Le développement du commerce électronique a révolutionné tous les aspects de l’activité marchande, et notamment les éléments du marketing-mix. En particulier, de nouvelles formes de prix ont émergé, et les académiciens aussi bien que les praticiens doivent désormais faire face à de nouveaux défis. Des prix ayant plusieurs composantes, communément appelés prix complexes, sont désormais légion. La plupart des travaux marketing qui se sont intéressés à cette forme de prix ont insisté sur les biais cognitifs affectant leur estimation, en appelant les vendeurs à en faire un moyen pour réduire le sacrifice monétaire perçu, ce qui permet de multiplier les ventes. Cependant, rares sont les chercheurs qui ont averti aux risques liés à de telles pratiques. S’inscrivant dans un objectif de pallier à cette limite, cette recherche a pour vocation de déterminer l’incidence de l’usage des prix complexes sur leur perception moyennant l’approche de trois aspects : (1) la détermination de certaines formes de présentation visuelle pouvant entacher le jugement de leur annonce (2) les répercussions de telles formes de présentation sur la justice perçue du prix, et en l’occurrence, sur des variables-clés de l’activité marchande telles que la valeur de l’offre et l’intention d’achat (3) et la prise en compte de différentes sources de variance à caractère situationnel. Les résultats d’une expérimentation conduite auprès de 504 répondants confirment l’intervention de la présentation visuelle d’un prix complexe dans la dégradation de sa justice perçue, en montrant le rôle déterminant du processus : La justice procédurale d’un prix complexe apparaît alors comme un pilier incontournable du jugement d’une offre. / One of e-commerce development implications is the metamorphosis of all marketing-mixaspects. Especially, new price forms have emerged, leading both academicians and managers to deal with new challenges. Prices with more than one component, known as complex prices, become the main form used within this channel. The dominant stream of marketing research interested within this area has focused on cognitive biases that affect complex price judgments. Most researchers have recommended managers to use this form of price in a manner that reduce perceived price, and therefore enhance sales. Regarding the lack of research considering negative effects of such tactics, the principal aim of this work is to put the spotlight on complex price incidence on its perception within three aspects: (1) the determination of visual presentation forms that may damage this perception (2) the effects of such presentation forms on complex price perceived fairness, and consequently, on determinant variables such as offer value and purchase intentions (3) and the control of moderating variables associated with situational differences. The results of an experiment conducted on 504 respondents show the presence of a degradation of complex price perceivedfairness caused by its visual presentation form, with a determinant contribution of the process: procedural fairness is henceforth an essential pillar of an offer judgment.

Avec le développement rapide du commerce électronique, la vente multi-canaux, du type « brick-and-mortar » et vente en ligne est le standard pour les vendeurs en 2016. Cependant, cette stratégie ne garantit pas toujours le succès des détaillants dans les campagnes commerciales. La plupart du temps les difficultés proviennent d’un manque de coordination efficace entre la boutique en ligne et son homologue hors ligne selon leurs attributs respectifs. Sur la base du concept de congruence perçu, cette thèse étudie l'évaluation par les sujets des attributs des magasins entre les différents canaux du marché multicanaux chinois. Les résultats d’études du type « Depth Interview » (étude 1), montrent que les consommateurs chinois préfèrent le comportement commercial multicanaux. Ils aiment la congruence entre les canaux, mais espèrent aussi profiter des situations non-congruentes, ce qui indique leur propension à comparer les prix et l'assortiment entre canaux. Les deux études quantitatives ont identifié la congruence perçue comme un facteur déterminant pour l'évaluation des détaillants par les sujets. Plus précisément, plus les sujets perçoivent de la congruence dans la politique de prix entre les canaux, plus les sujets jugent les prix justes. des prix équitables, se traduisent par une attitude plus favorable envers le vendeur (étude 2). En revanche, lorsque les sujets perçoivent plus d’incongruité dans l'assortiment cross-canaux, ils considèrent que le choix est plus important (étude 3). Mais cette conséquence ne se produit que lorsque le processus cognitif n’est pas contraint. En outre, quand un prix équitable est perçu et qu’une variété est perçue les deux sont identifiés comme médiateurs de l'effet de la perception de congruence sur l'attitude des sujets envers les détaillants. En outre, l’implication des sujets dans l’expérimentation ne supporte pas statistiquement l'effet de modération en interaction avec la congruence perception sur des sujets de l'évaluation en ce qui concerne les attributs du canal de distribution, mais l'effet marginal dans la visualisation indique que les chercheurs doivent, dans les études futures, continuer l'étude des influences pertinentes entre l’implioation et la congruence perçue. / Along with the globally rapid development of