Thesis (M.Sc.Eng.) PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / Recent regulations by the Federal Communication Commission (FCC) enable network service providers to lease their spectrum to short-term leased secondary users for opportunistic usage. Driven by earlier studies on spectrum leasing for voice and streaming traffic, this thesis derives optimal policies for the admission control of secondary users carrying data traffic. Additionally, it establishes profitability conditions of spectrum leasing. We consider a processor sharing network where bandwidth is equally shared among all users with no partitioning. We further consider homogeneous and elastic data traffic: All the users have the same traffic characteristics and adjust their access rate to the available bandwidth in the network. The contributions of this thesis are the following: First, we analyze the joint problem of bandwidth allocation and admission control of secondary users. Under the assumption of Poisson session arrivals and balanced bandwidth allocations, we show that the steady state distributions of the number of active users in the network are insensitive to track characteristics beyond their means. This result holds for arbitrary occupancy-based admission control policies. Next, we prove that the optimal occupancy-based admission control policy of secondary users is of threshold type, which means that secondary user arrivals are accepted when the total number of active users in the network is below a certain threshold; otherwise, they are rejected. Finally, under optimal occupancy-based admission control, we characterize profitable prices. We show that profitability is insensitive to the secondary demand function. We identify a price, referred to as the break-even price, that makes opening the network for secondary spectrum access profitable. Thus, we show that admitting secondary users when the network is empty is profitable for any price greater than the break-even price. Remarkably, all of our results hold for realistic data traffic models assuming Poisson session arrivals and general flow size distributions. / 2031-01-01

Annual Average Daily Traffic (AADT) data in the transportation industry today is an important tool used in various fields such as highway planning, pavement design, traffic safety, transport operations, and policy-making/analyses. Systematic literature review was used to identify the current methods of estimating AADT and ranked. Ordinary linear kriging occurred most. Also, factors that influence the accuracy of AADT estimation methods as identified include geographical location and road type amongst others. In addition, further analysis was carried out to determine the most apposite kriging algorithm for AADT data. Three linear (universal, ordinary, and simple), three nonlinear (disjunctive, probability, and indicator) and bayesian (empirical bayesian) kriging methods were compared. Spherical and exponential models were employed as the experimental variograms to aid the spatial interpolation and cross-validation. Statistical measures of correctness (mean prediction and root-mean-square errors) were used to compare the kriging algorithms. Empirical bayesian with exponential model yielded the best result.

With the mass availability of smartphones, mobile access to e-mail is gaining importance. Over the years, the IMAP protocol has been extended with many features ranging from extensions adding new functionality to those improving efficiency over an unreliable network. This thesis evaluates the available extensions based on their suitability for use in the context of a mobile client. Three new extensions have been developed, each improving the protocol in a distinct way. The thesis also discusses how most of these extensions were implemented in Trojitá, the author's free software open source IMAP e-mail client.

Telecommunications companies (telcos) and Internet Service Providers (ISPs) monitor the traffic passing through their networks for the purposes of network evaluation and planning for future growth. Most monitoring techniques currently use a form of packet sampling. However, exhaustive monitoring is a preferable solution because it ensures accurate traffic characterization and also allows encoding operations, such as compression and encryption, to be performed. To overcome the very high computational cost of exhaustive monitoring and encoding of data, this thesis suggests exploiting parallelism. By utilizing a parallel cluster in conjunction with load balancing techniques, a simulation is created to distribute the load across the parallel processors. It is shown that a very scalable system, capable of supporting a fairly high data rate can potentially be designed and implemented. A complete system is then implemented in the form of a transparent Ethernet bridge, ensuring that the system can be deployed into a network without any change to the network. The system focuses its encoding efforts on obtaining the maximum compression rate and, to that end, utilizes the concept of streams, which attempts to separate data packets into individual flows that are correlated and whose redundancy can be removed through compression. Experiments show that compression rates are favourable and confirms good throughput rates and high scalability.

