Dissertations / Theses on the topic 'Transmitters and transmission'
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1
Kot, Alan Douglas. "Optimal weighted partial decision combining for fading channel diversity." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26710.
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A diversity combining scheme is examined that utilizes a demodulator's hard decisions in conjunction with knowledge of each decision's reliability. A maximum-likelihood bit decision is made, based on these partial decisions from the demodulator
and on measurements of the state of the fading channel. The technique is sub-optimal since hard decisions are processed, but it may find application in low cost receiver design. The technique is optimal in the sense that a minimum probability of bit error is achieved, given a set of partial decisions and knowledge of their reliability.
Performance analysis for the case of non-coherent frequency shift keying on a slow Rayleigh fading channel with additive white Gaussian noise includes the derivation of a tight upper bound on the probability of bit error, and estimates of the asymptotic performance relative to standard diversity schemes such as majority-voting, selection diversity, square-law, and maximal ratio combining. These results are supported by simulation results for bit and packet error rates in an example system. With five independent bit repeats and a BER of 10⁻³, the receiver is about 3 dB more efficient than majority-voting, and about 1 dB more efficient than selection diversity. The gain in efficiency, relative to the standard partial decision combination schemes, increases with the number of repeats.
The degradation in performance in a practical receiver implementation is addressed,
and it is demonstrated that near ideal performance may be obtained with only a few reliability weights quantized to a small number of levels. Furthermore, this performance is maintained over a wide range of average signal to noise ratio without having to adapt the reliability weights. When the reliability estimate is corrupted by additive white Gaussian noise, it is demonstrated that simple low- pass filtering of the signal strength estimate is sufficient to obtain near ideal performance.
The performance is degraded in the presence of cochannel interference, but for a moderate level of interference the performance is demonstrated to be superior to majority-voting or selection diversity.
Other results include a method to estimate the optimal quantization thresholds, and a method to obtain the probability of error of selection diversity receivers employing signal to noise ratio measurement quantization. The selection diversity analysis is applicable to the more general case of Rician fading.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
2
Apostolou, Nikolaos. "Signal synthesis with dynamically-changed power spectral density in a software defined radio transmitter." Thesis, Monterey, California. Naval Postgraduate School, 2003. http://hdl.handle.net/10945/874.
Full textAbstract:
Approved for public release; distribution is unlimitedThe objective of this thesis is to synthesize signals with a dynamically change power spectral density, in a SDR transmitter, utilizing the most appropriate channels, modulation schemes and transmission rates for communication, based on the noise profile (AWGN plus interferences) of the link, in order to achieve performance within some predefined acceptable levels. The objective is obtained by simulation.
Major, Hellenic Army
3
Asyhari, Agustian Taufiq. "Nearest neighbour decoding for fading channels." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610448.
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Park, Youngcheol. "Dual-Band Transmitters Using Digitally Predistorted Frequency Multipliers for Reconfigurable Radios." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5107.
Full textAbstract:
The objective of the proposed research is to develop simplified reconfigurable transmission systems with frequency multipliers for the transmission of complex modulated signals. Because they rely on nonlinear properties, frequency multiplier-based transmission systems require proper linearization techniques and accurate modeling of the signal transfer function. To accomplish these two goals, the author has developed techniques to model and linearize frequency multipliers and to digitize feedback signals for nonlinear characterization.
First, adaptive predistortion techniques and zonal transfer theories have been developed for modeling and linearization. The predistortion system has been verified by applying an IS-95B signal to various frequency multipliers built by the author.
Second, because the output signals at higher harmonic zones occupy wider frequency bandwidths than the signal in the fundamental zone does and thus make it harder to use traditional sampling techniques, a simplified but effective method called the sub-Nyquist sampling rate was developed and verified.
Third, two methods for reconfigurable transmitters using frequency multipliers in conjunction with digital predistortion linearizers were developed. Both methods make it possible to transmit complex signals via frequency multipliers by using dual-band transmission systems that incorporate frequency multipliers that are based on linearization techniques. One of these methods uses a circuit topology that can be switched between a fundamental-mode in-phase combined amplifier and a push-push frequency doubler using input phasing. The second suggested method uses a fundamental-frequency power amplifier followed by a varactor multiplier that can be bypassed with an RF switch.
This work will contribute to the development of low-cost and size-effective reconfigurable transmission systems because it requires fewer transmitting components and needs less sampling of the feedback networks.
5
Coll, Eric. "Motion compensated interpolation for television standards conversion." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65468.
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6
Sweeney, Dennis G. "Adaptive power control as a fade countermeasure on satellite links." Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/39716.
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7
Lee, King F. "Space-time and space-frequency coded orthogonal frequency division multiplexing transmitter diversity techniques." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/14981.
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8
Lee, Chang-Ho. "Design and development of a ku-band transmitter for satellite communication applications." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/14722.
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王徐芳 and Xufang Wang. "Multiresolution joint source and channel coding for wireless communications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31225299.
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10
盧志明 and Chi-ming Lo. "Analytical evaluation of wireless digital communication performance over fading channels." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B3124208X.
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李世榮 and Sai-weng Lei. "Adaptive interleaving for orthogonal frequency division multiplexing systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31224702.
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吳萬雄 and Man-hung Ng. "Bandwidth-efficient pilot-symbol-aided techniques for fading estimation in multipath fading channels." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2001. http://hub.hku.hk/bib/B31242212.
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13
Wang, Xiangyang, and 王向陽. "Transmit diversity in CDMA for wireless communications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B31246072.
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14
Huang, Weifeng. "Simulation of adaptive equalization in two-ray, SIRCIM, and SMRCIM mobile radio channels." Thesis, Virginia Tech, 1991. http://hdl.handle.net/10919/42228.
Full textAbstract:
This work presents a study of the adaptive equalization techniques
designed to improve the bit error rates of digital transmissions degraded by
intersymbol interference in radio communication. This thesis considers the
following structures: the linear transversal equalizer (LTE), the decision feedback
equalizer (DFE), the lattice equalizer, and the maximum likelihood sequence
estimation (MLSE) equalizer. Least mean square (LMS) and recursive least
squares (RLS) algorithms are used as the adaptive algorithms for these equalizers.
Lattice-DFE, DFE, and MLSE with an RLS algorithm are recommended to be
implemented in mobile systems because of their better performances. A two-ray
Rayleigh fading channel model is used to simulate the mobile channels. The
results show that adaptive equalization can significantly improve the performance
of mobile communications if the channel does not change too fast. The simulation
shows that if the delay (T) of the second ray is too small, the adaptive
equalization will degrade the BER performance, and the value of T at which the
adaptive equalizer can improve the BER is determined by the speed of the mobile
channel variation. Also, simulation results obtained by using SIRCIM, a real
world indoor channel simulator, shows that adaptive equalization has good
performance in slowly varying channels. An equalizer working in indoor high data
rate systems has a BER less than 10-3 at 15 dB Eb/Noâ ¢ The SMRCIM urban
channel model is also developed and implemented for equalization simulation.
Finally, equalization structures for differential modulation techniques are
proposed.
Master of Science
15
劉慶強 and Hing-keung Lau. "Pilot-symbol-aided techniques for spectrally efficient signals in multipath-fading channels." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1997. http://hub.hku.hk/bib/B31237198.
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Bailey, Brian Douglas. "Design of a video measurement system." Thesis, Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/80071.
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Leonardo, Elvio João. "Produto e razão de variáveis generalizadas de desvanecimento e aplicações em desempenho de sistemas de comunicações = Product and ratio of generalized fading variables and applications in the performance of communication systems." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/261025.
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Orientador: Michel Daoud YacoubTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Resumo: O resumo poderá ser visualizado no texto completo da tese digital
Abstract: The abstract is available with the full electronic document
Doutorado
Telecomunicações e Telemática
Doutor em Engenharia Elétrica
18
Nunes, Adailton Antônio Galiza 1988. "Projeto e análise de desempenho de simuladores para canais de desvanecimento alpha-mu." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259345.
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Orientador: José Cândido Silveira Santos FilhoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: O resumo poderá ser visualizado no texto completo da tese digital
Abstract: The abstract is available with the full electronic document
Mestrado
Telecomunicações e Telemática
Mestre em Engenharia Elétrica
19
Ribeiro, Thatiane Cristina dos Santos de Carvalho 1982. "Analise de desempenho de transmissão de video em redes IEEE 802.11 visando a estruturação de canais de retorno para TV digital." [s.n.], 2008. http://repositorio.unicamp.br/jspui/handle/REPOSIP/261690.
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Orientador: Yuzo IanoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
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Resumo: A transmissão de vídeo em redes Wireless é abordada pela pesquisa, devido o grande aumento na utilização dessas redes na ultima década. O acesso à banda larga por essas redes é feito de forma eficiente, rápida e com baixo custo de implementação e manutenção da rede. A motivação para o desenvolvimento é utilizar essas redes e a rede IPTV para promover a interatividade e uma forma do canal de retorno para Sistemas de Televisão Digital, que estão sendo implementadas atualmente no Brasil. O canal de Retorno da TV Digital é importante para o sistema, pois um dos objetivos é prover a interatividade entre os usuários. Isso deve ser feito de forma simples com baixo custo e com tecnologia compatível a região do usuário. A simulação trata de um sistema de transmissão unicast que seria semelhante a uma interatividade local e dedicada. O usuário transmite o conteúdo de uma só vez. Os dados que são transmitidos pela provedora de serviços, são armazenados no set-top-box, e só são modificados em caso de novo fluxo de dados, quando há atualização ou acesso a nova área de serviços. Os testes feitos durante a pesquisa, transmitem conteúdo em tempo real e avaliam de forma quantitativa o desempenho das redes IEEE 802.11b e IEEE 802.11g.
