Dans un avenir proche, l'utilisation des bandes libres à 60 GHz permettra des débits de plusieurs Gb/s sur de courtes distances. Cependant, la conception de ces systèmes de communication sans fil dépendra fortement des caractéristiques du canal de propagation. L'objectif de cette thèse porte sur la caractérisation spatiotemporelle du canal de propagation afin de quantifier l'apport des techniques multi antennes (MIMO) sur les performances de la communication. Un sondeur de canal adapté à cette bande passante est développé afin d'effectuer des mesures intensives de caractérisation à l'intérieur des bâtiments. Pour la caractérisation théorique du canal, le modèle déterministe de tracé de rayons fut complété pour prendre en compte i) la diffraction sur les arêtes horizontales d'un obstacle rectangulaire, une nouvelle méthode hybride basée sur la théorie uniforme de la diffraction et de l'optique physique a été proposée et validée, ii) les caractéristiques de diffusion pour des matériaux typiquement rencontrés dans les constructions, ces caractéristiques ayant été estimées à partir de la caractérisation expérimentale. Ces résultats ont montré que l'introduction des coefficients de diffusion pour chaque matériau améliore la précision du modèle contrairement à ce qui peut être trouvé dans la littérature où un paramètre moyen de diffusion est proposé pour un environnement donné. Enfin, à partir des mesures de sondage de canal, les simulations des performances du standard IEEE 802.15c MIMO-OFDM montrent que l'utilisation des techniques multi antennes peut à la fois augmenter le débit d' un facteur de 3,7 et la distance de communication d'un mètre. / The use of the license-free 60-GHz frequency band will allow multi-Gb/s data transmission over short distances. The design of these wireless communication systems strongly depends on the propagation channel. The objective of the thesis focuses on the multidimensionnal channel characterization to quantify at the end the contribution of multi-antenna techniques (MIMO) on the performance of communication. A wideband mm-W frequency channel sounder was developed and has allowed extensive indoor channel measurements. In order to compare experimental results with theoretical value, the ray tracing tool was improved. Taking into account the diffraction that takes place at the top of a rectangular obstacle, a new method based on a hybrid uniform theory of diffraction-physical optics has been proposed and validated. Experimental results had also allowed to quantify the diffuse parameters for materials usually found in indoor environments. It was shown that introducing the contribution of diffuse scattering improves the accuracy of the RT tool unlike what it can be found in the literature where an average diffuse scattering parameter is proposed for a given environment. Finally, based on the channel measurements, the performance of IEEE 802.15.3c MIMO-OFDM systems was performed and the results show that the use of antennas array at both the transmitter and receiver side could increase both the throughput by a factor of 3.7 and the communication distance by 1 meter.

Typewritten copy Includes bibliography.

The central theme is the study of error propagation effects in decision feedback equalizers (DFEs). The thesis contains: a stochastic analysis of error propagation in a tuned DFE; an analysis of the effects of error propagation in a blindly adapted DFE; a deterministic analysis of error propagation through input-output stability ideas; and testing procedures for establishing correct tap convergence in blind adaptation. To a lesser extent, the decision directed equalizer (DDE) is also treated.¶ Characterizing error propagation using finite state Markov process (FSMP) techniques is first considered. We classify how the channel and DFE parameters affect the FSMP model and establish tight bounds on the error probability and mean error recovery time of a tuned DFE. These bounds are shown to be too conservative for practical use and highlight the need for imposing stronger hypotheses on the class of channels for which a DFE may be effectively used.¶ In blind DFE adaptation we show the effect of decision errors is to distort the adaptation relative to the use of a training sequence. The mean square error surface in a LMS type setting is shown to be a concatenation of quadratic functions exposing the possibility of false tap convergence to undesirable DFE parameter settings. Averaging analysis and simulation are used to verify this behaviour on some examples.¶ Error propagation in a tuned DFE is also examined in a deterministic setting. A finite error recovery time problem is set up as an input-output stability problem. Passivity theory is invoked to prove that a DFE can be effectively used on a channel satisfying a simple frequency domain condition. These results give performance bounds which relate well with practice.¶ Testing for false tap convergence in blind adaptation concludes our study. Simple statistic output tests are shown to be capable of discerning correct operation of a DDE. Similar tests are conjectured for the DFE, supported by proofs for the low dimensional cases.