Telecommunications companies (telcos) and Internet Service Providers (ISPs) monitor the traffic passing through their networks for the purposes of network evaluation and planning for future growth. Most monitoring techniques currently use a form of packet sampling. However, exhaustive monitoring is a preferable solution because it ensures accurate traffic characterization and also allows encoding operations, such as compression and encryption, to be performed. To overcome the very high computational cost of exhaustive monitoring and encoding of data, this thesis suggests exploiting parallelism. By utilizing a parallel cluster in conjunction with load balancing techniques, a simulation is created to distribute the load across the parallel processors. It is shown that a very scalable system, capable of supporting a fairly high data rate can potentially be designed and implemented. A complete system is then implemented in the form of a transparent Ethernet bridge, ensuring that the system can be deployed into a network without any change to the network. The system focuses its encoding efforts on obtaining the maximum compression rate and, to that end, utilizes the concept of streams, which attempts to separate data packets into individual flows that are correlated and whose redundancy can be removed through compression. Experiments show that compression rates are favourable and confirms good throughput rates and high scalability.

This study focuses on the integrity of students at Uppsala University that has used the university’s network, UpUnet. We’ve studied their opinions with the use of questionnaires that cover questions related to privacy and awareness about logging of data traffic. The results showed that more students than our hypothesis suggested were unaware of the surveillance on the network, and the majority of these also had a negative opinion towards logging of data traffic. However, we found that there were several relations between how the students responded on our questionnaire, and we’ve presented these in the analysis chapter towards the end of the essay.

Made available in DSpace on 2016-04-04T18:31:16Z (GMT). No. of bitstreams: 1 Joao Marcos Menon .pdf: 3167428 bytes, checksum: 96cc8c447b8b6a9f07be5f85fb5733dc (MD5) Previous issue date: 2006-06-13 / Research regarding voice and data dimensioning models applied to Telecommunication Networks. For circuit switched voice networks dimensioning, the Erlang formulas are used. When it comes to newer data networks, a packet based dimensioning is required, and the complexity is significantly increased due to the diversity of applications and its multiple features. This work goes from the mathematical model (proposed by Erlang) applied to circuit switched voice networks to a mathematical model applicable to data services and packet based network dimensioning. User and application requirements are detailed as well as the correlation between them, which is key to understanding the dimensioning model. The mathematical model is applied (and a study case is presented) to an existing 3G technology (1xEVDO) in Brazil using practical input values. A computer program is generated to run prompt tests or different study cases. Then, the obtained results for the given case are measured in the field to validate the packet based network dimensioning model. Computer simulations are run to test the edge of the 1xEVDO technology with the aid of appropriate software containing queuing theory concepts. The experiments permit the correct visualization of the possible values that can be obtained and should be ignored on the dimensioning of a packet based network. Although ITU s 1xEVDO technology is used for the experiments, the dimensioning model is proposed to be applicable to any technology which needs packet based dimensioning and has data applications (i.e. other ITU 3G technologies such as UMTS and IEEE technologies such as wifi e wimax). The model is constructed, applied to study cases, tested on the field with practical values, promptly validated and pushed to the edge during simulations. / Pesquisa sobre os modelos de dimensionamento de rede de voz e de dados aplicados nas redes de telecomunica??es. Para a aplica??o de voz, as redes s?o dimensionadas a circuito, realiza-se um resgate do dimensionamento desse servi?o utilizando-se as f?rmulas de Erlang. Destaca-se, em seguida, que as novas redes de dados requerem um dimensionamento baseado a pacotes e a complexidade aumenta significativamente devido a diversidade das aplica??es e de suas m?ltiplas caracter?sticas. Evolui-se, do modelo matem?tico proposto por Erlang, aplic?vel ?s redes de voz baseado em circuito, at? um modelo matem?tico aplic?vel aos servi?os de dados a ser utilizado no dimensionamento das redes a pacotes. Detalham-se os requisitos dos usu?rios e das aplica??es, bem como a correla??o entre eles, que ? a chave para o entendimento do modelo de dimensionamento. Aplica-se o modelo matem?tico (gera-se um case) para a tecnologia 3G existente em opera??o no Brasil no momento, 1xEVDO com valores de entrada utiliz?veis na pr?tica. Gera-se um programa para ensaios pontuais ou diferentes cases. Medem-se em campo os resultados obtidos do case utilizado para valida??o do modelo de dimensionamento de rede a pacotes. Para os extremos da tecnologia, 1xEVDO, s?o ensaiados com a utiliza??o de um simulador de um software aderente e alinhado a teoria das filas. Promovem-se ensaios que permitem a vis?o correta dos valores poss?veis de serem obtidos e que devem ser ignorados no dimensionamento de uma rede a pacotes. Destaca-se que, apesar de se haver utilizado a tecnologia 1xEVDO do ITU para ensaio, o modelo de dimensionamento ? proposto a ser aplicado em qualquer tecnologia que necessite de dimensionamento baseado em pacotes e com aplica??es de dados (demais da terceira gera??o do ITU como UMTS e do IEEE como wifi e wimax). O modelo ? conceituado, aplicado em case, testado em campo com valores pr?ticos, convalidado pontualmente e extremado em simula??o.

