Made available in DSpace on 2016-08-17T14:52:48Z (GMT). No. of bitstreams: 1 Aline lopes.pdf: 2261944 bytes, checksum: 0cbbb27a7a17ab362f4fce42298c4b45 (MD5) Previous issue date: 2008-06-26 / Mobile devices are increasing common reality in wireless networks and have integrated the wireless environment, helping to ease and to make available information. Meanwhile, the wireless environment is subject to vulnerabilities because of the way of spreading information that is given through the air, and is subject to interception or even information theft. Mobile Devices in addition of its vulnerability to these vulnerabilities common in wireless environments, are devices with some physical limitations such as lack of processing capacity and memory, beyond the limited battery life. These limitations become critical in this kind of environment, when unidentified threats attack are directed mobile devices. It is necessary to develop an intrusion detection system dedicated to these devices to identify intrusive behaviour, taking into account their physical limitations. This work proposes an intrusion detection system (IDS, Intrusion Detection System) for wireless networks and mobile devices. This is an adaptation and extension of NIDIA-IDS (Intrusion Detection System-Network Intrusion Detection System based on Intelligent Agents). The system acts with two processes: the first one is an information tracking on the device performance and the second one is a wireless network traffic monitoring, analyzing both the traffic of monitored devices. As proof of concepts a prototype was developed and some experiments were carried to validate this solution. / Os dispositivos móveis são uma realidade cada vez mais comum em redes wireless e se integraram ao ambiente wireless, contribuindo para facilidade e disponibilidade da informação. Entretanto, o ambiente wireless está sujeito a vulnerabilidades, devido à forma de propagação da informação que se dá através do ar, estando sujeito a intercepção ou até mesmo roubo das informações. Dispositivos móveis além de estarem sujeitos a essas vulnerabilidades comuns em ambientes wireless, são dispositivos com algumas limitações físicas, como pouca capacidade de processamento e memória, além da vida útil de bateria limitada. Estas limitações tornam-se críticas neste tipo ambiente, quando ameaças não identificadas são direcionadas a dispositivos móveis. Torna-se necessário a implementação de sistema de detecção de intrusão voltado para estes dispositivos a fim de identificar comportamentos intrusivos, levando em consideração suas limitações físicas. Este trabalho propõe um sistema de detecção de intrusão (IDS, Intrusion Detection System) em redes wireless destinados a dispositivos móveis como adaptação e extensão do IDS-NIDIA (Intrusion Detection System- Network Intrusion Detection System based on Intelligent Agents). O mecanismo utiliza dois processos: o primeiro faz o monitoramento de informações sobre o comportamento do dispositivo e o segundo através do monitoramento de tráfego da rede wireless, analisando o tráfego destinado e originado aos dispositivos monitorados. A implementação da arquitetura e os testes realizados demonstram a viabilidade da solução.

[pt] A combinação de computação móvel sem fio e tecnologias para a localização de dispositivos possibilitou o surgimento de um novo paradigma de computação conhecido como Serviços Baseados em Localização, cujo objetivo é estudar como prover ao usuário serviços personalizados que dependem da localidade onde este se encontra. Dentre esses serviços, destacam-se aqueles cuja principal função é dar apoio a diferentes formas de comunicação entre usuários de dispositivos móveis. Apesar de vários serviços terem sido desenvolvidos com esse intuito, são poucos os trabalhos que fizeram um levantamento de suas características comuns com o objetivo de projetar uma infra- estrutura genérica que sirva de base para o desenvolvimento de novos serviços. Isso serviu de motivação para esta dissertação, que trata do desenvolvimento de um framework que facilite a construção de serviços para comunicação baseada na localização de usuários móveis. Como estudos de caso, foram instanciados um aplicativo chamado Nita (Notes In The Air), que provê comunicação síncrona e assíncrona entre usuários presentes numa mesma localidade, e um aplicativo para comunicação instantânea similar ao BuddySpace. / [en] The combination of mobile wireless computing and location technology enabled the emergence of a new computing paradigm known as Location-Based Services, whose goal is to study how to provide personalized services to users depending on the their location. Among these services, very useful are the ones which support different kinds of communication between mobile users. Although several services have been developed with this goal, only few work aimed at identifying the common characteristics of these systems, with the goal of designing a generic infrastructure that serves as the basis for the development of new services. This was the main motivation for this thesis work, in which we designed an object framework facilitating the construction of applications for location-based communication among mobile users. As main case studies, we instantiated an application called Nita (Notes In The Air), which provides both synchronous and asynchronous communication between co- located users, and a location-enhanced instant messaging application similar to BuddySpace.

