Die vorliegende Dissertation untersucht die Kontextabhängigkeit von Konsumentenpräferenzen in Folge eines Marktaustritts in 4 Aufsätzen. Aufsatz 1 diskutiert Auswirkungen einer Auslistung auf Kundenreaktionen. Zwei empirische Studien belegen die Existenz eines negativen Ähnlichkeits-, Attraktions- und Kompromisseffektes und zeigen wesentliche Determinanten einer markentreuen Reaktion auf. Aufsatz 2 bestätigt die Hypothesen über negative Kontexteffekte für Markeneliminierungen in verschiedenen experimentellen Situationen und Produktkategorien. Das sich ergebende Substitutionsverhalten resultiert durchweg in höheren Verlusten für Hersteller als für Händler. Aufsatz 3 diskutiert das Substitutionsverhalten in Out-of-Stock Situationen. Promotion wird hierbei als wesentlicher Einflussfaktor herangezogen. Verschiedene Online-Experimente demonstrieren einen negativen Ähnlichkeitseffekt für die temporäre Nichtverfügbarkeit von Produkten, welcher sich jedoch für preisreduzierte Güter des täglichen Bedarfs verringert. Werden ähnliche Substitute preislich reduziert angeboten, wird der negative Ähnlichkeitseffekt verstärkt. Der Effekt wird hingegen von einem Attraktionseffekt überlagert, wenn unähnliche Alternativen im Sonderangebot sind. Aufsatz 4 untersucht wesentliche Einflussfaktoren eines negativen Attraktionseffektes. In Anlehnung an das von Mishra et al. (1993) entwickelte Kausalmodell zur Neuprodukteinführung, wird ein adaptiertes ganzheitliches Strukturgleichungsmodell für den Marktaustritt getestet. Als wesentliche Treiber des betrachteten Phänomens resultieren die Konstrukte Anteil des Decoys, Präferenzstärke und Informationsrelevanz. / This thesis investigates the context-dependence of preferences in consequence of market exits in 4 essays. Essay 1 discusses the effect of brand delisting on customer responses. On the basis of two empirical studies, the existence of a negative similarity, a negative attraction and a negative compromise effect is revealed and key determinants of a brand loyal reaction are analyzed. Essay 2 supports the hypotheses on negative context effects for brand removals across different experimental settings and product categories. The resultant switching patterns collectively lead to bigger damages for manufacturers than for retailers. Essay 3 investigates preference shifts in out-of-stock situations by including promotion as essential driver. A series of online experiments demonstrate that for temporal unavailability of products, substitution behavior correspond to a negative similarity effect which is, however, reduced for stock-outs of low involvement fast moving consumer goods on promotion. While the negative similarity effect is enforced for promotions of similar substitutes, it is ruled out by the simultaneous occurrence of an attraction effect when dissimilar substitutes are offered at a reduced price. Essay 4 studies important antecedent variables of the negative attraction effect. In reference to the causal model on product introduction developed by Mishra et al. (1993), an adapted holistic framework for product exit is tested by using structural equation modeling. The results emphasize decoy share, preference strength and information relevance as major drivers of the considered phenomenon.

This thesis deals with the role of Czech housing policy in the independence of young adults in relation to the problem of lack of adequate housing in the Czech Republic. This issue is investigated within the framework of the theoretical lifestyle concepts and the transition to adulthood. These concepts should identify the impact of lack of housing availability for young people during their life - both in the process of separation and in the transition to adulthood. The analytical part of this thesis describes the current situation on the housing market, which can be characterized by a lack of adequate housing, the main factors influencing the housing policy creation, and the tools of housing policy focusing explicitly or implicitly on young people. In the empirical part following areas are investigated: the current housing situation of young adults; the barriers that young people encounter when seeking independent housing; the position of independent housing in the life of young people; the attitude of young people towards housing policy according to their age category. The final part answers to the goals of this thesis - it evaluates the support of housing policy focused on young adults in the growing lack of housing; it describes the main barriers that young people encounter; explains the impact...

