Realistic mobility and cellular traffic modeling is key to various wireless networking applications and have a significant impact on network performance. Planning and design, network resource allocation and performance evaluation in cellular networks require realistic traffic modeling. We propose a Discrete Event Simulation framework, Diamond - (Discrete Event Simulation of Mobility and Spatio-Temporal Spectrum Demand) to model and analyze realistic activity based mobility and spectrum demand patterns. The framework can be used for spatio-temporal estimation of load, in deciding location of a new base station, contingency planning, and estimating the resilience of the existing infrastructure. The novelty of this framework lies in its ability to capture a variety of complex, realistic and dynamically changing events effectively. Our initial results show that the framework can be instrumental in contingency planning and dynamic spectrum allocation. / Master of Science

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International Telemetering Conference Proceedings / October 30-November 02, 1995 / Riviera Hotel, Las Vegas, Nevada / The driving force in modern space mission control has been directed towards developing cost effective and reliable communication and data systems. The objective is to maintain and ensure error-free payload commanding and data acquisition as well as efficient processing of the payload data for concurrent, real time and future use. While Mainframe computing still comprises a majority of commercially available communication and data systems, a significant diversion can be noticed towards utilizing a distributed network of workstations and commercially available software and hardware. This motivation reflects advances in modem computer technology and the trend in space mission control today and in the future. The development of communication and data involves the implementation of distributed and parallel processing concepts in a network of highly powerful client server environments. This paper addresses major issues related to developing and integrating communication and data system and the significance for future developments.

Analytical modelling and characterization of Weighted Fair Queueing (WFQ) have recently received considerable attention by several researches since WFQ offers the minimum delay and optimal fairness guarantee. However, all previous work on WFQ has focused on developing approximations of the scheduler with an infinite buffer because of supposed scalability problems in the WFQ computation. The main aims of this thesis are to study WFQ system, by providing an analytical WFQ model which is a theoretical construct based on a form of processor sharing for finite capacity. Furthermore, the solutions for classes with Poisson arrivals and exponential service are derived and verified against global balance solution. This thesis shows that the analytical models proposed can give very good results under particular conditions which are very close to WFQ algorithms, where accuracy of the models is verified by simulations of WFQ model. Simulations were performed with QNAP-2 simulator. In addition, the thesis presents several performance studies signifying the power of the proposed analytical model in providing an accurate delay bounds to a large number of classes. These results are not able to cover all unsolved issues in the WFQ system. They represent a starting point for the research activities that the Author will conduct in the future. The author believes that the most promising research activities exist in the scheduler method to provide statistical guarantees to multi-class services. The author is convinced that alternative software, for example, on the three class model buffer case, is able to satisfy the large number of buffer because of the software limitation in this thesis. While they can be a good topic for long-term research, the short-medium term will show an increasing interest in the modification of the WFQ models to provide differentiated services.

