We propose a simple, passive and deployable approach for fingerprinting traffic on the wired side as a solution for three critical stealth attacks in wireless networks. We focus on extracting traces of the 802.11 medium access control (MAC) protocol from the temporal arrival patterns of incoming traffic streams as seen on the wired side, to identify attacker behavior. Attacks addressed include unauthorized access points, selfish behavior at the MAC layer and MAC layer covert timing channels. We employ the Bayesian binning technique as a means of classifying between delay distributions. The scheme requires no change to the 802.11 nodes or protocol, exhibits minimal computational overhead and offers a single point of discovery. We evaluate our model using experiments and simulations.

Medan servervirtualisering växt väldigt mycket det senaste decenniet har Apple nyligen börjat tillåta virtualisering av deras operativsystem Mac OS X. På grund av Apples stora framgångar med att lyckas sälja sina produkter till hemanvändare har nu även Mac-datorer börjat hitta till arbetsplatsen. Detta gör att det kommer finnas ett behov av att virtualisera Mac OS X i företagsmiljöer i framtiden då servervirtualisering är väldigt kostnadseffektivt. För att kunna virtualisera krävs en så kallad hypervisor. Det finns två olika typer, typ 1 och typ 2. I denna uppsats ville vi undersöka prestandaskillnader mellan dessa två typer vid virtualisering av Mac OS X. Detta för att kunna se hur prestandan skiljer dem sinsemellan. Prestandatester genomfördes i en experimentmiljö där resultaten visar att en typ 1-hypervisor ger mindre prestandaförluster än en typ 2- hypervisor.

Το σύστημα του συμπληρώματος περιλαμβάνει περισσότερες από 30 πρωτεΐνες του ορού και της κυτταρικής επιφάνειας και αποτελεί έναν από τους αρχαιότερους φυλογενετικά μηχανισμούς ανοσίας του ξενιστή. Η ενεργοποίησή του, μέσω της κλασικής, της εναλλακτικής ή της λεκτινικής οδού, οδηγεί σε έναν καταρράκτη αντιδράσεων. Οι αντιδράσεις αυτές συγκλίνουν στην τελική λυτική οδό, οδηγώντας στη δημιουργία του συμπλόκου MAC, με αποτέλεσμα την ωσμωτική λύση του κυττάρου στόχου. Στην παρούσα εργασία, σχετικά με τη μελέτη της μοριακής εξέλιξης των γονιδίων της τελικής λυτικής οδού του συμπληρώματος, κλωνοποίηθηκε η αλληλουχία του cDNA του έκτου συστατικού του συμπληρώματος (C6). Στη συνέχεια, προκειμένου να εξαχθούν συμπεράσματα σχετικά με τη συντήρηση όλων των δομικών γονιδίων του συμπλόκου MAC κατά τη διάρκεια της φυλογενετικής εξέλιξης, δημιουργήθηκε φυλογενετικό δέντρο, στο οποίο συγκρίνονται τα παραπάνω γονίδια με τα αντίστοιχα ορθόλογα, σε διάφορους οργανισμούς. Από τη φυλογενετική ανάλυση φαίνεται ότι το C6 της όρνιθας ομαδοποιείται με τα αντίστοιχα ορθόλογα των θηλαστικών και του βατράχου, δημιουργώντας μια καλά καθορισμένη υποομάδα μέσα στην οικογένεια των πρωτεϊνών MACPF. Σύμφωνα με την υπάρχουσα βιβλιογραφία, εκτός από το ρόλο που διαδραματίζει το σύστημα του συμπληρώματος στην ανοσία, έχει δειχθεί η εμπλοκή του, μεταξύ άλλων, σε διαδικασίες αναγέννησης ιστών, ενεργοποίησης και πολλαπλασιασμού κυττάρων και ρύθμισης της απόπτωσης. Προκειμένου λοιπόν να διερευνηθεί περαιτέρω η πιθανότητα εμπλοκής του συστήματος του συμπληρώματος σε διαδικασίες που σχετίζονται με την ανάπτυξη, μελετήθηκε το αναπτυξιακό και ιστικό πρότυπο έκφρασης συστατικών του στην όρνιθα. Η ιστική μελέτη περιελάμβανε τη διερεύνηση και ημι-ποσοτική ανάλυση της έκφρασης, σε επίπεδο mRNA, σε οκτώ ιστούς της ενήλικης όρνιθας: εγκέφαλο, καρδιά, έντερο, νεφρό, ήπαρ, πνεύμονα, σπλήνα και στόμαχο. Η αναπτυξιακή μελέτη, περιελάμβανε τη διερεύνηση και ημι-ποσοτική ανάλυση της έκφρασης, σε επίπεδο mRNA, σε ολικό ομογενοποιημένο έμβρυο 4 και 6 