Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1993. / Vita. Abstract. Includes bibliographical references (leaves 128-132). Also available via the Internet.

Thesis (M. Eng.)--Carleton University, 2000. / Also available in electronic format on the Internet.

Thesis (Ph. D.)--Carleton University, 2001. / Includes bibliographical references (p. 159-167). Also available in electronic format on the Internet.

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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.

Telephony used to mean using a telephone to call another telephone on the Public Switched Telephone Network (PSTN), and data networks were used purely to allow computers to communicate. However, with the advent of the Internet, telephony services have been extended to run on data networks. Telephone calls within the IP network are known as Voice over IP. These calls are carried by a number of protocols, with the most popular ones currently being Session Initiation Protocol (SIP) and H.323. Calls can be made from the IP network to the PSTN and vice versa through the use of a gateway. The gateway translates the packets from the IP network to circuits on the PSTN and vice versa to facilitate calls between the two networks. Gateways have evolved and are now split into two entities using the master/slave architecture. The master is an intelligent Media Gateway Controller (MGC) that handles the call control and signalling. The slave is a "dumb" Media Gateway (MG) that handles the translation of the media. The current gateway control protocols in use are Megaco/H.248, MGCP and Skinny. These protocols have proved themselves on the edge of the network. Furthermore, since they communicate with the call signalling VoIP protocols as well as the PSTN, they have to be the lingua franca between the two networks. Within the VoIP network, the numbers of call signalling protocols make it difficult to communicate with each other and to create services. This research investigates the use of Gateway Control Protocols as the lowest common denominator between the call signalling protocols SIP and H.323. More specifically, it uses MGCP to investigate service creation. It also considers the use of MGCP as a protocol translator between SIP and H.323. A service was created using MGCP to allow H.323 endpoints to send Short Message Service (SMS) messages. This service was then extended with minimal effort to SIP endpoints. This service investigated MGCP’s ability to handle call control from the H.323 and SIP endpoints. An MGC was then successfully used to perform as a protocol translator between SIP and H.323.

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

The distribution of real-time multimedia streams is seen nowadays as the next step forward for the Internet. One of the most obvious uses of such streams is to support telephony over the Internet, replacing and improving traditional telephony. This thesis investigates the development and deployment of services in two Internet telephony environments, namely CINEMA (Columbia InterNet Extensible Multimedia Architecture) and VOCAL (Vovida Open Communication Application Library), both based on the Session Initiation Protocol (SIP) and open-sourced. A classification of services is proposed, which divides services into two large groups: basic and advanced services. Basic services are services such as making point-to-point calls, registering with the server and making calls via the server. Any other service is considered an advanced service. Advanced services are defined by four categories: Call Related, Interactive, Internetworking and Hybrid. New services were implemented for the Call Related, Interactive and Internetworking categories. First, features involving call blocking, call screening and missed calls were implemented in the two environments in order to investigate Call-related services. Next, a notification feature was implemented in both environments in order to investigate Interactive services. Finally, a translator between MGCP and SIP was developed to investigate an Internetworking service in the VOCAL environment. The practical implementation of the new features just described was used to answer questions about the location of the services, as well as the level of required expertise and the ease or difficulty experienced in creating services in each of the two environments. / KMBT_363 / Adobe Acrobat 9.54 Paper Capture Plug-in