L'interférence est un facteur de limitation de performance individuelle et globale dans les réseaux de communication sans fil. Dans ce travail, deux techniques classiques de gestion de l'interférence sont étudiées : le contrôle de puissance d'émission et l'égalisation du canal. Trois approches sont considérées pour Le contrôle de puissance décentralisé et opportuniste. La première est basée sur la théorie des jeux non-coopératifs statiques et les théories de fonctions itératives, d'où résulte la proposition d'une classe d'algorithmes. Dans la deuxième approche, nous proposons quelques algorithmes dérivés de formulations et de solutions traditionnelles de la commande H2 et de la commande mixte H2/H-infini. Finalement, nous appliquons la théorie des jeux dynamiques sur le problème, ce qui produit deux nouveaux algorithmes de contrôle de puissance. La deuxième partie de la thèse, où le problème d'intérêt est l'égalisation du canal, est divisée en deux thèmes. Dans le premier, nous développons une analyse de «pire cas» pour le retard d'égalisation par des concepts de la théorie des jeux non-coopératifs. Dans le deuxième thème, nous présentons deux approches pour la conjugaison des caractéristiques désirables des égaliseurs H2 et H-infini : une combinaison convexe des deux filtres et un schéma d'adaptation du niveau de robustesse du filtre H-infini. / Interference is a limiting factor of individual and global performance in wireless communication networks. In this work, two classical interference management techniques are studied: the transmission power control and the channel equalization. Three approaches are considered for distributed and opportunistic power control. The first one is based on static non-cooperative game theory and theories of iterative functions, providing a class of algorithms. In the second approach, we propose different algorithms derived from formulations and traditional solutions of H2 control and mixed H2/H-infinity control. Finally, we apply dynamic game theory to the problem for obtaining two new power control algorithms. The second part of the thesis, devoted to channel equalization, is divided into two topics. In the first one, we provide a "worst case" analysis for equalization delay by using concepts of non-cooperative game theory. In the second topic, we present two proposals for the combination of the desirable characteristics of H2 and H-infinity equalizers: a convex combination of the two filters and a scheme for adapting the robustness level of the H-infinity filter.

Syfte: Då tidigare forskning funnit motstridiga resultat gällande orsaken till val av hållbarhetsgranskare var syftet med denna studie att undersöka om företags seriösa intention med hållbarhetsarbetet påverkade valet mellan revisor eller konsult. Metod: Studien har utgått från den positivistiska forskningsfilosofin och har en hypotetisk-deduktiv ansats. Vidare har studien en kvantitativ forskningsstrategi och sekundärdata har inhämtats från databasen Thomson Reuters Eikon. Undersökningen har utförts i form av en tvärsnittsstudie, där insamlad datahar analyserats med hjälp av IBM SPSS. Urvalet är ett sannolikhetsurval som består av 433 företag med relevant inrapporterad information från Europa och USA. Dessa har först analyserats i en univariat analys, följt av korrelationsanalys och slutligen logistisk regression. Resultatenredovisas med hjälp av tabeller och figurer. Resultat & slutsats: Studien har visat att det finns signifikanta samband mellan två av sex valda CSR-dimensioner och valet av hållbarhetsgranskare. Det finns ett samband mellan ökande poäng av företagens kommunikation av CSR, CSR-strategy och sannolikheten för att en konsult anlitats. Det finns också ett samband mellan ökande poäng i CSR-dimensionen Human Rights och sannolikheten att en revisor anlitas. Förslag till fortsatt forskning: En begränsning i denna studie är att hänsyn inte tagits till om företag använt sig av en konsult vid hållbarhetsarbetet och senare en revisor vid bestyrkandet. Beaktande av en sådan kombination kan ge en bättre kunskap om hur företag väljer hållbarhetsgranskare, särskilt om intentionen med CSR-aktiviteter spelar någon roll för det valet. Det vore också önskvärt att undersöka vilkaföretag som själva upplever att de har en seriös intention med hållbarhetsarbetet och hur detta påverkar valet av hållbarhetsgranskare. Uppsatsens bidrag: Studien bidrar med ytterligare kunskap till CSR-litteraturen genom att istället för att undersöka allmänna faktorer som exempelvis