Quality of Service (QoS) routing considered as one of the major components of the QoS framework in communication networks. The concept of QoS routing has emerged from the fact that routers direct traffic from source to destination, depending on data types, network constraints and requirements to achieve network performance efficiency. It has been introduced to administer, monitor and improve the performance of computer networks. Many QoS routing algorithms are used to maximize network performance by balancing traffic distributed over multiple paths. Its major components include bandwidth, delay, jitter, cost, and loss probability in order to measure the end users' requirements, optimize network resource usage and balance traffic load. The majority of existing QoS algorithms require the maintenance of the global network state information and use it to make routing decisions. The global QoS network state needs to be exchanged periodically among routers since the efficiency of a routing algorithm depends on the accuracy of link-state information. However, most of QoS routing algorithms suffer from scalability problems, because of the high communication overhead and the high computation effort associated with marinating and distributing the global state information to each node in the network. The goal of this thesis is to contribute to enhancing the scalability of QoS routing algorithms. Motivated by this, the thesis is focused on localized QoS routing that is proposed to achieve QoS guarantees and overcome the problems of using global network state information such as high communication overhead caused by frequent state information updates, inaccuracy of link-state information for large QoS state update intervals and the route oscillating due to the view of state information. Using such an approach, the source node makes its own routing decisions based on the information that is local to each node in the path. Localized QoS routing does not need the global network state to be exchanged among network nodes because it infers the network state and avoids all the problems associated with it, like high communication and processing overheads and oscillating behaviour. In localized QoS routing each source node is required to first determine a set of candidate paths to each possible destination. In this thesis we have developed localized QoS routing algorithms that select a path based on its quality to satisfy the connection requirements. In the first part of the thesis a localized routing algorithm has been developed that relies on the average residual bandwidth that each path can support to make routing decisions. In the second part of the thesis, we have developed a localized delay-based QoS routing (DBR) algorithm which relies on a delay constraint that each path satisfies to make routing decisions. We also modify credit-based routing (CBR) so that this uses delay instead of bandwidth. Finally, we have developed a localized QoS routing algorithm for routing in two levels of a hierarchal network and this relies on residual bandwidth to make routing decisions in a hierarchical network like the internet. We have compared the performance of the proposed localized routing algorithms with other localized and global QoS routing algorithms under different ranges of workloads, system parameters and network topologies. Simulation results have indicated that the proposed algorithms indeed outperform algorithms that use the basics of schemes that currently operate on the internet, even for a small update interval of link state. The proposed algorithms have also reduced the routing overhead significantly and utilize network resources efficiently.

In this dissertation, I investigate predictors and consequences of transactive memory system (TMS) development. A transactive memory system is a shared system for encoding, storing, and recalling who knows what within a group. Groups with well-developed transactive memory systems typically perform better than groups lacking such memory systems. I study how communication enhances the development of TMS and how turnover disrupts both TMS and its relationship to group performance. More specifically, I examine how communication networks affect the amount of communication, how the structure of the communication network affects the extent to which the group members share a strong identity as a group, and how both of these factors affect a group’s TMS. I also analyze how turnover disrupts the relationship between transactive memory systems and group performance. In addition, I examine how the communication network and turnover interact to affect group performance. I analyze these effects in three laboratory studies. The controlled setting of the experimental laboratory permits me to make causal inferences about the relationship of turnover and the communication network to group outcomes. Results promise to advance theory about transactive memory systems and communication networks.

Dans la robotique mobile, le réseau de communication est un composant important du système global pour que le système accomplisse sa mission. Dans un tel type de système, appelé un système commandé en réseau sans fil (SCR sans fil ou WNCS), l’intégration du réseau sans fil dans la boucle de commande introduit des problèmes qui ont un impact sur la performance et la stabilité i.e, sur la qualité de commande (QoC). Cette QoC dépend alors de la qualité de service (QoS) et la performance du système va donc dépendre des paramètres de la QoS. C’est ainsi que l’étude de l’influence des défauts du réseau sans fil sur la QoC est cruciale. Le WNCS est un système temps réel qui a besoin d’un certain niveau de QoS pour une bonne performance. Cependant, la nature probabiliste du protocole de communication CSMA/CA utilisé dans la plupart des technologies sans fil ne garantit pas les contraintes temps réel. Il faut alors une méthode probabiliste pour analyser et définir les exigences de l’application en termes de QoS, c’est-à-dire en termes de délai, de gigue, de débit, et de perte de paquets. Une première contribution de cette thèse consiste à étudier les performances et la fiabilité d’un réseau sans fil IEEE 802.11 pour des WNCSs qui partagent le même réseau et le même serveur de commandes en développant