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Priority schemes employing the inherent properties of carrier-sense multiple-access (CSMA) schemes are investigated and then applied to the integrated transmission of voice and data. A priority scheme composed of 1-persistent and non-persistent CSMA protocols is proposed. The throughput and delay characteristics of this protocol are evaluated by mathematical analysis and simulation, respectively. The approach of throughput analysis is further extended to another more general case, p-persistent CSMA with two persistency factors, the throughput performance of which had not been analyzed before. Simulations are carried out to study the delay characteristics of this protocol. After careful consideration of the features of the priority schemes studied, two protocols are proposed for integrated voice and data transmission. While their ultimate purpose is for integrated services, they have different application. One of them is applied to local area network; the other is suitable for packet radio network. The distinctive features of the former are simplicity and flexibility. The latter is different from other studies in that collision detection is not required, and that it has small mean and variance of voice packet delay. Performance characteristics of both of these protocols are examined by simulations under various system parameter values. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

Le développement des réseaux de communication digitaux tel Internet a rendu omniprésents les protocoles de communication. Les différents appareils électroniques que nous utilisons au quotidien doivent interagir les uns avec les autres afin de réaliser les taches nombreuses et variées qui sont devenues courantes, comme d'utiliser d'un téléphone portable, envoyer ou recevoir des messages électroniques, faire des achats en ligne et ainsi de suite. Pour ces applications, la sécurité est une notion cruciale. Par exemple, dans le cas des achats en ligne, il faut que la transaction ait lieu sans divulguer les informations personnelles de l'acheteur à un tiers. Les protocoles de communications contiennent les règles qui régissent ces interactions. Afin de s'assurer qu'ils garantissent un certain niveau de sécurité, on souhaite pouvoir les analyser. Une analyse manuelle, ou leur faire subir des tests, n'est pas suffisant, les attaques pouvant se révéler subtiles. Certains protocols ont été utilisés pendant des années avant qu'une attaque soit découverte contre eux. Étant donnée leur ubiquité croissante dans de nombreuses applications importantes, comme le commerce électronique, un des défis importants auquel la recherche doit faire face consiste à développer des méthodes et des outils de vérification pour augmenter notre confiance dans les protocoles sécurisés, et dans les applications qui dépendent de ces protocoles. Par exemple, plus de 28 milliards d'euros sont dépensés en France au cours de transactions sur Internet, et cette quantité ne cesse d'augmenter. De plus, de nouveaux types de protocoles apparaissent continuellement afin de relever de nouveaux défis technologiques et de société, e.g. le vote électronique, le passeport numérique pour n'en citer que quelques-uns. / With the development of digital networks, such as Internet, communication protocols are omnipresent. Digital devices have to interact with each other in order to perform the numerous and complex tasks we have come to expect as commonplace, such as using a mobile phone, sending or receiving electronic mail, making purchases online and so on. In such applications, security is important. For instance, in the case of an online purchase, the right amount of money has to be paid without leaking the buyer personal information to outside parties. Communication protocols are the rules that govern these interactions. In order to make sure that they guarantee a certainlevel of security, it is desirable to analyze them. Doing so manually or by testing them is not enough, as attacks can be quite subtle. Some protocols have been used for years before an attack was discovered. Because of their increasing ubiquity in many important applications, e.g. electronic commerce, a very important research challenge consists in developing methods and verification tools to increase our trust on security protocols, and so on the applications that rely on them. For example, more than 28 billion Euros were spent in France using Internet transactions, and the number is growing. Moreover, new types of protocols are continuously appearing in order to face new technological and societal challenges, e.g. electronic voting, electronic passport to name a few.

