The radio-frequency spectrum is a precious resource, with many applications and users, especially with the recent spectrum auction in the United States. Future platforms and devices, such as radars and radios, need to be adaptive to their spectral environment in order to continue serving the needs of their users. This thesis considers an environment with one tracking radar, a single target, and a communications system. The radar-communications coexistence problem is modeled as a Markov decision process (MDP), and reinforcement learning is applied to drive the radar to optimal behavior. / Master of Science

The radio frequency spectrum is not being efficiently utilized partly due to the current policy of allocating the frequency bands to specific services and users. In opportunistic spectrum access (OSA), the ``white spaces'' that are not occupied by primary users (a.k.a. incumbent users) can be opportunistically utilized by secondary users. To achieve this, we need to solve two problems: (i) primary-secondary incumbent protection, i.e., prevention of harmful interference from secondary users to primary users; (ii) secondary-secondary network coexistence, i.e., mitigation of mutual interference among secondary users. The first problem has been addressed by spectrum sensing techniques in cognitive radio (CR) networks and geolocation database services in database-driven spectrum sharing. The second problem is the main focus of this dissertation. To obtain a clear picture of coexistence issues, we propose a taxonomy of heterogeneous coexistence mechanisms for shared spectrum access. Based on the taxonomy, we choose to focus on four typical coexistence scenarios in this dissertation. Firstly, we study sensing-based OSA, when secondary users are capable of employing the channel aggregation technique. However, channel aggregation is not always beneficial due to dynamic spectrum availability and limited radio capability. We propose a channel usage model to analyze the impact of both primary and secondary user behaviors on the efficiency of channel aggregation. Our simulation results show that user demands in both the frequency and time domains should be carefully chosen to minimize expected cumulative delay. Secondly, we study the coexistence of homogeneous CR networks, termed as self-coexistence, when co-channel networks do not rely on inter-network coordination. We propose an uplink soft frequency reuse technique to enable globally power-efficient and locally fair spectrum sharing. We frame the self-coexistence problem as a non-cooperative game, and design a local heuristic algorithm that achieves the Nash equilibrium in a distributed manner. Our simulation results show that the proposed technique is mostly near-optimal and improves self-coexistence in spectrum utilization, power consumption, and intra-cell fairness. Thirdly, we study the coexistence of heterogeneous CR networks, when co-channel networks use different air interface standards. We propose a credit-token-based spectrum etiquette framework that enables spectrum sharing via inter-network coordination. Specifically, we propose a game-auction coexistence framework, and prove that the framework is stable. Our simulation results show that the proposed framework always converges to a near-optimal distributed solution and improves coexistence fairness and spectrum utilization. Fourthly, we study database-driven OSA, when secondary users are mobile. The use of geolocation databases is inadequate in supporting location-aided spectrum sharing if the users are mobile. We propose a probabilistic coexistence framework that supports mobile users by locally adapting their location uncertainty levels in order to find an appropriate trade-off between interference mitigation effectiveness and location update cost. Our simulation results show that the proposed framework can determine and adapt the database query intervals of mobile users to achieve near-optimal interference mitigation with minimal location updates. / Ph. D.