e-commerce, multichannel retail including both brick-and-mortar and online stores is in 2016 the standard for the sellers. However, such justified strategy not always guarantee retailers’ success in commercial campaigns. Most of the time the difficulties arised from the lack of efficient coordination between the online store and its offline counterpart based upon their respective attributes. On the basis of the percieved congruence concept, this dissertation investigates subjects’ evaluation on store attributes between the different channels of the Chinese multichannel retail market. Through the Depth Interview (Study 1), it was found that Chinese multichannel consumers prefer the multichannel shopping behavior. They like the between-channel congruence but also expect to enjoy the incongruent situation which indicates their propensity to compare the between-channel prices and assortment. The two quantitative studies identified the perceived congruence as a determinant to the subjects’ evaluation towards the retailer. More precisely, the more congruence subjects perceive from the cross-channel price policy, the more price fairness subjects judge, turns in more favorable attitude toward the retailer (Study 2). In contrast, when the subjects perceive more schema incongruity, from the cross-channel assortment, they evaluate more variety (Study 3). But this consequence only occurs when the cognitive process is not constrained. In addition, both price fairness perception and variety perception are identified to mediate the effect of congruence perception on subjects’ attitude toward retailers. Besides, subjects’ experimental involvement, does not statistically support the moderation effect interacting with congruence perception on subjects’ evaluation regarding channel store attributes, but the marginal effect in visualization indicates that researchers must, in future study, keep investigating the relevant influences between involvement and congruence perception.

Over the past few decades, wireless local area networks (WLANs) have been widely deployed for data communication in indoor environments such as offices, houses, and airports. In order to fairly and efficiently use the unlicensed frequency band that Wi-Fi devices share, the devices follow a set of channel access rules, which is called a wireless medium access control (MAC) protocol. It is known that wireless devices following the 802.11 standard MAC protocol, i.e. the distributed coordination function (DCF), suffer from packet collisions when multiple nodes simultaneously transmit. This significantly degrades the throughput performance. Recently, several studies have reported access techniques to reduce the number of packet collisions and to achieve a collision free WLAN. Although these studies have shown that the number of collisions can be reduced to zero in a simple way, there have been a couple of remaining issues to solve, such as dynamic parameter adjustment and fairness to legacy DCF nodes in terms of channel access opportunity. Recently, In-Band Full Duplex (IBFD) communication has received much attention, because it has significant potential to improve the communication capacity of a radio band. IBFD means that a node can simultaneously transmit one signal and receive another signal in the same band at the same time. In order to maximize the performance of IBFD communication capability and to fairly share access to the wireless medium among distributed devices in WLANs, a number of IBFD MAC protocols have been proposed. However, little attention has been paid to fairness issues between half duplex nodes (i.e. nodes that can either transmit or receive but not both simultaneously in one time-frequency resource block) and IBFD capable nodes in the presence of the hidden node problem.

Dans cette thèse, nous nous intéressons aux modèles de calcul dans les réseaux d'objets à capacité restreinte, tels que les réseaux de capteurs sans fil. Nous nous focalisons sur les protocoles de population proposés par Angluin et al. Dans ce modèle, les objets sont représentés par des agents à états finis, passivement mobiles, communiquant entre paires et formant un réseau asynchrone et anonyme. Nous présentons deux études comparatives qui nous permettent par la suite de proposer une approche établissant le lien des protocoles de population avec deux autres modèles : le modèle des tâches avec les systèmes de réécritures de graphes, et le modèle asynchrone et anonyme d'échange de messages. Nous passons ensuite au problème d'ordonnancement dans les protocoles de population. Nous proposons un nouvel ordonnanceur probabiliste, 1-central, basé sur les rendez-vous randomisés et appelé HS Scheduler. Contrairement aux autres ordonnanceurs,il permet à plus d'une paire de communiquer à la fois. Nous prouvons qu'il est équitable avec probabilité 1. Nous analysons par la suite les termes Nous analysons par la suite les temps de stabilisation de certains protocoles s'exécutant sous le Random Scheduler ou le HS Scheduleret sur différentes topologies du graphe d'interaction. Nous prouvons que le HS Scheduler est équivalent en temps au Random Scheduler quand le graphe d'interaction est complet mais qu'il permet une stabilisation plus rapide quand le graphe est aléatoire. Par la suite,nous proposons un autre ordonnanceur qui prend en considération les états des agents et permet d'introduire la terminaison