ημερών, σε ήπαρ εμβρύου 12 και 17 ημερών και σε ήπαρ νεογένητου ατόμου 2 και 5 ημερών. Συγκεκριμένα, μελετήθηκε η έκφρασή του γονιδίου C3 σε διάφορα αναπτυξιακά στάδια, όπου και πιστοποιήθηκε η παρουσία του μορίου σε όλα τα στάδια. Επίσης, μελετήθηκε η ιστική και η αναπτυξιακή έκφραση των δομικών γονιδίων του συμπλόκου MAC (C6, C7, C8α, C8β, C8γ) και η αναπτυξιακή των ρυθμιστικών γονιδίων του (CD59, CLU,VTN). Η μελέτη του ιστοειδικού προτύπου έκφρασης για τα δομικά συστατικά του συμπλόκου, έδειξε ότι τα διάφορα συστατικά παρουσιάζουν ποικίλη έκφραση στους υπό μελέτη ιστούς, ενώ κύρια πηγή έκφρασής τους αποτελεί το ήπαρ. Κατά τη μελέτη του αναπτυξιακού προτύπου έκφρασης, δείχθηκε ότι τα δομικά συστατικά του συμπλόκου πρωτοεμφανίζονται τη 12η εμβρυική μέρα ενώ δεν παρατηρείται έκφρασή τους σε νεογέννητο άτομο 2 ημερών. Αντίθετα, η μελέτη του αναπτυξιακού προτύπου έκφρασης των ρυθμιστικών μορίων του συμπλόκου, έδειξε έκφραση όλων των συστατικών σε όλα τα υπό μελέτη στάδια. Το γεγονός αυτό αντανακλά πιθανώς την πλειοτροπική δράση των ρυθμιστικών αυτών πρωτεϊνών, καθώς εμπλέκονται σε πρόσθετες λειτουργίες οι οποίες δε σχετίζονται με τη δράση του συμπληρώματος, όπως είναι η ανάπτυξη και ωρίμανση οργάνων. Ανάλογα συμπεράσματα θα μπορούσαν να εξαχθούν και στην περίπτωση του μορίου C3, λόγω της έκφρασής του σε πρώιμα στάδια ανάπτυξης της όρνιθας, παρά την απουσία έκφρασης των γονιδίων του συμπλόκου MAC στα αντίστοιχα αναπτυξιακά στάδια. Συμπερασματικά, η παραπάνω εργασία αποτελεί την πρώτη αναφορά στη χωρική και χρονική μελέτη της έκφρασης γονιδίων του συμπληρώματος στην όρνιθα. Βάσει των παραπάνω, περαιτέρω διερεύνηση αναφορικά με τη συμμετοχή των συστατικών του συμπληρώματος σε αναπτυξιακές διεργασίες, παρουσιάζει πλέον ιδιαίτερο ενδιαφέρον. / The complement system includes more than 30 serum and membrane proteins and constitutes one of the most phylogenetically ancient immune mechanisms of the host. Its activation, via the classic, alternative or lectin pathway, leads to a cascade of reactions. All these reactions converge to the terminal lytic pathway, leading to the MAC complex creation, which results in osmotic lysis of the targeted cells. In the present work, concerning the study of the molecular evolution of the terminal complement pathway genes, the sixth complement component (C6) of the chicken (Gallus gallus) was cloned. Afterwards, a phylogenetic tree was created, in which the above genes are compared with the respective orthologs, in various organisms. As it seems from the phylogenetic analysis, chicken’s C6 clusters with the respective mammalian and frog orthologs, creating a well defined subgroup in the MACPF gene family. According to literature, besides the complement system’s role in immunity, it has been shown that it is also involved, in tissue regeneration, cell activation, proliferation and regulation of apoptosis. In order to further investigate the hypothesis of complement system’s involvement in developmental procedures, the developmental and tissue expression profile of complement components were studied in the chicken. The tissue study involved the investigation and semi-quantitative expression analysis, at the mRNA level, in eight tissues deriving from one adult chicken: brain, heart, intestine, kidney, liver, lung, spleen and stomach. The developmental study included the investigation and semi-quantitative expression analysis, at the mRNA level, of the whole homogenized 4 and 6 day embryo, in the liver from a 12 and 17 day embryo and the liver from a neonate chicken, 2 and 5 days old. In particular, the expression of C3 gene was studied in various developmental stages where the gene expression was certified in