Au cours des dernières décennies, l'utilisation généralisée des technologies numériques de communication dans la vie quotidienne a donné lieu à une nouvelle relation entre l'individu et le territoire. Cette relation, dans laquelle les différents acteurs sont de plus en plus intégrés, surpasse l'ancien paradigme dichotomique caractérisé par la relation l'homme versus la nature. De cette façon, une nouvelle notion d'environnement, interactif et intégrant de l'espace social surgit, résultat de la représentation technologique de la nature et du dialogue favorisé par les réseaux numériques avec le territoire. L'objectif général de cette recherche est d'étudier le phénomène imaginaire écologique contemporain à partir de la perspective de la contribution de nouvelles technologies de communication numérique aux formes de représentation de la nature et de l'interaction avec le territoire. À cette fin, les voies et moyens d'interaction entre les individus, les technologies de communication numérique et le territoire seront étudiés, compte tenu des exemples de l'utilisation pratique des technologies numériques déjà consolidés. D'après une étude participative sur les réseaux numériques, ainsi que des études de cas, nous avons l'intention d'approfondir l'étude sur la contribution des réseaux numériques comme un territoire informatif ouvert pour les changements par rapport à la sociabilité contemporaine et l'imaginaire écologique contemporain. / In recent decades, the widespread use of digital communication technologies in daily life gave rise to a new relationship between individual and territory. This relationship, in which different actors are increasingly integrated, surpasses the old dichotomous paradigm characterized by the man versus nature's relationship. Therefore, a new notion of environment, interactive and member of the social space is born as a result of technological representation of nature and the dialogue fostered by digital networks with the territory. The overall objective of this research is to investigate the contemporary ecological imaginary phenomenon from the perspective of the contribution of new digital communication technologies to the forms of representation of nature and interaction with the territory. To this end, the ways and means of interaction between individuals, digital communication technologies and territory will be studied, considering examples of practical use of digital technologies already consolidated. From a participatory study on digital networks, as well as case studies, we intend to further study on the contribution of digital networks as an open informative territory to changes in relation to contemporary sociability and contemporary ecological imaginary.

Quality of service differentiation has never achieved much attention and relevance until the advent of the convergence of mobile wireless network and the fixed Internet, that is, Internet Protocol ( IP ) based mobile wireless networks, or wireless Internet. These networks are poised to support multimedia applications ' traffic with diverse QoS sensitivities. To date, most traffic transferred over the Internet still undergo best - effort forwarding, which does not guarantee whether or not traffic sent by a source gets to the intended destination, let alone loss and timing bounds. The major contribution of this thesis is three - fold. First, the thesis proposes a QoS - enabled wireless Internet access architecture, which leverages the micromobility in wireless standards to reduce mobile IP weaknesses, such as long handoff delay, to achieve effective interworking between mobile wireless networks and the global, fixed Internet. Although the idea here is applicable to any wireless standard, the design examples in this thesis are based on the IEEE 802.11b wireless local area network ( WLAN ) standard. Second, it proposes a framework for a class of wireless channel state dependent packet scheduling schemes, which consider the QoS requirements of the applications ' traffic ; the wireless channel state ( reflected in instantaneous data rate or noise level ) ; and optimises the usage of the expensive wireless resource. The operation of the QoS - enabled, channel state - dependent packet scheduler is analysed using optimisation theory, eigenanalysis and stochastic modelling. Third, the thesis analyses the effects of wireless channel properties on differentiated QoS ( DQoS ) schemes, using two - dimensional, channel - state - dependent queuing theory, matrix analytic methods to stochastic modelling and eigenanalysis. The ana - lytical model of DQoS schemes, especially models accounting for user scenarios such as speed of motion and wireless channel properties, such as fading, spatio - temporarily varying quality and low rate, is not properly covered in the open literature, and hence was a motivation for this part of the thesis. The wireless channel is discretized into discrete - time Markovian states based on the received signal - to - noise plus interference ratio ( SNIR ), which also reflects on the instantaneous link quality. The link quality, in turn, influences the QoS experienced by the transported applications sitting on top of the ISO / OSI protocol hierarchy. The parameters of the Markovian states are evaluated using realistic physical channel noise models and transceiver characteristics, such as modem. [ Different modems ( modulator / demodulator ) yields different transceiver properties such as sensitivity. The analysis in the thesis adopts QPSKand BPSK modulation. ] Source traffic models are used in the analysis. Lastly, the thesis provides an extensive introduction to, and provides a detailed background material for the new area of mobile wireless Internet systems, upon which considerable future research can be based. / Thesis (Ph.D.)--School of Electrical and Electronic Engineering, 2003.