Made available in DSpace on 2016-04-26T20:21:34Z (GMT). No. of bitstreams: 1 Marcus Vinicius Fernandes Andrade da Silva.pdf: 1699688 bytes, checksum: b4d040259bdd9483f71b1b30c921ae25 (MD5) Previous issue date: 2013-04-15 / From something seen as clear-cut and uncontroversial this doctoral thesis intends to scrutinize in-depth the viability of the Judge s ex officio, ie, without the need of previous provocation by any of the litigants (ex officio), of the unfair terms in consumer-related contracts, and as corollary of such a possibility, of what was intended by the legislator of Consumer Protection Law when qualifying such a rule as a public one. The controversy was underestimated by this candidate. This underestimation has never been caused by disrespect or contemptuous treatment of the legal controversy, on the contrary. The challenges and difficulties arisen as something thought not possess such profound implications, not only within the material law, but also in procedural law (feared), only made the study and the search for answers more enticing. The Judge s expression in itself (ex officio) about the material law turned itself to certain immanentism of the material law with procedural law. So, as researcher of the Consumer Protection Law, it arises impacts or not on the Judge s expression of an unfair terms or any other contra legem interpretation it is not as simple as it might seem. Modulations, forces and various decisional effects had to be addressed in the search for a better answer. Variation which is amplified both on individual as well as on class actions. In parallel with such a confrontation (discovery), also came the complicating element of demystifying what would be the definition of public order. In Brazilian law, the rule is to perceive public order as something imperative, law binding, unattainable. Those features do not cover encompass all situations of the Brazilian Consumer Law (CDC) and forced the researcher to seek more details in foreign sources. The search for definitions, characteristics and effects in foreign law systems widened up even more what the research sought to analyze. Nevertheless the research s scope, it was realized the confrontation of the features of public order would of use to Brazilian law in itself as the focus on different foreign systems would aggrandize and justify the option for the CDC. Finally, as during this investigation the Superior Court of Justice (STJ) pronouncement number nº. 381, whose content goes against this thesis, came to light, its analysis and confrontation turned out to be inevitable / De algo tido como claro e pacífico a tese de doutorado que se propõe busca estudar a fundo a possibilidade da decretação de ofício, ou seja, sem provocação das partes, das cláusulas abusivas nos contratos relacionais de consumo e, como corolário a tal possibilidade, o que pretendeu o legislador do Código de Proteção e Defesa do Consumidor ao qualificar tal norma como de ordem pública. É confessado por este candidato que o tema, a controvérsia, foi subestimado. Tal subestimação jamais foi causada por um possível desrespeito ou um tratamento desdenhoso da controvérsia estritamente jurídica. Muito pelo contrário. Os desafios e as dificuldades que surgiram com algo que se imaginava não possuir um grau tão profundo de implicações não só dentro do direito material, mas principalmente, e mais desafiador sob o direito instrumental (temido) só tornaram o estudo e a busca por resposta mais apaixonantes. Da decretação em si sob o direito material retornou-se a certo imanentismo do direito material com o direito processual. Logo, como materialista do direito consumerista surgem impactos que a mera decretação de ofício ou não de uma cláusula ou qualquer outro ato jurídico contra legem não é simples como aparenta. Modulações, forças e diversos efeitos sentenciais tiveram que ser tratados na busca de uma melhor resposta. Variante que se amplifica tanto nas ações individuais, quanto nas coletivas. Paralelo a tal enfrentamento e a reboque do mesmo veio o complicador de desmistificar o que define a ordem pública. No direito pátrio as doutrinas só preveem a ordem pública como algo imperativo, norma cogente, indisponível. Característica que não engloba todas as situações do CDC e que obrigou o pesquisador a buscar fontes estrangeiras. As buscas no direito estrangeiro por definições, características e efeitos ampliaram mais ainda o que sempre se buscou delimitar na tese. Não obstante, ao olhar sobre a delimitação da tese, cientificamente, percebeu-se que o enfrentamento das características da ordem pública seria de grande valia ao direito pátrio e que o estudo sobre sistemas estrangeiros diferentes só engradeceria e justificaria ainda mais a opção do CDC. Por fim, como no decorrer do estudo surgiu à edição da Súmula 381 do STJ, cujo teor vai de encontro a presente tese, inevitável tornou-se seu estudo e enfrentamento

