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<p>Nowadays, the need for sharing information between different systems in a secure manner is common, not only in the corporate world but also in the military world. This information often resides at different locations, creating a distributed system. In order to share information in a secure manner in a distributed system, credentials are often used to attain authorization.</p><p>This thesis examines how such a distributed system for sharing information can be realized, using the technology readily available today. Accounting to the results of this examination a basic system is implemented, after which the overall security of the system is evaluated. The thesis then presents possible extensions and improvements that can be done in future implementations.</p><p>The result shows that dynamic roles do not easily integrate with a single sign-on system. Combining the two technologies leads to several synchronization issues, where some are non-trivial to solve.</p>

Au début des années 2000, les instances aéronautiques ont exprimé le besoin de développer un nouveau système de radiocommunication aéronautique du fait de l'augmentation du trafic aérien et de la saturation croissante des capacités de communication radio entre les aéronefs et les stations de contrôle aérien. L'une des composantes de ce système, nommée L-DACS (« L-band Digital Aeronautical Communication System »), devrait opérer dans la bande L-aéronautique (960-1164 MHz), dans laquelle fonctionnent également de nombreux autres systèmes radioélectriques. La compatibilité radioélectrique (CRE) de L-DACS avec ces systèmes est un des facteurs principaux à prendre en considération dans le développement d'un tel système.L'objectif principal de cette thèse est d'identifier les principaux problèmes reliés à la CRE et d'en étudier les cas critiques. Ces travaux sont fondamentaux en aéronautique, puisque tout dysfonctionnement dans la communication ou dans les systèmes de radionavigation peut mettre en danger la sécurité du vol. Les conclusions de cette thèse contribueront à la normalisation du système L-DACS et à la finalisation de ses spécifications.Dans une première étape, on étudie l'état de l'art dans les communications aéronautiques et en CRE. On analyse en particulier les dernières spécifications des deux systèmes candidats L-DACS. Ensuite, on propose un algorithme de calcul de brouillage dans le but d'étudier la CRE dans le domaine fréquentiel, d'en identifier et d'en traiter les cas critiques. L'analyse fréquentielle étant insuffisante dans plusieurs cas, on propose alors une approche temporelle d'étude de CRE. Après en avoir présenté les avantages, on présente un exemple d'étude de l'effet d'un système L-DACS sur un récepteur DME (« Distance Measuring Equipment ») à l'aide d'un banc de test CRE aéronautique.Cette thèse a été réalisée en collaboration avec la Direction Générale de l'Aviation Civile (DGAC), qui est un acteur principal pour la réglementation des communications et un affectataire de fréquence pour le spectre aéronautique en France. La thèse contribue aux études menées par la DGAC à l'échelle nationale et internationale.Dans les perspectives, on propose la poursuite de cette étude par une approche temporelle plus générale pour étudier la CRE entre des systèmes radioélectriques quelconques en tenant compte de paramètres supplémentaires liés à la dynamique des systèmes et aux propriétés de leurs technologies. / In the beginning of the 21th century, the aeronautical authorities expressed their need to develop a new system for aeronautical radiocommunications, because the air-traffic is increasing and that current communication systems between pilots and air-controllers are reaching their capacity limits. The L-band Digital Aeronautical Communication System (L-DACS) is the part of the future system that will be operating in a part of the aeronautical L-band (960-1164 MHz), already occupied by a large number of radio-frequency legacy systems. Consequently, it is essential to consider its radio-frequency compatibility (RFC) for the development of the future L-DACS system. This thesis aims at identifying the principal issues related to RFC and studying its critical situations. Such topics are fundamental in aeronautics, as any communication or radionavigation dysfunction may endanger flight and passengers security. Some obtained results will be used for the L-DACS standardization and its specifications finalization. We first analyze the state-of-the-art in both aeronautical communications and RFC, focalizing on updated specifications of both preselected L-DACS candidate systems. We then propose a deterministic algorithm to compute the interference level in order to study the RFC in the frequency domain under identified critical scenarios. Since the frequency-domain analysis seems to be insufficient in several cases, we develop a different methodology, called the time-frequency approach, to analyze the RFC for such situations. We apply this new approach to analyze the effect of an L-DACS interferer on a Distance Measuring Equipment (DME) receiver, using an aeronautical RFC test-bed that we implemented at SUPELEC. This work has been performed in collaboration with the French Civil Aviation Authorities (DGAC), which are an important actor in aeronautical communication regulations and aeronautical spectrum management in France. The thesis contributes to DGAC studies at national as well as international levels. For further work, we suggest to generalize the proposed time-frequency approach to analyze the RFC between any two radio-frequency systems, taking into account additional parameters related to system dynamics and their technology properties.