bolagsstorlek, belåningsgrad och likviditet i relation till valet av hållbarhetsgranskare, undersöka företags intention med CSR-arbetet i relation till valet av hållbarhetsgranskare. Teoretiskt utvidgar detta diskussionen om vad som kan påverka företags val av granskare, och praktiskt belyser studien skillnaden mellan att anlita en konsult och en revisor för hållbarhetsgranskning / Aim: Since previous research found conflicting results regarding the reason for choosing sustainability auditors, the purpose of this study was to investigate whether the company's serious intent with sustainability work affected the choice between auditor or consultant. Method: The study is based on the positivist research philosophy and has a hypothetical deduction. Furthermore, the study has obtained a quantitative research strategy and secondary data from the Thomson Reuters Eikon database. The survey has been conducted in a cross-sectional study, where collected data has been analyzed using IBM SPSS.The selection is a probability selection consisting of 433 companies with relevant reported information from Europe and the United States. These were first analyzed in a univariate analysis, followed by correlation analysis and finally logistic regression. The results are reported using tables and figures. Result & Conclusions: The study has shown that there are significant relationships between two of six selected CSR dimensions and the choice of sustainability examiners. There is a correlation between increasing points of corporate communication of CSR, CSR strategy and the likelihood of a consultant being engaged. There is also a connection between increasing points in the Human Rights CSR dimension and the likelihood of an accountant being hired. Suggestions for future research: A limitation in this study is that account has not been taken of whether companies have used a consultant for sustainability work and later an auditor in the field of certification. Considering such a combination can provide a better understanding of how companies choose sustainability auditors, especially if the intention of CSR activities is relevant to that choice. It would also be desirable to investigate which companies themselves find that they have a serious intentionof sustainability work and how this affects the choice of sustainability auditors. Contribution of the thesis: The study contributes with additional knowledge to the CSR literature by investigating the company's intentions with CSR work in relation to the choice of sustainability auditors instead of investigating general factors such as company size, loan ratio and liquidity in relation to the choice of sustainability auditors. Theoretically, this discussion expands on what can affect the company's choiceof reviewers, and the study clearly illustrates the difference between employing a consultant and an auditor for sustainability review

Dans cette thèse, nous abordons le problème fondamental de l'accès au spectre opportuniste dans un système de communication multi-canal. Plus précisément, nous considérons un système de communication dans lequel un utilisateur a accès à de multiples canaux, tout en étant limité à la détection et la transmission sur un sous-ensemble de canaux. Nous explorons comment l'utilisateur intelligent exploite ses observations passées et les propriétés stochastiques de ces canaux afin de maximiser son débit. Formellement, nous fournissons une analyse générique sur le problème d'accès au spectre opportuniste en nous basant sur le problème de `restless multi-bandit’ (RMAB), l'une des généralisations les plus connues du problème classique de multi-armed bandit (MAB), un problème fondamental dans la théorie de décision stochastique. Malgré les importants efforts de la communauté de recherche dans ce domaine, le problème RMAB dans sa forme générique reste encore ouvert. Jusqu'à aujourd'hui, très peu de résultats sont connus sur la structure de la politique optimale. L'obtention de la politique optimale pour un problème RMAB général est intraçable dû la complexité de calcul exponentiel. Par conséquent, une alternative naturelle est de se focaliser sur la politique myopique qui maximise la récompense à immédiate, tout en ignorant celles du futur. Donc, nous développons trois axiomes caractérisant une famille de fonctions que nous appelons fonctions régulières, qui sont génériques et pratiquement importantes. Nous établissons ensuite l'optimalité de la politique myopique lorsque la fonction de récompense peut être