La peau humaine est un élément singulier qui recouvre le corps et permet à chacun de bénéficier du sens du toucher. Qualifiée de tissu du corps humain, la peau est aujourd’hui soumise au même régime juridique que celui qui s’applique à l’égard du corps humain. Pourtant, si la peau est indéniablement une enveloppe qui entoure le corps et le protège, elle est également proche de la personne puisqu’elle en constitue l’apparence, renferme des éléments de son identité et contribue à son identification. Par conséquent, la peau recouvre la surface du corps et désigne aussi la personne, ce qui en fait un élément frontalier du corps et de la personne. Ainsi rattachée aux deux entités dominantes que sont la personne et le corps, la peau doit être envisagée dans une relation ternaire qui la placerait au centre des liens entretenus entre la personne et son corps. D’une part, la peau n’est pas seulement un élément du corps humain puisque la personne bénéficie d’un droit d’effectuer des choix concernant sa peau, voire de la modifier. D’autre part, la peau n’est pas seulement un élément rattaché à la personne puisqu’elle renferme le corps et en constitue une protection. Par conséquent, si ce lien entre la peau et la personne doit être mis en exergue, il doit également se conjuguer avec le lien qui existe entre la peau et le corps, afin d’assurer, non seulement une cohérence entre les différents principes juridiques qui s’appliquent alternativement à la peau en fonction de son entité de rattachement mais également, de garantir une protection effective de la peau quelle que soit cette entité de rattachement. / Human skin is a singular element that covers the body and allows everyone to benefit from the sense of touch. Described as a tissue of the human body, now the skin is subject to the same legal system enforced to the human body. However, if the skin is a protecting body shell, it is also akin to the person herself because it compose her appearence, contains elements of her identity and conduce to her identification. Therefore, if the skin covers the entire body, it also constitute the person. This makes of the skin a border element of the body and the person. Connected with this two dominant entities (person and body), the skin must be construed in a ternary relationship wich would place it in the center of the links between the person and her body. Indeed, the skin is not only an element of the human body because the person benefits from a right to make choices concerning it, even to modify it. But the skin cannot either only be an element of the person because it contains the body and constitutes a protection. However, if this link between the skin and the person must be hightlighted, it also has to merge with the link between the skin and the body to assure, on one hand, a coherence between the various legal principles alternately applied to the skin, according to its entity of pertaining, and, on the other hand, to guarantee an effective protection of the skin whatever is this entity of pertaining.

Submitted by Marcio Emanuel Paixão Santos (marcio.santos@ucsal.br) on 2017-02-21T18:39:01Z No. of bitstreams: 1 MestradoVersaoFinal-POSAcertosBANCA15.11.2016 GloriaaDeus.pdf: 3259476 bytes, checksum: 175e9ad0d2a4ef27f2bb39643d9bce0e (MD5) / Approved for entry into archive by Maria Emília Carvalho Ribeiro (maria.ribeiro@ucsal.br) on 2017-02-21T20:57:39Z (GMT) No. of bitstreams: 1 MestradoVersaoFinal-POSAcertosBANCA15.11.2016 GloriaaDeus.pdf: 3259476 bytes, checksum: 175e9ad0d2a4ef27f2bb39643d9bce0e (MD5) / Made available in DSpace on 2017-02-21T20:57:39Z (GMT). No. of bitstreams: 1 MestradoVersaoFinal-POSAcertosBANCA15.11.2016 GloriaaDeus.pdf: 3259476 bytes, checksum: 175e9ad0d2a4ef27f2bb39643d9bce0e (MD5) Previous issue date: 2016-09-13 / Esta dissertação tem a finalidade de pesquisar as possibilidades e as limitações da utilização do método da mediação diante de conflitos que envolvam o meio ambiente. Nesse sentido, o estudo faz uma análise da definição jurídica de meio ambiente, examina conceitos e faz um breve histórico das leis que dispõem sobre o direito ambiental. Analisa os instrumentos processuais utilizados para a tutela ambiental e estuda os termos de ajustamento de conduta celebrados pelo ministério público, na área ambiental. Investiga os posicionamentos doutrinários e legais sobre a questão da disponibilidade de direitos difusos e sua relação com os métodos extrajudiciais para a solução de controvérsias. Na sequência da pesquisa apresenta um estudo acerca dos métodos consensuais de solução de conflitos, com ênfase na mediação, quando são demonstradas as vantagens desse método e a sua disseminação em outros países e no Brasil. Diante dos resultados apresentados que apontam a possibilidade da mediação