Abstract: The streaming video transmission on Wireless networks is concerned in the research due to the large increase in the use of such networks in the last decade. Broadband access for these networks is made efficiently, quickly and with low implementation and maintenance costs of the network. The motivation for developing this research is to use these networks and IPTV network to promote interactivity and a return channel for digital television system, currently being implemented in Brazil. The return channel is important for the Digital TV system, because one of the goals is to provide interactivity for the users. This should be done in a simple, low cost way and with technology compatible in the region of the user. The simulation deals with a unicast transmission system which is similar to a local and dedicated interactivity. The user transmits all the contents at once. The data transmitted by a service provider are stored on set-top box and are modified only in case of new data flow, when there are updates or access to new area of services. The tests performed during the research, it was broadcasted contents in real time and evaluated quantitative the performance of IEEE 802.11b and IEEE 802.11g networks.
Mestrado
Telecomunicações e Telemática
Mestre em Engenharia Elétrica
20
Teixeira, Bernardo Vieira 1988. "Projeto e análise de desempenho de simulador para canais de desvanecimento Nakagami-m." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259344.
Full textAbstract:
Orientador: José Cândido Silveira Santos FilhoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: Em comunicações sem fio, o fenômeno de desvanecimento por múltiplos percursos é modelado por meio de várias distribuições estatísticas, como por exemplo, Rayleigh, Rice, Hoyt e Nakagami-m. Este trabalho propõe e analisa um novo esquema de simulação fase-envoltória para canais de desvanecimento do tipo Nakagami-m. As principais vantagens do esquema proposto são (i) permitir valores reais arbitrários do parâmetro de desvanecimento, (ii) corresponder às estatísticas de primeira ordem exatas do modelo Nakagami-m e (iii) fornecer uma excelente aproximação às estatísticas de segunda ordem associadas tradicionalmente ao modelo Nakagami-m. A análise do simulador proposto é feita com base na obtenção de expressões exatas e em forma fechada para estatísticas importantes de segunda ordem, a saber: (i) funções densidade de probabilidade conjuntas envolvendo a envoltória, a fase e suas derivadas temporais, (ii) função densidade de probabilidade de segunda ordem da envoltória, (iii) taxa de cruzamento de nível, (iv) duração média de desvanecimento e (v) taxa de cruzamento de fase. Como subproduto, são também obtidas expressões exatas em forma fechada para a função de distribuição acumulada da fase Nakagami-m e sua inversa. O esquema proposto á baseado na combinação em cascata de dois simuladores existentes para canais Nakagami-m, random-mixture e rank - matching, superando ambos em desempenho. Para efeito de comparação, algumas estatísticas de segunda ordem desconhecidas para estes dois simuladores são também obtidas de forma exata e fechada
Abstract: In wireless communications, the multipath fading phenomenon is modeled by various statistical distributions such as Rayleigh, Rice, Hoyt, and Nakagami-m. This work proposes and analyzes a new phase-envelope simulation scheme for Nakagami- m fading channels. The main advantages of the proposed scheme are (i) to allow for arbitrary real values of the fading parameter, (ii) to exactly match the Nakagami-m first order statistics, and (iii) to closely match the second-order statistics classically assigned to Nakagami-m fading. The analysis of the proposed simulator is performed by deriving exact closed-form expressions for important second-order statistics, namely (i) joint probability density functions involving the envelope, the phase, and their time derivatives, (ii) second-order probability density function of the envelope, (iii) level crossing rate, (iv) average fade duration, and (v) phase crossing rate. As a byproduct, we also obtain exact closed-form expressions for the cumulative distribution function of the Nakagami-m phase and its inverse. The proposed scheme is based on a cascade combination of two existing Nakagami-m fading channel simulators, random - mixture and rank - matching, outperforming the both. For comparison, some unknown second-order statistics of these two simulators are also obtained in exact closed form
Mestrado
Telecomunicações e Telemática
Mestre em Engenharia Elétrica
21
Krishnan, Aravind. "On the fading parameters characterization of the alpha-mu distribution = measurements and statistics = Caracterização dos parâmetros de desvanecimento da distribuição alfa-mu: medidas e estatísticas." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259680.
Full textAbstract:
Orientadores: Michel Daoud Yacoub, Ugo Silva DiasDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: Esta tese apresenta os resultados de medidas de campo conduzidas na freqüência de 5.5 GHz, com o objetivo de caracterizar os parâmetros do modelo de desvanecimento alpha-mu. Mais especificamente, uma quantidade de situações é investigada para se determinar a densidade de probabilidade e a função de autocorrelação destes parâmetros. O range de valores possíveis são então sugeridos baseado nos dados empíricos. Adicionalmente, as variações instantâneas da magnitude dos parâmetros correspondentes são mostradas em função do deslocamento do receptor ao longo do percurso. Os resultados provêem informações importantes sobre a utilidade prática do modelo alpha-mu mostrando, em seguida, que as estatísticas do sinal recebido se distanciam bem daquelas dos modelos conhecidos
Abstract: This thesis presents the results of field trial measurements conducted at a frequency of 5.5 GHz in order to characterize the parameters of the !-? fading model. More specifically, a number of situations are investigated in which the probability density function and the autocorrelation function of these fading parameters are described. The ranges of possible practical values of the parameters are then suggested as an outcome of the empirical data. In addition, the instantaneous magnitude variations of corresponding parameters are shown as a function of the receiver position along the path. The results provide important information about the practical usefulness of the !-? fading model, showing, in addition, that the received signal statistics greatly departs from the well known statistical models
Mestrado
Telecomunicações e Telemática
Mestre em Engenharia Elétrica
22
Tejerina, Gustavo Rodrigues de Lima 1987. "Distribuição conjunta fase-envoltória eta-mu generalizada." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259660.
Full textAbstract:
Orientador: Michel Daoud YacoubDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: Esta dissertação propõe um modelo generalizado para a distribuição de desvanecimento eta-mu. O novo modelo está fundamentado na introdução de um parâmetro que afeta o equilíbrio do número de clusters de multipercurso nos sinais fase e quadratura. Apesar da inserção deste novo parâmetro, algumas expressões relativas à distribuição da fase foram obtidas em sua forma fechada. Também, foi observado por meio de métodos numéricos que a distribuição da envoltória foi afetada pelo parâmetro em questão. Alguns gráficos são apresentados com o intuito de retratar o comportamento das novas distribuições marginais. Reescrevendo o novo parâmetro em termos do parâmetro de desvanecimento mu, novas expressões simplificadas de fase são definidas. Diante do proposto, estatísticas de ordem superior relativas à taxa de cruzamento de fase são determinadas e alguns gráficos são apresentados
Abstract: This dissertation proposes an improved and more realistic model for the eta-mu fading distribution. The principle behind this new model consists in the introduction of a parameter affecting the balance of number of multipath clusters in the phase and quadrature signals. Regardless of this new parameter, the phase-related formulations are still presented in closed-form expressions. On the other hand, the envelope distribution was affected by this parameter, unfortunately, no closed-form equations were found for this case. Plots are shown to describe the phase and the envelope of the new proposed distribution. Assuming some specific conditions, the new parameter may be rewritten as a function of fading parameter mu, and a new simplified phase distribution is attained. Moreover, with the proposed fading model, high order statistics related to phase crossing rate are then derived
Mestrado
Telecomunicações e Telemática
Mestre em Engenharia Elétrica
23
Hoefel, Roger Pierre Fabris. "CDMA/PRMA : um mecanismo de controle de acesso ao meio para transmissão de pacotes em sistemas sem fio de terceira geração." [s.n.], 2000. http://repositorio.unicamp.br/jspui/handle/REPOSIP/260670.