Over the last few decades, wireless networks have morphed from traditional cellular/wireless local area networks (WLAN), into a wide range of applications, such as the Internet-of-Things (IoT), vehicular-to-everything (V2X), and smart grid communication networks. This transition has been facilitated by research and development efforts in academia and industry, which has resulted in the standardization of fifth-generation (5G) wireless networks. To meet the performance requirements of these diverse use-cases, 5G networks demand higher performance in terms of data rate, latency, security, and reliability, etc. At the physical layer, these performance enhancements are achieved by (a) optimizing spectrum utilization shared amongst multiple technologies (termed as spectrum sharing), and (b) leveraging advanced spatial signal processing techniques using large antenna arrays (termed as massive MIMO). In this dissertation, we focus on enhancing the performance of next-generation vehicular communication and spectrum sharing systems. In the first contribution, we present a novel pilot configuration design and adaptation mechanism for cellular vehicular-to-everything (C-V2X) networks. Drawing inspiration from 4G and 5G standards, the proposed approach is based on limited feedback of indices from a codebook comprised of quantized channel statistics information. We demonstrate significant rate improvements using our proposed approach in terrestrial and air-to-ground (A2G) vehicular channels. In the second contribution, we demonstrate the occurrence of cellular link adaptation failure due to channel state information (CSI) contamination, because of coexisting pulsed radar signals that act as non-pilot interference. To mitigate this problem, we propose a low-complexity semi-blind SINR estimation scheme that is robust and accurate in a wide range of interference and noise conditions. We also propose a novel dual CSI feedback mechanism for cellular systems and demonstrate significant improvements in throughput, block error rate, and latency, when sharing spectrum with a pulsed radar. In the third contribution, we develop fundamental insights on underlay radar-massive MIMO spectrum sharing, using mathematical tools from stochastic geometry. We consider a multi-antenna radar system, sharing spectrum with a network of massive MIMO base stations distributed as a homogeneous Poisson Point Process (PPP) outside a circular exclusion zone centered around the radar. We propose a tractable analytical framework, and characterize the impact of worst-case downlink cellular interference on radar performance, as a function of key system parameters. The analytical formulation enables network designers to systematically isolate and evaluate the impact of each parameter on the worst-case radar performance and complements industry-standard simulation methodologies by establishing a baseline performance for each set of system parameters, for current and future radar-cellular spectrum sharing deployments. Finally, we highlight directions for future work to advance the research presented in this dissertation and discuss its broader impacts across the wireless industry, and policy-making. / Doctor of Philosophy / The impact of today's technologies has been magnified by wireless networks, due to the standardization and deployment of fifth-generation (5G) cellular networks. 5G promises faster data speeds, lower latency and higher user security, among other desirable features. This has made it capable of meeting the performance requirements of key infrastructure such as smart grid and mission-critical networks, and novel consumer applications such as smart home appliances, smart vehicles, and augmented/virtual reality. In part, these capabilities have been achieved by (a) better spectrum utilization among various wireless technologies (called spectrum sharing), and (b) serving multiple users on the same resource using large multi-antenna systems (called massive MIMO). In this dissertation, we make three contributions that enhance the performance of vehicular communications and spectrum sharing systems. In the first contribution, we present a novel scheme wherein a vehicular communication link adapts to the channel conditions by controlling the resource overhead in real-time, to improve spectral utilization of data resources. The proposed scheme enhances those of current 4G and 5G networks, which are based on limited feedback of quantized channel statistics, fed back from the receiver to the transmitter. In the second contribution, we show that conventional link adaptation methods fail when 4G/5G networks share spectrum with pulsed radars. To mitigate this problem, we develop a comprehensive signal processing framework, consisting of a hybrid SINR estimation method that is robust and accurate in a wide range of interference and noise conditions. Concurrently, we also propose a scheme to pass additional information that captures the channel conditions in the presence of radar interference, and analyze its performance in detail. In the third contribution, we focus on characterizing the impact of 5G cellular interference on a radar system in shared spectrum, using mathematical tools from stochastic geometry. We model the worst-case interference scenario, and study the impact of the system parameters on the worst-case radar performance. In summary, this dissertation advances the state-of-the-art in vehicular communications and spectrum sharing, through (a) novel contributions in protocol design and (b) development of mathematical tools for performance characterization.

