M.Sc. / The work is based on a project done by SAMES (South African Micro Electronic Systems) for the local production of an integrated circuit that previously had to be imported. The circuit finds application in the telecommunications field where it controls loop disconnect dialling in the telephones. The mechanical disc dial is thus replaced by an electronic network that makes use of push-button entry and full digital out-dialling. The push-button telephone is compatible with the rotary disc dial telephone with advantages in reliability, speed and ease of use. An access pause and re dial facility add towards a more efficient telephone. The circuit was bought from an American company for manufacturing purposes. A process fit and circuit modifications were done for product ion on the CMOS process line at SAMES. The work includes a circuit- and process study with modifications, computer aided design, prototype production and analysis. The original circuit is called the General Instruments AY-5-9151D and the re-designed version the SAMES SA 9151-A2.

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.

Voice over IP (VoIP) is a key enabling technology for the migration of circuit-switched PSTN architectures to packet-based IP networks. However, this migration is successful only if the present problems in IP networks are addressed before deploying VoIP infrastructure on a large scale. One of the important issues that the present VoIP networks face is the problem of unwanted calls commonly referred to as SPIT (spam over Internet telephony). Mostly, these SPIT calls are from unknown callers who broadcast unwanted calls. There may be unwanted calls from legitimate and known people too. In this case, the unwantedness depends on social proximity of the communicating parties. For detecting these unwanted calls, I propose a framework that analyzes incoming calls for unwanted behavior. The framework includes a VoIP spam detector (VSD) that analyzes incoming VoIP calls for spam behavior using trust and reputation techniques. The framework also includes a nuisance detector (ND) that proactively infers the nuisance (or reluctance of the end user) to receive incoming calls. This inference is based on past mutual behavior between the calling and the called party (i.e., caller and callee), the callee's presence (mood or state of mind) and tolerance in receiving voice calls from the caller, and the social closeness between the caller and the callee. The VSD and ND learn the behavior of callers over time and estimate the possibility of the call to be unwanted based on predetermined thresholds configured by the callee (or the filter administrators). These threshold values have to be automatically updated for integrating dynamic behavioral changes of the communicating parties. For updating these threshold values, I propose an automatic calibration mechanism using receiver operating characteristics curves (ROC). The VSD and ND use this mechanism for dynamically updating thresholds for optimizing their accuracy of detection. In addition to unwanted calls to the callees in a VoIP network, there can be unwanted traffic coming into a VoIP network that attempts to compromise VoIP network devices. Intelligent hackers can create malicious VoIP traffic for disrupting network activities. Hence, there is a need to frequently monitor the risk levels of critical network infrastructure. Towards realizing this objective, I describe a network level risk management mechanism that prioritizes resources in a VoIP network. The prioritization scheme involves an adaptive re-computation model of risk levels using attack graphs and Bayesian inference techniques. All the above techniques collectively account for a domain-level VoIP security solution.

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.

Thesis: M.S., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 1980 / Bibliography: leaves 165-166. / by Yoshitaka Omiya. / M.S. / M.S. Massachusetts Institute of Technology, Department of Aeronautics and Astronautics

Little research effort has been devoted to human interaction with telephone information systems. This study investigated the effects of system parameters and user characteristics on human behavior in an interactive telephone-based information system. The research method utilized a centraI-composite design to study four variables at five levels each. The four factors manipulated were: synthesized speech rate, time available for user input, subject age, and background music level. Subjects searched a fictitious department store database for 16 specific store items and transcribed 16 information messages which were spoken by a computer speech synthesizer. Subjective ratings of certain features of the system were solicited from the subjects and performance measures were also collected from the subjects on an on-line basis. Performance was evaluated by calculating regression equations relating the dependent measures and the independent variables. A response surface was plotted, and optimal settings for the Information system were also calculated. Two seconds was found to be an optimal time for users to enter their selection. The computer synthesized speech rate should be set close to 120-150 words per minute. Background music or noise level should be kept below 50 dB(A); sound level above 50 dB(A) seriously affected user's ability to understand synthetic speech. Younger subjects (age 14 - 22) performed better in this study than older subjects (age 36- 62). / Master of Science / incomplete_metadata

This study examined the effects of five dichotomous variables on human performance using a computer-based telephone information system. The five variables were: speech rate (120 or 240 words per minute), length of input time-out (two or ten seconds), feedback (available or not available), wallet guide - a graphical representation of the information (available or not available), and the database structure (8x2 or 2x6). The research methodology implemented a one-half fraction of a 2⁵ factorial design, requiring only 16 of the 32 possible treatment combinations. Two tasks were included in this study: a search task and a transcription task. The search task consisted of each subject accessing an information system through a touch-tone telephone. The subject listened to the computer as it used synthesized speech to list available menu options. The search task continued until the subject found the target item. The transcription task consisted of listening to and typing an information message for each target item. The experiment ended when 16 target items were found. Four dependent measures were used to evaluate user performance. The search task was evaluated with three measures: user added time (the amount of additional time the subject required to complete the search in excess of the minimum search time imposed by the system design); invalid key presses (the number of times undefined keys on the touch tone telephone were pressed during the search); and user added key presses (the number of additional, valid key presses the subject required to complete the search in excess of the minimum number of key presses required to complete the search). Only one measure was used to evaluate user performance of the transcription task: transcription accuracy score (the number of words that each subject transcribed correctly). The results show four of the five variables (speech rate, database structure, input time-out, and wallet guide) to have a significant effect on human performance. The following interactions were found to have a significant effect on at least one of the dependent measures: database structure by input timeout, database structure by wallet guide, input timeout by wallet guide, and speech rate by wallet guide. Twelve subjective ratings were also analyzed. The results show at least one of the 12 subjective ratings was significantly affected by speech rate, input time-out, or the database structure. Perhaps the most important finding of this research is that complicated auditory information structures can be accessed easily if a wallet guide is provided. In addition to decreasing search time, a wallet guide reduces the number of search errors users make. / Master of Science

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 (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2005. / Automatic speech recognition (ASR) systems are an attractive means for companies to deliver value added services with which to improve customer satisfaction. Such ASR systems require a telephony interface to connect the speech recognition application to the telephone system. Commercially available telephony interfaces are usually operating system specific, and therefore hardware device driver issues complicate the development of software applications for different platforms that require telephony access. The drivers and application programming interface (API) for telephony interfaces are often available only for the Microsoft Windows operating systems. This poses a problem, as many of the software tools used for speech recognition research and development operate only on Linux-based computers. These interfaces are also typically in PCI/ISA card format, which hinders physical portability of the device to another computer. A simple, cheaper and easier to use USB telephony interface device, offering cross-platform portability, was developed and presented, together with the necessary API.