Full textAbstract:
Orientador: Celso de AlmeidaTese (doutorado) - Umiversidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: O objetivo deste trabalho é o de analisar, caracterizar e apresentar soluções para o excitante desafio de projetar protocolos de acesso para o transporte de pacotes multimídia no enlace reverso de sistemas celulares terrestres que empregam interface do ar do tipo TD/DS-CDMA (Time Division/Direct Sequence Code Division Multiple Access). Os estudos relativos aos aspectos inerentes à transmissão de pacotes em sistemas TD/DS-CDMA são particularizados na análise dos protocolos CDMA/PRMA (Code Division Multiple Access/ Packet Reservation Multiple Access) e Slotted CDMA/ALOHA. CDMA/PRMA é um protocolo de múltiplo acesso híbrido, no qual se aplicam os conceitos de multiplexação no tempo~por código e de alocação de recursos por meio de reserva. O acesso controlado ao canal do protocolo CDMA/PRMA permite a redução da variação da carga instantânea do canal e, conseqüentemente, redução da interferência de múltiplo acesso em relação ao protocolo Slotted CDMA/ ALOHA, onde os terminais acessam no próximo slot de tempo tão logo tenham pacotes a transmitir. Utiliza-se simulação computacional de maneira intensiva para à obtenção de resultados concernentes ao desempenho dos protocolos CDMA/PRMA e Slotted CDMA/ ALOHA em distintas condições operacionais. Estes resultados são validados por análises numéricas. Entre outros aspectos deste trabalho, destaca-se: (i) o modelo do ponto de equilíbrio proposto para os protocolos CDMA/PRMA e Slotted CDMA/ ALOHA; (ii) as expressões numéricas propostas para uma análise de desempenho do protocolo CDMA/PRMA; (iii) o desenvolvimento de um simulador de rede de pacotes para a investigação dos efeitos da interferência externa nas redes de pacotes CDMA/PRMA e Slotted CDMA/ ALOHA; (iv) efeitos dos parâmetros de projeto no desempenho dos protocolos CDMA/PRMA e Slotted CDMA/ ALORA; (v) estudo do desempenho dos protocolos CDMA/PRMA e Slotted CDMA/ ALORA com tráfego de vídeo com taxa variável e tráfego de dados WWW; (vi) a investigação dos efeitos do controle de potência, do desvanecimento rápido e do desvanecimento lento no desempenho dos protocolos CDMA/PRMA e Slotted CDMA/ ALORA com tráfego multimídia; (vii) o projeto integrado do protocolo CDMA/PRMA com receptor de detecção conjunta descorrelacionadora
Abstract: This thesis has the objective of to analyze, to characterize and to propose solutions to the challenge of design medium access control protocols for transmission of multimedia packets over the reverse channel of land mobile cellular systems based on TD/DS-CDMA (Time Division/Direct Sequence Code Division Multiple Access) air interface. Some inherent aspects of packet transmission over the reverse link of TD/DS-CDMA systems are particularized in the analysis of the CDMA/PRMA (Code Division Multiple Access/Packet Reservation Multiple Access) and Slotted CDMA/ ALOHA protocols. The joint CDMA/PRMA protocol is a hybrid multiple-access technique that combines time-division, code-division and Reservation ALOHA concepts. The CDMA/PRMA medium access control brings to reduction of the users variance on the channel, so a larger capacity is obtained in relation to the Slotted CDMA/ ALOHA protocol, where a mobile station accesses a time slot as soon as it has packets to transmit. It is used intensely computational simulation techniques to obtain some performance results concerning to CDMA/PRMA Slotted and CDMA/ ALOHA behavior over distinct operational conditions. It is utilized numerical techniques to validate some of obtained results. It is emphasized the following aspects of this Thesis: (i) a equilibrium point analysis model for the CDMA/PRMA and Slotted CDMA/ ALOHA protocols; (ii) some numerical expressions that permits to analyze the CDMA/PRMA behavior on voice-only traffic; (iii) a system level network simulator developed to assess and to compare the intercell interference effects on the CDMA/PRMA and Slotted CDMA/ ALOHA protocols performance; (iv) the design parameters effects on the performance of CDMA/PRMA and Slotted CDMA/ALOHA systems; (v) some studies of CDMA/PRMA and Slotted CDMA/ALOHA behavior on mixed voice/variable bit rate video and voice/WWW browsing traffic; (vi) some analysis of the imperfect power control effects, slow and fast fading effects on the capacity of CDMA/PRMA and Slotted CDMA/ ALOHA protocols; (vii) a integrated design of CDMA/PRMA protocol and a multiuser decorrelator detector
Doutorado
Telecomunicações e Telemática
Doutor em Engenharia Elétrica
24
Ferdinando, Érick Mascagni 1988. "Estatísticas de ordem superior do desvanecimento Kappa-Mu extreme." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259663.
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Orientador: Michel Daoud YacoubDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: Estudos recentes têm mostrado a relevância da pesquisa de modelos de desvanecimento em condições severas. Um desses modelos mais recentes é conhecido como desvanecimento k-? Extreme. Esta dissertação apresenta algumas aproximações em fórmula fechada para as estatísticas de ordem superior do modelo de desvanecimento k-? Extreme. A razão para as aproximações surge do fato de que a formulação clássica para encontrar a taxa de cruzamento de nível possui limitações, que afetam sua aplicação no modelo de desvanecimento aqui estudado. A limitação básica diz respeito ao fato de a formulação clássica aplicar-se apenas a processos contínuos, o que não reflete o caso k-? Extreme. Com base nisso, e na análise de curvas empíricas, cujos diversos dados de campo enquadram-se nas estatísticas de primeira ordem do modelo k-? Extreme, as propostas de aproximações foram formuladas. As comparações com os dados de campo mostram que as aproximações propostas fornecem excelentes resultados
Abstract: Recent studies have shown the research relevance of fading models under severe fading conditions. One of these newest models is known as k-? Extreme fading. This dissertation presents some closed-form approximations to the high-order statistics of the k-? Extreme model. The reason for the approximations arises from the fact that the classical formulation to find the level crossing rate has limitations, which affect its applicability in the fading model studied here. The basic limitation of the classic formulation concerns the fact that it applies to continuous processes, which is not the case of the k-? Extreme. In light of this, and in the analysis of empirical curves, whose different field data closely follow the first-order statistics of the k-? Extreme model, the proposed approximations have been formulated. The comparisons with field data show that the proposed approximations yield excellent results
Mestrado
Telecomunicações e Telemática
Mestre em Engenharia Elétrica
25
Minango, Negrete Juan Carlos 1987. "Avaliação de desempenho da técnica de multiplex espacial na presença de interferência de co-canal." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258819.
Full textAbstract:
Orientador: Celso de AlmeidaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
Made available in DSpace on 2018-08-26T09:28:35Z (GMT). No. of bitstreams: 1 MinangoNegrete_JuanCarlos_M.pdf: 1358924 bytes, checksum: 0b87bf307832cb8c65d04765674c0306 (MD5) Previous issue date: 2014
Resumo: O uso da técnica de multiplex espacial, transmissão de feixes de símbolos independentes usando múltiplas antenas de transmissão, tem sido proposta para atingir a exigência de taxas de dados maiores dos futuros sistemas de comunicações sem fio de banda larga. No entanto, quando a técnica de multiplex espacial é aplicada a uma rede celular, seu desempenho é afetado pela interferência de co-canal. Este trabalho avalia e compara os efeitos da interferência de co-canal na taxa de erro de bit média, BER, entre sistemas de transmissão digital com multiplex espacial e sistemas de transmissão digital com uma única antena de transmissão, onde os parâmetros da potência de transmissão e eficiência espectral são levados em consideração, a fim de se fazer comparações justas entre os dois sistemas. O enlace direto em um ambiente com desvanecimento plano e lento do tipo Rayleigh na presença de um interferente de co-canal dominante foi considerado. Além disso, o uso do detector ótimo, MV, no receptor e os esquemas de modulação BPSK, QPSK e M-QAM foram também considerados. Simulações de Monte Carlo foram feitas para a obtenção dos desempenhos em termos da BER como uma função da relação sinal-ruído por bit, Eb/N0, e da relação sinal-interferência, SIR. Os resultados da avaliação e comparação de desempenho entre os sistemas com multiplex espacial e com uma única antena de transmissão apresentados neste trabalho, constituem uma ferramenta importante a fim de se conhecer os benefícios reais da técnica de multiplex espacial aplicada a uma rede celular, como por exemplo nos padrões WiMAX ou LTE
Abstract: Spatial multiplexing technique, consisting of independent symbol transmission on multiple transmission antennas, has been proposed to meet the requirement for higher data rates of future wireless broadband communication systems. However, when spatial multiplexing technique is applied to a cellular network, the performance is affected by co-channel interference. This work evaluates and compares the effects of co-channel interference on the mean bit error rate, BER, of spatial multiplexing systems and single transmission antenna systems, where transmit power and spectral efficiency parameters are taken into consideration, in order to make a fair comparison between both systems. The downlink of a cellular network in slowly-varying flat Rayleigh fading environment and in the presence of a dominant co-channel interferer is considered. Furthermore, the use of Optimum Detector on the receiver and BPSK, QPSK and M-QAM modulations is also considered. Monte Carlo simulations are realized for obtaining the performance in terms of the BER as a function of per-bit signal-to-noise ratio, Eb/N0, and signal-to-interference ratio, SIR. The evaluation and comparison performance results between spatial multiplexing and a single transmission antenna systems presented in this work, are important tools in order to know the real benefits of spatial multiplexing technique applied to a cellular network, as the standards WiMAX or LTE
Mestrado
Telecomunicações e Telemática
Mestre em Engenharia Elétrica
26
Mello, Renata Valverde. "Contribuições ao dimensionamento de redes sem fio." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259665.
Full textAbstract:
Orientador: Michel Daoud YacoubDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
Made available in DSpace on 2018-08-13T23:58:49Z (GMT). No. of bitstreams: 1 Mello_RenataValverde_M.pdf: 868177 bytes, checksum: 291f0f645a4f99467efc3f39b3164f5e (MD5) Previous issue date: 2009
Resumo: Este trabalho aborda o dimensionamento de redes sem fio por meio da análise da probabilidade de outage visando contemplar sistemas com múltiplas classes de serviço. Esta é uma tarefa complexa, uma vez que deve considerar aspectos como o desvanecimento e a interferência do canal sem fio e o tráfego de diferentes classes de serviço. Inicialmente é analisada uma rede ad hoc com uma única classe de serviço a partir da probabilidade de outage conjunta. Em seguida, determina-se uma nova formulação analítica fechada para o cálculo da probabilidade de outage em sistemas com múltiplas classes de serviço. Esta foi prontamente validada por meio de simulações a eventos discretos. Desta maneira, a formulação proposta pode ser utilizada para o dimensionamento de redes sem fio multi-serviço sem a necessidade da realização de simulações. Este método apresenta vantagens como fácil implementação e baixo esforço computacional. Isto significa que foi obtida uma ferramenta de dimensionamento rápida e precisa.
Abstract: This work tackles with the problem of dimensioning wireless networks through the analysis of the outage probability aiming to contemplate multiservice traffic. This is an intrincate task, since it must consider aspects such as fading and interference in the wireless channel as well as multiservice traffic. First, an ad hoc network with only one class of service is analysed through the joint outage probability. Then, a novel closed formulation for the outage probability in multiservice systems is found. This formulation was promptly validated through discrete-event simulation. Therefore, the proposed formulation may be used for the dimensioning in multiservice wireless networks without the necessity of simulations. This method presents the advantages of easy implementation and low computational effort. This means that this tool enables a fast and precise dimensioning.