Les villages et les domaines coutumiers de la région de Riung, dans le centre-ouest de l'île de Florès (Indonésie orientale), constituent un ensemble hétérogène marqué par une variabilité culturelle, linguistique, et religieuse. Cette diversité prend place dans un contexte ethno-historique caractéristique du monde austronésien : un paysage traversé par des dynamiques structurantes de mobilité, de dispersion et d'agrégation de groupes humains ; autant de processus qu'accompagne une nécessaire flexibilité sociale et politique. S'éparpillant à partir d'une montagne locale ou débarquant sur la côte, les communautés de Riung s'organisent selon un mode essentiellement dualiste fondé sur un principe de préséance. L'altérité, conçue localement comme un invariant du « vivre ensemble », participe à l'émergence et à l'entretien d'une ethnicité. Cette thèse interroge la construction du paysage social Riung à travers trois axes d'analyse principaux : d'abord les élaborations culturelles et sociales liées à la conception locale de l' « origine », ensuite les processus ethno-historiques d'organisation sociale, enfin les pratiques, notamment matrimoniales, qui articulent et alimentent les espaces d'interrelations. A ces différents niveaux de la vie sociale correspondent par ailleurs des dynamiques identitaires elles-mêmes variées : la continuité d'une identité « ancestrale » de lignage ; la gestion d'une division religieuse de la population entre catholiques et musulmans ; et l'émergence d'une identité « ethnique ». / The villages and traditional domains of the Riung region, in west-central Flores (eastern Indonesia) constitute a heterogeneous assemblage marked by cultural, linguistic, and religious variability. This diversity takes place in a typical Austronesian ethno-historical context: a landscape crossed by structuring dynamics of mobility, dispersion, and aggregation of human groups. Such processes necessarily go with a social and political flexibility. Scattered from a local mountain or landed on the coast, Riung communities are organized according to an essentially dualistic way founded on a principle of precedence. The ‘otherness', locally conceived as an invariant of the ‘togetherness', contributes to the emergence and the sustaining of an ethnicity. This dissertation questions the construction of Riung social landscape through three main analytical axes: the social and cultural elaborations concerned by the local conception of ‘origin', the ethno-historical processes of social organization, and the social practices, notably alliance and marriage, which articulate and maintain spaces of interrelations. To these different levels of social life corresponds a variety of dynamics of identity: the continuity of the lineage ‘ancestral' identity; the management of the religious division between Catholics and Muslims; and the emergence of an ‘ethnic' identity.

Investigamos o sistema formado por dois condensados aprisionados em estados hiperfinos diferentes do Rubídio, num potencial em forma de charuto, ou seja, num sistema físico real e quase-unidimensional. É investigada a dependência das soluções das equações de Gross-Pitaevski com a separação entre as armadilhas, bem como com o parâmetro de acoplamento de Josephson, para três valores diferentes do número total de átomos aprisionados. Para alguns conjuntos de parâmetros constatamos a existência de estados metaestáveis. O observável que escolhemos para caracterizar tal sistema físico foi a separação média entre os pacotes, pois os dois ramos de soluções encontramos correspondem a soluções mais juntas ou mais separadas espacialmente. / We study the system formed by two coupled condensates of different Rubidium hyperfine states trapped in a cigar shaped potential, that is, a real quasi one-dimensional system. The dependency of the solution of the Gross-Pitaevski equations is investigated as a function of trap displacement and Josephson coupling parameter for three different values of the total trapped atoms number. For some sets of parameters we report the existence of metastable states. The observable we chose to characterize this system was the mean separation between the packages, because we found two branches which correspond to closer or more separated solutions.