Data converters, i.e., analog-to-digital converters (ADCs) and digital-to-analog converters (DACs), are interface circuits between the analog and digital domains. They are used in, e.g., digital audio applications, data communication applications, and other types of applications where conversion between analog and digital signal representation is required. This work covers different aspects related to modeling, error correction, and implementation of DACs for communication applications where the requirements on the circuits in terms of speed and linearity are hard. The DAC architecture considered in this work is the current-steering DAC, which is the most commonly used architecture for high-speed applications. Transistor-level simulation of complex circuits using accurate transistor models require long simulation times. A transistor-level model of a DAC used in a system simulation is likely to be a severe bottleneck limiting the overall system simulation speed. Moreover, investigations of stochastic parameter variations require multiple simulation runs with different parameter values making transistor-level models unsuitable. Therefore, there is a need for behavioral-level models with reasonably short simulation times. Behavioral-level models can also be used to find the requirements on different building blocks on high abstraction levels, enabling the use of efficient topdown design methodologies. Models of different nonideal properties in current-steering DACs are used and developed in this work. Static errors typically dominates the low-frequency behavior of the DAC. One of the limiting factors for the static linearity of a current-steering DAC is mismatch between current sources. A well-known model of this problem is used extensively in this work for evaluation of different ideas and techniques for linearity enhancement. The highfrequency behavior of the DAC is typically dominated by dynamic errors. Models oftwo types of dynamic errors are developed in this work. These are the dynamic errors caused by parasitic capacitance in wires and transistors and glitches caused by asymmetry in the settling behavior of a current source. The encoding used for the digital control word in a current steering DAC has a large influence on the circuit performance, e.g., in terms static linearity and glitches. In this work, two DAC architectures are developed. These are denoted the decomposed and partially decomposed architectures and utilize encoding strategies aiming at a high circuit performance by avoiding unnecessary switching of current sources. The developed architectures are compared with the well-known binary-weighted and segmented architectures using behavioral-level simulations. It can be hard to meet a DAC design specification using a straightforward implementation. Techniques for compensation of errors that can be applied to improve the DAC linearity are studied. The well-known dynamic element matching (DEM) techniques are used for transforming spurious tones caused by matching errors into white or shaped noise. An overview of these techniques are given in this work and a DEM technique for the decomposed DAC architecture is developed. In DS modulation, feedback of the quantization error is utilized to spectrally shape the quantization noise to reduce its power within the signal band. A technique based on this principle is developed for spectral shaping of DAC nonlinearity errors utilizing a DAC model in a feedback loop. Two examples of utilization of the technique are given. Four different current-steering DACs implemented in CMOS technology are developed to enable comparison between behavioral-level simulations and measurements on actual implementations and to provide platforms for evaluation of different techniques for linearity improvement. For example, a 14-bit DEM DAC is implemented and measurement results are compared with simulation results. A good agreement between measured and simulated results is obtained. Moreover, a configurable 12-bit DAC capable of operating with different degrees of segmentation and decomposition is implemented to evaluate the proposed decomposed architecture. Measurement results agree with results from behavioral-level simulations and indicate that the decomposed architecture is a viable alternative to the commonly used segmented architecture.