all stages. Moreover, the tissue and developmental expression of MAC complex structural genes (C6, C7, C8α, C8β, C8γ) was studied, as well as the developmental expression of the regulatory genes of MAC complex (CD59, CLU,VTN). The study of the tissue expression profile for the structural MAC components was shown that the various components exhibit a variable expression, with the liver being the major source of expression. In the developmental expression 117 profile study, it was shown that all structural MAC components initially appear in the 12th embryonic day, while no expression of them was detected in the 2 day old neonate chicken. On the contrary, the developmental expression profile study of the regulatory MAC genes was shown that they expressed throughout the developmental stages. This fact possibly reflects the regulatory proteins pleiotropic action, as they are involved in additional functions, which are not related to complement functions, such as development and organs maturation. Analogous conclusions could be drawn in the case of C3 gene, because of its expression in stages of chicken early development, despite the absence of expression of structural MAC genes in the respective developmental stages. Concluding, the above study is the first reference to the spatial and temporal expression of complement genes in the chicken. In accordance with the above mentioned, further investigation concerning the involvement of complement components in developmental procedures, appears to be of great interest.

The scarcity of bandwidth in the radio spectrum has become more vital since the demand for wireless applications has increased. Most of the spectrum bands have been allocated although many studies have shown that these bands are significantly underutilized most of the time. The problem of unavailability of spectrum bands and the inefficiency in their utilization have been smartly addressed by the cognitive radio (CR) technology which is an opportunistic network that senses the environment, observes the network changes, and then uses knowledge gained from the prior interaction with the network to make intelligent decisions by dynamically adapting transmission characteristics. In this thesis, recent research and survey about the advances in theory and applications of cognitive radio technology has been reviewed. The thesis starts with the essential background on cognitive radio techniques and systems and discusses those characteristics of CR technology, such as standards, applications and challenges that all can help make software radio more personal. It then presents advanced level material by extensively reviewing the work done so far in the area of cognitive radio networks and more specifically in medium access control (MAC) protocol of CR. The list of references will be useful to both researchers and practitioners in this area. Also, it can be adopted as a graduate-level textbook for an advanced course on wireless communication networks. The development of new technologies such as Wi-Fi, cellular phones, Bluetooth, TV broadcasts and satellite has created immense demand for radio spectrum which is a limited natural resource ranging from 30KHz to 300GHz. For every wireless application, some portion of the radio spectrum needs to be purchased, and the Federal Communication Commission (FCC) allocates the spectrum for some fee for such services. This static allocation of the radio spectrum has led to various problems such as saturation in some bands, scarcity, and lack of radio resources to new wireless applications. Most of the frequencies in the radio spectrum have been allocated although many studies have shown that the allocated