Orientador: Michel Daoud Yacoub / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-25T07:51:39Z (GMT). No. of bitstreams: 1 Tejerina_GustavoRodriguesdeLima_M.pdf: 2552947 bytes, checksum: 548284b36d8cce64c55081cadc010fe4 (MD5) Previous issue date: 2014 / 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

Orientador: Michel Daoud Yacoub / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-22T18:11:07Z (GMT). No. of bitstreams: 1 Ferdinando_ErickMascagni_M.pdf: 4072305 bytes, checksum: 524e54d5ac7720b7285629f0cf0b5059 (MD5) Previous issue date: 2013 / 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

Orientador: José Cândido Silveira Santos Filho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-22T19:49:43Z (GMT). No. of bitstreams: 1 Teixeira_BernardoVieira_M.pdf: 1970441 bytes, checksum: 67f065ec5f220f208a22685648840f7e (MD5) Previous issue date: 2013 / 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

Orientadores: Michel Daoud Yacoub, Ugo Silva Dias / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-20T07:39:19Z (GMT). No. of bitstreams: 1 Krishnan_Aravind_M.pdf: 14799172 bytes, checksum: ef1f7ee0181d66e5163ba0926643ca9e (MD5) Previous issue date: 2011 / 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

Fade and inter-fade duration data obtained from the three beacons at 12, 20, and 30 GHz aboard the OLYMPUS satellite were analyzed. The different types of signal impairments and their causes were highlighted and a literature survey conducted. Twelve months of fade and inter-fade data were analyzed and the results of these statistics are presented in the form of tables and figures. The analysis was done on both the monthly and annual data. These tables and figures show that at the higher fade levels, the number of fade events and the fade time is smaller than at the lower thresholds. For the same fade level the number of fade events and the fade time goes down as the fade duration which it exceeds is increased. Inter-fade durations also showed similar results. The fades exhibited seasonal dependencies. The number of fades (and consequently the fade time) were much higher for the months of May through August and for the months of March and December. The other months showed very little fade activity. A model was also constructed that can predict the fade time as a function of frequency, attenuation level, and fade duration interval. The predicted fade times agree well with the measured fade duration data. An alternate simplified version of the model is also presented. / Master of Science

Frequency scaling of attenuation is the prediction of attenuation at a desired frequency from attenuation values at a base frequency. The attenuation at the base frequency is often known from prior measurements. Frequency scaling of attenuation is of interest because of the eventual need to exploit higher frequency bands. Most satellite communications traffic now use C-band (4-8 GHz) and Ku-band (12-18 GHz). The next approved, yet largely unused, frequency allocation for domestic use is in the K-band (18-27 GHz) to Ka-band (27-40 GHz). At these higher frequencies, however, earth-space radio links suffer atmospherically induced impairments as frequency increases. In particular, rain causes severe fading. Consequently, satellite systems in these higher bands are very susceptible to outages due to rain-induced fades. Reliable frequency scaling models are needed in system design to estimate the effect of these rain-induced fades. Between August 1990 and August 1992, V.P.I. & S.U.'s SATCOM Group performed extensive measurements of slant path attenuation using the 12, 20, and 30 GHz beacon signals (in the Ku/Ka-bands) of the European OLYMPUS experimental satellite. The experimental results are used to evaluate the usefulness of scaling models proposed by other researchers, both for instantaneous and statistical purposes. New models are presented for accurate scaling of attenuation within the Ku/Ka-bands. / Master of Science

Two algorithms for estimating the frequency and power of the carriers of 20 GHz and 30 GHz satellite signals are compared. Both algorithms operate on a prefiltered sequence generated by lowpass filtering followed by signal decimation for the purpose of sampling rate reduction. The lowpass filtering is accomplished via the overlap-add method of FIR filtering using the FFT. Carrier frequency prediction and tracking is accomplished with a Kalman predictor, for which the frequency drift process is modeled via polynomial extrapolation. The Kalman predictor operates on frequency measurements provided by one of two frequency estimators. One of the frequency estimation algorithms, a refinement of the DFT-automatic frequency control technique, uses the Chirp-Transform algorithm in its aim for the maximum likelihood estimate of frequency and power. The averaged periodogram is computed from the prefiltered sequence and is used to measure the frequency of the drifting frequency signal as well as its power. One of the disadvantages of this algorithm is the bias present in the estimation of power. The bias can be removed only with knowledge of the noise power. The algorithm has the advantage of being almost exclusively a convolution and therefore is accomplished with minimal computation via the FFT. An alternative parametric approach to frequency estimation is also investigated. In this approach the weighted least-squares modified Yule-Walker method of autoregressive model estimation is used on the prefiltered sequence to yield frequency estimates. Power estimation is accomplished next via modal decomposition of the estimated correlation sequence. The advantage of this approach is that for slowly varying frequency drift paths (24 hour cycle) the frequency estimates exhibit MSE approximately 3 dB less than the Chirp-Transform algorithm over a wide range of SNR. There are two disadvantages to the parametric algorithm. First the parametric algorithm estimates power with MSE approximately 2 dB greater than the nonparametric algorithm. Secondly the algorithm is more complicated than the nonparametric Chirp-Transform algorithm because it requires matrix inversions and the determination of the roots of a polynomial. For the digital beacon receiver problem investigated here both algorithms perform similarly in two important respects. First both algorithms can lock onto a carrier signal whose frequency is drifting at the rate of 5 Hertz per second in a noise environment corresponding to a 15 dB/Hz SNR. Secondly both algorithms can make unbiased frequency estimates of the carrier signal allowing the receiver to track the carrier at 7 dB/Hz SNR. Both algorithms attain the Cramer-Rao bound for estimation of constant frequency sinusoids. For a simulated satellite signal with maximum frequency drift of 5 Hertz per second the Kalman frequency predictor is able to reduce the problem to nearly that of the constant frequency case so that the resulting performance corresponds to the Cramer-Rao bound for estimation of constant frequency sinusoids. Where computational considerations are critical the nonparametric algorithm is preferred. In fact, unless the superior accuracy of the frequency prediction afforded by the parametric algorithm is paramount, the nonparametric algorithm is to be chosen. / Master of Science