<p>The present Master Thesis analyzes the DVB-H radio Frequency Network Planning</p><p>problematic, studying the influence of a propagation model used in the calculation of</p><p>network coverage. In this way, the aim of this work is the design of a procedure and</p><p>algorithm to adjust a propagation model considering measurement campaigns performed in</p><p>different environments (dense-urban, urban, sub-urban and rural).</p><p>The methodology relies on the adjustment of the Xia-Bertoni propagation model</p><p>parameters using the Least Mean Square (LMS) method, considering the collected</p><p>measurements and the simulation model parameters obtained from a Geographic</p><p>Information System (GIS). Coverage simulations and measurement results are compared</p><p>using a 3-Dimensional city model (terrain and buildings) for different terrain topologies</p><p>(flat, hills and canyons) and environments.</p><p>The resulting adjusted model has been tested and compared with other common</p><p>models (COST231 and Okumura-Hata) using specific metrics, thus proving its validity for</p><p>different frequencies, environments and terrain topologies. In order to validate the</p><p>procedure and designed algorithm, this Master Thesis gathers real data from measurement</p><p>campaigns carried out in different cities: Gävle (Sweden), Bucaramanga (Colombia),</p><p>Valencia (Spain) and Munich (Germany). Besides, this work provides an insight on best</p><p>practices to perform measurement campaigns.</p><p>The outcome of this work is a useful tool in radio network planning for DVB-H</p><p>systems, which ensures reliable results in all environments and terrain topologies.</p>

<p>This thesis is a project carried out at the “Centre for RF measurements Technology“at the University of Gävle. The first aim was basically the characterization of different industrial indoor environments to get a model that describes dispersive features of each environment.</p><p> </p><p>The results of previous measurements campaign on three industrial environments as steel mill, storage paper and industrial process mill are used. Also new Power Delay Profile (PDP) on corridor and laboratory has been developed.</p><p> </p><p>Measurements for three frequency bands are done (183-683 MHz, 1640-2140MHz and 2200-2700MHz) and for line-of-sight (LOS) and non-line-of-sight (NLOS) industrial and laboratory scenaries cases are presented.</p><p> </p><p>All these models have been compared with other existing models as Saleh-Valenzuela Model, Two Cluster Model and Indoor Power Delay Profile Model (IPDP Model) and fit-line, typical deviation are shown.</p><p> </p><p>Finally we present a study of the different systems used in the industry and the best suited system to the conditions is chosen.</p><p><strong> </strong></p>

A mechanical design "compiler" has been developed which, given an appropriate schematic, specifications, and utility function for a mechanical design, returns catalog numbers for an optimal implementation. The compiler has been successfully tested on a variety of mechanical and hydraulic power transmission designs and a few temperature sensing designs. Times required have been at worst proportional to the logarithm of the number of possible combinations of catalog numbers.

Studying the acceleration and propagation mechanisms of Galactic cosmic rays can provide information regarding astrophysical sources, the properties of our Galaxy, and possible exotic sources such as dark matter. To understand cosmic ray acceleration and propagation mechanisms, accurate measurements of different cosmic ray elements over a wide energy range are needed. The PAMELA experiment is a satellite-borne apparatus which allows different cosmic ray species to be identified over background. Measurements of the cosmic ray antiproton flux and the antiproton-to-proton flux ratio from 1.5 GeV to 180 GeV are presented in this thesis, employing the data collected between June 2006 and December 2008. Compared to previous experiments, PAMELA extends the energy range of antiproton measurements and provides significantly higher statistics. During about 800 days of data collection, PAMELA identified approximately 1300 antiprotons including 61 above 31.7 GeV. A dramatic improvement of statistics is evident since only 2 events above 30 GeV are reported by previous experiments. The derived antiproton flux and antiproton-to-proton flux ratio are consistent with previous measurements and generally considered to be produced as secondary products when cosmic ray protons and helium nuclei interact with the interstellar medium. To constrain cosmic ray acceleration and propagation models, the antiproton data measured by PAMELA were further used together with the proton spectrum reported by PAMELA, as well as the B/C data provided by other experiments. Statistical tools were interfaced with the cosmic ray propagation package GALPROP to perform the constraining analyses. Different diffusion models were studied. It was shown in this work that only current PAMELA data, i.e. the antiproton-to-proton ratio and the proton flux, are not able to place strong constraints on propagation parameters. Diffusion models with a linear diffusion coefficient and modified diffusion models with a low energy dependence of the diffusion coefficient were studied in the $\chi^{2}$ study. Uncertainties on the parameters and the goodness of fit of each model were given. Some models are further studied using the Bayesian inference. Posterior means and errors of the parameters base on our prior knowledge on them were obtained in the Bayesian framework. This method also allowed us to understand the correlation between parameters and compare models. Since the B/C ratio used in this analysis is from experiments other than PAMELA, future PAMELA secondary-to-primary ratios (B/C, $^{2}$H/$^{4}$He and $^{3}$He/$^{4}$He) can be used to avoid the data sets inconsistencies between different experiments and to minimize uncertainties on the solar modulation parameters. More robust and tighter constraints are expected. The statistical techniques have been demonstrated useful to constrain models and can be extended to other observations, e.g. electrons, positrons, gamma rays etc. Using these channels, exotic contributions from, for example, dark matter will be further investigated in future. / QC 20120523

No description available.