bands are not being used efficiently. The CR technology is one of the effective solutions to the shortage of spectrum and the inefficiency of its utilization. In this thesis, a detailed investigation on issues related to the protocol design for cognitive radio networks with particular emphasis on the MAC layer is presented. A novel Dynamic and Decentralized and Hybrid MAC (DDH-MAC) protocol that lies between the CR MAC protocol families of globally available common control channel (GCCC) and local control channel (non-GCCC). First, a multi-access channel MAC protocol, which integrates the best features of both GCCC and non-GCCC, is proposed. Second, an enhancement to the protocol is proposed by enabling it to access more than one control channel at the same time. The cognitive users/secondary users (SUs) always have access to one control channel and they can identify and exploit the vacant channels by dynamically switching across the different control channels. Third, rapid and efficient exchange of CR control information has been proposed to reduce delays due to the opportunistic nature of CR. We have calculated the pre-transmission time for CR and investigate how this time can have a significant effect on nodes holding a delay sensitive data. Fourth, an analytical model, including a Markov chain model, has been proposed. This analytical model will rigorously analyse the performance of our proposed DDH-MAC protocol in terms of aggregate throughput, access delay, and spectrum opportunities in both the saturated and non-saturated networks. Fifth, we develop a simulation model for the DDH-MAC protocol using OPNET Modeler and investigate its performance for queuing delays, bit error rates, backoff slots and throughput. It could be observed from both the numerical and simulation results that when compared with existing CR MAC protocols our proposed MAC protocol can significantly improve the spectrum utilization efficiency of wireless networks. Finally, we optimize the performance of our proposed MAC protocol by incorporating multi-level security and making it energy efficient.

This thesis describes the design and development of the SmartBadge; an electronic replacement for the standard paper name badge worn at conferences and similar events. Both hardware and software have been designed for the SmartBadge; the hardware has been developed around a CC1010 microcontroller and RF transceiver. Attached to this are an infrared transceiver, an LCD display, some LEDs, buttons and a piezoelectric buzzer. There is also an antenna for the RF transceiver whose design is the result of SuperNEC [1] simulations. Protocol software development has focussed on the communication between a SmartBadge and other badges and base stations, yet there is still space available in the CC1010s flash memory to develop applications beyond the business card exchange example developed to demonstrate the communication software. The SmartBadge communicates with other badges by using the infrared transceiver. In the business card application a SmartBadge is worn by a person and is collecting the ID and a time counter from SmartBadges worn by other facing people as this person mingles through a conference or similar event. This data is then collected in real time using the RF transceiver to communicate with base stations which would be scattered around the venue. The RF network has been designed as a single hop network and a new Medium Access Control (MAC) protocol has been designed to allow the SmartBadges to share the links to the base stations while conserving as much energy as possible. This protocol is called Uplink MAC (or U-MAC) and is described in section 6.2.