à certains protocoles : le Prorotol Aware HS Scheduler.Nous prouvons qu'il est équitable avec probabilité 1. Nous faisons l'analyse des temps de stabilisation de certains protocoles s'exécutant sous cet ordonnanceur en considérant différentes topologies du graphe d'interaction. Finalement, nous implémentons et simulons sur ViSiDiA l'ensemble des scénarios étudiés et validons nos résultats théoriques. / In this work, we consider computing models for networks of tiny objects suchas wireless sensor networks. We focus on the population protocols, a pairwise computationalmodel introduced by Angluin et al. where the tiny objects are represented byanonymous, passively mobile, finite state agents forming asynchronous networks. Weestablish two comparative studies between the population protocol model (and its extensions)and the two following ones: tasks with graph relabeling systems, and anonymousasynchronous message passing. These studies aim to establish possible mappings betweenthe population protocols and these two models. We then focus on the scheduling of thepairwise interactions in population protocols. We propose the HS Scheduler, a new probabilistic1-central scheduler based on randomized handshakes. Compared to the existingschedulers, this scheduler allows to more than one pair of agents to communicate simultaneously.We prove that this scheduler is fair with probability 1. We thereafter presentanalyses of the complexity of the stabilization time of some protocols running under thescheduling of the Random Scheduler and the HS Scheduler, and over different topologiesof the interaction graph. We prove that these two schedulers are time equivalent withComputing Models for Networks of Tiny Objects iiirespect to these protocols when the interaction graph is complete, however computationsunder the HS Scheduler stabilize faster when the interaction graph is random. We then introducethe Protocol Aware HS Scheduler, a slightly modifed version of the HS Schedulerthat takes into account the states of the agents and allows termination in some protocols.We also prove that this scheduler is fair with probability 1. We present analyses of thetime complexity of some protocols running under the scheduling of the Protocol AwareHS Scheduler and over dfferent structures of the interaction graph. We implement thedifferent scenarios in ViSiDiA, and validate through simulations our theoretical results.

Esta dissertação é o resultado de um estudo de caso que abordou as relações entre o financiamento do ensino fundamental e as condições de oferta de educação de qualidade em escolas do município de Porto Alegre, à luz dos princípios do direito à educação e da igualdade de condições de acesso e permanência e equidade, princípios esses amparados na legislação nacional e nos acordos internacionais. No plano conceitual, essa dissertação foi orientada pelos conceitos de igualdade e eqüidade, os quais ofereceram o suporte para as defesas que se buscou fazer ao tratar da necessidade do Poder Público garantir investimentos na escola pública e desenvolver políticas reparadoras às classes sociais desfavorecidas para que o acesso ampliado à escola possa se converter em sucesso escolar. Da mesma forma, defendeu-se a necessidade de que seja (re)introduzido o conceito de igualdade na agenda das políticas do setor educacional, pensado como distribuições desiguais justas, tendo o cuidado de alertar que essa acepção de igualdade não se contrapõe ao respeito à diversidade reivindicada pelos setores que defendem os direitos dessa fatia dos excluídos. Como recurso metodológico foram utilizadas as técnicas da aplicação de questionários semiestruturados, entrevistas, análise documental e observação direta. A pesquisa foi desenvolvida em três escolas de ensino fundamental da cidade de Porto Alegre, sendo uma escola privada que atende alunos de classe média e duas escolas da Rede Municipal de Ensino, situadas na periferia da cidade, que atendem alunos de classe popular. / This work is the result of a case study that approaches the relationship between public education financing and the conditions of provision of qualified education in the schools of Porto Alegre municipality, under the principles of education rights and equality of access, permanence and equity, all of them protected by national law and international agreements. The theoretical framework of this work was oriented by the concepts of equality and equity, which gave support to the defence we tried to make of the idea that Public Power needs to assure investments in basic school, and to develop policies that repair impoverished social classes so that the widened access to school leads to school success. In the same way, we defended the (re)introduction of the concept of equality in the agenda of the educational sector policies, seen as fair yet not equal distribution, noting that this meaning of the word equality is not disrespectful of the idea of diversity claimed by the sectors that defend the rights of this category of excluded people. As a methodological resource, semi-structured questionnaires, interviews, documentary analysis, and direct observation were used as techniques. The research was carried on in three basic schools in Porto Alegre: a private school attended by middle class students and two schools attended by popular class students, located in a suburb, and belonging to the Rede Municipal de Ensino.