Ultrafast electron diffraction (UED) is a method of directly imaging system dynamics at the atomic scale with picosecond time resolution. In this thesis I present theoretical analyses of the experimental processes, and construct models in order to better understand UED experiments and to guide future refinements. In particular, I derive a model of electron bunch propagation and a model of electron bunch diffraction, where both models take into account all bunch parameters. To analyse the propagation of electron bunches, I present a mean-field analytic Gaussian (AG) model. I derive a system of ordinary differential equations that are solved quickly and easily to give the bunch dynamics. The AG model is compared to N -body numerical simulations of initially Gaussian bunches, and I demonstrate excellent agreement between the two result sets. I also present a comparison of the AG model with numerical simulations of quasi-Gaussian and non-Gaussian distributions, extending the applicability of the AG model to the propagation of ``real-world'' bunches. During propagation, electron bunches can be shaped by electron-optic devices, which are necessary to attain high brightness, sub-100 fs bunches. I investigate two types of electron-optic devices: one is a magnetic lens used for collimating or focusing bunches, the other is a bunch compressor. I derive bunch parameter transformations for each of the electron-optic devices, and present numerical calculations using these transformations along with the AG model showing the effects of the devices on the evolution of the bunch parameters. To analyse electron bunch diffraction in UED experiments, I present a general scattering formalism. Using single-scattering and far-field approximations, I derive an expression for the diffracted signal that depends on the electron bunch properties just before scattering. Using this expression I identify the transverse and longitudinal coherence lengths and discuss the importance of these length scales in diffraction pattern formation. I also discuss the effects of different bunch parameters on the measured diffracted flux, and present sample numerical calculations for scattering by nanosize particles based on this model. This simulation demonstrates the cumulative effects of the bunch parameters, and shows the complex interplay of the bunch and target properties on the diffracted signal.

The enhanced Polar Outflow Probe (ePOP) satellite is to be launched in 2007. One of the 8 instruments it will carry is a Radio Receiver Instrument (RRI) which is a passive radio receiver. The RRI will detect HF (High Frequency band 3 to 30 MHz) radio waves from ground transmitters, one of which is the Saskatoon SuperDARN radar. The modification of an HF radar wave as it propagates through the ionosphere to the satellite is the dominant scientific interest of this thesis. The modification of a radar wave as it propagates through the ionosphere can be used to characterize the ionosphere and reveal a better understanding of magnetoionic radar wave propagation. A ray tracing program has been written to determine characteristics of the wave, including the wave path and the full polarization state, at the satellite receiver. </p> As a confirmation of the ray tracing program abilities, data from a similar transionospheric experiment in 1978, the ISIS II satellite mission, has been analyzed and compared with simulated results. The ISIS II transionospheric experiment received radar signals from a transmitter (9.303 MHz) located in Ottawa, Canada. These signals were analyzed and it was noted that the signal periodically faded in and out both due to differential Faraday rotation effects (due to propagation through an ionized medium and reception on a single dipole antenna) and due to satellite spin rotation at rates up to 13 Hz. Also observed was a splitting of the received signal into Ordinary (O-mode) and Extraordinary (X-mode) components causing a delay between the arrival of the modes at ISIS II of up to 0.8 ms. Simulations have been carried out to model the radar wave propagation from the ground transmitter through the ionized medium of the ionosphere to the spacecraft. The modelled signal shows very similar trends to the observed signal. A linear regression analysis comparing observed to simulated fade rates gave values of slope equal to 1.07 and regression coefficient equal to 0.934. The regression analysis of mode delay gave values of slope equal to 1.14 and regression coefficient equal to 0.930. </p>Ray path modelling has also been simulated for the RRI experiment on ePOP. These simulations have been carried out for various ionospheric and satellite pass configurations. The expected fade rates, mode delays, and latitudinal range of received signal was determined from the simulated data in each case. The dependence of these characteristics on the various pass configurations are presented and discussed.