Le monde actuel connaît de profondes mutations démographiques étroitement liées au développement du domaine de la santé publique. L’accroissement de l’espérance de vie s’accompagne d’une augmentation du nombre des personnes âgées, en particulier celles atteintes de maladies chroniques. Plusieurs projets de recherche existants ont comme objectif d’assurer le maintien à domicile des personnes âgées, par un meilleur suivi en utilisant les nouvelles technologies. Parmi eux, nous trouvons le projet CANet qui propose l’utilisation de la canne comme un outil de surveillance non intrusif par l’intégration d’une multitude de capteurs. La canne utilise un système de communication sans fil qui lui permet d’échanger avec un centre de collecte ou de surveillance. Cette solution technologique permet le respect de la vie privée des personnes âgées, sans limiter leur liberté. Notre sujet de thèse s’inscrit dans le cadre de ce projet CANet. Les travaux de thèse sont principalement organisés autour de la conception d’une architecture topologique protocolaire, et des méthodes d’accès aux réseaux sans fil qui permettent la surveillance des personnes âgées à travers un réseau de capteurs embarqués dans une canne. L’objectif principal de la thèse est l’étude des architectures et des protocoles mis en œuvre au niveau communication sans fil pour offrir une infrastructure réseau fiable pour divers services de surveillance, de mesures, d'acheminement de données vers un centre de contrôle distant (cabinet médical, membres de la famille, etc.). Ces propositions ont fait l’objet d’une étude théorique et d’analyses de performances par simulation. / The world is undergoing profound demographic changes closely linked with the development of the field of public health. The increase in life expectancy is accompanied by an increase in the number of elderly people, in particular those with chronic diseases. Several existing research projects have as objective to ensure the maintenance to homes of the elderly, by a better follow-up by using new technologies. Among them, we find the proposed CANet who proposed the use of sugar cane as a tool for monitoring non-intrusive by the integration of a multitude of sensors. The cane used a wireless communication system, which allows him to exchange with a collection center or surveillance. This technological solution allows the respect of the private life of older persons, without limiting their freedom. Our thesis subject is inscribed in the framework of this project CANet. The work of this thesis is organized primarily around the design of an architecture protocol topology, and access methods for wireless networks, which allow monitoring of older persons through a network of sensors embedded in a cane. The main objective of the thesis is the study of architectures and protocols implemented at the level wireless communication to provide a reliable network infrastructure for various services for monitoring, measures, routing of data to a control center remote (medical office, members of the family, etc.). These proposals have been the subject of a theoretical study and analysis of performance by simulation.

Ce mémoire de thèse s’intéresse aux réseaux hétérogènes de capteurs sans fil (Wireless Sensor Networks – WSNs) constitués par une multitude de dispositifs de détection qui coexistent malgré leurs caractéristiques différentes. Contrairement aux réseaux homogènes de capteurs, chaque capteur d’un réseau hétérogène est capable de détecter et mesurer différents phénomènes physiques (température, pression, humidité) et générer ainsi un trafic avec des caractéristiques spécifiques, différentes d’un capteur à l’autre.En effet, selon l’application visée, le déploiement initial des nœuds peut être aléatoire, résultant en une répartition non-homogène des nœuds dans l’environnement. Autres facteurs comme l’extinction d’un nœud suite à l’épuisement de sa batterie ou à une faute générique peuvent impacter l’hétérogénéité de la répartition des nœuds. Tous ces phénomènes peuvent être perçus comme une source supplémentaire d’hétérogénéité dans les réseaux de capteurs sans fil. Puisque les facteurs d’hétérogénéité peuvent évoluer tant au cours du temps que dans l’espace, il est indispensable de concevoir des mécanismes adaptatifs pour les réseaux hétérogènes de capteurs afin de réagir et de s’adapter à la dynamique du réseau. De tels mécanismes adaptatifs sont toutefois difficiles à mettre en place. L’objectif majeur de cette thèse est d’étudier les problèmes liés à l’hétérogénéité dans les réseaux de capteurs sans fil afin de concevoir des méthodes de contrôle de l’accès au canal (Medium Access Control – MAC) qui s’adaptent à la dynamique de l’hétérogénéité tout en étant économe d’un point de vue énergétique. Deux sources d’hétérogénéité sont envisagées.Dans un premier temps, nous considérons les problématiques liées aux sources dans trafics multiples chacune dotée de caractéristiques et contraintes spécifiques. Pour pallier ce problème, un protocole MAC adaptatif basé sur une approche asynchrone est proposé ; il consiste en une méthode MAC de préservation de l’énergie, couplée à l’utilisation d’un instant de rendez-vous pour la transmission des données. Le protocole proposé, LA-MAC pour Low-Latency MAC, permet de garantir de façon efficace le transport de messages au travers d’un réseau multi-sauts grâce à la transmission d’agrégats de données (bursts). De vastes campagnes de simulations numériques corroborent la supériorité de LA-MAC en termes de latence, de taux de paquets