Après l'arrivée au pouvoir des révolutionnaires cubains en 1959, l'Amérique latine s'insère de plain-pied dans la« guerre froide pour les idées», suscitant un intérêt croissant de la part des deux superpuissances : les États-Unis et l'Union soviétique. Quant à cette dernière, le bouleversement social à Cuba incite le Kremlin à porter un regard intéressé sur l'île des Caraïbes, un pays qui deviendra plus tard, après une phase de divergences (1962-1968), un allié fidèle de Moscou. Mais le rapprochement de l'URSS avec La Havane entraîne également une doctrine spécifique envers d'autres pays du continent latino-américain. C'est le cas du Chili, un État qui, sous la présidence d'Eduardo Frei (1964-1970), noue des accords ambitieux avec l'Est, encourageant des échanges accrus. Cette tendance, interrompue tragiquement suite au coup d'État de Pinochet en septembre 1973, se renforcera après la victoire électorale de Salvador Allende en 197 0. Outre l'essor des relations politiques ou économiques, l'administration soviétique à l'ère de Nikita Khrouchtchev s'efforce de mettre en place une vigoureuse diplomatie culturelle, ce qui se traduira par des interactions grandissantes avec la Cuba castriste et le Chili des années 1960 et 1970. Alors qu'à Santiago, la culture soviétique est appelée à dévoiler un côté positif d'un pays méconnu, à Cuba, elle devient vite un indice des liens privilégiés tissés entre deux États qui font désormais partie du même« camp idéologique». Cependant, les effets que les échanges culturelles produisent ne sont pas les mêmes dans les deux régions analysées, engendrant des représentations sociales hétérogènes, voire ambivalentes, indissociables de chaque contexte. Par le biais d'une perspective comparative, fondée sur les priorités soviétiques à Cuba et au Chili, il est possible de prendre la mesure des spécificités de la politique extérieure du Kremlin en Amérique latine ainsi que des effets variés que la nouvelle proximité provoque. Cette approche nous autorise aussi à constater que les rapports à l'égard d'un État conditionnent souvent la politique menée envers l'autre, érigeant une « logique triangulaire» des relations URSS-Chili-Cuba. / After the Cuban Revolution in 1959, Latin America became a crucial point of the "Cold War for the ideas", generating a growing interest of both United States and Soviet Union. Concerning USSR, social transformation of Cuba encouraged the Kremlin to have an attentive eye on the Caribbean island, a country that will become, after a phase of divergences (1962-1968), a faithful Moscow's ally. But the rapprochement between USSR and Havana also foster a specific doctrine with regard to other Latin American countries. It was the case of Chile, a state that during Eduardo Frei's administration (1964-1970) signed ambitious agreements with the East, encouraging bilateral exchanges. This trend, brutally interrupted by Pinochet’s coup d'état in September 1973, strengthened after the election of Salvador Allende in 1970. Beyond the growth of political and economic relations, Khrushchev’s administration made an effort to consolidate a powerful cultural diplomacy, which will result in increasing interactions with Castro’s Cuba and Chile of the 1960s and the early 1970s. While in Santiago, Soviet culture was supposed to unveil a positive facet of a largely ignored country, in Cuba, it became rapidly a mark of the privileged links built between two states belonging to the same "ideological camp". Nonetheless, the effect of cultural exchanges was not the same in the different areas analyzed, engendering heterogeneous and even ambivalent social representations that were deeply associated to each context. On the basis of a comparative approach, focused on Soviet priorities in Cuba and Chile, it is possible to measure the nature of Kremlin's foreign policy in Latin America, as well as the various consequences of the new international proximity. This standpoint also allows us to remark that relations with one state may determine the policy towards other nations, configuring a "triangular articulation" of Soviet-Chilean-Cuban relations.

Depuis 2011, le droit local alsacien-mosellan est un principe fondamental reconnu par les lois de la République. Il est un droit particulier applicable ratione loci dans les départements du Bas-Rhin, du Haut-Rhin et de la Moselle. Ratione materiae, il régit un ensemble hétérogène de matières. En 1914, alors que la Première Guerre mondiale vient de débuter, la France commence à anticiper une éventuelle réintégration de l’Alsace-Lorraine sous la souveraineté nationale. La préparation de la désannexion du territoire cédé à l’Empire allemand après la guerre franco-prussienne conduit au maintien provisoire, en 1919, de la législation applicable dans les « provinces reconquises ». De 1920 à 1925, la réalisation de la désannexion entraîne ensuite l’institutionnalisation d’un droit alsacien-mosellan, puis sa consolidation. La formalisation du droit local alsacien-mosellan dans l’ordre juridique français semble dès lors apparaître comme une conséquence indirecte de la désannexion. / The local law in Alsace-Moselle is a distinctive legal system in effect in the Bas-Rhin, Haut-Rhin and Moselle French departments. Covering a heterogeneous group of topics, the local law became in 2011 a constitutional principle (known as « principe fondamental reconnu par les lois de la République »).In 1914, after the outbreak of the First World War, France started to anticipate a potential return of Alsace-Lorraine to the French rule. The preparation of the « désannexion » of the area annexed by the German Empire after the Franco-Prussian War ended in the temporary upholding of the legislation in force in the « recaptured provinces », in 1919. Between 1920 and 1925, the carrying out of the « désannexion » of this territory brought about the institutionalization of an Alsace-Moselle special legal system, and then its consolidation.Therefore, the formalization of the local law in Alsace-Moselle within the French legal order seems to appear as an indirect consequence of the « désannexion ».

