the asymptotic range limitation of phased arrays when the angular spread exceeds the array beamwidth is derived. / Thesis (PhD (Electronic Engineering))--University of Pretoria, 2006. / Electrical, Electronic and Computer Engineering / unrestricted

User modeling enables in the computation of the traffic density in a cellular network, which can be used to optimize the placement of base stations and radio network controllers as well as to analyze the performance of resource management algorithms towards meeting the final goal: the calculation and maximization of network capacity and throughput for different data rate services. An analytical model is presented for approximating the user distributions in multi-cell third generation wideband code division multiple access (WCDMA) networks using 2-dimensional Gaussian distributions by determining the means and the standard deviations of the distributions for every cell. This model allows for the calculation of the inter-cell interference and the reverse-link capacity of the network. An analytical model for optimizing capacity in multi-cell WCDMA networks is presented. Capacity is optimized for different spreading factors and for perfect and imperfect power control. Numerical results show that the SIR threshold for the received signals is decreased by 0.5 to 1.5 dB due to the imperfect power control. The results also show that the determined parameters of the 2-dimensional Gaussian model match well with traditional methods for modeling user distribution. A call admission control algorithm is designed that maximizes the throughput in multi-cell WCDMA networks. Numerical results are presented for different spreading factors and for several mobility scenarios. Our methods of optimizing capacity and throughput are computationally efficient, accurate, and can be implemented in large WCDMA networks.

Manter e ampliar relacionamentos com clientes, na área de serviços, é estimular a retenção de clientes e, consequentemente, fazer com que as empresas passem a ser vistas de forma diferenciada pelo mercado. Entretanto, as empresas prestadoras de serviços devem compreender o processo que envolve os clientes nos encontros de serviços, investigando os construtos que implicam na captação e na retenção dos mesmos, para que sejam desenvolvidas estratégias adequadas. Sendo assim, esta pesquisa propôs a replicação e testagem de um Modelo Teórico, considerando os construtos Valor Percebido, Reputação do Provedor de Serviços, Confiança e Custos de Troca como determinantes da Retenção de Clientes. Desenvolveu-se, então, a construção teórica acerca da Retenção de Clientes e dos demais construtos contemplados nesta pesquisa, com a intenção de compreender e analisar a atuação dos mesmos no relacionamento entre clientes e prestadores de serviços, bem como suas relações com as estratégias competitivas das empresas. Dando sequência ao estudo, foi realizada a pesquisa quantitativa, por meio da aplicação de uma survey. Para a análise dos dados, foram utilizadas estatísticas multivariadas, incluindo a Modelagem de Equações Estruturais, para que fossem testadas e analisadas as hipóteses levantadas pelo estudo aqui proposto. Os resultados evidenciaram que: o valor percebido pelos clientes influencia positivamente a reputação do provedor de serviços; o valor percebido pelos clientes não influencia positivamente os custos de troca; a reputação do provedor de serviços influencia positivamente a confiança do cliente no provedor de serviços; a reputação do provedor de serviços não influencia positivamente os custos de troca; a confiança depositada pelo cliente em relação ao provedor de serviços influencia positivamente a retenção de clientes; os custos de troca não influenciam positivamente a retenção de clientes; e a reputação do provedor de serviços influencia positivamente a retenção de clientes. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior, CAPES. / Maintaining and expanding relationships with customers in the service area, is to encourage customer retention and thus cause the corporation to be viewed differently by the market. However, the service providers must understand the process involving customers in service encounters, investigating the constructs involving the capture and retention of the same, so that appropriate strategies can be developed. Thus, this research has proposed replication and testing a theoretical model, considering the constructs Perceived Value, Reputation of Service Provider, Reliability and Cost of Exchange as determinants of Customer Retention. Developed the theoretical construction about Customer Retention and others constructs included in this study, with the intent to understand and analyze the performance of the same in the relationship between clients and service providers, as well as its relations with the competitive strategies of firms. Giving sequence to the study, was realized a quantitative research by the application of a survey. For data analysis, multivariate statistics, including Structural Equation Modeling, to be tested and analyzed the hypotheses proposed by the study presented here. The results showed that: perceived value positively influences the reputation of the service provider; perceived value by customers not positively influences switching costs; the reputation of the service provider positively influences customer trust in the provider; the reputation of the service provider not positively influences the switching costs; the trust placed by the customer in relation to the provider positively influences customer retention; the switching costs not positively influences customer retention; and the reputation of the service provider positively influences customer retention.

This thesis presents enhancements made to software designed for simulating digital mobile radio communication systems. Internally generated two-ray Rayleigh fading channel models as well as imported spatially varying complex channel impulse responses can be utilized in simulations. Implementation of receiver timing jitter and timing recovery models, as well as modifications of the channel generation (two-ray model) and conversion (imported channel), are among the enhancements that have been added. The bit error rate and outage performance of the simulator is compared with analytical results. A study of the impact of the distribution of magnitude and phase components within a channel impulse response is performed. A study utilizing both timing recovery and timing jitter models is also included. It has been found that for site specific BER and outage prediction, more descriptive channel parameters than narrowband fading statistics and statistical moments of a channel's power delay profile are needed. The studies also indicate that for simulations of channels with large delay spread timing recovery is essential. / Master of Science

Thesis (MComm (Business Management))--Stellenbosch University, 2008. / Measuring advertising effectiveness has become an increasingly important issue due to the substantial sums of money invested in the advertising industry. The purpose of this research was to design an Advertising Balanced Scorecard (ABSC), which is an adaptation to the advertising field of the managerial Balanced Scorecard (BSC). The ABSC was developed to identify a balanced pattern between the perspectives leading to effectiveness, namely strategy, execution, media and creative, in order to measure and control advertising effectiveness. This study reviews the South African mobile communication industry and Vodacom in particular. It examines Vodacom’s successful marketing and advertising strategy with a special attention given to iconic advertising by the use of a character such as Maurice the meerkat. After investigating the elements of Vodacom’s award winning advertisements, a balance between strategy, execution, media and creative could not be isolated systematically. However, when fewer perspectives were involved balance could be reached. The results therefore confirm the complexity of advertising effectiveness measurement and indicate that measurement of advertising effectiveness is possible when focus is placed on fewer perspectives.

Thesis (M. App. Sc.)--Carleton University, 2004. / Includes bibliographical references (p. 80-83). Also available in electronic format on the Internet.