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Modelling, information capacity, and estimation of time-varying channels in mobile communication systemsSadeghi, Parastoo, School of Electrical Engineering And Telecommunications, UNSW January 2006 (has links)
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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Distribuição conjunta fase-envoltória eta-mu generalizada / Generalized eta-mu phase-envelope joint distributionTejerina, Gustavo Rodrigues de Lima, 1987- 25 August 2018 (has links)
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
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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
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Estatísticas de ordem superior do desvanecimento Kappa-Mu extreme / High-order statistics of the Kappa-Mu extreme fadingFerdinando, Érick Mascagni, 1988- 22 August 2018 (has links)
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
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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
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Projeto e análise de desempenho de simulador para canais de desvanecimento Nakagami-m / Design and performance analysis of Nakagami-m fading channel simulatorTeixeira, Bernardo Vieira, 1988- 04 February 2013 (has links)
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
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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
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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 / Caracterização dos parâmetros de desvanecimento da distribuição alfa-mu : medidas e estatísticasKrishnan, Aravind 20 August 2018 (has links)
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
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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
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CMOS-based amplitude and phase control circuits designed for multi-standard wireless communication systemsHuang, Yan-Yu 05 July 2011 (has links)
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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The Design of Linear Space-Time Codes for Quasi-static Flat-fading ChannelsVaradarajan, Badri 09 July 2004 (has links)
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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Dual-Band Transmitters Using Digitally Predistorted Frequency Multipliers for Reconfigurable RadiosPark, Youngcheol 12 July 2004 (has links)
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.
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Multiuser demodulation for DS-CDMA systems in fading channels.Singh, Navin Runjit. January 2000 (has links)
The problems of optimal as well as suboptimal detection for CDMA
transmissions over an additive white Gaussian noise (AWGN) channel, have
been the focus of study in the recent past. However, CDMA transmissions
are frequently made over channels which exhibit fading and/or dispersion;
hence receivers need to be designed which take into account this behaviour.
In spite of the major research effort invested in multiuser demodulation
techniques, several practical as well as theoretical open problems still exist.
Some of them are considered in more detail in this thesis. The aim of the
thesis is to develop multiuser demodulation algorithms for mobile
communication systems in frequency-selective fading channels, and to
analyze their implementation complexity. The emphasis is restricted to the
uplink of an asynchronous DS-CDMA system where the users transmit in an
uncoordinated manner and are received by one centralized receiver.
The original work that is undertaken for the MScEng study is the evaluation
of a multiuser receiver structure for a frequency-selective fading channel,
where there exists a steady specular path and two fading paths.
Furthermore, the effect of using selection diversity is investigated by
examining the bit error rate, asymptotic multi user efficiency and near-far
resistance of the proposed detector structure. These results are confirmed
both analytically and by simulation in the thesis. An investigation is also
conducted into the application of neural networks to the problem of
multiuser detection in code division multiple access systems. The neural
network will be used as a classifier in an adaptive receiver which
incorporates an extended Kalman filter for joint amplitude and delay
estimation. Finally, some open problems for future research will be pointed
out in the thesis.
Keywords: AWGN channel , DS-CDMA system, frequency-selective,
multi user demodulation, asymptotic multiuser efficiency, near-far resistance,
neural network, Kalman filter. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2000.
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Contribuições ao dimensionamento de redes sem fio / Contributions on the dimensioning of wireless networksMello, Renata Valverde 07 March 2009 (has links)
Orientador: Michel Daoud Yacoub / Dissertação (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
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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
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