Several emerging wireless communication systems require direct transmission between mobile terminals to support efficient data transfer and user mobility. Such mobile-to-mobile communication systems differ from the conventional cellular systems where only the user unit is mobile. In addition, there might be a relay, also called a repeater, between the original transmitter and the final receiver to improve the network range and coverage. Potential applications for mobile-to-mobile systems include Intelligent Highways for coordinated traffic control and ad-hoc networks meant for military and disaster management. Relays may be deployed in cellular networks and IEEE 802.16 mesh networks for wireless broadband access. Extensive research in cellular radio channels has led to the successful deployment of cellular networks. However, our knowledge of the radio channels encountered in mobile-to-mobile and relay-based systems is still inadequate. This forms the primary motivation behind our research in addressing wireless channel modeling, simulation, and estimation issues for these systems. Specifically, we investigate frequency-flat mobile-to-mobile channels and develop simulation models by using the sum-of-sinusoids method, which is widely used for cellular channels. In addition, we present the properties of amplify and forward relay channels via theoretical analysis. This analysis, to the best of our knowledge, is the first of its kind. Further, we address the unique challenges, which arise because of the different underlying channel model, for channel estimation in amplify and forward relay systems. Our work would provide other researchers the necessary tools for the design and testing of these emerging communication systems.

Indoor/Outdoor Location of Cellular Handsets Based on Received Signal Strength Jian Zhu 123 pages Directed by Dr. Gregory D. Durgin Accurate geo-location is an important emerging technology for public safety, commercial use, and military application. Especially, in the United States, the wireless Enhanced 911 (E911) rules by the Federal Communication Commission (FCC) seek to provide 911 dispatchers with additional information on wireless 911 calls. This dissertation presents a novel technique for indoor/outdoor location of cellular handsets based on received signal strength (RSS) measurements taken by a cellular handset of the surrounding base stations. RSS location accuracy for different environments is studied as a function of base station separation distance, cell sector density, measurement density, radio propagation environment, and accuracy of measurement. The analytical and experimental results in this thesis serve as a guideline for the accuracy of RSS signature location technology under different conditions. Accurate outdoor to indoor penetration models are proposed and validated for dense urban areas by introducing pseudo-transmitters to simulate the wave-guiding effects in urban canyon environments. A set of location algorithms is developed to improve location accuracy. Furthermore, an algorithm to discriminate between indoor and outdoor users is proposed and validated. The research results demonstrate the feasibility of RSS location techniques to meet the FCCs requirements for E911 accuracy in urban and semi-urban environments. The techniques remain accurate for indoor handsets. The results also suggest that a hybridization of the handset-based GPS method and the RSS signature method may prove to be the most effective solution for locating handsets across a range of environments; including rural, suburban, dense urban, and indoor.

The area of deterministic noise cancellation in mobile radio communication systems is investigated and analyzed. Several interoperation problems in the mobile wireless radio space are identified and interference concerns for the Bluetooth - WLAN networks are characterized and quantified in the physical layer. A mathematical framework has been created for describing interference in the 2.4 GHz band. An adaptive noise suppression system has been developed that is able to alleviate the encroachment of the aggressor signal on the victim without sacrificing any of the original signal. This system is demonstrated to improve the victim SNR in a spread spectrum communication scenario. The research is extended to construct an interference canceller that is easy to assimilate into existing RF front-ends. A low-power small form-factor analog active canceller has been designed in 0.18-ìm Si-CMOS IC technology that delivers adequate noise suppression performance while operating in the RF domain. This includes novel implementations of phase rotator circuits based on delay interpolation and an integrated low-current quadrature modulator-based continuously variable analog phase shifter. This canceller is capable of up to 30 dB of in-band cancellation for the Bluetooth - WLAN problem. Other versions of the canceller are configured to protect GPS and DVB-H receivers from unintentional radiators transmitting in the vicinity. These demonstrate noise mitigation of at least 15 dB in their respective bands while generating very low broadband noise at the output. A simple low-power mixed-signal automatic control mechanism is also developed to operate the canceller adaptively. The work described in this dissertation advances the state-of-the-art in the area of mobile wireless radio coexistence.

published_or_final_version / abstract / toc / Asian Studies / Doctoral / Doctor of Philosophy

Thesis (M.B.A.)--University of Hong Kong, 1992.

