Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-02-11T10:56:22Z No. of bitstreams: 1 juandavidvalenciapayan.pdf: 2769602 bytes, checksum: f450fbb83bbe8b4e5a8cdb7c9b4fa338 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-02-26T11:57:12Z (GMT) No. of bitstreams: 1 juandavidvalenciapayan.pdf: 2769602 bytes, checksum: f450fbb83bbe8b4e5a8cdb7c9b4fa338 (MD5) / Made available in DSpace on 2016-02-26T11:57:12Z (GMT). No. of bitstreams: 1 juandavidvalenciapayan.pdf: 2769602 bytes, checksum: f450fbb83bbe8b4e5a8cdb7c9b4fa338 (MD5) Previous issue date: 2014-03-27 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Esta contribuição descreve uma caracterização estatística da rede de baixa tensão Brasileira residencial como meio de comunicação. As discussões são baseadas em canais estimados obtidos em uma campanha de medição realizada em quatro apartamentos diferentes, com tamanhos que variam de 50 até 90 metros quadrados. Os parâmetros considerados para esta análise são o Root Mean Square Delay Spread, o ganho médio do canal e a capacidade do canal. Para efeitos de comparação com a rede de potencia dos Estados Unidos, a banda de frequência utilizada foi de 1:705 até 30 MHz. A análise relatada mostra que o Root Mean Square Delay Spread e o ganho médio do canal não podem ser modelados como variáveis log-normal. Os resultados obtidos geram dúvidas em relação aos atuais encontrados na literatura, em que se afirma que tanto o Root Mean Square Delay Spread quanto o ganho médio do canal seguem uma distribuição log-normal. Foram medidos também a impedância de acesso e o ruído do canal de comunicação via rede elétrica. Além disso, os conceitos de cooperação para melhorar o desempenho dos sistemas de comunicação via rede elétrica foram analisados, mais especificamente na rede de baixa tensão Brasileira residencial. Para isso, foram analisados a performance dos protocolos de Amplify-and-Forward e Decode-and-Forward, em conjunto com as técnicas de combinação Equal-Gain Combining, Selection-Combining e Maximal-Ratio Combining. A análise sobre os dados medidos cobriram uma faixa de frequência de 1:705 a 100 MHz. Os dados medidos abordam quatro cenários para possíveis localizações do nó Relay. Os resultados obtidos mostram que o Amplify-and- Forward é de aplicabilidade limitada no contexto de comunicação via rede elétrica e o oposto é válido para o protocolo de Decode-and-Forward, principalmente se a probabilidade de erro de detecção de símbolos no nó Relay tende a zero. / This thesis outlines a statistical characterization of the Brazilian In-Home Low-Voltage Electric Power Grid as a communication medium. The discussions are based on estimated channels obtained in a measurement campaign carried out in four different apartments with sizes ranging from 50 up to 90 square meters. The parameters considered for this analysis are the Root Mean Square Delay Spread, the average channel gain, and the channel capacity. For the sake of comparison with the Electric Power Grid in United States, the frequency band ranging from 1:705 up to 30 MHz was set. The reported analysis shows that the Root Mean Square Delay Spread and the average channel gain cannot be modeled as log-normal variables, this cast doubt the current results found in the literature, in which is stated that both the Root Mean Square Delay Spread and the average channel gain follow a log-normal distribution. This was followed by the Power Line Communication access impedance and noise measurements in the In-Home Low-Voltage Electric Power Grid. Additionally, the suitability of cooperation concepts for improving the performance of Power Line Communication systems was analyzed, more specifically in the Brazilian In-Home Low-Voltage Electric Power Grid. For this purpose, the performance of the Amplify-and-Forward and Decode-and- Forward protocols, together with the Equal-Gain Combining, Selection Combining, and Maximal-Ratio Combining techniques were analyzed. The analysis was carried out on the measured data covering a frequency band from 1:705 up to 100 MHz. The measured data addresses four scenarios for possible relay node locations. The attained results show that the Amplify-and-Forward is of limited applicability in the Power Line Communication context and the opposite is valid to the Decode-and-Forward protocol, mainly if the error probability of detecting symbols at the relay node is zero.