envolvendo questões ambientais conclui-se com a proposta de criação de uma câmara-escola de mediação, de modo a preparar os futuros profissionais para a solução consensual de conflitos, disseminar o método para a sociedade, contribuir para que a tutela do meio ambiente aconteça com mais celeridade, legitimidade e eficiência, além de promover a cultura de pacificação social. / This dissertation is intended to investigate the possibilities and limitations of the use of the mediation method on conflicts involving the environment. In this sense, the study analyzes the legal definition of environment, examines concepts and gives a brief history of laws that provide for the environmental law. Analyzes the procedural instruments used for environmental protection and studying the terms of adjustment of conduct signed by the public ministry, in the environmental area. Investigates the doctrinal and legal positions on the issue of availability of diffuse law and its relation to the extra-judicial methods for dispute settlement. Following the research presents a study about the consensual methods of conflict resolution, with emphasis on mediation, when shown the advantages of this method and its spread in other countries and in Brazil. On the presented results that point to the possibility of mediation involving environmental issues concludes with the proposal to create a camera-school mediation, in order to prepare future professionals for consensual conflict resolution, disseminate the method to society, contribute to the protection of the environment happen more quickly, legitimacy and efficiency, and to promote the culture of social peace.

[ES] La seguridad ha sido, es y seguirá siendo una prioridad en la operación de las centrales nucleares para la producción de energía eléctrica. Uno de los grandes retos a los que se enfrenta la industria nuclear es el envejecimiento de las estructuras, sistemas y componentes (ESC) de seguridad. Actualmente, este hecho cobra especial relevancia porque un gran número de reactores está alcanzando el fin de su vida de diseño, debiendo afrontar próximamente una Revisión Periódica de Seguridad (RPS), que garantice el funcionamiento seguro de la central durante un periodo adicional denominado Opera-ción a Largo Plazo (OLP). El Análisis Probabilista de Seguridad (APS) es una herramienta fundamental para la gestión integral de la seguridad de una planta, tanto en el marco de la RPS como en la Toma de Decisiones Informada en el Riesgo (TDIR), siendo capaz de evaluar el incremento o disminución en el riesgo producido por un cambio determinado. Sin embargo, los modelos y datos actuales que lo integran no tienen en cuenta factores que influyen de forma determinante en el riesgo de una central. Por un lado, no tienen en cuenta el envejecimiento o la estrategia de pruebas y mantenimiento, en el caso del modelado de la fiabilidad e indisponibilidad de componentes. Por otro lado, no con-templan la imprecisión en el modelado de las acciones humanas, ni la inexactitud en la cuantificación de sus probabilidades de error. La presente tesis doctoral pretende actualizar y mejorar los modelos del APS, con vistas a su aplicación en el contexto de la RPS y de la TDIR. En este sentido, se establecen dos objetivos principales. En primer lugar, el desarrollo de un modelo RAM (fiabilidad, mantenibilidad y disponibilidad) dependiente del tiempo para componentes de seguridad, ajustado con datos reales de planta y con un nivel de detalle suficiente para recoger explícitamente en la edad del mismo, el efecto de las pruebas y el mantenimiento. En segundo lugar, mostrar las aplicaciones del APS para la TDIR. En primer término, se define un modelo de riesgo dependiente de la edad, a partir del mode-lo RAM previamente formulado, con el que seleccionar la mejor estrategia de pruebas y mantenimiento en un horizonte temporal dado. En segundo término, para mejorar el modelado del APS y la cuantificación de las probabilidades de error humano (PEH), se propone una metodología de evaluación de impacto en el riesgo para cambios en las acciones humanas y las Especificaciones Técnicas de Funcionamiento, que aprovecha los resultados del uso conjunto de los análisis de seguridad determinista y probabilista. Las aportaciones que conforman esta tesis doctoral se integran en la línea de investigación financiada por el Ministerio de Economía y Empresa en el proyecto ENE2016-80401-R, "Armonización de requisitos de vigilancia y mantenimiento en centrales nucleares con información en el riesgo" y la ayuda para contratos predoctorales para la formación de doctores BES-2014-067602. / [CA] La seguretat ha sigut, és i continuarà sent una prioritat en l'operació de les centrals nuclears par a la producció d'energia elèctrica. Un del grans reptes als que s'enfronta la industria nuclear es l'envelliment