O tema do acesso à justiça é aquele que mais diretamente equaciona as relações entre o processo e a justiça social, entre igualdade jurídico-formal e desigualdade socioeconômica. A consagração constitucional dos novos direitos econômicos e sociais e sua expansão paralela à do Estado-Providência transformou o direito ao acesso efetivo à justiça em um direito-chave, um direito cuja denegação acarretaria a de todos os demais. Daí a constatação de que a organização da justiça não pode ser reduzida à sua dimensão técnica, socialmente neutra, devendo investigar-se as funções sociais por elas desempenhadas e, em particular, o modo como as possibilidades técnicas no seu seio veiculam opções a favor ou contra interesses sociais divergentes ou mesmo antagônicos. Desde a década de 70 do século passado, diversos pesquisadores e analistas sociais têm contribuído para colocar em questão as formas de resolução de conflitos características do Estado Moderno, bem como para apontar caminhos e problematizar as experiências concretas de informalização, desjudicialização, mediação e arbitragem que vão surgindo. Pensando no acesso à justiça como um direito primordial sem o qual os demais direitos não se concretizam e nesses meios de resolução de conflitos, o objetivo desse trabalho é analisar se a Justiça Restaurativa é capaz de ampliar o acesso à justiça em sua dimensão material e formal. Atualmente, a importância da Justiça Restaurativa é reconhecida inclusive pela ONU, já que sua prática tem possibilitado a pacificação social, na medida em que sugere uma reavaliação do fenômeno criminológico desde suas causas, passando pela aplicação da justiça ate suas consequências futuras. Para chegar ao objetivo do trabalho, a teoria de John Rawls sobre a justiça como equidade é importante para, por meio do instituto do equilíbrio reflexivo, a Justiça Restaurativa ser pensada justamente como um mecanismo de adequação aos princípios essenciais de uma sociedade cooperativa. / Access to justice is the theme that more directly equates the relations between process and social justice, formal-legal equality and socioeconomic inequality. The constitutional praise of the new economic and social rights and their expansion alongside the Welfare State turned the right to effective access to justice into a key one, a right whose denial would lead to the denial of all other rights. Hence the conclusion that the organization of justice cannot be reduced to its technical, socially neutral dimension; instead, its social functions must be investigated, particularly in regard to the way technical possibilities convey options in favor of or against social interests that may diverge or even antagonize. Since the 1970s, many researchers and social analysts have contributed to question the ways of conflict resolution that characterize the Modern State, as well as to point ways and problematize concrete experiences of informalization, non-judicialization, mediation and arbitration that emerge. Considering access to justice as a primordial right without which the other ones do not materialize and taking into account these ways of conflict resolution, this work aims to analyze whether Restorative Justice is able to extend the access to justice in its material and formal dimensions. Currently, the United Nations recognizes the importance of Restorative Justice, since its practice enables social pacification by means of suggesting a reevaluation of the criminologic phenomenon already in its causes and also of the application of justice and its future consequences. To get to the central point of the work, John Rawls\' theory on justice as fairness, by means of the institute of the reflective equilibrium, is important for Restorative Justice to be thought exactly as a mechanism of adequacy to the essential principles of a cooperative society.