exprimée comme une fonction régulière et le facteur de discount est borné par un seuil déterminé par la fonction de récompense. Nous illustrons également l'application des résultats pour analyser une classe de problèmes RMAB dans l'accès opportuniste. Ensuite, nous étudions un problème plus difficile, où l'utilisateur doit configurer le nombre de canaux à accéder afin de maximiser son utilité (par exemple, le débit). Après avoir montré la complexité exponentielle du problème, nous développons une stratégie heuristique v-step look-ahead. Dans la stratégie développée, le paramètre v permet de parvenir à un compromis souhaité entre l'efficacité sociale et de la complexité de calcul. Nous démontrons les avantages de la stratégie proposée via des simulations numériques sur plusieurs scénarios typiques. / In the thesis, we address the fundamental problem of opportunistic spectrum access in a multi-channel communication system. Specifically, we consider a communication system in which a user has access to multiple channels, but is limited to sensing and transmitting only on one at a given time. We explore how the smart user should exploit past observations and the knowledge of the stochastic properties of these channels to maximize its transmission rate by switching channels opportunistically. Formally, we provide a generic analysis on the opportunistic spectrum access problem by casting the problem into the restless multi-armed bandit (RMAB) problem, one of the most well-known generalizations of the classic multi-armed bandit (MAB) problem, which is of fundamental importance in stochastic decision theory. Despite the significant research efforts in the field, the RMAB problem in its generic form still remains open. Until today, very little result is reported on the structure of the optimal policy. Obtaining the optimal policy for a general RMAB problem is often intractable due to the exponential computation complexity. Hence, a natural alternative is to seek a simple myopic policy maximizing the short-term reward. Therefore, we develop three axioms characterizing a family of functions which we refer to as regular functions, which are generic and practically important. We then establish the optimality of the myopic policy when the reward function can be expressed as a regular function and the discount factor is bounded by a closed-form threshold determined by the reward function. We also illustrate how the derived results, generic in nature, are applied to analyze a class of RMAB problems arising from multi-channel opportunistic access. Next, we further investigate the more challenging problem where the user has to decide the number of channels to sense in each slot in order to maximize its utility (e.g., throughput). After showing the exponential complexity of the problem, we develop a heuristic v-step look-ahead strategy. In the developed strategy, the parameter v allows to achieve a desired tradeoff between social efficiency and computation complexity. We demonstrate the benefits of the proposed strategy via numerical experiments on several typical settings.

Masters of Art / This project suggested that HIV people in Region A (Nelson Mandela Metropole, formerly Port Elizabeth) health district of the Eastern Cape, seek HIV testing when they are already in stages three (late disease) and four (AIDS) of HIV infection. Data had been obtained from the AIDS Training Information and Counselling Centre in the Nelson Mandela Metropole in 2000. The consequences of diagnoses only in the advanced stages of HIV infection will have a devastating impact on case management. Therefore, this paper yielded important data for South African policy makers to write health and welfare policies that might improve the quality of life of those terminally infected with HIV. / South Africa

[EN] Intelligent Transportation Systems (ITS) can make transportation safer, more efficient, and more sustainable by applying various information and communication technologies. One of these technologies are \acfp{VN}. \acp{VN} combine different communication solutions such as cellular networks, \acfp{VANET}, or IEEE 802.11 technologies to provide connectivity among vehicles, and between vehicles and road infrastructure. This thesis focuses on VNs, and considers that the high speed of the nodes and the presence of obstacles like buildings, produces a highly variable network topology, as well as more frequent partitions in the network. Therefore, classical \ac{MANET} protocols do not adapt well to