Mestrado
Telecomunicações e Telemática
Mestre em Engenharia Elétrica
27
Snyman, A. (Anton). "Synthesizer modulation for wideband FM generation." Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/49736.
Full textAbstract:
Thesis (MScEng)--University of Stellenbosch, 2002.ENGLISH ABSTRACT: The high performance of present digital phase-locked loops makes it the preferred choice for the generation of stable, low noise, tunable local oscillators in wireless communications applications. Most transmitters use superheterodyn techniques for up-conversion of the modulated signal to the required transmission frequency. Another technique is to inject the modulation signal into a phase-locked loop and consequently generate a frequency modulated signal directly at the transmission frequency. The aim of this study is to obtain a synthesizer configuration for the effective generation of wideband FM, considering both passive and active loop filters. The selection is based on synthesizer output signal quality, settling time and loop response to the modulation signal.
AFRIKAANSE OPSOMMING: Die hoe werksverrigting van fase-sluit lusse maak dit die verkiesde keuse vir die generasie van stabiele, lae ruis, verstelbare ossillators vir draadlose kommunikasie toepassings. Meeste senders gebruik "superheterodyn" tegnieke vir die op-menging van die gemoduleerde sein na die verlangde uitsaai frekwensie. 'n Ander tegniek is om die modulasie sein in 'n fase-sluit Ius te voer en so doende 'n gemoduleerde sein direk by die transmissie frekwensie te genereer. Die doel van hierdie studie is om 'n sintetiseerder konfigurasie te verkry vir die effektiewe opwekking van 'n wyeband FM sein, deur beide passiewe en aktiewe Ius filters in konsiderasie te neem. Die seleksie geskiet gebaseer op sintetiseerder uittree sein kwaliteit, sluit tyd en Ius gedrag as gevolg van die modulasie sein.
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Akamine, Cristiano. "Contribuições para distribuição, modulação e demodulação do sistema de TV digital ISDB-TB." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/261229.
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Orientador : Yuzo IanoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
Made available in DSpace on 2018-08-18T12:22:10Z (GMT). No. of bitstreams: 1 Akamine_Cristiano_D.pdf: 23517707 bytes, checksum: c51b616b01118b57a56b6af1f6bec625 (MD5) Previous issue date: 2011
Resumo: Este trabalho apresenta contribuições para o sistema brasileiro de TV digital. Considera-se a incompatibilidade do BTS (Broadcast Transport Stream) com os sistemas de distribuição de TV digital existentes e a dificuldade de implementação do modulador e demodulador ISDB-TB. Em primeiro lugar um algoritmo inovador capaz de realizar a compressão e adaptação do BTS tomando-o compatível com a maioria dos equipamentos comerciais do sistema DVB, é proposto. Em seguida, um detalhamento do funcionamento do modulador e demodulador é realizado utilizando-se expressões matemáticas e resultados obtidos em simulações computacionais. A partir do BTS, foi desenvolvido um simulador do modulador capaz de monitorar a entrada e saída de todos os blocos de processamento. No último estágio, vetores de RF são criados e podem ser utilizados em simulações computacionais e geradores de forma de onda arbitrária. Utilizando vetores de RF de emissoras de TV, foi desenvolvido um simulador do demodulador ISDB-TB. Esse simulador realiza as operações de sincronismo, estimação de canal, demodulação e decodificação de canal. Além disso, monitores da relação sinal ruído, constelação, resposta em frequência, perfil de atraso e taxa de erro de bits são utilizados para monitorar a reconstrução do BTS
Abstract: This paper presents contributions to the Brazilian digital TV system. It considers the incompatibility of (BTS) Broadcast Transport Stream with the existing digital TV distribution systems. The difficulty of implementation of the ISDB-TB modulator and demodulator are also taken into account. Firstly, an innovative algorithm able to compress and adapt the BTS in order to make it compatible with most DVB commercial equipment is implemented. Then, the detailed operation of the modulator and emodulator are obtained sing mathematical expressions and results from computer simulations. Using the BTS, it has been developed a simulator capable of monitoring the modulation input and output of all processing blocks. In the last stage, the RF vectors are created and can be used on computer simulations and arbitrary waveform generators. Using RF vectors of TV stations, an ISDB-Ts demodulator simulator was developed. This simulator performs the operations of synchronization, channel estimation, demodulation and channel decoding. In addition, monitors of signal to noise ratio, constellation, frequency response, delay profile and bit error rate are used to monitor the reconstruction of the BTS
Doutorado
Telecomunicações e Telemática
Doutor em Engenharia Elétrica
29
Guerreiro, André Saito 1986. "Capacidade de sigilo e indisponibilidade de sigilo em sistemas MIMOME." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259132.
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Orientador: Gustavo FraidenraichDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: Neste trabalho, considera-se a transmissão de mensagem confidencial em um canal sem fio em que transmissor, receptor e escuta possuem múltiplas antenas. O trabalho divide-se em duas partes. Na primeira parte analisamos a capacidade de sigilo ergódica e a probabilidade de indisponibilidade de sigilo para os cenários em que o canal é ergódico e não ergódico respectivamente, ambos na presença de desvanecimento estacionário com distribuição Rayleigh e considerando conhecimento do estado do canal (CSI) no receptor e na escuta. No cenário ergódico, deriva-se uma nova expressão fechada para a capacidade ergódica de sistemas em que há conhecimento do estado do canal no transmissor (CSIT) do canal principal e do canal de escuta, no qual permite-se que matriz covariância varie no tempo. Também deriva-se um limite inferior para capacidade de sigilo com CSIT, no qual a matriz covariância é fixa no período de transmissão. A primeira expressão é restrita ao limite da alta relação sinal ruído (SNR), n_t antenas no transmissor, n_r antenas no receptor (n_r > n_t) e n_e=n_t antenas na escuta (arranjo n_t x n_r x n_t). A segunda expressão é restrita ao arranjo de antenas n_t x n_t x n_t e potência do ruído do canal principal e do canal de escuta iguais. No cenário não ergódico, deriva-se uma nova expressão fechada para a probabilidade de indisponibilidade de sigilo no limite da alta SNR, em um arranjo de antenas 2 nr x 2 com n_r > 2. Também calcula-se um limite superior para a probabilidade de indisponibilidade de sigilo para outros arranjos de antena. Na segunda parte, considera-se uma escuta ativa que é capaz de atacar de forma inteligente o processo de estimação de canal. Focando em sistemas de transmissão baseados na decomposição generalizada em valores singulares (GSVD), diferentes técnicas de ataque são propostas e simulações computacionais são utilizadas para avaliar a eficiência de cada uma delas
Abstract: In this thesis, we consider the transmission of confidential information over a multiple-input multiple-output multiple-eavesdropper (MIMOME) wireless channel. The content is largely divided in two. In the first part we analyse the ergodic secrecy capacity and the secrecy outage probability in the ergodic and non-ergodic scenario respectively, both with stationary Rayleigh distributed fading channels and channel state information (CSI) at the receiver and eavesdropper. For the ergodic scenario we derive a new closed-form expression for the ergodic secrecy capacity with channel state information at the transmitter (CSIT) of the main and the eavesdropper channels, allowing the covariance matrix to be time-varying. A lower bound for the ergodic capacity with CSIT, in which the covariance matrix is fixed for the entire transmission period is also derived. The first expression is restricted to the high-SNR limit, with n_t transmit antennas, n_r receive antennas (n_r >= n_t) and n_e=n_t eavesdropper antennas (n_t x n_r x n_t setup). The second expression is restricted to the n_t x n_t x n_t antenna setup and equal noise power at both channels. For the non-ergodic scenario, we derive a new closed-form expression for the secrecy outage probability in the high-SNR limit, in a 2x n_r x 2 setup with n_r \ge 2. We also calculate an upper-bound for the secrecy outage probability in other antenna setups. In the second part we consider an eavesdropper which is able to attack the channel sounding process through intelligent jamming. We focus on transmission systems based on generalized singular value decomposition (GSVD). We propose and analyze, through computer simulations, the efficiency of several attack techniques that intend to disrupt the secret communication between legitimate users
Mestrado
Telecomunicações e Telemática
Mestre em Engenharia Elétrica
30
Kannan, Arumugam. "Communication Strategies for Single-User and Multiuser Slow Fading Channels." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19850.
Full textAbstract:
Technological progress in the field of wireless communications over the past few years has only been matched by the increasing demand for sophisticated services at lower costs. A significant breakthrough was achieved in the design of efficient wireless communication systems with the advent of the diversity concept. Spatial diversity exploits the availability of multiple spatial paths between the transmitter and receiver by placing antenna arrays at either end. In addition to improving the reliability of communication by creating redundant copies of the transmitted information at the receiver, wireless transceivers with multiple antennas exploit the spatial degrees of freedom to multiplex multiple streams of data and achieve significant gains in spectral efficiencies.
In this thesis, we design spatial diversity techniques for slow-fading wireless channels. There are two parts to this thesis: In Part I we propose spatial diversity techniques for point-to-point single-user wireless systems, while in Part II we propose multiuser cooperative diversity techniques for multiuser wireless communication systems.
In the first part, we propose a set of new wireless communication techniques for multiple-input, multiple-output (MIMO) channels over Rayleigh slow-fading wireless channels. We introduce MIMO transceivers that achieve high data rates and low error rates using a class of MIMO systems known as layered space-time (ST) architectures, which use low complexity, suboptimal decoders such as successive cancellation (SC) decoders. We propose a set of improved layered space-time architectures and show that it is possible to achieve near-optimal error performance over MIMO channels while requiring just SC decoding at the receiver. We show that these architectures achieve high rate and diversity gains. We also show that some of the proposed layered space-time architectures could find applications in multiple-access communications as low-complexity solutions for achieving near-optimum performance.