un modèle stochastique. Ce modèle est une chaîne de Markov qui modélise la méthode d’accès au canal de communication. Ce modèle a servi pour définir les paramètres de la QoS qui peuvent garantir une bonne QoC. Nous appliquons notre approche à un robot mobile commandé par une station distante. Le robot mobile a pour mission d’atteindre une cible en évitant les obstacles. Pour garantir l’accomplissement de cette mission, une méthode de diagnostic probabiliste est primordiale puisque le comportement du système n’est pas déterministe. La deuxième contribution a été d’établir la méthode probabiliste qui sert à surveiller le bon déroulement de la mission et l’état du robot. C’est un réseau bayésien (RB) modulaire qui modélise les relations de dépendance cause-à-effet entre les défaillances qui ont un impact sur la QoC du système. La dégradation de la QoC peut être due soit à un problème lié à l’état interne du robot, soit à un problème lié à la QoS, soit à un problème lié au contrôleur lui-même. Les résultats du modèle markovien sont utilisés dans le RB modulaire pour définir l'espace d'état de ses variables (étude qualitative) et pour définir les probabilités conditionnelles de l'état de la QoS (étude quantitative). Le RB permet d’éviter la dégradation de la QoC en prenant la bonne décision qui assure la continuité de la mission. En effet, dans une approche de co-design, quand le RB détecte une dégradation de la QoC due à une mauvaise QoS, la station envoie un ordre au robot pour qu'il change son mode de fonctionnement ou qu'il commute sur un autre contrôleur débarqué. Notre hypothèse est que l’architecture de diagnostic est différente en fonction des modes de fonctionnement : nous optons pour un RB plus global et partagé lorsque le robot est connecté à la station et pour RB interne au robot lorsqu’il est autonome. La commutation d’un mode de fonctionnement débarqué à un mode embarqué implique la mise à jour du RB. Un autre apport de cette thèse est la définition d’une stratégie de commutation entre les modes de diagnostic : commutation d’un RB distribué à un RB monolithique embarqué quand le réseau de communication ne fait plus partie de l'architecture du système et vice-versa. Les résultats d’inférence et de scénario de diagnostic ont montré la pertinence de l’utilisation des RBs distribués modulaires. Ils ont aussi montré la capacité du RB développé à détecter la dégradation de la QoC et de la QoS et à superviser l’état du robot. L’aspect modulaire du RB a permis de faciliter la reconfiguration de l’outil de diagnostic selon l’architecture de commande ou de communication adaptée (RB distribué ou RB monolithique embarqué). / In mobile robotics systems, the communication network is an important component of the overall system, it enables the system to accomplish its mission. Such a system is called Wireless Networked Control System WNCS where the integration of the wireless network into the control loop introduces problems that impact its performance and stability i.e, its quality of control (QoC). This QoC depends on the quality of service (QoS) therefore, the performance of the system depends on the parameters of the QoS. The study of the influence of wireless network defects on the QoC is crucial. WNCS is considered as a real-time system that requires a certain level of QoS for good performance. However, the probabilistic behavior of the CSMA / CA communication protocol used in most wireless technologies does not guarantee real-time constraints. A probabilistic method is then needed to analyze and define the application requirements in terms of QoS: delay, jitter, rate, packet loss. A first contribution of this thesis is to study the performance and reliability of an IEEE 802.11 wireless network for WNCSs that share the same network and the same control server by developing a stochastic model. This model is a Markov chain that models the access procedure to the communication channel. This model is used to define the QoS parameters that can guarantee the good QoC. In this thesis, we apply our approach to a mobile robot controlled by a remote station. The mobile robot aims to reach a target by avoiding obstacles, a classic example of mobile robotics applications. To ensure that its mission is accomplished, a probabilistic diagnostic method is essential because the system behavior is not deterministic. The second contribution of this thesis is to establish the probabilistic method used to monitor the robot mission and state. It is a modular Bayesian network BN that models cause-and-effect dependency relationships between failures that have an impact on the system QoC. The QoC degradation may be due either to a problem related to the internal state of the robot, a QoS problem or a controller problem. The results of the Markov model analysis are used in the modular BN to define its variables states (qualitative study) and to define the conditional probabilities of the QoS (quantitative study). It is an approach that permits to avoid the QoC degradation by making the right decision that ensures the continuity of the mission. In a co-design approach, when the BN detects a degradation of the QoC due to a bad QoS, the station sends an order to the robot to change its operation mode or to switch to another distant controller. Our hypothesis is that the diagnostic architecture depends on the operation mode. A distributed BN is used when the robot is connected to the station and a monolithic embedded BN when it is autonomous. Switching from a distributed controller to an on-board one involves updating the developed BN. Another contribution of this thesis consists in defining a switching strategy between the diagnostic modes: switching from a distributed BN to an on-board monolithic BN when the communication network takes no longer part of the system architecture and vice versa -versa. The inference and diagnostic scenarii results show the relevance of using distributed modular BNs. They also prove the ability of the developed BN to detect the degradation of QoC and QoS and to supervise the state of the robot. The modular structure of the BN facilitates the reconfiguration of the diagnostic policy according to the adapted control and communication architecture (distributed BN or on-board monolithic RB).