de les estructures, sistemes i components de seguretat. Actualment, aquest fet té especial rellevància perquè un gran nombre de reactors està arribant a la fi de la seua vida de disseny, havent d'afrontar pròximament una Revisió Periòdica de Seguretat (RPS), que garantirà el funcionament segur de la central durant un període addicional conegut com Operació a Llarg Termini (OLP). L'Anàlisi Probabilista de Seguretat es una ferramenta fonamental per a la gestió integral de la seguretat d'una planta, tant en el marc de la RPS com en la presa de decisions informades en el risc (TDIR), sent capaç d'avaluar l'increment o disminució en el risc produït per un canvi determinat. No obstant això, els models i dades actuals que ho integren no tenen en compte factors que influeixen de forma determinant en el risc d'una central. Per una banda, no consideren l'envelliment o l'estratègia de proves i manteniment, en el cas del modelat de la fiabilitat i indisponiblitat de components. Per altra banda, no contemplen la imprecisió en el modelat de les acciones humanes, ni la inexactitud en la quantificació de la probabilitat d'error de les mateixes. La present tesi doctoral pretén actualitzar i millorar els models APS, amb la intenció d'aplicar-los en el context de la RPS y la TDIR. En aquest sentit, s'estableixen dos objectius principals. En primer lloc, el desenvolupament d'un model RAM (fiabilitat, mantenibilitat i disponibilitat) dependent del temps per a components de seguretat, ajustat amb dades reals de planta i amb un nivell de detall suficient per a recollir explícitament en l'edat del mateix, la política de proves i manteniment a la que es sotmès. En segon lloc, mostrar les aplicacions de l'APS per a la TDIR. En primer terme, es defineix un model de risc dependent de l'edat, a partir del model RAM prèviament formulat, amb el qual seleccionar la millor estratègia de proves i manteniment en un horitzó temporal determinat. En segon terme, per a millorar el modelat de l'APS i la quantificació de les probabilitats d'error humà (PEH), es proposa una metodologia d'avaluació d'impacte en el risc per a canvis en les accions humanes i en les Especificacions Tècniques de Funcionament, que aprofita els resultats de l'ús conjunt dels anàlisis determinista i probabilista. Les aportacions que formen part d'aquesta tesi doctoral s'integren en la línia d'investigació finançada pel Ministeri d'Economia i Empresa en el projecte ENE2016-80401-R, "Armonización de requisitos de vigilancia y mantenimiento en centrales nucleares con información en el riesgo" i l'ajuda per a contractes predoctorals per a la formació de doctors BES-2014-067602. / [EN] Safety always has been and always will be a priority in nuclear power plant operation to generate electricity. One of the major challenges of nuclear industry is the ageing of safety-related structures, systems and components (SSC). Presently, this fact gains relevance due to several reactors are reaching their design life, having to conduct a Periodic Safety Review (PSR) that assures safety operation for an additional period better-known as Long Term Operation (LTO) Probabilistic Safety Assessment (PSA) is an essential tool in an integral NPP safety management, both PSR framework and Risk Informed Decision Making (RIDM), being able to evaluate a risk increase or decrease for any specific change on the plant. However, current PSA models and data do not consider factors, which have an impact in the overall risk of the plant. On the one hand, they do not take into account the effect of ageing nor maintenance and testing program, in the case of reliability and unavailability modelling. On the other hand, human actions modelling and their associated error probabilities are characterized by its inaccuracy and uncertainty. This Ph. Dissertation aims to update and improve PSA models, in order to apply with-in the framework of PSR and RIDM. In this sense, two main objectives are established. Firstly, the development of a time dependent RAM (reliability, availability and maintainability) for safety-related components, fitted with a historical plant data and with enough level of detail to include the effects of testing and maintenance activities in the age of the component. Secondly, it shows PSA applications of new models in RIDM. In the first place, it defines an age-dependent risk model based on the RAM model previously formulated, which helps to select the best approach of maintenance and testing activities for a specific timeline. In the second place, to improve PSA modelling and human error probabilities (HEP) quantification, a methodology is pro-posed to evaluate the risk impact of human actions and TS changes, taking advantage of combining DSA and PSA insights. The work of this thesis is part of the research supported by the Ministry of Economy and Business in