In the second part of this thesis, we propose novel techniques for cooperative communication between terminals in multiuser wireless communication systems. Cooperative communication is a concept where neighboring terminals share their antennas and signal processing resources to create a virtual transmit array . In addition to transmitting their own information, users in a cooperative communication system listen to transmission from other users and relay this information to the destination, thus creating multiple paths between transmitter and receiver. This form of diversity, known as cooperative diversity, helps improve the overall reliability of all the users in a network.
We start with a simple three node multiple-access system where two users are communicating with a common destination. We propose new high-rate cooperation strategies which achieve the full diversity gain offered by the cooperative channel for this simple system. We propose a new framework to address the tradeoff between cooperation and independent transmission over a multiple access channel and determine the conditions under which each idea is better than the other. Finally, we propose a high rate cooperation protocol which achieves the maximum diversity over a multiple access system with an arbitrary number of users and achieves high rates which scale favorably as the number of users increases.
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Benítez, Olivo Edgar Eduardo 1985. "Avaliação da eficiência espectral média do enlace reverso de redes celulares na presença de interferência de co-canal." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258821.
Full textAbstract:
Orientador: Celso de AlmeidaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
Made available in DSpace on 2018-08-19T05:03:35Z (GMT). No. of bitstreams: 1 BenitezOlivo_EdgarEduardo_M.pdf: 1173114 bytes, checksum: 1fc0181244059954a5184599ee11635c (MD5) Previous issue date: 2011
Resumo: A análise da eficiência espectral de uma rede celular é fundamental para se otimizar o aproveitamento da banda com cobertura na célula. Neste trabalho, o desempenho do enlace reverso de redes celulares é obtido em termos de sua eficiência espectral média. O cenário estudado considera um canal com perda de propagação exponencial, desvanecimento plano e lento Rayleigh e interferência de co-canal (ICC). A modelagem matemática do sistema leva em consideração vários parâmetros de planejamento, incluindo o fator de reuso de frequência, arranjo de antenas na estação rádio base (ERB), esquema de combinação por diversidade do tipoMRC (maximal ratio combining), modulação adaptativa e controle de potência. Neste contexto, uma expressão analítica da probabilidade de erro de bit (PEB) para o esquema de modulação M-QAM (multilevel quadrature amplitude modulation) é obtida em função da relação sinal-ruído por bit (Eb/N0) e da relação sinal-interferência (SIR, do inglês signal-to-interference power ratio), considerando a presença de um interferente dominante. Esta expressão constitui uma ferramenta importante para a avaliação correta do desempenho de sistemas digitais celulares. Os resultados mostram que utilizar um fator de reuso de 1, conjuntamente com controle de potência, em geral, é a maneira mais eficiente de se usar o espectro, garantindo cobertura total na célula
Abstract: The analysis of the spectral efficiency of a cellular network is essential to optimize the bandwidth usage with coverage, which is one of the major limitations on network planning. In this work, the performance of the uplink of cellular networks in terms of the mean spectral efficiency is obtained. The studied scenario considers a channel with exponential path-loss, slowly-varying flat Rayleigh fading and co-channel interference (CCI). The mathematical modeling of the system takes in consideration many parameters, including frequency reuse factor, antenna array at the base station, maximal ratio combining (MRC) diversity scheme, adaptive modulation and power control. In this context, an analytical expression of the bit error probability for the M-QAM (multilevel quadrature amplitude modulation) scheme as a function of the signal-to-noise ratio per bit (Eb/N0) and the signal-tointerference power ratio (SIR) is obtained, by considering the presence of a single dominant interferer. This expression is an important tool for the correct evaluation of the performance of digital cellular systems. The results show that using a frequency reuse of 1, jointly with power control, in general, is the most efficient way to use the spectrum, by ensuring full coverage in the cell
Mestrado
Telecomunicações e Telemática
Mestre em Engenharia Elétrica
32
Kim, Eung Jung. "Highly efficient supply modulator for mobile communication systems." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41058.
Full textAbstract:
Switching frequency modulation techniques, an inductor current sensing circuit for fast switching converter, and a dual converter are proposed, and the simulation results and experimental results are drawn. The experimental results for monotonic and pseudo-random modulation techniques show that the switching noise peak was effectively reduced as much as -19 dBc. The inductor current sensing circuit accurately tracks the output current of the switching converter that switches up to 30MHz. This current sensing circuit is used to drive the slow converter in the dual converter. The dual converter consists of a fast converter and a slow converter. The fast converter provides only the high frequency conponents in the output current, and the slow converter provides the majority portion of the output current with a higher efficiency. Therefore, the dual converter can have a fast transient response without sacrificing its efficiency. All chips are fabricated in a standard CMOS 0.18um process.
33
Sadeghi, Parastoo School of Electrical Engineering And Telecommunications UNSW. "Modelling, information capacity, and estimation of time-varying channels in mobile communication systems." Awarded by:University of New South Wales. School of Electrical Engineering And Telecommunications, 2006. http://handle.unsw.edu.au/1959.4/32310.
Full textAbstract:
In the first part of this thesis, the information capacity of time-varying fading channels is analysed using finite-state Markov channel (FSMC) models. Both fading channel amplitude and fading channel phase are modelled as finite-state Markov processes. The effect of the number of fading channel gain partitions on the capacity is studied (from 2 to 128 partitions). It is observed that the FSMC capacity is saturated when the number of fading channel gain partitions is larger than 4 to 8 times the number of channel input levels. The rapid FSMC capacity saturation with a small number of fading channel gain partitions can be used for the design of computationally simple receivers, with a negligible loss in the capacity. Furthermore, the effect of fading channel memory order on the capacity is studied (from first- to fourth-order). It is observed that low-order FSMC models can provide higher capacity estimates for fading channels than high-order FSMC models, especially when channel states are poorly observable in the presence of channel noise. To explain the effect of memory order on the FSMC capacity, the capacities of high-order and low-order FSMC models are analytically compared. It is shown that the capacity difference is caused by two factors: 1) the channel entropy difference, and 2) the channel observability difference between the high-order and low-order FSMC models. Due to the existence of the second factor, the capacity of high-order FSMC models can be lower than the capacity of low-order FSMC models. Two sufficient conditions are proven to predict when the low-order FSMC capacity is higher or lower than the high-order FSMC capacity. In the second part of this thesis, a new implicit (blind) channel estimation method in time- varying fading channels is proposed. The information source emits bits ???0??? and ???1??? with unequal probabilities. The unbalanced source distribution is used as a priori known signal structure at the receiver for channel estimation. Compared to pilot-symbol-assisted channel estimation, the proposed channel estimation technique can achieve a superior receiver bit error rate performance, especially at low signal to noise ratio conditions.
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Muñoz, Gallego David Alfonso. "Estimação da capacidade de redes sem fio do tipo Mesh." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/261829.
Full textAbstract:
Orientador: Paulo CardieriDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
Made available in DSpace on 2018-08-07T23:43:16Z (GMT). No. of bitstreams: 1 MunozGallego_DavidAlfonso_M.pdf: 701198 bytes, checksum: b2030ec2292717eca9c4a897402834ab (MD5) Previous issue date: 2005
Resumo: Este trabalho apresenta uma estimação da capacidade das redes sem fio tipo Mesh. As redes deste tipo têm topologias e padrões de tráfego únicos que as diferenciam das redes sem fio convencionais. Nas redes sem fio tipo mesh os nós atuam como clientes e como servidores e o tráfego e encaminhado para uma ou várias gateways em um modo multi-salto. A estimação da capacidade é baseada em estudos da Camada Física e MAC. Efeitos da propagação do canal são avaliados
Abstract: This work addresses the capacity of wireless mesh networks (WMN). This kind of networks has unique topologies and traffic patterns that differentiate them from conventional wireless networks. In WMN, the nodes act as clients and hosts and the traffic is forwarded to one or more gateways in a multihop fashion. The capacity estimation presented in this work is based on the physical and link layer investigation, using computer simulation
Mestrado
Telecomunicações e Telemática
Mestre em Engenharia Elétrica
35
Orozco, Garzón Nathaly Verónica 1986. "Análise de desempenho de uma proposta de transmissão oportunista sem fio em canais com desvanecimento Rayleigh e na presença de interferência de co-canal para diferentes esquemas de modulação." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258816.
Full textAbstract:
Orientador: Celso de AlmeidaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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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
36
Huang, Yan-Yu. "CMOS-based amplitude and phase control circuits designed for multi-standard wireless communication systems." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44908.
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Designing CMOS linear transmitter front-end, specially the power amplifiers (PAs), in multi-band wireless transceivers is a major challenge for the single-chip integration of a CMOS radio. In some of the linear PA systems, for example, polar- or predistortion-PA system, amplitude and phase control circuits are used to suppress the distortion produces by the PA core. The requirements of these controlling circuits are much different from their conventional role in a receiver or a phase array system. In this dissertation, the special design issues will be addressed, and the circuit topologies of the amplitude and phase controllers will be proposed.
In attempt to control the high-power input signal of a PA system, a highly linear variable attenuator with adaptive body biasing is first introduced. The voltage swing on the signal path is intentionally coupled to the body terminal of the triple-well NMOS devices to reduce their impedance variation. The fabricated variable attenuator shows a significant improvement on linearity as compared to previous CMOS works. The results of this research are then used to build a variable gain amplifier for linear PA systems that requires gain of its amplitude tuning circuits. Different from the conventional attenuator-based VGAs, the high linearity of the suggested attenuator allows it to be put after the gain stage in the presented VGA topology. This arrangement along with the current boosting technique gives the VGA a better noise performance while having a linear-in-dB tuning curve and better worst-case linearity.