Values matter in both legal decision (lawmaking and lawapplying) and discourse (lawshaping and lawinfluencing). Yet, their purported subjectivity means that gaining or improving knowledge about values (whether they be epistemic, legal, moral, ethical, economic, political, cultural, social, or religious) in the context of analytic legal thought and understanding is often said to be at odds with its goal of objectivity. This phenomenon is amplified at the international level where the infusion of seemingly subjective political values by sovereigns, and the decisionmakers to whom they delegate, can, and does, interfere with an idealized and objective rule of law. The discourse on value subjectivity, and its relation to the purpose and function of the law, is particularly apparent in evolving international legal orders such as investment treaty arbitration. The primary aim of this work is to provide a new method for gaining empirical knowledge about value subjectivity that can help close a weak link in all nonpositivist (value-laden) legal theory: a weakness that has manifest itself as skepticism about the possibility of measuring value objectively enough to permit its incorporation as a necessary component of analytic jurisprudence. This work proposes a theory of configurative fairness for addressing the problem related to the development or evolution of legal regimes, and how legal regimes perceived as subjectively unfair can be remedied. Such a theory accepts the premise that perceptions of fairness matter in directing the way that legal orders develop, and that perceptions of fairness relate to the manner in which values are distributed and maximized in particular legal orders. It is posited that legal orders perceived as fair by their participants are more likely to be endorsed or accepted as legally binding (and are therefore more likely to comply with the processes and outcomes that such laws mandate). The purpose of a theory of configurative fairness is an attempt to provide a methodological bridge for improving knowledge about value in the context of legal inquiry through the employment of a technique called Q methodology: an epistemological and empirical means for the measurement and mapping of human subjectivity. It is a method that was developed in the early twentieth century by physicist-psychologist William Stephenson: the last research student of the inventor of factor analysis, Charles Spearman. What Stephenson did was to create a way for systematically measuring subjective perspectives, and although not previously used in jurisprudential thought, Q methodology will facilitate a means for the description and evaluation of shared subjectivities. In the context of law generally, and in investment treaty arbitration specifically, these are the subjectivities that manifest themselves as the conflicting perspectives about value that are omnipresent in both communicative lawshaping discourse and authoritative and controlling lawmaking and lawapplying decision. Knowledge about these shared value subjectivities among participants in investment treaty arbitration will allow the legal analyst to delineate and clarify points of overlapping consensus about the desired distribution of value as they relate to the regime-building issues of evolving legal orders. The focus for a theory of configurative fairness pertains to the identification of the various value positions that participants hold about a particular legal order and to configure those values, through its rules and principles, in a manner that is acceptable (and perceived as fair) by all of its participants. If such a value consensus can be identified, then particular rules in the legal order can be configured by decisionmakers in a way so as to satisfy participants’ shared value understandings. To engage such a theory, a means for identifying shared value subjectivities must be delineated. This work conducts a Q method study on the issues under debate relating to regime-building questions in investment treaty arbitration. The Q method study asked participants knowledgeable about investment treaty arbitration to rank-order a set of statements about the way that the values embraced by this legal order ought to be configured. The results of the study demonstrate that there is significant overlap about how participants in investment treaty arbitration perceive the desired distribution of values across the regime. The Q method study identified six distinct perspectives that represent shared subjectivities about value in the context of the development of investment treaty arbitration. The Q method study was also able to identify where there is an overlapping consensus about value distribution across the distinct perspectives. It is these areas of overlapping consensus that are most likely to reflect shared value understandings, and it is proposed that it is upon these shared value understandings that the future development of investment treaty arbitration ought to aim.

Submitted by Silvana Teresinha Dornelles Studzinski (sstudzinski) on 2016-08-22T19:42:17Z No. of bitstreams: 1 Fabrício José Rodrigues de Lemos_.pdf: 1128559 bytes, checksum: b0f111c3f1defefc8a80daa19003f118 (MD5) / Made available in DSpace on 2016-08-22T19:42:17Z (GMT). No. of bitstreams: 1 Fabrício José Rodrigues de Lemos_.pdf: 1128559 bytes, checksum: b0f111c3f1defefc8a80daa19003f118 (MD5) Previous issue date: 2016-06-30 / Nenhuma / O filósofo norte-americano John Rawls possui o grande mérito de revitalizar as discussões sobre justiça com a publicação de sua obra A theory of justice, de 1971. Nela, lançou base à teoria de justiça como equidade, sendo que, desde então, muito se comentou acerca das responsabilidades morais das entidades e indivíduos no plano doméstico. Em um artigo publicado em 1993 e, em 1999, transformado na obra Law of peoples and the public reason revisited, Rawls ampliou o escopo de suas preocupações e dissertou acerca das responsabilidades dos povos uns para os outros. Nas últimas duas décadas, a teoria de justiça global consolidou-se como um legítimo campo de indagações filosóficas, que visa possibilitar uma melhor compreensão das relações globais e do