La plasticité phénotypique, i.e. la capacité d’un génotype à exprimer plusieurs phénotypes en fonction des conditions environnementales, représente une source de variabilité phénotypique, et tient donc un rôle majeur dans l’évolution. Dans un environnement variable, les stratégies généralistes, capables de maintenir une valeur d’aptitude phénotypique (fitness) stable sur une plus large gamme de conditions environnementales grâce à une plus grande plasticité de traits sous-jacents, devraient être favorisées. L’analyse de normes de réaction, au laboratoire et en conditions naturelles, de traits physiologiques et de traits liés à la fitness en fonction de la température, révèle chez le parasitoïde Venturia canescens, que (i) la variabilité thermique de l’habitat détermine la forme des normes de réaction selon le compromis entre stratégies généraliste et spécialiste, (ii) les différences entre individus généralistes et spécialistes se maintiennent face à des fluctuations de la température mimant les conditions naturelles et (iii) les individus subissant une plus grande variabilité thermique dans leur habitat possèdent une capacité d’acclimatation au froid plus importante. Ces résultats montrent l’existence de deux stratégies chez V. canescens et donc une différenciation de leur niche thermique, autorisant leur coexistence en environnement hétérogène / Phenotypic plasticity, i.e. the ability of a genotype to express several phenotypes depending on environmental conditions, represents an important source of phenotypic variability and so plays a major role in evolution. In a variable environment, generalist strategies, able to maintain a stable value of fitness over a wide range of environmental conditions, thanks to a greater plasticity of underlying traits, should be favored. The analysis of reaction norms of physiological traits and traits related to fitness as a function of temperature reveals in the parasitoid Venturia canescens that (i) thermal variability of the habitat determines the shape of reaction norms, according to the trade-off between generalist and specialist strategies, (ii) differences between generalist and specialist individuals are maintained face to rapid fluctuations in temperature that mimic natural conditions and (iii) individuals experiencing greater variability in their thermal habitat have a greater capacity for cold acclimation. These results indicate the existence of two different strategies in V. canescens and therefore a thermal niche differentiation, allowing their coexistence in a heterogeneous environment

Addressing school climate and violence in schools requires school management skills. The 2011 School Violence Act in Chile promulgated the mandatory creation of the school climate coordinator (SCC). However, the law did not establish a defined profile, specific functions, or working hours for the SCC, and only recently have school administrators given SCCs more time for this position. This has created a flexible operating framework for the position, which could have implications in terms of the labor identity of the SCCs. This exploratory study employed a qualitative case study. An exploratory focus group was conducted with the school climate committee and three in-depth interviews with the SCC of one municipal school. Content analyses revealed the ambiguity of the SCC figure due to a fragmentation of roles in the areas of pedagogy, administration and school climate, creating a scenario where the roles of teacher, inspector, and SCC are segmented. We discuss how the notion of school climate is separated within the school practice from the dimensions of pedagogy school management, and its possible effects. / Abordar la convivencia y violencia en las escuelas requiere de capacidades de gestión escolar. La Ley de Violencia Escolar en Chile de 2011 promulgó la creación obligatoria de la figura del encargado de convivencia escolar (ECE). Sin embargo, la ley no estableció un perfil definido, funciones específicas, ni horas de trabajo para el ECE, y solo paulatinamente los sostenedores han ido aumentando las horas laborales para ejercer este cargo. Ello ha generado un marco flexible de funcionamiento para el ECE, que podría tener implicancias en la construcción de su identidad laboral. Este estudio exploratorio utilizó un método de investigación cualitativa