Um estudo sobre as principais causas de quedas de chamadas em célula de rede móvel GSM é realizado por meio da análise estatística do tráfego. O objetivo é minimizar o efeito dessas causas, por meio da alteração de parâmetros de cobertura, como controle dinâmico de potência, borda de cobertura entre células e definição correta de células vizinhas. Para uma operadora celular reduzir a taxa de queda de chamadas (TQC), por intermédio da otimização de parâmetros de cobertura, alterados via comandos remotos, elimina os custos com alterações físicas, como altura das antenas e instalações de novas estações rádio base. Entretanto, alterações de parâmetros devem ser cuidadosamente realizadas, pois podem degradar outros indicadores e acarretar redução da área de cobertura e do tráfego. As duas principais causas da TQC são as quedas repentinas, ocasionadas por falha nos equipamentos envolvidos, ou comportamento dos assinantes e falha na execução do handover e as quedas devido ao nível baixo de sinal na interface aérea. Neste trabalho, com base em dados estatísticos do tráfego na rede GSM, foi escolhida uma célula operando em 900 MHz que apresentava alta TQC. Ajustando os parâmetros de cobertura, a TQC mensal passou de 8,6% para 1,6% e não houve degradação nos demais indicadores de desempenho. / A study about the main causes of dropped calls in mobile network cell GSM is made by means of statistical traffic analysis. The aim is to minimize the effect of these causes through coverage parameters changes, such as dynamical potency control, coverage border between cells, correct definition of neighboring cells. The reduction of dropped call rate by means of optimization of coverage parameters, changed via remote commands, eliminates costs with physical changes, such as the height of the antennas and installation of new radio base station. Parameter changes, however, must be carefully made because they can degrade other indicators and bring coverage area and traffic reduction. The two main causes of dropped call are sudden loss of connection, due to failure in the equipment used, behavior of subscribers and the failure in handover and drops due to the low signal strength in the air interface. In this study, based on statistical data of GSM traffic, a cell operating in 900 MHz that presented high dropped call rate was chosen. Adjusting the coverage parameters, the monthly dropped call rate went from 8.6% to 1.6% and there wasn\'t any degradation of any other performance indicators.

A utilização dos sistemas de navegação global por satélite, conhecidos pela sigla GNSS (Global Navigation Satellite System), cresceu vertiginosamente durante a última década. Atualmente, os receptores GNSS são ferramentas seguras, eficientes e altamente produtivas para a realização de observações aos satélites, possibilitando determinar coordenadas geodésicas sobre a superfície terrestre. As ferramentas e tecnologias disponíveis no mercado são de essencial importância no desenvolvimento eficiente dos projetos de engenharia. No entanto, o domínio das técnicas de trabalho e o conhecimento profundo de todos os métodos de execução são os principais obstáculos para a introdução de uma nova metodologia em projetos de engenharia. Este trabalho tem por objetivo esclarecer e testar a associação dessa tecnologia com o uso da telefonia celular, em especial com a utilização da conexão GSM (Global System for Mobile Communication) / GPRS (General Packet Radio Service), disponíveis no Brasil. O posicionamento preciso em tempo real tradicionalmente envia as observações de fase da onda portadora entre o receptor GNSS base e móvel através de frequências de rádio. Isso possibilita a determinação de coordenadas geodésicas e topográficas instantaneamente. Entretanto, obstáculos como áreas de relevo acidentado, edificações ou a baixa potência do rádio que envia os sinais fazem com que a comunicação entre os equipamentos seja interrompida com a perda frequente da solução instantânea. Apesar disso, este método de trabalho está consagrado como o mais produtivo, mantendo precisões topográficas, sendo que superar as restrições citadas seria uma inovação na área de Geodésia e Topografia. Com o avanço de tecnologias correlatas, criou-se uma nova maneira de enviar as observações de fase utilizando a conexão GSM através do pacote de dados GPRS. A conexão GSM é aplicada na tecnologia móvel padrão, que se tornou a mais popular para telefones celulares, de fácil acesso a qualquer usuário. Adequando o tradicional protocolo RTCM (Radio Technical Commission for Maritime Services) em um formato capaz de ser transmitido por GPRS, desenvolveu-se assim o serviço NTRIP (Network Transport of RTCM via Internet Protocol). Com esta nova concepção da conexão GSM/GPRS é possível realizar levantamentos com a técnica RTK (Real Time Kinematic) com vetores de até 100 km, mantendo as precisões atingidas com a metodologia atual de pós-processamento. Os tipos de equipamentos, os limites de distâncias e a qualidade dos dados obtidos estão sendo discutidos nesta pesquisa e analisados de forma a verificar os resultados atingidos em termos de precisão e acurácia. / The use of Global Navigation Satellite System has dramatically grown over the last decade. Currently, GNSS receivers are secure, efficient and highly productive for carrying out observations for the geodetic coordinates determination on the Earth\'s surface. The tools and technologies available on the market are essential in the establishment of engineering projects. However, the total knowledge of the techniques and the total domain of the execution methods are the first obstacles to the full incorporation of the technology in the engineering projects. This work is to clarify and to teste the technology described in this dissertation related to the facilities of cell phone coverage, particularly the GSM/GPRS connection able to be used in Brazil. The precise positioning in real-time traditionally involves the transmission of phase measurements between base and rover GNSS receivers; this is traditionally carried out through radio frequencies. This allows determining geodetic and topographic coordinates instantaneously. However, obstacles like accident topography terrain, buildings or low power of radio basis transmission, provoke constant interruptions in the communication among the radios and the consequent losing of the instant solution. Nevertheless, this methodology is the most productive for a centimetric accuracy; so the major challenge in geodetic positioning is to overcome the mentioned difficulties. With the high development of technologies related to mobile phone, a new way to transmit the observations using the GSM/GPRS connection was created. The GSM connection is a standard mobile technology, the most popular for cell phones, which became of easy access to any person. The traditional RTCM protocol in a convenient format can be transmitted by GSM/GPRS connection which is known as NTRIP service, becoming a full digital communication system. As of this new concept, it is possible to note vectors up to 100 km in RTK technique employment with the same high quality measurement. The equipment characteristics, distance limits and quality of the data recorded have been discussed and analyzed here in order to verify whether the results can achieve the necessary precision and accuracy.