Made available in DSpace on 2016-03-15T19:31:15Z (GMT). No. of bitstreams: 1 Sergio Lex.pdf: 2651823 bytes, checksum: 468b06e5f075bd40d1d9b01209cdedb1 (MD5) Previous issue date: 2008-03-06 / The causal relationship between the use of technological innovation and gain of sustainable competitive advantages has been observed and studied within several organizations and in different environments. However there has been no concern on how organizations can establish such relationship and which other variables may exert influence on it. Therefore, the aim of this study is based on such concern and on the Brazilian Cellular Telephone Sector, which is undergoing fast structural changes and experiencing great technological improvement. These changes have triggered the digital convergence, which allows sound, image and data to be transmitted through the same medium. Initially, an analysis of the recent evolution of the Telecommunication Industry, where the studied Sector is located, was conducted to attain better comprehension of the role of the Sector s organizations, operators and cellular manufacturers. Following, a broad conceptual revision on technological innovation, sustainable competitive advantages and consumers value was made to give a solid theoretical support to the study. This study involved a double-folded descriptive field research. In the first part, a qualitative research, 13 specialists from the main organizations of the Sector were interviewed. Content Analysis made it evident that intervenient variables, digital convergence and consumer s value perception, are responsible for the link between technological innovation and the gain of sustainable competitive advantages. Other variables that influence this relationship were also identified: Government regulation, economic conditions and strategic positioning of companies. A descriptive Model was used to represent these relationships. In the second part, a quantitative research was based on a employed sample of 350 respondents for statistical validation of the Model. As part of this research, two pre-tests involving 220 respondents were made. Data were analyzed through univariate and multivariate statistical procedures: Factor Analysis and Structural Equation Modeling. The study concluded that cellular operators and equipment manufacturers in the Brazilian Cellular Telephone Sector are searching for digital convergence based on technological innovation to obtain innovative products and services to be offered to consumers. Nevertheless, it also became evident that these companies can only achieve sustainable competitive advantages if consumers are able to perceive significant added values. / A relação de causalidade entre o emprego de inovações tecnológicas e a obtenção de vantagens competitivas sustentáveis tem sido observada e estudada em diversas organizações e em diferentes ambientes, sem, no entanto, procurar entender de que modo as organizações estabelecem essa relação e que outras variáveis podem exercer influência, que é o objetivo deste estudo. Ele está focado no Setor de Telefonia Celular brasileiro, no qual a evolução tecnológica é a mola propulsora da contínua transformação, cuja evidência está na convergência digital, que possibilita que som, imagem e dados sejam transmitidos através do mesmo aparelho. Inicialmente, procurou-se analisar a evolução recente da Indústria de Telecomunicações, em que se situa o Setor estudado, para poder compreender o papel das organizações que o compõem, as operadoras e os fabricantes de aparelhos celulares. A seguir, foi feita uma revisão ampla dos conceitos sobre inovação, sobre vantagens competitivas e sobre valor do consumidor, que pudessem dar sustentação teórica aos estudos. O trabalho compreendeu uma pesquisa descritiva, desenvolvida em duas fases. Na primeira fase, qualitativa, foram realizadas entrevistas com 13 especialistas das principais organizações do Setor. Aos dados colhidos foi aplicada a Análise de Conteúdo, que levou à identificação de duas varáveis moderadoras, a convergência digital e a percepção de valor pelos consumidores que representam o vínculo entre a inovação tecnológica e a obtenção de vantagens competitivas sustentáveis. Outras variáveis também foram identificadas e que exercem influência sobre esse vínculo, a regulação Governamental, as Condições Econômicas e a Atitude estratégica das Empresas. Um Modelo esquemático foi usado para registrar e facilitar a visualização dessas relações. Na segunda fase, foi desenvolvida uma pesquisa quantitativa junto a uma amostra de 350 consumidores de celulares com o objetivo de validar o Modelo. Na fase preparatória, foram realizados dois pré-testes, envolvendo 220 consumidores. Para a análise dos dados colhidos, foram aplicados procedimentos estatísticos univariados e multivariados; a Análise Fatorial e a Modelagem de Equações Estruturais foram as duas técnicas aplicadas. O estudo concluiu que as operadoras e os fabricantes de aparelhos celulares buscam a convergência digital a partir do emprego de inovações tecnológicas, obtendo serviços e produtos inovadores que são oferecidos aos consumidores. Entretanto, para que essas organizações consigam gerar vantagens competitivas e sustentá-las, é necessário que os consumidores sejam capazes de perceber que os produtos e serviços inovadores apresentem valor agregado significativo.