VANETs. Under these conditions, \ac{DTN} have been proposed as an alternative able to cope with these adverse characteristics. In DTN, when a message cannot be routed to its destination, it is not immediately dropped but it is instead stored and carried until a new route becomes available. The combination of VN and DTN is called \acp{VDTN}. In this thesis, we propose a new VDTN protocol designed to collect information from vehicular sensors. Our proposal, called \ac{MSDP}, combines information about the localization obtained from a GNSS system with the actual street/road layout obtained from a Navigation System (NS) to define a new routing metric. Both analytical and simulation results prove that MSDP outperforms previous proposals. Concerning the deployment of VNs and VANET technologies, technology already left behind the innovation and the standardization phases, and it is about time it reach the first early adopters in the market. However, most car manufacturers have decided to implement VN devices in the form of On Board Units (OBUs), which are expensive, heavily manufacturer dependent, and difficult to upgrade. These facts are delaying the deployment of VN. To boost this process, we have developed the GRCBox architecture. This architecture is based on low-cost devices and enables the establishment of V2X, \emph{i.e.} V2I and V2V, communications while integrating users by easing the use of general purpose devices like smartphones, tablets or laptops. To demonstrate the viability of the GRCBox architecture, we combined it with a DTN platform called Scampi to obtain actual results over a real VDTN scenario. We also present several GRCBox-aware applications that illustrate how developers can create applications that bring the potential of VN to user devices. / [ES] Los sistemas de transporte inteligente (ITS) son el soporte para el establecimiento de un transporte más seguro, más eficiente y más sostenible mediante el uso de tecnologías de la información y las comunicaciones. Una de estas tecnologías son las redes vehiculares (VNs). Las VNs combinan diferentes tecnologías de comunicación como las redes celulares, las redes ad-hoc vehiculares (VANETs) o las redes 802.11p para proporcionar conectividad entre vehículos, y entre vehículos y la infraestructura de carreteras. Esta tesis se centra en las VNs, en las cuales la alta velocidad de los nodos y la presencia de obstáculos como edificios producen una topología de red altamente variable, así como frecuentes particiones en la red. Debido a estas características, los protocolos para redes móviles ad-hoc (MANETs) no se adaptan bien a las VANETs. En estas condiciones, las redes tolerantes a retardos (DTNs) se han propuesto como una alternativa capaz de hacer frente a estos problemas. En DTN, cuando un mensaje no puede ser encaminado hacia su destino, no es inmediatamente descartado sino es almacenado hasta que una nueva ruta esta disponible. Cuando las VNs y las DTNs se combinan surgen las redes vehiculares tolerantes a retardos (VDTN). En esta tesis proponemos un nuevo protocolo para VDTNs diseñado para recolectar la información generada por sensores vehiculares. Nuestra propuesta, llamada MSDP, combina la información obtenida del servicio de información geográfica (GIS) con el mapa real de las calles obtenido del sistema de navegación (NS) para definir una nueva métrica de encaminamiento. Resultados analíticos y mediante simulaciones prueban que MSDP mejora el rendimiento de propuestas anteriores. En relación con el despliegue de las VNs y las tecnologías VANET, la tecnología ha dejado atrás las fases de innovación y estandarización, ahora es el momento de alcanzar a los primeros usuarios del mercado. Sin embargo, la mayoría de fabricantes han decidido implementar los dispositivos para VN como unidades de a bordo (OBU), las cuales son caras y difíciles de actualizar. Además, las OBUs son muy dependientes del fabricante original. Todo esto esta retrasando el despliegue de las VNs. Para acelerar la adopción de las VNs, hemos desarrollado la arquitectura GRCBox. La arquitectura GRCBox esta basada en un dispositivo de bajo coste que permite a los usuarios usar comunicaciones V2X (V2V y V2I) mientras utilizan dispositivos de propósito general como teléfonos inteligentes, tabletas o portátiles. Las pruebas incluidas en esta tesis demuestran la viabilidad de la arquitectura GRCBox. Mediante la combinación de nuestra GRCBox y una plataforma de DTN llamada Scampi hemos diseñado y probado un escenario VDTN real. También