Au début des années 2000, les instances aéronautiques ont exprimé le besoin de développer un nouveau système de radiocommunication aéronautique du fait de l'augmentation du trafic aérien et de la saturation croissante des capacités de communication radio entre les aéronefs et les stations de contrôle aérien. L'une des composantes de ce système, nommée L-DACS (" L-band Digital Aeronautical Communication System "), devrait opérer dans la bande L-aéronautique (960-1164 MHz), dans laquelle fonctionnent également de nombreux autres systèmes radioélectriques. La compatibilité radioélectrique (CRE) de L-DACS avec ces systèmes est un des facteurs principaux à prendre en considération dans le développement d'un tel système.L'objectif principal de cette thèse est d'identifier les principaux problèmes reliés à la CRE et d'en étudier les cas critiques. Ces travaux sont fondamentaux en aéronautique, puisque tout dysfonctionnement dans la communication ou dans les systèmes de radionavigation peut mettre en danger la sécurité du vol. Les conclusions de cette thèse contribueront à la normalisation du système L-DACS et à la finalisation de ses spécifications.Dans une première étape, on étudie l'état de l'art dans les communications aéronautiques et en CRE. On analyse en particulier les dernières spécifications des deux systèmes candidats L-DACS. Ensuite, on propose un algorithme de calcul de brouillage dans le but d'étudier la CRE dans le domaine fréquentiel, d'en identifier et d'en traiter les cas critiques. L'analyse fréquentielle étant insuffisante dans plusieurs cas, on propose alors une approche temporelle d'étude de CRE. Après en avoir présenté les avantages, on présente un exemple d'étude de l'effet d'un système L-DACS sur un récepteur DME (" Distance Measuring Equipment ") à l'aide d'un banc de test CRE aéronautique.Cette thèse a été réalisée en collaboration avec la Direction Générale de l'Aviation Civile (DGAC), qui est un acteur principal pour la réglementation des communications et un affectataire de fréquence pour le spectre aéronautique en France. La thèse contribue aux études menées par la DGAC à l'échelle nationale et internationale.Dans les perspectives, on propose la poursuite de cette étude par une approche temporelle plus générale pour étudier la CRE entre des systèmes radioélectriques quelconques en tenant compte de paramètres supplémentaires liés à la dynamique des systèmes et aux propriétés de leurs technologies.

The present study investigated the cognitive styles of Indian, Metis, Inuit and non-native adults and adolescents of northern Canada and Alaska. The study identified three relational and two analytical cognitive styles. The styles differed significantly from each other in relation to cultural background, language facility, level of post-secondary education, sex and age of the respondents. Cultural background was found to be the most significant discriminator of those under investigation.<p> Procedure of the study involved the collection of verbalized responses to five open-ended questions concerning education from one hundred northern residents. A total of 528 minutes 32 seconds of taperecorded responses was available from twenty treaty and status Indians, twenty Metis, twenty Inuit and forty non-natives. Subjects included parents, university students, high school students, teacher trainees, teachers, education administrators, native politicians and general community members. The data were submitted to content analysis procedures with items coded according to the Data Analysis of Cognitive Style (DACS) Scale which had been adapted for use in the present study from the work of E. S. Schneidman (1966). Scale item frequencies for each respondent were tabulated and submitted for statistical analyses to the SPSS program discriminant analysis. This analysis identified significantly different functions which translated into patterns of thinking or cognitive styles. In addition this analysis identified the relative importance of functions as discriminators among groups and computed predictability scores which showed the percentage of respondents who were correctly classified according to cognitive styles. and demographic variables.<p>Findings of this study must be considered in relation to the following limitations: the size and nature of the stratified random sample; the reliability of the coders; the use of the unvalidated DACS scale; the ability of the analytical procedures to correctly discriminate among the study groups.<p> The study found that the groups which tended to think in relational styles were: Natives (Indian, Metis, Inuit), people with no university education or with less than one year at university; bilinguals (English and a native language); males; people under twenty years and over forty years of age. The terms Conflict-relational, Moral-relational and Inexactrelational were used to more precisely identify differing cognitive behaviors within the overall relational category. The groups which were found to exhibit analytical cognitive style behaviors included: the nonnative group; those respondents with two to four years of university education; and respondents between thirty and forty years of age. Subcategories within analytical styles were Conflict-analytical and Inexactanalytical.<p>When the Indian, Metis and Inuit respondents were combined into a "native" cultural group they strongly identified with the Moral-relational cognitive style (people-oriented, subjective, holistic, concerned with morals and ethics). The non-native group showed a strong negative relationship to this style. However, when each cultural group was analyzed separately, it was found that the Indian and Inuit subjects were somewhat more analytical (objective, linear, field-independent) than the Metis but less so than the non-natives. On the analysis of four groups, the nonnatives were found to relate to both relational and analytical styles of thinking, indicating a wide range of differences within the group.<p>It was concluded that significant differences existed in the cognitive styles preferred by respondents of different cultural, language, education, sex and age groups in this study. Cultural background was found to be the strongest discriminator in relation to cognitive style differences. It was further concluded that according to extrapolation of findings to the theoretical model it may be possible and desirable to modify curricula content and teaching techniques to achieve a closer match between teaching styles and cognitive and learning styles of. students of indigenous cultural backgrounds.