correctement délivrés et de consommation énergétique par rapport à d’autres protocoles présentés dans l’état de l’art.Dans un second temps, nous étudions des réseaux dynamiques de capteurs sans fil, dont la densité de nœuds varie en temps et en espace. Cette densité des nœuds dans le réseau peut se définir comme étant le nombre de dispositifs avec des données à émettre par mètre carré. En effet, de brusques augmentations de la densité résultent en un accroissement du taux de paquets perdus en raison d’une hausse de la probabilité de collision des trames. En outre, une baisse de la densité des nœuds peut causer un gaspillage énergétique dû à une écoute oisive. Dans ce mémoire, nous traitons des réseaux dynamiques de capteurs sans fils dans lesquels les nœuds et les liens radio entre ces nœuds peuvent apparaître ou disparaître au cours du temps en raison de l’épuisement de leurs batterie, ou de toute autre opération d’administration du réseau, comme par exemple le déploiement de nœuds additionnels. Le travail présenté démontre qu’il est possible de fournir un support à la qualité de service (QoS) dans les réseaux dynamiques grâce à une méthode MAC adaptative et consciente de la densité, baptisée DA-MAC pour Density Aware MAC. Avec DA-MAC, les nœuds s’appuient sur la valeur de la densité locale et adaptent périodiquement les paramètres locaux qui régissent le protocole afin d’accéder au canal sans collision. L’efficacité du protocole proposé est présentée en comparaison d’autres protocoles de l’état de l’art dans de vastes campagnes de simulations numériques. / In this PhD thesis, we consider heterogeneous Wireless Sensor Networks (WSNs) in which several sensing devices with different characteristics coexist. In contrast to a homogeneous sensor network, in heterogeneous networks different sensors may sense different physical phenomena generating traffic that have different characteristics such as monitoring temperature, pressure, and humidity. Moreover, also information criticality can be heterogeneous. Deployment of nodes also introduces heterogeneity in the network. Depending on the specific application in fact, initial deployment can be random with the result that the distribution of nodes across the playground may be non-homogeneous. In addition to this, other factors such as node death because of energy resource exhaustion, mobility, or generic fault influence the heterogeneity of the distribution of nodes. All these characteristics can be considered as sources of heterogeneity of a WSN. Heterogeneity conditions may evolve during time and space, therefore, the design of a heterogeneous sensor networks requires adaptive mechanisms able to react to different characteristics, which is difficult to achieve. The goal of the thesis is to investigate the problems related to heterogeneity of sources in WSNs to design adaptive MAC methods that are able to take into account heterogeneity variations and are energy-efficient. We focus on two sources of heterogeneity.First, we study the problem of multiple traffic sources with different characteristics and constraints. Providing differentiated Quality of Service (QoS) such as low latency and high delivery ratio in large and multi-hops networks is a challenge due to limited energy resources of nodes. To solve this problem we propose an adaptive MAC protocol based on the asynchronous preamble sampling (PS) approach, a simple energy saving MAC technique, coupled with the idea of using a rendezvous time for data transmission. The proposed protocol (Low-Latency MAC, LA-MAC), is able to ensure efficient message forwarding throughout a multi-hop network thanks to the transmission of bursts. When messages need to be forwarded, each receiver behaves like coordinator to organize efficient transmission of contending senders. The innovation of the proposed protocol comes from combining enriched PS preambles to locally organize data transmission in a collision limited way. Extensive numerical simulations show that LA-MAC outperforms other state-of-the- art protocols in terms of latency, delivery ratio, and energy consumption.The precise evaluation of the energy consumption in large wireless sensor networks that use preamble sampling MAC is difficult. In this thesis, we propose an analytic model for energy evaluation of PS that depends on the instantaneous traffic load of localized regions so that it is independent of the network traffic patterns that can also be heterogeneous. Second, we study dynamic WSNs with density of nodes that varies across space and time. Such networks are characterized by high variability in terms of node densities. Rapid density variation may affect the network state effecting the collision probability and energy consumption of devices. We address the case of dynamic wireless sensor networks in which nodes and/or radio links may appear and disappear over time due to battery exhaustion, node mobility, or network management operations. With the work presented in this thesis we show that it is possible to provide QoS support in dynamic networks using an adaptive Density Aware MAC (DA-MAC) method. The proposed protocol offers a configurable channel sensing phase during which nodes request transmission opportunity in a way that avoids collisions. With DA-MAC, nodes periodically adapt their local protocol parameters to access the channel without collisions depending on local density state. The efficiency of the proposed protocol with respect to other state-of-the-art protocols is shown with extensive numerical simulations.