presentamos como los desarrolladores pueden crear nuevas aplicaciones GRCBox para llevar el potencial de las VN a los dispositivos de usuario. / [CAT] Els sistemes de transport intel·ligent (ITS) poden crear un transport més segur, més eficient i més sostenible mitjançant l'ús de tecnologies de la informació i les comunicacions aplicades al transport. Una d'aquestes tecnologies són les xarxes vehiculars (VN). Les VN combinen diferents tecnologies de comunicació, com ara les xarxes cel·lulars, les xarxes ad-hoc vehiculars (VANET) o les xarxes 802.11p, per a proporcionar comunicació entre vehicles, i entre vehicles i la infraestructura de carreteres. Aquesta tesi se centra en les VANET, en les quals l'alta velocitat dels nodes i la presència d'obstacles, com els edificis, produeixen una topologia de xarxa altament variable, i també freqüents particions en la xarxa. Per aquest motiu, els protocols per a xarxes mòbils ad-hoc (MANET) no s'adapten bé. En aquestes condicions, les xarxes tolerants a retards (DTN) s'han proposat com una alternativa capaç de fer front a aquests problemes. En DTN, quan un missatge no pot ser encaminat cap a la seua destinació, no és immediatament descartat sinó que és emmagatzemat fins que apareix una ruta nova. Quan les VN i les DTN es combinen sorgeixen les xarxes vehicular tolerants a retards (VDTN). En aquesta tesi proposem un nou protocol per a VDTN dissenyat per a recol·lectar la informació generada per sensors vehiculars. La nostra proposta, anomenada MSDP, combina la informació obtinguda del servei d'informació geogràfica (GIS) amb el mapa real dels carrers obtingut del sistema de navegació (NS) per a definir una nova mètrica d'encaminament. Resultats analítics i mitjançant simulacions proven que MSDP millora el rendiment de propostes prèvies. En relació amb el desplegament de les VN i les tecnologies VANET, la tecnologia ha deixat arrere les fases d'innovació i estandardització, ara és temps d'aconseguir als primers usuaris del mercat. No obstant això, la majoria de fabricants han decidit implementar els dispositius per a VN com a unitats de bord (OBU), les quals són cares i difícils d'actualitzar. A més, les OBU són molt dependents del fabricant original. Tot això està retardant el desplegament de les VN. Per a accelerar l'adopció de les VN, hem desenvolupat l'arquitectura GRCBox. L'arquitectura GRCBox està basada en un dispositiu de baix cost que permet als usuaris usar comunicacions V2V mentre usen dispositius de propòsit general, com ara telèfons intel·ligents, tauletes o portàtils. Les proves incloses en aquesta tesi demostren la viabilitat de l'arquitectura GRCBox. Mitjançant la combinació de la nostra GRCBox i la plataforma de DTN Scampi, hem dissenyat i provat un escenari VDTN pràctic. També presentem com els desenvolupadors poden crear noves aplicacions GRCBox per a portar el potencial de les VN als dispositius d'usuari. / Martínez Tornell, S. (2016). Delay Tolerant Networks for Efficient Information Harvesting and Distribution in Intelligent Transportation Systems [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/68486 / TESIS

The federal communications commission (FCC) has predicted that, under the current regulatory environment, a spectrum shortage may be faced in the near future. This impending spectrum shortage is in part due to a rapidly increasing demand for wireless services and in part due to inefficient usage of currently licensed bands. A new paradigm pertaining to wireless spectrum allocation, known as cognitive radio (CR), has been proposed as a potential solution to this problem. This dissertation seeks to contribute to research in the field of CR through an investigation into the effect that a primary user (PU) channel occupancy model will have on the performance of a secondary user (SU) in a CR network. The model assumes that PU channel occupancy can be described as a binary process and a two state Hidden Markov Model (HMM) was thus chosen for this investigation. Traditional algorithms for training the model were compared with certain evolutionary-based training algorithms in terms of their resulting prediction accuracy and computational complexity. The performance of this model is important since it provides SUs with a basis for channel switching and future channel allocations. A CR simulation platform was developed and the results gained illustrated the effect that the model had on channel switching and the subsequently achievable performance of a SU operating within a CR network. Performance