The following part of the dissertation is about a compact, linear-in-degree tuned variable phase shifter as the phase controller in the PA system. This design uses a modified RC poly-phase filter to produce a set of an orthogonal phase vectors with smaller loss. A specially designed control circuit combines these vectors and generates an output signal with different phases, while having very small gain mismatches at different phase setting. The proposed amplitude and phase control circuits are then verified with a system level analysis. The results show that the proposed designs successfully reduce the non-linear effect of a wireless transmitter.
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Ribeiro, Antonio Marcelo Oliveira 1970. "Contribuições à caracterização estatística do canal de rádio móvel e estimação de parâmetros por máxima verossimilhança." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/260749.
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Orientador: Evandro ConfortiTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: Os efeitos provocados pelo ambiente de propagação sobre o sinal transmitido, assim como as condições impostas pela mobilidade do receptor, afetam diretamente a qualidade de serviço em sistemas de comunicação sem fios. Portanto, é necessário compreender e analisar os efeitos de degradação que o canal terá sobre um dado sistema de comunicação de dados e, dessa forma, avaliar a necessidade de medidas para mitigar os eventuais efeitos prejudiciais do canal. Neste trabalho, apresenta-se uma caracterização estatística do canal de rádio móvel, a partir de medições em campo nas bandas de 1800, 2500 e 3500 MHz, através de uma técnica simples de aquisição da envoltória do sinal. Em particular, são calculadas, para a envoltória, funções de distribuição de probabilidade, taxas de cruzamentos, duração de desvanecimento e sua distribuição, funções de correlação espacial e em frequência, tempo de coerência e largura de banda de coerência. Realiza-se, igualmente, uma análise comparativa destes resultados com os seguintes modelos estatísticos: Rayleigh, Nakagami, Rice, Weibull, Hoyt (Nakagami-q) e ?-?. Além disso, é dada ênfase à estimação de parâmetros dos modelos de canal de rádio, através de dois métodos: momentos (MoM) e máxima verossimilhança (ML). Neste contexto, obtém-se expressões para a variância e o intervalo de confiança, assintóticos, de estimadores ML, baseadas na informação de Fisher que uma amostra aleatória contém a respeito do parâmetro a ser estimado. De forma geral, foi observado um bom ajuste entre as medidas em campo e correspondentes curvas teóricas, para estatísticas de primeira e segunda ordem da envoltória. As medições em campo deste trabalho mostraram que os estimadores ML agruparam mais as curvas teóricas, em torno da curva experimental, quando comparados aos estimadores MoM. Adicionalmente, a matriz de covariância dos estimadores ML para ? e ?, obtida a partir das medições em campo, mostrou que a variância do estimador de ? é, pelo menos, dez vezes maior que aquela do estimador de ?. Igualmente, valores medidos de correlação espacial apresentaram bom ajuste aos modelos teóricos, em termos de uma tendência geral de variação. Em particular, curvas de distribuição cumulativa do tempo de coerência, , para medidas em campo em 3500MHz, mostraram que é maior que 1,7 ms, para 90% do tempo, quando o receptor se move a 30 km/h. Por fim, medidas em campo da largura de banda de coerência, em 1800MHz, revelaram que um valor de ?f < 60 kHz irá garantir um nível de correlação da envoltória maior que 0,9, para 90% do tempo
Abstract: The propagation environment effects on the transmitted signal as well as the conditions imposed by the receiver mobility directly affect the quality of service (QoS) in wireless communication systems. Therefore, it is necessary to understand and analyze the degradation effects inflicted by the channel on a given data communication system, in order to evaluate the measures to mitigate these deleterious effects. In this thesis, we present a statistical characterization of the mobile radio channel based on field measurements performed over the 1800, 2500, and 3500 MHz bands, using a simple technique for acquiring the signal envelope. In particular, envelope statistics for probability distribution functions were calculated, as well as the crossing rates, duration of fading and its distribution, spatial and frequency correlation functions, coherence time, and coherence bandwidth. A comparative analysis of these results was also carried out against the following statistical models: Rayleigh, Nakagami, Rice, Weibull, Hoyt (Nakagami-q), and ?-?. Also, emphasis is given to the parameter estimation of radio channel models using two methods: moments (MoM) and maximum likelihood (ML). In this context, expressions for the asymptotic variance and confidence interval of ML estimators were obtained, based on the Fisher information a random sample contains over the parameter to be estimated. In general, there was a good fit between the field measurements and corresponding theoretical curves for envelope statistics of first and second order. Field measurements of this work have shown that ML estimators grouped more the theoretical curves around the experimental one, when compared to MoM estimators. Additionally, the covariance matrix of ML estimators for ? and ?, obtained from field measurements, showed that the variance of ? estimator is at least ten times greater than the one of ? estimator. Moreover, measured values of spatial correlation showed a good .t to the theoretical models, in terms of a general tendency of variation. Particularly, cumulative distribution curves of the coherence time , for field measurements at 3500MHz, showed that is greater than 1,7 ms for 90% of time when the receiver is moving at 30 km/h. Finally, 1800- MHz field measurements of coherence bandwidth revealed that a value of ?f < 60 kHz will ensure a level of envelope correlation greater than 0.9 for 90% of time
Doutorado
Telecomunicações e Telemática
Doutor em Engenharia Elétrica
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Koloskova, O. A. "Magnifying transmitter." Thesis, Sumy State University, 2014. http://essuir.sumdu.edu.ua/handle/123456789/45600.
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The magnifying transmitter was intended by Nicola Tesla for the wireless transmission of electrical energy. It is a high power harmonic oscillator, an air-core, multiple-resonant transformer that can generate very high voltages. In normal operation the magnifying transmitter is relatively silent, generating a high power electric field, but if the output voltage exceeds the design voltage of the elevated terminal, high-voltage sparks will strike out from the electrode into the air. In his autobiography, Tesla stated that "...I feel certain that of all my inventions, the Magnifying Transmitter will prove most important and valuable to future generations."
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Schuartz, Fábio César. "Múltiplas antenas como alternativa para aumentar a taxa de extração de chaves secretas em redes veiculares com desvanecimento lento." Universidade Tecnológica Federal do Paraná, 2015. http://repositorio.utfpr.edu.br/jspui/handle/1/1797.
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A comunicação em redes veiculares ad hoc (VANETs) é comumente dividida em dois cenários, chamados veículo-a-veículo (V2V) e veículo-a-infraestrutura (V2I). Objetivando estabelecer uma comunicação segura contra espiões, trabalhos recentes tem proposto a troca de chaves secretas baseado na variação da força do sinal recebido (RSS). Entretanto, o bom desempenho de tal método depende da taxa de variação do canal, sendo mais apropriado a cenários em que o canal varia rapidamente, como geralmente é o caso da comunicação V2V. Já na comunicação V2I, o canal normalmente possui desvanecimento lento. Neste trabalho, é proposta a utilização de múltiplas antenas com o intuito de gerar artificialmente um canal de desvanecimento rápido, permitindo assim a extração de chaves secretas através da RSS em um cenário V2I. Análises numéricas mostram que o modelo proposto pode obter desempenho superior, em termos de taxa de extração de bits secretos, do que o modelo de salto em frequência proposto na literatura.The communication in vehicular ad hoc networks (VANETs) is commonly divided in two scenarios, namely vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I). Aiming at establishing secure communication against eavesdroppers, recent works have proposed the exchange of secret keys based on the variation in received signal strength (RSS). However, the performance of such scheme depends on the channel variation rate, being more appropriate for scenarios where the channel varies rapidly, as is usually the case with V2V communication. In the communication V2I, the channel commonly undergoes slow fading. In this work we propose the use of multiple antennas in order to artificially generate a fast fading channel so that the extraction of secret keys out of the RSS becomes feasible in a V2I scenario. Numerical analysis shows that the proposed model can outperform, in terms of secret bit extraction rate, a frequency hopping-based method proposed in the literature.
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Knight, David. "Pre-synaptic regulation of transmitter release probability /." St. Lucia, Qld, 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16101.pdf.
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Moya, Osorio Diana Pamela 1985. "Simulador para avaliação da eficiência espectral média de redes celulares na presença de interferência de co-canal." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258823.
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Orientador: Celso de AlmeidaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: Na próxima geração de redes celulares, a ICC (Interferência de Co-Canal ) constitui a causa principal para a degradação do desempenho, especialmente para os usuários na borda da célula, o que é um grande obstáculo para alcançar amplas áreas de cobertura e alta eficiência espectral. Neste trabalho, o desempenho do enlace reverso de uma rede celular em termos da eficiência espectral média e na presença de ICC é avaliado mediante uma simulação semi-analítica. Foram considerados dois cenários, canal AWGN(Additive White Gaussian Noise) e canal com desvanecimento plano do tipo Rayleigh, além de um modelo de propagação com perda de percurso exponencial. A avaliação é feita para fatores de reuso clássicos e modulações M-QAM (Multi-Level Quadrature Amplitude Modulation). Considera-se também uma estratégia de controle de potência e modulação adaptativa baseada na SIR (Signal-to-Noise Interference) e a BER (Bit Error Rate). Adicionalmente, é analisada a utilização de arranjo de antenas para diminuição dos efeitos da interferência e técnicas de diversidade para mitigação dos efeitos do desvanecimento
Abstract: In the next generation of wireless cellular networks, the CCI (Co-Channel Interference) constitutes the primary cause of performance degradation, specially for cell edge users, which is a big obstacle to attain wide area coverage and high spectral efficiency. In this work, the performance of the uplink of cellular networks in terms of the mean spectral efficiency is evaluated through a semi-analytical simulation, by considering the presence of CCI. It was considered two sceneries, an AWGN (Additive White Gaussian Noise) channel and a Rayleigh flat fading channel, as well as an exponential pathloss propagation model. The evaluation is done for classical reuse factors and M-QAM (Multi-Level Quadrature Amplitude Modulation) modulations. It is also considered a power control strategy and adaptive modulation based on the SIR (Signal-to-Noise Interference) and BER (Bit Error Rate). Besides, it is analyzed the utilization of an antenna array to reduce the interference effects and diversity techniques to mitigate fading effects
Mestrado
Telecomunicações e Telemática
Mestre em Engenharia Elétrica
42
Gendron, Paul John. "A comparison of digital beacon receiver frequency estimators." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-09292009-020307/.