Les systèmes de communication de l'aviation civile sont soumis à une demande de capacité toujours croissante pour répondre à l'augmentation du nombre de vols et au développement de nouveaux services. Dans ce contexte, les réseaux ad hoc aéronautiques, aussi appelés AANET (Aeronautical Ad-hoc NETwork), sont étudiés comme une solution de communication innovante et complémentaire des systèmes existants. Un AANET est un réseau ad hoc dont les nœuds sont des avions. Il exploite les capacités de communication directe entre les nœuds pour transmettre des données au delà de la portée radio en utilisant une chaîne de nœuds relais. Cette thèse a pour objectif de proposer des solutions à deux problématiques complexes dans les réseaux ad hoc en tenant compte des contraintes spécifiques aux AANET : la gestion de l'accès au canal et le routage des données. La faisabilité de tels réseaux a déjà été démontrée dans la littérature, et une architecture de communication basée sur le CDMA (Code Division Multiple Access) a été proposée afin de pouvoir discriminer des transmissions concurrentes entre plusieurs utilisateurs. Cependant, aucune méthode d'attribution des codes d'étalement n'a été spécifiée. Pour résoudre ce problème dans un réseau à grande échelle tel qu'un AANET, nous proposons d'améliorer une méthode existante : le RP-CDMA (Random Packet CDMA). Nous présentons ensuite le protocole de routage novateur que nous avons conçu : NoDe-TBR (Node Density TBR). Dans le paradigme de routage TBR (Trajectory Based Routing), les paquets sont transférés de manière à suivre un chemin géographique appelé geopath, spécifié par l'émetteur. Nous avons conçu à travers NoDe-TBR une méthode pour déterminer ces chemins dans un AANET. Dans ce protocole, les geopath sont calculés en tant que géodésiques qui prennent en compte la densité effective des avions. Cette approche a été choisie car elle devrait présenter les avantages des algorithmes de routage géographique (très faible signalisation générée) tout en étant robuste aux conditions spécifiques rencontrées dans les AANET (mobilité, densité d'avions non uniforme). Afin d'évaluer les performances des solutions que nous proposons, nous avons développé des modèles avec le simulateur Omnet++. Nous avons utilisé une approche basée sur le rejeu de trajectoires réelles d'avions afin de rendre compte au mieux de la diversité des contraintes qui s'y appliquent. Le trafic de données simulé représente des communications bidirectionnelles entre des avions en vol et des services de contrôle au sol. Nos simulations mettent en évidence que les modifications que nous avons apportées au RP-CDMA améliorent les performances globales du système. Ces simulations montrent aussi que l'algorithme NoDe-TBR est sensiblement plus performant que des algorithmes de routage classiques en termes de délai et de joignabilité, tout en générant un volume négligeable de messages de signalisation. / The communication systems used in civil aviation are subject to an ever increasing capacity demand because of the air traffic growth and the development of new services. In this context, the AANETs (Aeronautical Ad-hoc NETworks) are studied as an innovative communication solution that would complement existing systems. An AANET is an ad hoc network in which the nodes are aircraft. It makes use of direct inter-aircraft communications to transmit data beyond the radio range by using a chain of relays. The objective of this thesis is to propose a solution to two complex problematics present in AANETs : the channel access management and the routing. Previous studies have shown the feasibility of such networks, and a communication architecture based on CDMA (Code Division Multiple Access) has been proposed in the literature. The CDMA allows concurrent receptions between users. However, no spreading code assignment method have been specified. In order to solve this problem on large scale networks such as AANETs, we propose to improve an existing method : the RP-CDMA (Random Packet CDMA). We then describe the innovative routing protocol that we have designed: NoDe-TBR (Node Density TBR). In the TBR (Trajectory Based Routing) paradigm, the packets are forwarded along a geographical path (geopath), specified by the sender. We specify through NoDe-TBR a method to compute these paths. In this protocol, the geopaths are computed as geodesics which take into account the actual node density. This approach has been selected because it should have the benefits of geographic routing (very low overhead) while being robust to the specific conditions encountered in AANETs (mobility, uneven aircraft density). To assess the performances of our propositions, we have developed models for the simulator Omnet++. We have used an approach based on the replay of actual aircraft trajectories in order to take into account the variety of constraints applied to the movements of the aircraft. The simulated data traffic represents bidirectional communications between aircraft and ground stations. Our simulations shows that the modification we propose for RP-CDMA improve the overall performances of the system. The simulations results also shows that NoDe-TBR outperforms more classical routing methods in terms of reachability and delay, while generating less overhead.