[pt] Este trabalho aborda a utilização de repetidores na implantação de sistemas móveis celulares. Esta técnica permite estender a cobertura dos sistemas móveis celulares com baixo custo e curto tempo de implantação a áreas ou ambientes onde a utilização de estações rádio base seria dispendiosa ou demorada.O impacto da inclusão deste elemento na interface rádio é detalhadamente analisada visando obter uma metodologia para o seu dimensionamento e para o cálculo das degradações produzidas na rede. É apresentada ainda uma metodologia completa para projetos com repetidores e descrita sua aplicação na implantação de um sistema GSM. / [en] This work deals with the use of active repeaters in the planning and deployment of cellular mobile systems. This technique allows the extension of the coverage of the cellular systems, with low cost and short building time, to areas where the use of radio base stations would be costly or difficult to implement.The impact of the inclusion of the active element in the radio interface is analyzed in full detail to provide methods for the calculation of the degradations produced in the network. A complete design methodology for projects with repeaters is also presented, as well as a case study for a GSM system.

The theoretical part focuses on actual trends of the modern organizational structure and its positive and negative sides as indicated by some of the relevant authors. The practical part focuses on the particular organizational structure of the retail sales department of the Vodafone CZ company. It analyses the defections of the present state and propounds improvements.

Um estudo sobre as principais causas de quedas de chamadas em célula de rede móvel GSM é realizado por meio da análise estatística do tráfego. O objetivo é minimizar o efeito dessas causas, por meio da alteração de parâmetros de cobertura, como controle dinâmico de potência, borda de cobertura entre células e definição correta de células vizinhas. Para uma operadora celular reduzir a taxa de queda de chamadas (TQC), por intermédio da otimização de parâmetros de cobertura, alterados via comandos remotos, elimina os custos com alterações físicas, como altura das antenas e instalações de novas estações rádio base. Entretanto, alterações de parâmetros devem ser cuidadosamente realizadas, pois podem degradar outros indicadores e acarretar redução da área de cobertura e do tráfego. As duas principais causas da TQC são as quedas repentinas, ocasionadas por falha nos equipamentos envolvidos, ou comportamento dos assinantes e falha na execução do handover e as quedas devido ao nível baixo de sinal na interface aérea. Neste trabalho, com base em dados estatísticos do tráfego na rede GSM, foi escolhida uma célula operando em 900 MHz que apresentava alta TQC. Ajustando os parâmetros de cobertura, a TQC mensal passou de 8,6% para 1,6% e não houve degradação nos demais indicadores de desempenho. / A study about the main causes of dropped calls in mobile network cell GSM is made by means of statistical traffic analysis. The aim is to minimize the effect of these causes through coverage parameters changes, such as dynamical potency control, coverage border between cells, correct definition of neighboring cells. The reduction of dropped call rate by means of optimization of coverage parameters, changed via remote commands, eliminates costs with physical changes, such as the height of the antennas and installation of new radio base station. Parameter changes, however, must be carefully made because they can degrade other indicators and bring coverage area and traffic reduction. The two main causes of dropped call are sudden loss of connection, due to failure in the equipment used, behavior of subscribers and the failure in handover and drops due to the low signal strength in the air interface. In this study, based on statistical data of GSM traffic, a cell operating in 900 MHz that presented high dropped call rate was chosen. Adjusting the coverage parameters, the monthly dropped call rate went from 8.6% to 1.6% and there wasn\'t any degradation of any other performance indicators.