ambiente globalizado: as profundas modificações oriundas da mudança do paradigma westfaliano em razão da interconectividade e do aumento da complexidade das relações no plano global levaram críticos como Thomas Pogge a se questionar acerca da nova dinâmica mundial. A assunção de responsabilidades, tanto estatais e corporativas quanto as individuais, fazem parte da temática. Nesse sentido, com método de pesquisa eminentemente bibliográfico e documental, partindo da teoria rawlsiana, a dissertação visa demonstrar de que maneira essa mudança de paradigma ocorreu, tendo como referenciais teóricos tanto John Rawls quanto um dos maiores expoentes da teoria de justiça global, o filósofo alemão, atualmente radicado nos Estados Unidos, Thomas Pogge. Assim, a dissertação apresentará as mais recentes formulações teoréticas acerca do que pode ser chamado de justiça global e investigará as críticas e os avanços da obra de Pogge em relação ao pensamento de Rawls. / The American philosopher John Rawls has the great merit of revitalizing justice discussions with the publication of his 1971 work A theory of justice. In it, he gave base to theory of justice as fairness, and, since then, much was said about the moral responsibilities of organizations and individuals in domestic field. In an article published in 1993 and, in 1999, transformed in the work Law of peoples and the public reason revisited, Rawls expanded the scope of his concerns and lectured about the responsibilities of peoples to each other. In the last two decades, the global justice theory has established itself as a legitimate field of philosophical inquiry, which aims to enable a better understanding of global relations and the global environment: the profound changes arising from the change of the westphalian paradigm due to the interconnectivity and the increasing complexity of relationships globally, led critics like Thomas Pogge to wonder about the new world dynamics. The intake of responsibilities, both state and corporate, as well of the individual, are all part of the theme. In this sense, with the research method of eminently bibliographic research and documental, from the starting point of Rawlsian theory, the dissertation aims to demonstrate how this paradigm shift occurred, with the theoretical references of both John Rawls as of one of the greatest exponents of the global justice theory, the German philosopher, currently living in the United States, Thomas Pogge. Thus, the dissertation will present the latest theoretical formulations on what can be called global justice and will investigate the critiques and advances of Pogge's work in relation to Rawls‟s thinking.

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Les réseaux sans fil multisauts présentent un certain nombre d'intérêts car ils n'ont pas besoin d'infrastructure fixe, sont peu coûteux et sont simples d'utilisation. Le mode DCF de IEEE 802.11 est souvent utilisé comme le protocole d'accès au canal pour les nœuds dans ces réseaux. Un avantage de ce protocole est qu'il est facile à implémenter. Pourtant, ses performances dépendent de deux facteurs importants : le partage du canal sans fil et les collisions entre paquets provenant des nœuds cachés. L'évaluation de ces paramètres est donc importante afin d'améliorer la performance de ce protocole. La première partie de la thèse est consacrée à l'évaluation de la bande passante disponible. C'est un paramètre qui est souvent utilisé pour le contrôle d'admission ou pour le routage dans ces réseaux. Dans la littérature, il existe de nombreuses méthodes qui permettent d'estimer la bande passante disponible sur un lien sans fil. Pourtant, ces méthodes ne prennent pas en compte la notion de retransmission qui est définie dans IEEE 802.11 et qui a clairement des impacts sur la bande passante disponible. Nous proposons donc une nouvelle méthode passive, appelée RABE (Retransmission-based Available Bandwidth Estimation). Notre méthode se base principalement sur des informations locales qui peuvent être détectées par chaque nœud du lien. Nous évaluons également la probabilité de collisions non conditionnelle des paquets provenant des nœuds cachés via un modèle analytique. Cette probabilité nous permet d'estimer le nombre moyen de retransmissions qui est ensuite utilisé pour évaluer d'autres paramètres utilisé par RABE. Les simulations réalisées avec le simulateur ns2.33 montrent que notre méthode produit des résultats plus précis que d'autres méthodes existantes / The first part of the thesis is devoted to the evaluation of the available bandwidth. This is a parameter that is often used for admission control in these networks. In the literature, there are many methods for estimating the available bandwidth on a wireless link. However, these methods do not take into account the concept of retransmission which is defined in IEEE 802.11 and have clear impacts on the available bandwidth. We propose therefore a new passive method called RABE (Retransmission-based Available Bandwidth Estimation). Our method is based mainly on local information that can be detected by each node. We also evaluate the unconditional collision probability of packets from hidden nodes via an analytical model. This probability allows us to estimate the average number of retransmissions, which is then used to evaluate other parameters used by RABE. The simulations performed with the simulator ns2.33 show that our method produces more accurate results than other existing solutions. In the second part, we focus on the distribution of idle periods of a node that is often used to evaluate the performance of wireless networks based on IEEE 802.11. The problem is that there are different assumptions for this distribution in literature. We first characterize different types of idle periods in some fundamental scenarios such as the scenario as asymetric hidden stations and the scenario of flow in the middle. We then generalize these types of idle periods for relatively highly loaded networks. The obtained simulation results in ns2.33 are similar to our proposed model. This work also brings out that these distributions are multimodal, unlike what is often assumed in the literature