Este estudo trata do desenvolvimento da rede de arte postal na América Latina desde o seu início no final da década de 1960 até a sua presença da XVI Bienal de São Paulo em 1981. Para isso, são retomadas as redes latino-americanas de trocas de poesia experimental estruturadas na década de 1960. Em seguida, são descritas as trajetórias de alguns dos protagonistas da arte postal nesta região, bem como as exposições e publicações coletivas que eles organizaram. Nesse momento, são abordadas as manifestações da rede de arte postal na Argentina, Brasil, Chile, Colômbia, El Salvador, México, Uruguai e Venezuela. Por fim, é analisado o caso específico do Museu de Arte Contemporânea da Universidade de São Paulo (MAC USP), explicitando como essa instituição conectou-se organicamente à rede. Esta pesquisa tem como ponto de partida acervo de arte conceitual do MAC USP e acompanha a expansão da rede a partir das grandes mostras coletivas realizadas entre 1972 e 1981 na América Latina. Além disso, destaca a relação da arte postal com as ditaduras militares como decisiva na caracterização desta prática entre os latino-americanos. / This study is about the development of the mail art network in Latin America since its beginning at the end of the 60s until its presence on the XVI Biennial of São Paulo in 1981. For this purpose, the Latin American networks of experimental poetry exchange, structured in the 60s, are recaptured. After this, the trajectories of some of the mail art protagonists in this region are described, as well as the collective exhibitions and publications that they organized. At this point, the demonstrations of the mail art networks in Argentina, Brazil, Chile, Colombia, El Salvador, Mexico, Uruguay and Venezuela are approached. Finally, the specific case of the Museum of Contemporary Art of the University of São Paulo (MAC USP) is analyzed, explaining how that institution connected itself organically to the mail art network. This research starts with the conceptual art collection of the MAC USP and follows the expansion of the network from the large collective exhibitions performed between 1972 and 1981 in Latin America. Besides that, it emphasizes the relation between mail art and the military dictatorships as a decisive part of the characterization of this practice among Latin American.

This diploma thesis represents a sum of theoretical findings about correlates and antecedents of boredom and an empirical investigation of opened questions about boredom, according to the literature. This was done through a laboratory experiment in which the author of the thesis, in order to investigate the research questions, induced boredom in the research participants. The research aim of this thesis involves three topics. The primary purpose of the experiment is to assess the experimental manipulation effects of causal attribution of attentional failure on the intensity of boredom. In order to investigate the main research questions, the author of this thesis created a specific experimental design. This includes a fictive subliminal distracting element representing an alternative cause explaining attentional failure during a task reliably eliciting boredom. Experimental design was also developed to fulfil a secondary aim of this thesis, to explore some of the correlates of boredom with emphasis on the question of relation between activation and boredom. The third aim is to investigate hypothesis about the type of activities preferred after the boredom induction by giving a choice to participants between interesting and an enjoyable videoclip. The results of the experiment do not support the main...