Abstract According to industry estimates, monthly global mobile data traffic will surpass 30.6 exabytes by 2020 and global mobile data traffic will increase nearly eightfold between 2015 and 2020. Most of the mobile data traffic is generated by smartphones, and the total number of smartphones is expected to continue growing by 2020, which results in rapid traffic growth. In addition, the upcoming 5G networks and Internet of Things based communication are estimated to involve a large amount of network traffic. The increase in mobile data traffic and in the number of connected devices poses a challenge to network operators, service providers, and data center operators. If the transmission capacity of the network and the amount of data traffic are not in line with each other, congestion may occur and ultimately the quality of experience degrades. Mobile networks are also becoming more reliant on data centers that provide efficient computing power. However, the energy consumption of data centers has grown in recent years, which is a problem for data center operators. A traditional strategy to overcome these problems is to scale up the resources or by providing more efficient hardware. Resource over-provisioning increases operating and capital expenditures without a guarantee of increased average revenue per user. In addition, the growing complexity and dynamics of communication systems is a challenge for efficient resource management. Intelligent and resilient methods that can efficiently use existing resources by making autonomous decisions without intervention from human administrators are thus needed. The goal of this research is to implement, develop, model, and test algorithms that can enable efficient and energy-aware network resource management in autonomous communications systems. First, an energy-aware algorithm is introduced for high-performance computing data centers to reduce the energy consumption within a single data center and across a federation of data centers. For network access selection in heterogeneous wireless networks, two algorithms are proposed, a client side algorithm that tries to optimize users' quality of experience and a network side algorithm that focuses on optimizing the global resource usage of the network. Finally, for a video service, an algorithm is presented that can enhance the video content delivery in a controllable and resource-efficient way without major changes in the mobile network infrastructure. / Tiivistelmä Langattoman tietoliikenteen nopean kasvun ennustetaan jatkuvan edelleen lähivuosinakin ja alan teollisuuden arvioiden mukaan matkapuhelinliikenteen määrä ylittäisi globaalisti 30,6 eksatavua vuoteen 2020 mennessä. Tämä tarkoittaisi liikennemäärän kahdeksankertaistumista ajanjaksolla 2015–2020. Älypuhelimet tuottavat suurimman osan matkapuhelinliikenteestä, ja älypuhelimien lukumäärän arvioidaan jatkavan kasvuaan vuoteen 2020 saakka, mikä johtaa nopeaan liikenteen kasvuun. Tämän lisäksi arvioidaan, että 5G verkot ja esineiden Internet tuottavat suuren määrän verkkoliikennettä. Matkapuhelinliikenteen ja laitteiden määrän kasvu tuo haasteita verkko-operaattoreille, palvelun tarjoajille, ja datakeskusoperaattoreille. Mikäli verkossa ei ole tarpeeksi siirtokapasiteettia dataliikenteen määrää varten, verkko ruuhkautuu ja lopulta palvelukokemus kärsii. Matkapuhelinverkot tulevat myös tulevaisuudessa tarvitsemaan datakeskusten laskentakapasiteettia. Datakeskusten energiankulutus on kuitenkin kasvanut viime vuosina, mikä on ongelma datakeskusoperaattoreille. Perinteinen strategia ongelmien ratkaisemiseksi on lisätä resurssien määrää tai tarjota tehokkaampaa laitteistoa. Resurssien liiallinen lisääminen kasvattaa kuitenkin sekä käyttö- että pääomakustannuksia ilman takuuta siitä, että keskimääräinen myyntitulo per käyttäjä kasvaisi. Tämän lisäksi tietoliikennejärjestelmät ovat monimutkaisia ja dynaamisia järjestelmiä, minkä vuoksi tehokas resurssienhallinta on haastavaa. Tämän vuoksi tarvitaan älykkäitä ja kestäviä metodeja, jotka pystyvät käyttämään olemassa olevia resursseja tehokkaasti tekemällä autonomisia päätöksiä ilman ylläpitäjän väliintuloa. Tämän tutkimuksen tavoitteena on toteuttaa, kehittää, mallintaa, ja testata algoritmeja, jotka mahdollistavat tehokkaan ja energiatietoisen verkkoresurssien hallinnan autonomisissa tietoliikennejärjestelmissä. Tutkimus