Our research addresses two important problems that arise in modern large-scale distributed systems: 1. The necessity to virtualize their data flows by applying actions such as filtering, format translation, coalescing or splitting, etc. 2. The desire to separate such actions from application level logic, to make it easier for future service-oriented codes to inter-operate in diverse and dynamic environments. This research considers the runtimes of the `information appliances used for these purposes, particularly with respect to their ability to provide diverse levels of Quality of Service (QoS) in lieu of dynamic application behaviors and the consequent changes in the resource needs of their data flows. Our specific contribution is the enrichment of these runtimes with methods for QoS-awareness, thereby giving them the ability to deliver desired levels of QoS even under sudden requirement changes IQ-appliances. For experimental evaluation, we enrich a prototype implementation of an IQ-appliance, based on the Intel IXP network processor, with the additional functionality needed to guarantee QoS constraints for diverse data streams. Measurements demonstrate the feasibility and utility of the approach. Further, we enhance the Self-Virtualized Network Interface developed in previous work from our group with QoS awareness and demonstrate the importance of such functionality in end-to-end virtualized infrastructures.

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Quality of service differentiation has never achieved much attention and relevance until the advent of the convergence of mobile wireless network and the fixed Internet, that is, Internet Protocol ( IP ) based mobile wireless networks, or wireless Internet. These networks are poised to support multimedia applications ' traffic with diverse QoS sensitivities. To date, most traffic transferred over the Internet still undergo best - effort forwarding, which does not guarantee whether or not traffic sent by a source gets to the intended destination, let alone loss and timing bounds. The major contribution of this thesis is three - fold. First, the thesis proposes a QoS - enabled wireless Internet access architecture, which leverages the micromobility in wireless standards to reduce mobile IP weaknesses, such as long handoff delay, to achieve effective interworking between mobile wireless networks and the global, fixed Internet. Although the idea here is applicable to any wireless standard, the design examples in this thesis are based on the IEEE 802.11b wireless local area network ( WLAN ) standard. Second, it proposes a framework for a class of wireless channel state dependent packet scheduling schemes, which consider the QoS requirements of the applications ' traffic ; the wireless channel state ( reflected in instantaneous data rate or noise level ) ; and optimises the usage of the expensive wireless resource. The operation of the QoS - enabled, channel state - dependent packet scheduler is analysed using optimisation theory, eigenanalysis and stochastic modelling. Third, the thesis analyses the effects of wireless channel properties on differentiated QoS ( DQoS ) schemes, using two - dimensional, channel - state - dependent queuing theory, matrix analytic methods to stochastic modelling and eigenanalysis. The ana - lytical model of DQoS schemes, especially models accounting for user scenarios such as speed of motion and wireless channel properties, such as fading, spatio - temporarily varying quality and low rate, is not properly covered in the open literature, and hence was a motivation for this part of the thesis. The wireless channel is discretized into discrete - time Markovian states based on the received signal - to - noise plus interference ratio ( SNIR ), which also reflects on the instantaneous link quality. The link quality, in turn, influences the QoS experienced by the transported applications sitting on top of the ISO / OSI protocol hierarchy. The parameters of the Markovian states are evaluated using realistic physical channel noise models and transceiver characteristics, such as modem. [ Different modems ( modulator / demodulator ) yields different transceiver properties such as sensitivity. The analysis in the thesis adopts QPSKand BPSK modulation. ] Source traffic models are used in the analysis. Lastly, the thesis provides an extensive introduction to, and provides a detailed background material for the new area of mobile wireless Internet systems, upon which considerable future research can be based. / Thesis (Ph.D.)--School of Electrical and Electronic Engineering, 2003.

Thesis (M. Eng.), Memorial University of Newfoundland, 1998. / Bibliography: leaves 107-112.

Thesis (M. Eng.)--Carleton University, 1999. / Also available in electronic format on the Internet.