Dans cette thèse nous étudions l'impatience des usagers dans les réseaux mobile et nous quantifions son impact sur la performance du système en présence d'usagers téléchargeant des données dans lequel nous développons deux expressions approximatives de la distribution stationnaire du systéme : un modèle agrégé et un modèle détaillé et nous montrons qu'ils sont très proches du modèle exact. Nous étudions la mobilité de l'usager téléchargeant des données et pouvant s'impatienter, et nous quantifions son impact sur la performance des réseaux mobile. Nous considérons le cas de la mobilité due à l'impatience et le cas de la mobilité spontanée des usagers tout en considérant la mobilité intra et inter cellulaire. Nous étudions également l'impatience de l'usager qui regarde une vidéo streaming durant les phases de pré-chargement de la vidéo et de mise en tampon pendant que la vidéo est arrêtée dès le début de la mise en tampon. Nous étudions à la fin un système constitué d'usagers pouvant s'impatienter, qui est sous contrôle d'un gestionnaire de système, qui à chaque instant de décisions, choisit une action à exécuter dans le but d'optimiser la performance définie du système. Nous considérons un système dans lequel les usagers arrivent dans le système à des différents instants et le quittent après la fin de leurs transferts de données, ou plus tôt à l'expiration de leurs durées de patience. Les applications numériques et les simulations nous ont permis de fournir divers métriques de performance telles que le nombre moyen d'usagers, la proportion d'usagers impatients qui quittent le système avant la fin de leurs transferts de fichiers, le débit, la probabilité d'impatience en tenant compte de la localisation de l'usager dans la cellule, la probabilité d'être impatient durant les phases de mise en tampon, la probabilité de mise en tampon lors d'une séance de vidéo streaming, la politique optimale, la taille limite optimale du système dans le but d'optimiser la performance définie du système, etc... / In this thesis we study user impatience and quantify its impact on the performance of mobile networks in the presence of elastic user in which we develop two approximate expressions for the stationary distribution of the system: an aggregate one and a detailed one and show their closeness to the exact model. We study mobility of elastic user who may be impatient and quantify its impact on system performance in mobile networks. We consider the case of mobility due to impatience during the prefetching and the re-buffering phases when starvation happens. We finally study a system with impatient users controlled by a system manager who has to choose at each decision epoch an action to make in order to optimize the defined system performance. We consider a system in which users come to the system at different time instants and leave it after a finite duration, either after completion of their data transfers or earlier, at the expiry of some patience duration. Numerical analysis and simulations allow us to derive several performance metrics such as mean number of users, the proportion of impatient users who quit the system before completing their file transfers, the throughput, the probability of starvation, the optimal system size in order to optimize the defined performance of the system, etc...