Le système nerveux central est la cible la plus probable d'effets biologiques dûs à l'exposition aux radiofréquences (RF) de la téléphonie mobile. Plusieurs études sur l’EEG (électroencéphalogramme) ont montré des variations dans le spectre de la bande alpha pendant et / ou après l'exposition aux radiofréquences, avec les yeux fermés ou pendant le sommeil. Dans ce contexte, l'observation de l'activité électrique spontanée des réseaux neuronaux sous exposition aux radiofréquences représente un outil efficace pour détecter de possibles effets des RF de faible niveau sur le système nerveux. Dans ce travail de thèse, nous avons développé un dispositif expérimental dédié à l'exposition dans la gamme des GHz de réseaux neuronaux et permettant simultanément l’enregistrement de l'activité électrique des neurones. Une cellule électromagnétique transversale (TEM) a été utilisée afin d'exposer les réseaux neuronaux aux signaux GSM-1800 à un niveau de DAS de 3,2 W / kg. L'enregistrement de l'activité électrique neuronale et la détection en termes de spikes et bursts sous exposition ont été réalisées à l'aide de réseaux de micro-électrodes (MEAs). Ce travail démontre la faisabilité de l’étude (culture de réseaux de neurones primaires, enregistrement de l'activité électrique et analyse des signaux obtenus sous exposition aux radiofréquences) et expose des résultats préliminaires. Dans l'expérience principale (16 cultures), il y avait une diminution réversible de 30% du taux moyen de spikes (MFR) et de bursts (BR) pendant les 3 min d’exposition aux RF. Des expériences supplémentaires sont nécessaires pour mieux caractériser cet effet, notamment en termes d'élévation de la température au niveau microscopique. / The central nervous system is the most likely target of mobile telephony radiofrequency field (RF) exposure in terms of biological effects. Several EEG (electroencephalography) studies have reported variations in the alpha-band power spectrum during and/or after RF exposure, in resting EEG and during sleep. In this context, the observation of the spontaneous electrical activity of neuronal networks under RF exposure can be an efficient tool to detect the occurrence of low-level RF effects on the nervous system. In this thesis research work we developed a dedicated experimental setup in the GHz range for the simultaneous exposure of neuronal networks and monitoring of electrical activity. A transverse electromagnetic (TEM) cell was used to expose the neuronal networks to GSM-1800 signals at a SAR level of 3.2 W/kg. Recording of the neuronal electrical activity and detection of the extracellular spikes and bursts under exposure were performed using Micro Electrode Arrays (MEAs). This work provides the proof of feasibility and preliminary results of the integrated investigation regarding exposure setup, culture of the neuronal network, recording of the electrical activity and analysis of the signals obtained under RF exposure. In the main experiment (16 cultures), there was a 30% reversible decrease in mean firing rate (MFR) and bursting rate (BR) during the 3 min exposures to RF. Additional experiments are needed to further characterize this effect, especially in terms of temperature elevation at the microscopic level.