Este estudo tem como temas centrais as noções de acontecimento público e de comunicação pública. O problema de pesquisa destina-se à análise da configuração das redes de comunicação que constituem o acontecimento público, formadas a partir do acionamento de temas limítrofes entre interesses públicos e privados. A hipótese que norteia esta investigação é de que a visibilidade e a permanência do acontecimento público Tragédia Kiss são sustentadas por Redes de Comunicação Pública, pois estas potencializam o debate sobre a responsabilidade, o julgamento, a legislação e a assistência do Estado aos sobreviventes e familiares das vítimas da tragédia. Entre visibilidades desejadas e indesejadas, são estabelecidos pactos e disputas nos pontos nodais em que as subjetividades dos interlocutores encontram-se. Neste sentido, o objetivo geral de pesquisa é: analisar a configuração das Redes de Comunicação Pública sobre a Tragédia Kiss. Os objetivos específicos são: a) identificar as principais instituições e atores do acontecimento a partir da sua vinculação/ modo como foram atingidos/responsabilizados; b) identificar os processos de visibilidade constitutivos do acontecimento público Tragédia Kiss; c) identificar a dinâmica dos processos comunicacionais sediados em torno de temas de interesse público relacionados à Tragédia Kiss; d) identificar episódios estruturantes do acontecimento, dos quais derivam os temas acionados pelos atores nos processos comunicacionais em rede; e) definir eixos\categorias estruturais que permitam a análise da configuração do acontecimento público a partir das Redes de Comunicação Pública. A tese está estruturada em três partes: primeiramente, é realizada a descrição do objeto de pesquisa, com a descriminação da Tragédia Kiss, a cronologia do acontecimento, a relação com tragédias similares e os processos judiciais em curso. A segunda parte, com o referencial teórico, é dividida em três capítulos. No primeiro, estão diferentes acepções do público - na oposição dicotômica com o privado -, que visam delinear normativamente o horizonte tensional entre os termos, nos processos comunicacionais estabelecidos entre os atores. No segundo capítulo, estão as noções de esfera pública, esfera de visibilidade e de discussão pública, de opinião pública, de públicos – sociabilidade; de comunicação pública e de Redes de Comunicação Pública. O último capítulo teórico é dedicado à compreensão de acontecimento público; e sobre o impacto da morte coletiva. Na terceira parte, estão as referências metodológicas, formadas por pesquisa histórico-descritiva, com base na genealogia, e a técnica de pesquisa documental, de onde resultou o acervo de dados que serviram à análise; em seguida, a análise do funcionamento das redes do acontecimento público Tragédia Kiss, a partir das categorias visibilidade e permanência. Os resultados obtidos apontam para a confirmação da hipótese, pois mostram a manutenção do debate por intermédio da atividade das redes, em mídias tradicionais e alternativas. / This study has as central themes the public event notions and the public communication. The research problem is intended to analyze the communication networks configuration that make up the public event, formed from the actuation borderline issues between public and private interests. The hypothesis that guides this research is that the visibility and permanence of Kiss Nightclub Tragedy public event are supported by Networks of Public Communication, as they potentiate the debate on responsibility, judgment, legislation and State assistance to survivors and families of the victims from the tragedy. Between desired and unwanted visibilities, pacts and disputes are laid down in the nodal points where the subjectivities of the interlocutors are inserted. In this sense, the overall research objective is: to analyze the Public Communication Networks configuration on the Kiss Nightclub Tragedy. The specific objectives are: a) identify the main institutions and actors of the event from their own connection/ how they have been affected / accountable; b) identify the constituent visibility process of the public event Kiss Nightclub Tragedy; c) identify the dynamics of communication processes based around issues of public interest related to Kiss Nightclub Tragedy; d) identify structuring episodes of the event, of which derive from the issues triggered by the actors in network communication processes; e) define axes\ structural categories that allow the analysis of the public event configuration from the Public Communication Networks. The thesis is structured in three parts: first, the description of the research object is carried out with