A tese teve como objetivo analisar os processos de desenvolvimento e compartilhamento intra-empresarial de competências organizacionais. Foi analisada a relação entre a Telemig Celular e as empresas que com ela compunham, em junho de 2002, a cadeia de valor para provimento de serviços de telefonia celular. O desenvolvimento das competências organizacionais foi analisado à luz da perspectiva de oferta dos serviços de 3G. A Telemig Celular foi analisada por meio de entrevistas e um workshop junto ao corpo gerencial. As demais empresas da cadeia foram abordadas via entrevistas junto às gerências de RH e estratégia. A utilização do modelo de Fransman mostrou que as relações entre as empresas ainda não constituem efetivas parcerias. Os elos mais forte da cadeia – indústria de equipamentos, baseada no domínio tecnológico, e operadoras, baseadas no acesso ao usuário final - têm liderado as decisões mais importantes da cadeia. Observou-se que o desenvolvimento das competências organizacionais é mais estruturado na camada 1, em que há claras regras de desenvolvimento e proteção das competências, além de diretrizes e alocação de recursos para a realização de pesquisas. Também os investimentos em RH são existentes e mais conectados com a estratégia organizacional. Nas demais empresas da cadeia encontraram-se áreas de RH reduzidas, quando existentes, e que adotam práticas e políticas de gestão tradicionais. A pesquisa mostrou que falta às empresas e, principalmente, ao RH uma visão integrada de negócios e cadeia de valor, o que tem levado à subordinação das empresas brasileiras e menores às empresas multinacionais e maiores. / This paper aimed to analyze the processes of development and intra-company sharing of organizational competencies. It looked at the relationship between Telemig Celular company and its counterparts making up the value chain in June 2002 for providing cellular telephone services. The organizational competency development was considered in the light of the 3G-service supply perspective. Telemig Celular was analyzed through interviews and a workshop with its managers. The other companies in the chain were approached through interviews with their strategy and HR managements. By using Fransman's model it was shown that the company relationships are not effective partnerships yet. The strongest links in the chain —equipment industry relying on their technological supremacy, and carriers relying on end user access— have been taking the chain's most important decisions. The development of organizational competencies was observed to be more structured in layer 1, where there are clear development rules and competency protection, as well as guidelines and fund allocation for research. Also, HR investments are present, and they are more connected to organizational strategy. In the rest of the chain companies, the research found small HR areas, if any, adopting traditional management practices and policies. And it showed that companies, mainly their HR, lack an integrated view of business and value chain, which has been leading to the subordination of the Brazilian and smaller companies to the multinational and larger ones.

Orientador: Celso de Almeida / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-24T01:46:06Z (GMT). No. of bitstreams: 1 Mello_RodolphoContiGianiniFerreira_M.pdf: 1434278 bytes, checksum: c9d50dad0686c63ee7429ff495370ace (MD5) Previous issue date: 2013 / Resumo: Os fatores responsáveis pela vazão de dados em uma rede celular são o número de usuários alocados em uma célula e a taxa de dados de cada usuário. Desta forma, para alcançar melhores resultados em termos de vazão de dados, deve-se utilizar de técnicas que trabalhem com foco no produto destes dois parâmetros. Este trabalho consiste em uma análise comparativa entre diferentes sistemas CDMA sob a ótica da vazão de dados, tendo como foco sequências de espalhamento do tipo aleatórias e também de Walsh e detecção com filtro casado e com o detector multiusuário descorrelacionador (MUD-D - Multiuser Detector Decorrelator), além de considerar a presença de interferência interna e externa no sistema. O método utilizado para a análise e comparação consiste na modelagem matemática do enlace reverso de um sistema celular DS-CDMA em canal AWGN com controle perfeito de potência e com alguns parâmetros fixos, tais como, a taxa máxima de erro de bit ( ), a taxa mínima de dados por usuário (10 kbps, referente ao serviço de voz) e a potência máxima de transmissão de 0,5W por estação móvel. Este trabalho apresenta também uma análise comparativa entre um sistema DS-CDMA com filtro casado e outro com o detector MUD-D na presença de interferência externa. A análise comparativa do detector MUD-D com o filtro casado em ambiente com interferência externa e toda a análise da vazão de dados do sistema são contribuições do autor / Abstract: The factors responsible for the data throughput in a cellular network are the number of users allocated in a cell and the users' data rate. This way, to reach better results in terms of data throughput, one must use techniques that act with focus on the product of those two parameters. This work consists in a comparative analysis among different CDMA systems from the perspective of the data throughput, focusing on random and Walsh spreading sequences and detection method with matched filter and with the multi-user detector decorrelator (MUD-D), besides considering the presence of internal and external interference in the system. The analysis and comparison methods consist in the CDMA cellular system uplink mathematical modelling in an AWGN channel considering a perfect power control and some fixed parameters such as the maximum bit error rate ( ), minimum data rate per user (10 kbps, referring to the voice service) and maximum transmitting power of 0.5 W per mobile station. This work also presents a comparative analysis between a DS-CDMA system with matched filter and another with the MUD-D detector in the presence of external interference. The MUD-D and matched filter comparative analysis in a scenario with external interference and the whole system's data throughput analysis are the author's contribution / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