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Ajaz, Haroon. "Study of fade and inter-fade durations in Ku- and Ka- band frequencies using OLYMPUS satellite beacons." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-12042009-020112/.
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Laster, Jeff D. "Frequency scaling of rain attenuation on satellite links in the Ku/Ka-bands using OLYMPUS satellite data." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06162009-063211/.
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Varadarajan, Badri. "The Design of Linear Space-Time Codes for Quasi-static Flat-fading Channels." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5030.
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The reliability and data rate of wireless communication have traditionally been limited by the presence of multipath fading in wireless channels. However, dramatic performance improvements can be obtained by the use of multiple transmit and receive antennas. Specifically, multiple antennas increase reliability by providing diversity gain, namely greater immunity to deep channel fades. They also increase data rates by providing multiplexing gain, i.e., the ability to multiplex multiple symbols in one signaling interval.
Harvesting the potential benefits of multiple antennas requires the use of specially designed space-time codes at the transmitter front-end. Space-time codes introduce redundancy in the transmitted signal across two dimensions, namely multiple transmit antennas and multiple signaling intervals. In this work, we focus on linear space-time codes, which linearly combine the real and imaginary parts of their complex inputs to obtain transmit vectors for multiple signaling intervals.
We aim to design optimum linear space-time codes. Optimality metrics and design principles for space-time codes are shown to depend strongly on the codes' function in the overall transmitter architecture. We consider two cases, depending on whether or not the space-time code is complemented by a powerful outer error-control code.
In the absence of an outer code, the multiplexing gain of a space-time code is measured by its rate, while its diversity gain is measured by its raw diversity order. To maximize multiplexing and diversity gains, the space-time code must have maximum possible rate and raw diversity order. We show that there is an infinite set of maximum-rate codes, almost all of which also have maximum raw diversity order. However, different codes in this set have different error rate for a given input alphabet and SNR. Therefore, we develop analytical and numerical optimization techniques to find the code in this set which has the minimum union bound on error rate. Simulation results indicate that optimized codes yield significantly lower error rates than unoptimized codes, at the same data rate and SNR.
In a concatenated architecture, a powerful outer code introduces redundancy in the space-time code inputs, obtaining additional diversity. Thus, the raw diversity order of the space-time inner code is only a lower limit to the total diversity order of the concatenated transmitter. On the other hand, we show that the rate of the space-time code places an upper limit on the multiplexing ability of the concatenated architecture. We conclude that space-time inner codes should have maximum possible rate but need not have high raw diversity order. In particular, the serial-to-parallel converter, which introduces no redundancy at all, is a near-optimum space-time inner code. This claim is supported by simulation results.
On the receiver side, we generalize the well known sphere decoder to develop new detection algorithms for stand-alone space-time codes. These new algorithms are extended to obtain efficient soft-output decoding algorithms for space-time inner codes.
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Schmidt, David Glenn. "Digital-high definition television servicing curriculum for Santa Ana Community College." CSUSB ScholarWorks, 2002. https://scholarworks.lib.csusb.edu/etd-project/2202.
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The purpose of this project was to develop a semester length community college curriculum for a course in the theory and servicing of digital-high definition television for the students in the service technology field of electronics at Santa Ana Community College in Santa Ana, California. Additionally, it is designed with the current electronic service industry in mind.
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Heinrich, Ralph Robert 1954. "Análise das características de propagação em radio enlace de canais banda larga na faixa de UHF." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259662.
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Orientador: Michel Daoud YacoubDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: Este projeto de pesquisa objetiva responder a algumas questões sistêmicas levantadas por ocasião do início do desenvolvimento do sistema LTE-450, parte integrante do projeto RASFA - Redes de Acesso Sem Fio Avançadas, conduzido pelo CPqD - Fundação Centro de Pesquisa e Desenvolvimento em Telecomunicações, com recursos do FUNTTEL - Fundo para o Desenvolvimento Tecnológico das Telecomunicações. Esse projeto visa, como um de seus objetivos, o desenvolvimento de um sistema de rádio acesso sem fio LTE-450, operando na faixa de 450 a 470 MHz, baseado na tecnologia LTE - Long Term Evolution. A faixa de 450 a 470 MHz está atribuída em base global desde 2007 para o Serviço Móvel, conforme identificado pela União Internacional de Telecomunicações na World Radiocommunication Conference 2007. A Anatel - Agência Nacional de Telecomunicações - publicou a nova destinação de uso para a faixa de 450 a 470 MHz em 20 de dezembro de 2010, através da Resolução n º 558. Várias ações vêm sendo empreendidas em apoio ao uso da faixa 450 a 470 MHz, para a prestação de serviços banda larga sem fio para áreas rurais, como consta do Programa Nacional de Telecomunicações Rurais, publicado pela Portaria 431/2009 do Ministério das Comunicações, e do Plano Nacional de Banda Larga, publicado em 13 de maio de 2010. Entende-se que a faixa de 450 a 470 MHz é ideal para a implantação de serviços de banda larga sem fio em áreas rurais, devido às suas características de propagação. Por outro lado, a base de conhecimento sobre o canal rádio em sistemas de rádio acesso móvel banda larga considera o uso, em áreas urbanas, de faixas de frequências situadas entre 850 MHz e 3500 MHz. São notórias as diferenças entre as características de propagação nessas faixas e nas faixas de UHF, principalmente quando a área de prestação do serviço deixa de ser a urbana e passa a ser a rural. Nesse sentido, alguns requisitos sistêmicos podem ser questionados e mesmo redimensionados. Esses requisitos foram aqui endereçados através de levantamento de dados em campo e posterior análise crítica contra a base de conhecimento disponível. São questões como a amplitude do desvanecimento seletivo e por despolarização, a intensidade do ruído impulsivo, os modelos de propagação aplicáveis à área rural e à faixa de UHF, a variação da perda de percurso com a altura da antena do terminal e a discriminação de polarização da antena do terminal
Abstract: This research project aims to answer some systemic issues raised during the early development of the LTE-450 radio access system, part of a project RASFA - Advanced Wireless Networks Access, led by CPqD Foundation - Center for Research and Development in Telecommunications with resources of FUNTTEL - Technological Development of Telecommunications Fund. This project aims, as one of its objectives, the development of a LTE-450 wireless system, operating in the 450-470 MHz band, based on LTE - Long Term Evolution technology. The 450-470 MHz band is allocated, on a global basis, since 2007 for Mobile Service, as identified by the International Telecommunication Union in the World Radiocommunication Conference 2007. Anatel - The Brazilian National Telecommunications Agency has published a new destination for the 450-470 MHz band on December 20, 2010, through Resolution No. 558. Several actions have been undertaken in support of the use of the 450-470 MHz band, to provide wireless broadband services to rural areas, as set out in the National Rural Telecommunications Plan, published by the Decree 431/2009 of the Ministry of Communications and the National Broadband Plan (PNBL), published on May 13, 2010. It is understood that the 450-470 MHz band is ideal for deploying wireless broadband services in rural areas, due to its propagation characteristics. On the other hand, the base of knowledge about the mobile broadband access radio systems channel, considering the use in urban areas, situated between 850 MHz and 3500 MHz bands have notable differences between the propagation characteristics of these bands and the UHF bands, especially when the area of service provision ceases to be the urban and goes to the rural areas. Thus, some systemic requirements can be questioned and even resized. These requirements are addressed here through field data gathering and subsequent critical analysis against the knowledge base available. These issues are such as the extent of selective fading and depolarization, the intensity of the impulse noise, the propagation models applicable to the rural area and the UHF band, the variation of the path loss with the height of the terminal antenna and of terminal antenna polarization discrimination
Mestrado
Telecomunicações e Telemática
Mestre em Engenharia Elétrica
48
Gutierrez, Leon Jorge. "Universal digital radio transmitter for multistandard applications." Cergy-Pontoise, 2008. http://biblioweb.u-cergy.fr/theses/08CERG0433.pdf.