M.Ing. (Electrical and Electronic Engineering) / With all the talk about the Information Highway and its construction, there is also a channel which is highly underestimated and thus almost ignored. On normal FM radio transmissions extra bandwidth exists, suitable for the transmission of audio and data. In this thesis the effects of interference on data transmission over the Supplementary Signal Transmission (SST) channel are analysed. The channel is characterized in terms of the Bit Error Rate (BER) versus field strength and distance from a transmitter ...

Au cours des dernières années, les communications inter-véhicule (IVC) sont devenues un domaine de recherche intensif, en particulier dans le cadre des systèmes de transport intelligents. Il suppose que la totalité ou une partie des véhicules est équipé de dispositifs radio permettant la communication entre eux. La norme IEEE 802.11p (normalisé pour la communication des véhicules) devrait être la technologie de facto pour ces communications. En utilisant son mode ad hoc, cette technologie radio permet aux véhicules d'étendre la portée de leur communication en formant un réseau multi-saut sans fil Ad - hoc, également appelé Vehicle ad hoc NETwork (VANET). Cette thèse aborde un problème fondamental des VANET : la capacité du réseau. Deux modèles théoriques simples ont été proposés dans cette thèse pour calculer cette capacité: un « packing problem » (la traduction française nous est inconnue) et un modèle Markovien. Ils offrent des formules simples et fermées sur le nombre maximum d'émetteurs simultanés, et sur la distribution de la distance entre eux. Une borne supérieure sur cette capacité a été proposée. De plus, le modèle Markovien a permis de proposer une formule analytique sur la distribution spatiale des émetteurs. Ces quantités nous permettent, entre autres, de paramétrer le mécanisme d’accès au medium du 802.11p, comme par exemple le seuil du CCA (Clear Channel Assessment), amenant à une optimisation de la capacité du réseau. Afin de valider les différentes contributions théoriques de cette thèse, les résultats des modèles analytiques ont été comparés à des simulations effectuées avec le simulateur de réseau NS-3. Les paramètres de simulations ont été estimés à partir d’expérimentations réelles. De plus, différentes distributions de trafic (trafic de véhicules) ont été considéré afin d’évaluer leur impact sur la capacité du réseau. L’une des applications de cette thèse est le dimensionnement des applications de sécurité routière vis-à-vis de la consommation des ressources réseau. Dans ce cadre, nous nous sommes intéressés aux reconstructions de cartes. Il faut comprendre ICI LA reconstitution de l’environnement d’un véhicule (perception map). Ces applications utilisent des informations provenant de capteurs locaux et distants afin d’offrir un système d’aide à la conduite (conduite autonome, alerte sur des collisions, annonce de situations accidentogènes, etc.). Ces applications nécessitent une bande passante élevée. Notre étude théorique a montré que cette bande passante ne sera sans doute pas disponible en pratique dans les réseaux IEEE 802.11p. Par conséquent, UN algorithme adaptatif de contrôle de puissance a été proposé et optimisé pour cette application particulière. Nous avons montré que notre algorithme, par le biais d'un modèle analytique et d'un grand nombre de simulations que la capacité du réseau est augmentée de manière significative. / In recent years, Inter Vehicle Communication (IVC) has become an intensive research area, as part of Intelligent Transportation Systems. It supposes that all, or a subset of the vehicles is equipped with radio devices, enabling communication between them. IEEE 802.11p (standardized for vehicular communication) shows a great deal of promise. By using ad hoc mode, this radio technology allows vehicles to extend their scopes of communication and thus forming a Multi-hop wireless Ad-hoc NETwork, also called Vehicular Ad-hoc NETwork (VANET). This thesis addresses a fundamental problem of VANET: the network capacity. Two simple theoretical models to estimate this capacity have been proposed: a packing model and a Markovian point process model. They offer simple and closed formulae on the maximum number of simultaneous transmitters, and on the distribution of the distance between them. An accurate upper bound on the maximum capacity had been derived. An analytical formula on distribution of the transmitters had been presented. This distribution allows us to optimize Clear Channel Assessment (CCA) parameters that leads to an optimization of the network capacity.In order to validate the approach of this thesis, results from the analytical models are compared to simulations performed with the network simulator NS-3. Simulation parameters was estimated from real experimentation. Impact of different traffic distributions (traffic of vehicles) on the network capacity is also studied. This thesis also focuses on extended perception map applications, which use information from local and distant sensors to offer driving assistance (autonomous driving, collision warning, etc.). Extended perception requires a high bandwidth that might not be available in practice in classical IEEE 802.11p ad hoc networks. Therefore, this thesis proposes an adaptive power control algorithm optimized for this particular application. It shows through an analytical model and a large set of simulations that the network capacity is then significantly increased.

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.