The thesis deals with the topic of computer crime. Foremost, it demonstrates on an example of the operation of a medical image information processing system some selected aspects of this issue. It shows that it is always necessary to monitor the current state of the technical knowledge at the time, but also the need of addressing the issue within the corresponding legal limits. The thesis presents criminal law reality as a complex system. The links between different parts of the system are examined, and possible shortcomings are considered. The legal instruments and legal limits of the procedures that can be used against cybercrime are evaluated. The thesis focuses especially on the issue of obtaining evidence under the Czech Criminal Procedure Code. It presents a proposal on how to understand individual procedural legal institutes and for what purposes and how to use them. Consequently it suggests legal procedures for specific selected practical situations.

El presente trabajo de tesis tiene como finalidad, explicar cómo las redes definidas por software se convierten en un elemento clave de una estrategia de diferenciación para las redes de campus. Mediante la priorización del consumo de tráfico de datos y la administración de la red LAN a través de un controlador SDN que permita distribuir adecuadamente el ancho de banda, reducir el tiempo de comunicación entre los dispositivos de red y gestionar la red adecuadamente en la organización. En el primer capítulo, se presentará los aspectos introductorios del proyecto. En esta parte, se describirá la organización objetivo y su campo de acción, la problemática a la cual está expuesta la organización. Además, se planteará el objetivo general y los objetivos específicos del proyecto y también, la justificación, los indicadores de logro. así como el estado del arte que comprende la solución propuesta. En el segundo capítulo, se detallará las tecnologías asociadas a las redes definidas por software y toda información sujeta a este tema de investigación. A partir de los cuales, se identificarán el contexto, la muestra, el diseño principal y los procedimientos a realizar. Asimismo, se analizarán normas, estándares, políticas y buenas prácticas usadas para el tema de investigación. En el tercer capítulo, se plantea el problema identificado en la organización objetivo. Analizando su alcance, causa e impacto en la organización. De igual manera, se describirá en detalle, el entorno donde será desplegada la solución y los requerimientos necesarios para cumplir con el tema propuesto. En el cuarto capítulo, la propuesta del diseño de red definida por software será desarrollada, en donde se elaborarán las especificaciones y seleccionarán los recursos que logren cumplir el diseño de la solución. Finalmente, en el quinto capítulo se realizará la evaluación mediante pruebas y resultados que serán debidamente justificados para el logro del proyecto de tesis. / The purpose of this tesis is to explain how software-defined networks become a key element of a differentiation strategy for campus networks. By prioritizing the consumption of data traffic and managing the LAN network through an SDN controller that allows to properly distribute the bandwidth, reduce the communication time between network devices and manage the network properly in the organization. In the first chapter, the introductory aspects of the project will be presented. In this part, the target organization and its field of action will be described, the problem to which the organization is exposed. In addition, the general objective and the specific objectives of the project will be raised, as well as the justification, the achievement indicators. as well as the state of the art that comprises the proposed solution. In the second chapter, the technologies associated with software-defined networks and all information subject to this research topic will be detailed. From which, the context, the sample, the main design and the procedures to be carried out will be identified. Likewise, norms, standards, policies and good practices used for the research topic will be analyzed. In the third chapter, the problem identified in the target organization is posed. Analyzing its scope, cause and impact on the organization. Likewise, the environment where the solution will be deployed and the necessary requirements to comply with the proposed topic will be described in detail. In the fourth chapter, the software-defined network design proposal will be developed, where the specifications will be elaborated and the resources that manage to fulfill the solution design will be selected. Finally, in the fifth chapter, the evaluation will be carried out through tests and results that will be duly justified for the achievement of the tesis. / Tesis