GSM has changed the face of communication and information exchange, much as the Internet did. With the advances made in the mobile technology arena, new opportunities are created. Mobile Commerce (m-Commerce) is one such opportunity. Each new advance in technology brings with it associated risks. This dissertation focuses on the risks involved with m-Commerce for the banking industry. This dissertation provides a detailed overview of basic services that any m-Commerce application should provide to the banking industry. These principles provide the foundation for securing any financial transaction over untrusted networks. Several mechanisms to provide these services are also discussed. Examples of such mechanisms include hash functions, Message Authentication Codes and Digital Signatures. The security of GSM networks has come under attack in the past. This is largely due to the fact that the GSM consortium opted to develop their security technologies in secret, rather than in the public domain. This dissertation aims to evaluate the security offered by GSM and assess potential attacks in order to further understand risks associated with m-Commerce applications over GSM. In recent years there have been significant additions to the GSM enabling technology family. The arrival of the SIM Application Toolkit and the Wireless Application Protocol promised to again change the face of commerce. Although market acceptance of these technologies proved to be initially slow, usage is set to increase exponentially within the next couple of years. A detailed analysis of these enabling technologies is presented in the dissertation. Possible attacks on these technologies are discussed in the latter part or this document. Based on the findings of the research, some changes to either the application architectures or the processing of the data have been suggested in order to enhance the security offered by these services. It is not the intent of this dissertation to redesign these applications, but to rather leverage off the current technologies in order to enable secure m-Commerce over these channels. This dissertation provides a detailed overview of basic services that any m-Commerce application should provide to the banking industry. These principles provide the foundation for securing any financial transaction over untrusted networks. Several mechanisms to provide these services are also discussed. Examples of such mechanisms include hash functions, Message Authentication Codes and Digital Signatures. The security of GSM networks has come under attack in the past. This is largely due to the fact that the GSM consortium opted to develop their security technologies in secret, rather than in the public domain. This dissertation aims to evaluate the security offered by GSM and assess potential attacks in order to further understand risks associated with m Commerce applications over GSM. In recent years there have been significant additions to the GSM enabling technology family. The arrival of the SIM Application Toolkit and the Wireless Application Protocol promised to again change the face of commerce. Although market acceptance of these technologies proved to be initially slow, usage is set to increase exponentially within the next couple of years. A detailed analysis of these enabling technologies is presented in the dissertation. Possible attacks on these technologies are discussed in the latter part or this document. Based on the findings of the research, some changes to either the application architectures or the processing of the data have been suggested in order to enhance the security offered by these services. It is not the intent of this dissertation to redesign these applications, but to rather leverage off the current technologies in order to enable secure m-Commerce over these channels. / Dissertation (M.Sc (Electronics))--University of Pretoria, 2005. / Electrical, Electronic and Computer Engineering / unrestricted

Plack i arteria carotis kan ha olika utseende beroende på innehåll och morfologi. Det kan vara lågekogena eller högekogena plack. De lågekogena placken är mest problematiska eftersom de består av lipider och inflammationsceller som ger en mjuk konsistens och kan spricka och ledda till embolisering med stroke och kardiovaskulära incidenter som följd. För mätning av plack-ekogenicitet används i forskningssyfte ett GSM-värde, grey scale median som mäts med en ultraljudapparat med GSM-inställning. Ju lägre GSM-värde desto mer lågekogen är placken. Syftet med denna studie är att jämföra två GSM-värde för samma plack, den ena mätt med ultraljudstandardinställning och den andra mätt med GSM-inställningen för att avgöra om det blir en bra överensstämmelse mellan värdena. Om så är fallet innebär detta att plack-ekogenicitet kan avgöras i framtiden med mätning av GSM-värde med en ultraljudsapparat med standardinställning i forskningssyfte. Resultatet visade att det fanns en god överensstämmelse mellan en stor del av GSM-värdena, men det fanns en del värde där det blev en signifikant skillnad som gjorde att studien inte var tillräcklig övertygande för förväntade utfallet. / Plaque in the carotid artery can have different appearances depending on the content and morphology. It can be echolucent or more-echogenic plaques. The echolucent plaques are most problematic because they consist of lipids and inflammatory cells that give a soft consistency and can crack and lead to embolization with stroke and cardiovascular incidents as a result. For measuring plaque echogenicity for research purposes, a GSM value, gray scale median is used and is measured with an ultrasound device with a GSM setting. The lower the GSM value, the lower echolucent is the plaque. The purpose of this study is to compare two GSM values for the same plaque, one measured with the ultrasonic standard setting and the other measured with the GSM setting to determine if there is a good agreement between the values. If this is the case, this means that plaque echogenicity can be determined in the future by measuring GSM value with an ultrasound device with a standard setting for research purpose. The results showed that there was a good agreement between a large part of the GSM values, but there were some values where there was a significant difference which made the study not sufficiently convincing for the expected outcome.

The aim of this Master's thesis is to design a local flood warning system. The system consists of two basic types of units. The first unit is placed in the field usingsensors and evaluates the presence of water in an otherwise dry area. In the event of flooding sends a warning message using wireless technology. The second unit evaluates the warning messages and informs the personabout the situation via text messaging. Outdoor equipment is fullyautonomous and permanently placed in an outdoor environment. The system is designed based 8-bit microcontrollers. The main parametersinclude low power devices, mechanical durability and reliability.

Today Moblity Management is one of the most important tasks that need to be accomplished to secure availability and performance of communication between people. This paper explains how moblity management is currently structured and what algorithms and approaches from Peer-To-Peer technology could be used to increase availability and performance.