with regard to achievable SU data throughput, PU disruption rate and SU power consumption, were examined for both theoretical test data as well as data obtained from real world spectrum measurements (taken in Pretoria, South Africa). The results show that a trade-off exists between the achievable SU throughput and the average PU disruption rate. Significant SU performance improvements were observed when prediction modelling was employed and it was found that the performance and complexity of the model were influenced by the algorithm employed to train it. SU performance was also affected by the length of the quick sensing interval employed. Results obtained from measured occupancy data were comparable with those obtained from theoretical occupancy data with an average percentage similarity score of 96% for prediction accuracy (using the Viterbi training algorithm), 90% for SU throughput, 83% for SU power consumption and 71% for PU disruption rate. / Dissertation (MEng)--University of Pretoria, 2012. / Electrical, Electronic and Computer Engineering / unrestricted

Trots ett stort akademiskt intresse för kultur, förtroende och multinationella relationer finns ett behov av mer kvalitativ forskning som undersöker interaktionen i svensk-colombianska företagsinterna relationer. Studien, som är en kvalitativ fallstudie med en socialkonstruktionistisk och interkulturell ansats, har som syfte att åskådliggöra kulturella skillnader som kommer till uttryck när svenskar och colombianer ingår i en företagsintern relation. Studien avser att ge ytterligare kunskap inom forskningsområdet och ge en djupare förståelse för den sociala verkligheten som de företagsinterna relationerna står inför. Empirin analyseras på ett tematiskt tillvägagångssätt där resultatet kopplas till studiens utvalda teoretiska perspektiv om förtroende. Teorin utgår från att ett gott förtroende mellan två parter gynnar den företagsinterna relationer och förtroendenivån bestäms av parternas delade värderingar, kommunikation och opportunistiska beteenden gentemot varandra. Via fem semistrukturerade djupintervjuer med respondenter som har erfarenhet av svensk-colombianska företagsinterna relationer, undersökte författarna erfarenheter som ligger till grund för studiens analys och slutsatser. Resultatet tyder på att de kulturella skillnaderna som finns är många och missgynnar ofta förtroendet i företagsinterna relationer, varför ett gott förtroende är svårt att uppnå. Vad parterna värderar, hur parterna kommunicerar och vilket beteende som uppfattas opportunistiskt tycks huvudsakligen grunda sig i vem som tycks förtjäna respekt, huruvida professionella företagsinterna relationer får vara privata samt på vilket sätt människor är tydliga. Slutsatserna är ämnade att bidra till kunskap som kan hjälpa parter i svensk-colombianska relationsutbyten att vända kulturella hinder till möjligheter. / Despite a great academic interest in culture, trust and multinational relationships, there is a need for more qualitative research and research that examines the interaction in Swedish-Colombian internal partnerships. The study, which is a qualitative case study with a social constructivist and intercultural approach, aims to explore cultural differences that are expressed when Swedes and Colombians are part of an internal partnership. Moreover, the study intends to provide further knowledge in the research area and to provide a deeper understanding of the social reality facing the different national contexts. The result is presented with a thematic analysis and linked to selected theoretical perspectives. The theories are antecedents of trust which, according to Morgan and Hunt (1994) are shared values, communication, and opportunistic behavior. Five semi-structured in-depth interviews were conducted with respondents with experiences from Swedish-Colombian internal partnerships and it is the individuals’ experiences that form the basis of the study´s analysis and conclusions. The results indicate several cultural differences which often have a negative effect on the trust in relational exchanges, thus trustable relationships are difficult to achieve. One's values, how one communicates and what behavior is perceived as opportunistic seems to be mainly based on who deserves respect, whether professional relationships also can be private and how people show clarity. The conclusions contribute with knowledge that can help parties in Swedish-Colombian relational exchange to turn cultural barriers into opportunities.