discrimination of the Kiss Nightclub Tragedy, the event chronology, the relationship with similar tragedies and legal proceedings in course. The second part, with the theoretical framework, is divided into three chapters. In the first, there are different meanings of public - in dichotomous opposition with the private -, aimed at delineating normatively the horizon tension between the terms, in the communication processes established between the actors. In the second chapter, there are the public sphere notions, visibility sphere and public discussion, public opinion, public - sociability; public communication and public communication networks. The last theoretical chapter is devoted to understanding the public event; and the impact of collective death. In the third part, there are the methodological references, formed by historical and descriptive research, based on genealogy, and documentary research technique, which resulted in the data collection that served the analysis; then the analysis of the functioning of the Kiss Nightclub Tragedy public event networks, from the visibility and permanence categories. The results point to the confirmation of the hypothesis, because they show the maintenance of the debate through the networks' activity, in traditional and alternative media.

Password based logon schemes have many security weaknesses. For secure environments smart card and biometric based authentication solutions are available as replacement for standard password based systems. Nevertheless, the cost of deployment and maintenance of these systems is quite high. On the other hand, mobile network operators have a huge base of deployed smart cards that can be reused to provide authentication in other spheres significantly reducing costs. In this project we present a study of how mobile phones can be used to provide a secure low-cost two-factor workstation logon solution.To find and study the available mobile phone based authentication architectures and come up with workstation logon architecture the study of relevant technologies utilized in these solutions: UMTS networks, Bluetooth communication, Remote Authentication Dial in User Service (RADIUS), authentication and authorization in Windows, Linux, and MAC OS X. The analysis of available mobile phone based authentication schemes like SIM Strong schemes based on EAP-SIM, Session-ID based schemes, and OTP based schemes are also added.A solution for Linux workstation logon process has been proposed in the thesis using the Pluggable Authentication Module (PAM). The Solution uses 2 factors for authentication, one is the static password and the second factor is the mobile based authentication using a 13 character long OTP. With adding the existing technology and giving the administrator the option of selecting the authentication method for user makes the solution more suitable for an enterprise.

The pervasive computing environment for heterogeneous network is on a continuous rise. The ability to interact and control network devices with different functionalities within office and home environment could be very beneficial to a lot of users. The service discovery in computers and mobile devices enabled them to interact with one another through wireless and heterogeneous wired networks. Services advertise their existence in a dynamic way and devices are designed with this capability to discover these services and its properties automatically. These devices are though based on different technologies but are still able to communicate and discover one another based on existing service discovery architectures. It is notable that a significant number of networked devices are now mobile and these mobile devices make service discovery more challenging.In future mobile multi-domain multi-language environments, a service can be anything and introduced by anybody. Consequently, same or equivalent services may have different names and services with same name or type may be completely different. Existing service discovery systems are incapable of handling these situations. We have implemented a service discovery system which supports semantics to service descriptions. It allows any user to act as a service provider and introduce any service at any time. The service provider can define any service as equivalent to any existing service and in any language as wanted. In addition, it is capable to find services that are not exact matches of the requested ones. More semantics are introduced through attributes like EquivalenceClass, ParentType and Keywords. The test conducted on this system in real time proves that the system is efficient and can be applied in real life.