the project ENE2016-80401-R, "Risk Informed Harmonization of Surveillance Requirements and Maintenance in Nuclear Power Plants", and in the Doctoral Fellowship BES-2014-067602. / Las aportaciones que conforman esta tesis doctoral se integran en la línea de investigación financiada por el Ministerio de Economía y Empresa en el proyecto ENE2016- 80401-R, “Armonización de requisitos de vigilancia y mantenimiento en centrales nucleares con información en el riesgo” y la ayuda para contratos predoctorales para la formación de doctores BES-2014-067602. / Martorell Aigües, P. (2019). Aportaciones al modelado de la indisponibilidad de componentes y la fiabilidad humana para la mejora de la seguridad de las centrales nucleares informada en el riesgo [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/118794 / TESIS

[pt] Grande parte da literatura de problemas de escalonamento assume que todas as máquinas estão disponíveis durante todo o período de análise o que, na prática, não é verdade, pois algumas das máquinas podem estar indisponíveis para processamento sem aviso prévio devido a problemas ou a políticas de utilização de seus recursos. Nesta tese, exploramos algumas das poucas heurísticas disponíveis na literatura para a minimização do makespan para este tipo de problema NP-difícil e apresentamos uma nova heurística que utiliza estatísticas de disponibilidade das máquinas para gerar um escalonamento. O estudo experimental com dados reais mostrou que a nova heurística apresenta ganhos de makespan em relação aos demais algoritmos clássicos que não utilizam informações de disponibilidade no processo de decisão. A aplicação prática deste problema está relacionada a precificação de ativos de uma carteira teórica de forma a estabelecer o risco de mercado da forma mais rápida possível através da utilização de recursos tecnológicos ociosos. / [en] Most literature in scheduling theory assumes that machines are always available during the scheduling time interval, which in practice is not true due to machine breakdowns or resource usage policies. We study a few available heuristics for the NP-hard problem of minimizing the makespan when breakdowns may happen. We also develop a new scheduling heuristic based on historical machine availability information. Our experimental study, with real data, suggests that this new heuristic is better in terms of makespan than other algorithms that do not take this information into account. We apply the results of our investigation for the asset-pricing problem of a fund portfolio in order to determine a full valuation market risk using idle technological resources of a company.

Le transport multicast est une solution efficace pour envoyer le même contenu à plusieurs récepteurs en même temps. Ce mode est principalement utilisé pour fournir des flux multimédia en temps réel. Cependant, le multicast classique de l’IEEE 802.11 n'utilise aucun mécanisme d’acquittement. Ainsi, l’échec de réception implique la perte définitive du paquet. Cela limite la fiabilité du transport multicast et impact la qualité des applications vidéo. Pour résoudre ce problème, 802.11v et 802.11aa sont définis récemment. Le premier amendement propose Direct Multicast Service (DMS). D'autre part, le 802.11aa introduit GroupCast with Retries (GCR). GCR définit deux nouvelles politiques de retransmission : Block Ack (BACK) et Unsolicited Retry (UR).Dans cette thèse, nous évaluons et comparons les performances de 802.11v/aa. Nos résultats montrent que tous les nouveaux protocoles multicast génèrent un overhead de transmission important. En outre, DMS a une scalabilité très limitée, et GCR-BACK n'est pas approprié pour des grands groupes multicast. D’autre part, nous montrons que DMS et GCR-BACK génèrent des latences de transmission importantes lorsque le nombre de récepteurs augmente. Par ailleurs, nous étudions les facteurs de pertes dans les réseaux sans fil. Nous montrons que l'indisponibilité du récepteur peut être la cause principale des pertes importantes et de leur nature en rafales. En particulier, nos résultats montrent que la surcharge du processeur peut provoquer un taux de perte de 100%, et que le pourcentage de livraison peut être limité à 35% lorsque la carte 802.11 est en mode d’économie d'énergie.Pour éviter les collisions et améliorer la fiabilité du transport multicast, nous définissons le mécanisme Busy Symbol (BS). Nos résultats montrent que BS évite les collisions et assure un taux de succès de transmission très important. Afin d'améliorer davantage la fiabilité du trafic multicast, nous définissons un nouveau protocole multicast, appelé Block Negative Acknowledgement (BNAK). Ce protocole opère comme suit. L’AP envoi un bloc de paquets suivi par un Block NAK Request (BNR). Le BNR permet aux membres de détecter les données manquantes et d’envoyer une demande de retransmission, c.