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L'objectif de la thèse était l'étude des nouvelles architectures d’émetteur permettant l'utilisation des amplificateurs de puissance (PA) non linéaires et à forte rendement. Parmi les techniques étudiées, une solution utilisant un codage Sigma Delta de l'enveloppe a été retenue. Cette technique représente une évolution de la méthode classique dite EER. Un signal est séparé dans ses composantes enveloppe et phase. L'enveloppe est codée par un modulateur Sigma Delta. Les signaux de phase (I et Q normalises par l'enveloppe du signal) sont combinés avant le PA donnant l'ensemble un signal à enveloppe constante. Cette méthode représente le meilleur compromis possible en termes de bande passante (utilisation d'un modulateur sigma delta et absence de système de contre-réaction pouvant limiter la bande complexité et linéarité. D'autre part, une étude de l'architecture d'émetteur a été effectuée donnant les caractéristiques suivantes: besoin d'un émetteur purement numérique pour des raisons de coût, intégration et simplicité, intérêt d'une architecture multistandard et multibande (émetteur reconfigurable), besoin de supprimer le bruit de quantification du point bloquant au niveau du combineur de sortie (haute vitesse, forte consommation), contrôle de puissance de 45 dB (systèmes CDMA). Nous avons apporté dans notre etude des solutions aux problèmes cités précédemment : un filtre interpolateur à fréquence variable de type Sample-and-Hold permet de réduire le bruit loin de la bande de transmission, mélangeur IQ large bande numérique à base de fonctions logiques (très base consommation et surface) qui simplifie le mélangeur 3 entrées analogique, la combinaison en sortie est faite en courant à l'aide de 2 convertisseurs numérique analogique 9bits (CNA). La conception d'un CNA en technologie BiCMOS a permis de valider son fonctionnement à 1. 4GHz et avec un contrôle de gain de 45dB. Sa consommation maximale (puissance de sortie=-6dBm ) est de 25 mW (résultats de mesure). Dans une deuxième partie, on a réalisé le design de toute l'architecture d'émetteur (sauf le modulateur sigma delta en technologie BiCMOS 0. 13um de STMicroelectronics. Les résultats de mesure montrent la validité du principe. Cet émetteur bas-coût a eté mesuré à 1. 8 Géch/s et il a une taille de 300x320 µm2. Le niveau de signal image mesuré es de -15 dBc pour cette fréquence d’échantillonnage. La plage dynamique de l’émetteur designé est de 35 dB pour des fréquences d’échantillonnage inférierures à 800 MHz et 25 dB pour des fréquences jusqu’à 1. 8 GHz. La puissance maximale differentielle en sortie est égale à –28 dBm pour chaque raie et la puissance dissipée est de 35 mW. Une nouvelle architecture d’émetteur radio multistandard reconfigurable et contrôlable en puissance permettant d’utiliser un amplificateur de puissance à fort rendement a eté intégrée sur silicium et validée. On considère que cette architecture represente une revolution dans les radiocommunications mobiles. On est capable de générer un signal à enveloppe constante et donc d'amplifier par n'importe quel amplificateur de puissance d'une façon très efficace. Dans le cadre d'une application multistandard, on est capable d'adresser tout type de normes de communication, n'étant pas limité par la bande et avec un contrôle de gain de 45 dB. Cet émetteur s'avère être une solution très prometteuse pour les nouveaux systèmes de transmission, d'autant plus de sa faible consommation (35 mW à forte puissance)The advance of technologies makes that the wireless terminals must handle not only with voice and data but also more complex functionalities such as music, video and so on resulting in high data rates. It involves the use of more and more complex modulation schemes to be handled in the system (non-constant envelope signals). To overcome the trade-off existing in actual communication systems in the design of both high efficient and linear multimode transmitters and to reduce the number of building blocks, a new low power, wideband wireless transmitter able to convert any RF signal into a constant envelope signal enabling the use of a nonlinear and efficient power amplifier is presented. In the transmitter architecture, two normalized phase signals and the envelope are separated and processed separately. A 1-bit 2nd order sigma delta modulator codes the envelope. Quantization noise is attenuated by a S&H interpolator introducing notches at multiples of the sampling frequency. Phase and Envelope signals are recombined and upconverted directly to radio frequencies using a novel full-digital, wideband quadrature modulator. This mixer takes advantage of the 1-bit sigma delta output. As both LOs and envelope signals are represented by two-level signals, the product of these signals (XOR function) leads to a two-level signal, which can be used as command signal in the multiplexors. Phase signals or theirs complements that are generated by a simple Inversion Block are passed through this multiplexor at the rate of driving signals. This enables to implement a high frequency, wideband mixer instead of a more complex three-input modulator. This IQ mixer is very simple to implementate as it uses only CMOS logic gates. The generation of the quadrature clock signals in the mixer is obtained by carefully design of two paths to avoid mismatch to assure an error less than 1o (only demonstrated in simulation) and the use of SR flip-flops to generate correctly the complementary signal prior to the divide-by-two circuit. Two asynchronous 9-bit DACs eliminate the 10-bit high-speed digital adder at the output of the IQ modulator and the 10-bit DAC before the PA, saving power and relaxing adder design constraints. Each DAC is divided into two full binary-weighted DACs of 4 and 5 bits. This topology enables to reduce the size ratios between the most and least significant bits related to a classic 9-bit binary-weighted structure (16 instead of 256). To test the speed and the gain control of the stand-alone DAC over 45 dB, a prototype DAC is designed in 0. 13 µm BiCMOS technology from STMicroelectronics together with a 1. 4 GHz 9-bit CMOS ROM-less direct digital frequency synthesizer (DDFS). Over the output power range, measurements show a SFDR>25 dB with a power dissipation of 25 mW at the maximum differential output power of -3 dBm (RL=50 Ω). The whole transmitter is designed and implemented and a protoype transmitter is built in 0. 13 m BiCMOS STMicroeletronics process. This low cost single chip digital radio transmitter demonstrates a data rate of 1. 8 GHz. The image level is measured to be -12 dBc at this sampling frequency. Dynamic range in the transmitter is 35 dB for sampling frequencies lower than 800 MHz and 25 dB for higher sampling frequencies up to 1. 8 GHz. For a two-tone signal, the maximum single-ended output power is -31dBm for each tone and the power dissipation is about 35 mW. This architecture enables flexible and software-defined transmitter. Sampling frequency in the sigma delta coder can be varied to adapt to different communications standards in terms of in-band and out-of-band noise requirements and variable LO frequencies can be used. Moreover, the transmitter can adapt dynamically the output power to the power amplifier depending of the required transmitted power at the output of the PA. The transmitter has demonstrated its potential for use as a universal transmitter for applications targeting any frequency band and modulation schema up to 900 MHz (carrier frequency) and occupies a die area of 300x320 µm2. The generated differential signal can be easily amplified by a switched-mode Power Amplifier (PA) in an efficient way because it presents constant-envelope and the PA can work in the saturation zone, which represents its optimal operation point
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Carvajal, Mora Henry Ramiro 1986. "Avaliação de desempenho do enlace reverso de redes celulares que utilizam a técnica CDMA com multiportadoras (MC-CDMA) em um canal rayleigh seletivo em frequência." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/258815.
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Orientador: Celso de AlmeidaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: Neste trabalho, é avaliado o desempenho do enlace reverso de redes celulares que utilizam a técnica de múltiplo acesso por divisão de código com multiportadoras (MC-CDMA) em termos da probabilidade de erro de bit média (BER) e da eficiência espectral média. O sistema de comunicações analisado utiliza a técnica MC-CDMA, um arranjo linear de antenas na estação rádio base, entrelaçamento em frequência, combinação de máxima razão (MRC), modulação adaptativa, controle de potência e um prefixo cíclico grande o suficiente para eliminar os efeitos da interferência intersimbólica (ISI) e da interferência entre portadoras (ICI). O cenário estudado considera a presença de interferência de múltiplo acesso (MAI) e interferência de co-canal (CCI). A caracterização do canal considera a presença de ruído aditivo gaussiano branco (AWGN), perda de propagação exponencial e desvanecimento lento e seletivo em frequência que segue a distribuição de Rayleigh. Neste contexto, expressões analíticas exatas e fechadas para a BER média tanto para a modulação BPSK, quanto para a modulação M-QAM são obtidas. A exatidão das expressões é validada através de simulações de Monte Carlo. Ademais, uma expressão para a eficiência espectral celular média é determinada, a qual é uma função do fator de reuso de canais, do incremento da largura de banda devido ao prefixo cíclico, do carregamento do sistema, do fator de espalhamento, dos raios da célula e da modulação utilizada. Os resultados indicam que utilizar um fator de reuso de canais de 1 é a maneira mais eficiente de usar o espectro. No entanto, esse fator de reuso é crítico em relação às taxas de transmissão. Ademais, evidenciando que a técnica de múltiplo acesso por divisão de frequências ortogonais (OFDMA) é um caso particular da técnica MC-CDMA, os resultados mostram que a máxima eficiência espectral média obtida com a técnica OFDMA é menor do que aquela obtida com a técnica MC-CDMA
Abstract: In this work the performance of cellular networks uplink is evaluated using the multicarrier-code division multiple access (MC-CDMA) technique in terms of the mean bit error rate (BER) and the mean spectral efficiency. The analyzed communications system is supposed to employ the MC-CDMA technique, a linear antenna array in the base station, frequency interleaving, maximal ratio combining (MRC), adaptive modulation, control power and a cyclic prefix large enough to eliminate the effects of intersymbol interference (ISI) and intercarrier interference (ICI). The studied scenario assumes the presence of multiple access interference (MAI) and co-channel interference (CCI). The channel characterizations considers the presence of additive white gaussian noise (AWGN), exponential path-loss and slow and frequency selective Rayleigh fading. In this context, exact and closed analytical expressions for the mean BER for both BPSK modulation, as for M-QAM modulation are obtained. The accuracy of the expressions is validated through Monte Carlo simulations. Also, an expression for the mean cellular spectral efficiency is determined, which is a function of the channel reuse factor, the bandwidth increases due to the cyclic prefix, the system load, the spreading factor, the cell radius and the modulation employed. The results show that using an unitary channel reuse factor of 1 is the most efficient way to use the spectrum. However, this reuse factor is critical in relation to transmission rates. Moreover, considering that the orthogonal frequency division multiple access (OFDMA) technique is a particular case of MC-CDMA, the results show that the maximum mean spectral efficiency achieved with the OFDMA technique is lower than that obtained with the MC-CDMA technique
Mestrado
Telecomunicações e Telemática
Mestre em Engenharia Elétrica
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Lin, Luyang. "The transmission and control of syphilis in Guangzhou." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B41711191.
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