The present study investigated the cognitive styles of Indian, Metis, Inuit and non-native adults and adolescents of northern Canada and Alaska. The study identified three relational and two analytical cognitive styles. The styles differed significantly from each other in relation to cultural background, language facility, level of post-secondary education, sex and age of the respondents. Cultural background was found to be the most significant discriminator of those under investigation.<p> Procedure of the study involved the collection of verbalized responses to five open-ended questions concerning education from one hundred northern residents. A total of 528 minutes 32 seconds of taperecorded responses was available from twenty treaty and status Indians, twenty Metis, twenty Inuit and forty non-natives. Subjects included parents, university students, high school students, teacher trainees, teachers, education administrators, native politicians and general community members. The data were submitted to content analysis procedures with items coded according to the Data Analysis of Cognitive Style (DACS) Scale which had been adapted for use in the present study from the work of E. S. Schneidman (1966). Scale item frequencies for each respondent were tabulated and submitted for statistical analyses to the SPSS program discriminant analysis. This analysis identified significantly different functions which translated into patterns of thinking or cognitive styles. In addition this analysis identified the relative importance of functions as discriminators among groups and computed predictability scores which showed the percentage of respondents who were correctly classified according to cognitive styles. and demographic variables.<p>Findings of this study must be considered in relation to the following limitations: the size and nature of the stratified random sample; the reliability of the coders; the use of the unvalidated DACS scale; the ability of the analytical procedures to correctly discriminate among the study groups.<p> The study found that the groups which tended to think in relational styles were: Natives (Indian, Metis, Inuit), people with no university education or with less than one year at university; bilinguals (English and a native language); males; people under twenty years and over forty years of age. The terms Conflict-relational, Moral-relational and Inexactrelational were used to more precisely identify differing cognitive behaviors within the overall relational category. The groups which were found to exhibit analytical cognitive style behaviors included: the nonnative group; those respondents with two to four years of university education; and respondents between thirty and forty years of age. Subcategories within analytical styles were Conflict-analytical and Inexactanalytical.<p>When the Indian, Metis and Inuit respondents were combined into a "native" cultural group they strongly identified with the Moral-relational cognitive style (people-oriented, subjective, holistic, concerned with morals and ethics). The non-native group showed a strong negative relationship to this style. However, when each cultural group was analyzed separately, it was found that the Indian and Inuit subjects were somewhat more analytical (objective, linear, field-independent) than the Metis but less so than the non-natives. On the analysis of four groups, the nonnatives were found to relate to both relational and analytical styles of thinking, indicating a wide range of differences within the group.<p>It was concluded that significant differences existed in the cognitive styles preferred by respondents of different cultural, language, education, sex and age groups in this study. Cultural background was found to be the strongest discriminator in relation to cognitive style differences. It was further concluded that according to extrapolation of findings to the theoretical model it may be possible and desirable to modify curricula content and teaching techniques to achieve a closer match between teaching styles and cognitive and learning styles of. students of indigenous cultural backgrounds.

Nowadays, the need for sharing information between different systems in a secure manner is common, not only in the corporate world but also in the military world. This information often resides at different locations, creating a distributed system. In order to share information in a secure manner in a distributed system, credentials are often used to attain authorization. This thesis examines how such a distributed system for sharing information can be realized, using the technology readily available today. Accounting to the results of this examination a basic system is implemented, after which the overall security of the system is evaluated. The thesis then presents possible extensions and improvements that can be done in future implementations. The result shows that dynamic roles do not easily integrate with a single sign-on system. Combining the two technologies leads to several synchronization issues, where some are non-trivial to solve.

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A 4 bit, Rom-Less Direct Digital Frequency Synthesizer (DDFS) is designed in 65nm CMOS technology. Interleaving with Return-to-Zero (RTZ) technique is used to increase the output bandwidth and synthesized frequencies. The performance of the designed synthesizer is evaluated using Cadence Virtuoso design tool. With 3.2 GHz sampling frequency, the DDFS achieves the spurious-free dynamic range (SFDR) of 60 dB to 58 dB for synthesized frequencies between 200 MHz to 1.6 GHz. With 6.4 GHz sampling frequency, the synthesizer achieves the SFDR of 46 dB to 40 dB for synthesized frequencies between 400 MHz to 3.2 GHz. The power consumption is 80 mW for the designed mixed-signal blocks.