Orientador: Hugo Enrique Hernandez Figueroa / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-22T03:58:50Z (GMT). No. of bitstreams: 1 Moraes_MuriloOliveirade_M.pdf: 26552033 bytes, checksum: 9a9022f8aa6d5e4e72047f0798ad57da (MD5) Previous issue date: 2013 / Resumo: A complexidade dos sistemas eletrônicos atuais cria a demanda por mais componentes num mesmo sistema, ao mesmo tempo em que exige sistemas mais compactos. Esta dissertação apresenta o desenvolvimento, fabricação e testes de uma antena GSM quadribanda, integrada a um módulo rastreador automotivo produzido no mercado nacional. A antena opera dentro das faixas de freqüências correspondentes _as bandas GSM 850/900/1800/1900, com desempenho adequado para uso no sistema de comunicação GSM, estando em conformidade com testes de TRP, sendo o produto final homologado pela ANATEL e agências reguladoras de outros países. A antena é um monopolo com dobras especiais para ajuste de ressonância. O casamento da antena com o sistema _e realizado via um toco em curto dobrado, não trivial, otimizado para um casamento banda-larga ao longo do espectro GSM ocupado / Abstract: The complexity of today's electronic systems creates demand for more quantity and less cost of components in a system, at the same time that the system must be made smaller. This dissertation presents the design and tests of a quadband GSM antenna, embedded into an existing automotive tracking module produced in Brazil. The antenna operates within the GSM 850/900/1800/1900 bands, with performance suitable for its use in the GSM system, being in conformance with TRP tests. The final product is approved by Brazil's regulatory agency ANATEL and by other countries' agencies. The antenna is a monopole with special bandings for resonance adjustment. The antenna matching is achieved with a shorted bent stub, non-trivial, optimized for a broadband matching over the occupied GSM spectrum / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

Orientador: Celso de Almeida / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-26T13:51:01Z (GMT). No. of bitstreams: 1 OrozcoGarzon_NathalyVeronica_M.pdf: 2420238 bytes, checksum: 44b2e62e1f4262ea3a2a169999209c79 (MD5) Previous issue date: 2014 / Resumo: A principal contribuição desta tese é a proposta de um mecanismo com transmissão oportunista. Este método de transmissão é realizado apenas quando o desvanecimento no receptor estiver acima de um certo limiar. Neste sistema oportunista o transmissor e o receptor estão em constante comunicação através de um canal de realimentação e o receptor indica ao transmissor quando ele deve transmitir. Para a análise de desempenho do sistema oportunista vamos considerar um canal com ruído e desvanecimento plano e lento Rayleigh e também interferência de co-canal (CCI) vamos também considerar diferentes esquemas de modulação (BPSK, QPSK, 4-QAM, 16-QAM e 64-QAM). A análise de desempenho do sistema proposto baseia-se na probabilidade de erro de bit média (BER), para a qual expressões analíticas foram obtidas. Estas expressões foram verificadas usando o método de simulação de Monte Carlo, com excelente concordância entre os dois resultados. Além disso, foram consideradas a eficiência espectral e a potência de transmissão do sistema. Os resultados obtidos mostram que a transmissão oportunista pode combater o desvanecimento de forma eficiente, pois o sistema oportunista elimina os efeitos do desvanecimento quase em sua totalidade. Foi feita também uma comparação entre o sistema oportunista e um sistema ordinário para a comparação de desempenho. Além disso, a transmissão oportunista é menos sensível à interferência de co-canal. Várias curvas são apresentadas ilustrando a eficiência do mecanismo oportunista proposto em termos da probabilidade de erro de bit média / Abstract: This thesis proposes, as the main contribution, a new mechanism with an opportunistic transmission. This transmission method is realized just when the fading at receiver is above a threshold value. In this opportunistic system the transmitter and the receiver are in constant communication through a feedback link and the receiver indicates when the transmitter should transmit. To analyze the performance of the opportunistic system we consider a noise channel and a flat and slow Rayleigh fading channel in the presence of co-channel interference (ICC). We also consider different modulation schemes (BPSK, QPSK, 4-QAM, 16-QAM e 64-QAM). The performance analysis of the proposed system is based on the mean bit error probability (BER), for which analytical expressions are established. These expressions are verified using Monte-Carlo simulation method with excellent agreement between both results. Furthermore, we consider the spectral efficiency and the power transmission of this system. The opportunistic transmission can combat the fading efficiently. That is, once it eliminates the fading effects almost entirely. Moreover, it is made a comparison between the opportunistic system and the ordinary system performance. Furthermore, the opportunistic transmission is less sensitive to co-channel interference. Several figures are presented illustrating the efficiency of the proposed mechanism in terms of mean bit error probability / Mestrado / Telecomunicações e Telemática / Mestra em Engenharia Elétrica