à.d. un Block NAK Response (BNAK). Un BNAK est transmis en utilisant la procédure classique d’accès au canal afin d'éviter toute collision avec d'autres paquets. En plus, cette demande est acquittée. Sous l'hypothèse que 1) le récepteur est situé dans la zone de couverture du débit de transmission utilisé, 2) les collisions sont évitées et 3) le terminal a la bonne configuration, très peu de demandes de retransmission sont envoyées, et la bande passante est préservée. Nos résultats montrent que BNAK a une très grande scalabilité et génère des délais très limités. En outre, nous définissons un algorithme d'adaptation de débit pour BNAK. Nous montrons que le bon débit de transmission est sélectionné moyennant un overhead très réduit de moins de 1%. En plus, la conception de notre protocole supporte la diffusion scalable de lavvidéo. Cette caractéristique vise à résoudre la problématique de la fluctuation de la bande passante, et à prendre en considération l'hétérogénéité des récepteurs dans un réseau sans fil. / The multicast transport is an efficient solution to deliver the same content to many receivers at the same time. This mode is mainly used to deliver real-time video streams. However, the conventional multicast transmissions of IEEE 802.11 do not use any feedback policy. Therefore missing packets are definitely lost. This limits the reliability of the multicast transport and impacts the quality of the video applications. To resolve this issue, the IEEE 802.11v/aa amendments have been defined recently. The former proposes the Direct Multicast Service (DMS). On the other hand, 802.11aa introduces Groupcast with Retries (GCR) service. GCR defines two retry policies: Block Ack (BACK) and Unsolicited Retry (UR).In this thesis we evaluate and compare the performance of 802.11v/aa. Our simulation results show that all the defined policies incur an important overhead. Besides, DMS has a very limited scalability, and GCR-BACK is not appropriate for large multicast groups. We show that both DMS and GCR-BACK incur important transmission latencies when the number of the multicast receivers increases. Furthermore, we investigate the loss factors in wireless networks. We show that the device unavailability may be the principal cause of the important packet losses and their bursty nature. Particularly, our results show that the CPU overload may incur a loss rate of 100%, and that the delivery ratio may be limited to 35% when the device is in the power save mode.To avoid the collisions and to enhance the reliability of the multicast transmissions, we define the Busy Symbol (BS) mechanism. Our results show that BS prevents all the collisions and ensures a very high delivery ratio for the multicast packets. To further enhance the reliability of this traffic, we define the Block Negative Acknowledgement (BNAK) retry policy. Using our protocol, the AP transmits a block of multicast packets followed by a Block NAK Request (BNR). Upon reception of a BNR, a multicast member generates a Block NAK Response (BNAK) only if it missed some packets. A BNAK is transmitted after channel contention in order to avoid any eventual collision with other feedbacks, and is acknowledged. Under the assumption that 1) the receiver is located within the coverage area of the used data rate, 2) the collisions are avoided and 3) the terminal has the required configuration, few feedbacks are generated and the bandwidth is saved. Our results show that BNAK has a very high scalability and incurs very low delays. Furthermore, we define a rate adaptation scheme for BNAK. We show that the appropriate rate is selected on the expense of a very limited overhead of less than 1%. Besides, the conception of our protocol is defined to support the scalable video streaming. This capability intends to resolve the bandwidth fluctuation issue and to consider the device heterogeneity of the group members.

This dissertation deals with the problematic of the free space optical link availability determination. For the presumption of the free space optical link unavailability we have to know statistical distribution of the atmospheric attenuations. In this work is also presented the measurement of these atmospheric attenuations with the specially designed optical link. Measurement is using switching of the two separate transmitters with wavelengths of 830 nm and 1550 nm. Presented statistic distribution let us determine the suitability of the link in the chosen locality during its design. Comparison of our measurement with other models like model based on the meteorological visibility is also presented. The last part of this work is focused on the preconditions for the hi-speed network bit error rate determination. Sample of the bit error rate measurement obtained by our designed bit error rate tester is attached.