Chronic granulomatous disease (CGD) is associated with defective function of the NADPH-oxidase system in conjunction with phagocytic defects which leads to granuloma formation and serious infectious complications. This is often associated with significant morbidity and mortality. The association of defective phagocyte function with other coincidental immune defects is unknown. Defects in innate pathways seen with CGD, including complement systems, and toll-like and dectin receptor pathways, have not been described before. We present the case of a 2-year old male patient hospitalized with recurrent pneumonia, a non-healing skin ulcer, necrotizing lung granulomas, and epididymo-orchitis. Defective neutrophil chemiluminescence was detected by dihydrorhodamine (DHR) testing. Further evaluation demonstrated characteristic molecular mutations of CYBB consistent with CGD. Immune evaluation demonstrated polyclonal hyperglobulinemia, but a greatly reduced mannose binding lectin (MBL) level. Six biallelic polymorphisms in MBL gene and its promoter were analyzed using Light Cycler™ Real-time PCR assay. The LXPA/LYPB haplotype of MBL was detected in our patient; the latter is the defective haplotype associated with low MBL levels. Due to the implications for innate immunity and the protection against bacterial, viral, and fungal infections provided by MBL, a deficiency of this protein may have disastrous consequences on the long term outcomes of CGD. MBL deficiency can also complicate other disorders affecting the immune system, significantly increasing the risk of infection in such patients. Further studies looking at the frequency and implications of MBL deficiency in CGD are needed.

La pénétration du marché des appareils mobiles a connu une croissance impressionnante ces dernières années. Smartphones, tablettes et ordinateurs portables sont devenus soit producteurs soit consommateurs de contenus générés par les utilisateurs. Les communications opportunistes permettent une couverture étendue dans les endroits où il n'existe aucune infrastructure réseau disponible et des stratégies de délestage de données pour aider les opérateurs à soulager la charge de leurs infrastructures. Dans cette thèse, nous considérons le cas de la diffusion opportuniste de plusieurs grands contenus d'un point de vue expérimental. Dans la première partie nous commençons par implémenter EPICS, un protocole réseau conçu pour l'échange opportuniste de grands contenus, dans des terminaux Android. Après sa évaluation nous proposons DAD, un nouveau protocole, qui envoie une rafale de paquets de données de façon adaptative. Nous comparons les deux protocoles expérimentalement et, à l'aide des traces de contacts, soit réelles, soit synthétiques, nous obtenons des gains importants avec cette nouvelle approche. La deuxième partie est dédiée au passage à l'échelle des systèmes de surveillance passive. Nous proposons deux approches. La première est basée sur la similarité des traces et des algorithmes de détection de communautés. La deuxième est basée sur des mesures collaboratives. / The market penetration of mobile devices has experienced an impressive growth. Smartphones, tablets, and laptops have become both producers and consumers of user-generated contents. They also motivate novel communication paradigms such as the possibility to establish, in an opportunistic fashion, direct device-to-device links whenever two mobile nodes enter within the wireless range of each other. In this thesis, we consider the case of opportunistic dissemination of multiple large contents from an experimental point of view. This implies revisiting, among others, the common assumption that contacts have enough capacity to transfer any amount of data.In the first part of this thesis, we start from an Android implementation of EPICS, a network protocol designed for exchanging large contents in opportunistic networks, on off-the-shelf devices. After an deep analysis of application-level logs and captured wireless traces we found out limitations and uncovered improving possibilities. We then propose DAD, a new content dissemination protocol that adaptively sends bursts of data instead of the per-fragment transmission strategy of EPICS.The second part of this thesis deals with the scalability of legacy WLAN monitoring systems. We propose two original approaches. With the first one, based on trace similarity and community detection algorithms, we are able to identify how many monitor we need in a target area and where to place them. The second approach in based on collaborative measurements. In this case we face the risk of biased measures due attacks of malicious users generating adulterated traces. We then propose a method to detect such malicious behaviors.

No description available.