a partir del desarrollo de un estudio caso único de un ECE. Se produjo información a través de un grupo focal con el comité de convivencia escolar y entrevistas en profundidad al ECE de la escuela. Usando el método de análisis de contenido, los resultados revelan la ambigüedad de la identidad del ECE, por contar con roles segmentados en las áreas de pedagogía, administración y convivencia escolar. Se discute cómo en la práctica escolar la noción de convivencia es separada de las dimensiones de pedagogía y gestión, y cuáles son sus efectos. / L’approche de la coexistence et de la violence dans les écoles nécessite des compétences en gestion scolaire. La loi sur la violence scolaire au Chili de 2011 a promulgué la création obligatoire de la personne en charge de la coexistence scolaire (ECE). Cependant, la loi n’a pas établi de profil défini, de fonctions spécifiques ou d’heures de travail pour la ECE, et ce n’est que progressivement que les partisans ont augmenté leurs heures de travail pour exercer ce poste. Cela a généré un cadre opérationnel souple pour la ECE, ce qui pourrait avoir des implications pour la construction de leur identité de travail. Cette étude exploratoire a utilisé une méthode de recherche qualitative à partir du développement d’une seule étude de cas d’une ECE. L’information a été produite à travers un groupe de discussion avec le comité de coexistence de l’école et des entretiens approfondis avec l’ECE de l’école. À l’aide de la méthode d’analyse de contenu, les résultats révèlent l’ambiguïté de l’identité de la ECE, pour avoir des rôles segmentés dans les domaines de la pédagogie, de l’administration et de la coexistence scolaire. Il est discuté comment dans la pratique scolaire la notion de coexistence est séparée des notions de pédagogie et de gestion, et quels sont leurs effets. / Abordar a convivência e a violência nas escolas requer habilidades de gestão escolar. A Lei de Violência Escolar de 2011 no Chile promulgou a criação obrigatória do coordenador de convivência escolar (CCE). No entanto, a lei não estabeleceu um perfil definido, funções específicas ou horas de trabalho para a CCE, e gradualmente a equipe de suporte estava aumentando o horário de trabalho para essa posição. Isso criou um quadro operacional flexível para a CCE, que poderia ter implicações para a construção de sua identidade de trabalho. Este estudo exploratório utilizou um método de pesquisa qualitativa a partir do desenvolvimento de um único estudo de caso de um CCE. A informação foi produzida através de um grupo focal com o comitê de convivência escolar e entrevistas em profundidade com a CCE da escola. Usando o método de análise de conteúdo, os resultados revelam a ambiguidade da identidade da ECE, porque tem papéis segmentados nas áreas de pedagogia, administração e convivência escolar. É discutido como na prática escolar a noção de convivência é separada das dimensões da pedagogia e gestão, e quais são seus efeitos.

Investigamos o sistema formado por dois condensados aprisionados em estados hiperfinos diferentes do Rubídio, num potencial em forma de charuto, ou seja, num sistema físico real e quase-unidimensional. É investigada a dependência das soluções das equações de Gross-Pitaevski com a separação entre as armadilhas, bem como com o parâmetro de acoplamento de Josephson, para três valores diferentes do número total de átomos aprisionados. Para alguns conjuntos de parâmetros constatamos a existência de estados metaestáveis. O observável que escolhemos para caracterizar tal sistema físico foi a separação média entre os pacotes, pois os dois ramos de soluções encontramos correspondem a soluções mais juntas ou mais separadas espacialmente. / We study the system formed by two coupled condensates of different Rubidium hyperfine states trapped in a cigar shaped potential, that is, a real quasi one-dimensional system. The dependency of the solution of the Gross-Pitaevski equations is investigated as a function of trap displacement and Josephson coupling parameter for three different values of the total trapped atoms number. For some sets of parameters we report the existence of metastable states. The observable we chose to characterize this system was the mean separation between the packages, because we found two branches which correspond to closer or more separated solutions.