Cette thèse s’inscrit dans le domaine de la caractérisation des systèmes de communication sans fil utilisant la diversité des antennes. En effet, ces systèmes permettent de lutter contre les évanouissements des signaux, lorsque le terminal est placé dans un environnement riche en multi-trajets. L’objectif d'une telle recherche est : d’étudier l'association de plusieurs antennes à l'émission et / ou la réception pour améliorer le bilan de liaison, et la capacité des systèmes sans fil, (diminution de BER (Bit Error Rate), augmentation de débit ...). Cette thèse s’intéresse à l'aspect électromagnétique et traitement du signal. Afin de comprendre les phénomènes mis en jeu, et de caractériser les performances du terminal, il doit être placé dans un environnement de propagation multi-trajets contrôlable dans le temps et dans l'espace.Cela nous amène à trouver des méthodes de mesures capables de reproduire des modèles de canaux de propagation réalistes. Dans le cadre de cette thèse la méthode utilisée est la chambre réverbérante. Dans cette thèse, nous nous intéressons à l'aspect temporel. La chambre réverbérante (RC) est considérée comme un outil utile pour émuler des environnements riches en multi-trajets. Dans cette contribution, ce dispositif est utilisé pour émuler des modèles canaux multi-trajets, et évaluer la performance des systèmes de communication sans fil. Cette évaluation est effectuée avec des mesures en temps réel et non temps réel. Parmi les objectifs de cette thèse est d'obtenir un modèle de simulation électromagnétique de la chambre réverbérante basé sur une approche circuit, afin de déterminer la fonction de transfert de canal en fonction des pertes. / This thesis is part of the field of the characterization of wireless communication systems using antennas diversity. Indeed, such systems allow fighting against the signals fading, when the terminal is inside a strong multipath environment. The issue of such research is: to study the association of multiple antennas at transmitting and/or receiving sides to improve the link budget, and the capacity of wireless systems, (decrease of BER (Bit Error Rate), increase of throughput …). This thesis takes an interest to the electromagnetic aspect, and signal processing. In order to understand the involved phenomena, and to characterize the terminal performance, it should be placed in a controlled multipath propagation environment in time, and in space. This brings us to find measurement methodologies able to reproduce models of realistic propagation channels. As part of this thesis the method used is the reverberation chamber. In this thesis we are interested in the time aspect. Reverberation chamber (RC) is considered as a useful tool to emulate rich multipath environments. In this contribution, this device is employed to emulate multi clusters channel models (cluster is defined as a group of multipath), and evaluate performance of wireless communication systems. This evaluation is performed with real time and not-real time measurements. It remains to note that among the objectives set out in this PhD thesis is to obtain electromagnetic simulation model of the reverberation chamber based on circuit approach, in order to determine the channel transfer function versus losses quantities.

This thesis aims to contribute to the developments of wireless communication systems. The work generally consists of three parts: the first part is a discussion on general digital communication systems, the second part focuses on wireless channel modelling and fading mitigation techniques, and in the third part we discuss the possible application of advanced digital signal processing, especially time-frequency representation and blind source separation, to wireless communication systems. The first part considers general digital communication systems which will be incorporated in later parts. Today's wireless communication system is a subbranch of a general digital communication system that employs various techniques of A/D (Analog to Digital) conversion, source coding, error correction, coding, modulation, and synchronization, signal detection in noise, channel estimation, and equalization. We study and develop the digital communication algorithms to enhance the performance of wireless communication systems. In the Second Part we focus on wireless channel modelling and fading mitigation techniques. A modified Jakes' method is developed for Rayleigh fading channels. We investigate the level-crossing rate (LCR), the average duration of fades (ADF), the probability density function (PDF), the cumulative distribution function (CDF) and the autocorrelation functions (ACF) of this model. The simulated results are verified against the analytical Clarke's channel model. We also construct frequency-selective geometrical-based hyperbolically distributed scatterers (GBHDS) for a macro-cell mobile environment with the proper statistical characteristics. The modified Clarke's model and the GBHDS model may be readily expanded to a MIMO channel model thus we study the MIMO fading channel, specifically we model the MIMO channel in the angular domain. A detailed analysis of Gauss-Markov approximation of the fading channel is also given. Two fading mitigation techniques are investigated: Orthogonal Frequency Division Multiplexing (OFDM) and spatial diversity. In the Third Part, we devote ourselves to the exciting fields of Time-Frequency Analysis and Blind Source Separation and investigate the application of these powerful Digital Signal Processing (DSP) tools to improve the performance of wireless communication systems.