esittää aluksi supertietokonedatakeskuksiin energiatietoisen algoritmin, jonka avulla voidaan vähentää energiankulutusta yhden datakeskuksen sisällä sekä usean eri datakeskuksen välillä. Verkkoyhteyden valintaan heterogeenisissä langattomissa verkoissa esitetään kaksi algoritmia. Ensimmäinen on käyttäjäkohtainen algoritmi, joka pyrkii optimoimaan yksittäisen käyttäjän palvelukokemusta. Toinen on verkon puolen algoritmi, joka keskittyy optimoimaan verkon kokonaisresurssien käyttöä. Lopuksi esitetään videopalvelulle algoritmi, joka parantaa videosisällön jakoa kontrolloidusti ja resurssitehokkaasti ilman että matkapuhelinverkon infrastruktuurille tarvitaan muutoksia.

We address several problems that arise in a multihop wireless mesh network. First, we study the problem of joint congestion control, routing and MAC layer scheduling. We formulate the problem as an aggregate utility maximization problem and apply duality theory to decompose the problem into two sub-problems, namely, network layer congestion control and routing problem, and MAC layer scheduling problem. Given the link “prices", the source adjusts its rate based on the cost of the least-cost path to the destination, and sends traffic to the destination along the least-cost path, while link scheduling is carried out based on link prices. Optimal link scheduling for a wireless network is known to be NP-hard. We explore the use of a known centralized greedy heuristic, and develop a distributed algorithm that can schedule independent links based on local information. While the link scheduling algorithm above is for a given set of link prices, the solution to our problem depends on the sequence of price vectors generated by the price update algorithm. This leads us to study convergence issues related to the price update algorithm. Next, we develop a practical protocol which maximizes aggregate utility in a wireless mesh network. We simulate our protocol using Qualnet 4.5 and compare the result with a baseline protocol that uses IEEE 802.11 for link scheduling and AODV for routing. Our proposed protocol requires the durations of slots and subslots to be defined. We develop an approach in which given a single cell wireless mesh network using IEEE 802.11 as a reliable message delivery mechanism, one can find upper and lower bounds on the durations of slots. We employ stochastic ordering to compare distributions of random variables and using some properties of stochastic ordering along with the central limit theorem, we devise a way to compute the above mentioned bounds on the durations. In the second part, we shift our focus to model delays incurred by application packets sent over a WLAN. In this section we model the WLAN as a Random Polling System. The packet arrival process at each node i is assumed to be a stationary and independent increment random process with mean ai and second moment a(2)i . The packet lengths at node i are assumed to be i.i.d random variables Pi with finite mean and second moment. Utilizing available results, we obtain expressions for mean packet delay. Extensive simulations are conducted to verify the analytical results.

The popularity of the wireless networks is so great that we will soon reach the point where most of the devices work based on that, but new challenges in wireless channel access will be created with these increasingly widespread wireless communications. Multi-channel CSMA protocols have been designed to enhance the throughput of the next generation wireless networks compared to single-channel protocols. However, their performance analysis still needs careful considerations. In this thesis, a set of techniques are proposed to model and analyse the CSMA protocols in terms of channel sensing and channel access. In that respect, the performance analysis of un-slotted multi-channel CSMA protocols is studied through considering the hidden terminals. In the modelling phase, important parameters such as shadowing and path loss impairments are being considered. Following that, due to the high importance of spectrum sensing in CSMA protocols, the Double-Threshold Energy Detector (DTED) is thoroughly investigated in this thesis. An iterative algorithm is also proposed to determine optimum values of detection parameters in a sensing-throughput problem formulation. Vehicle-to-Roadside (V2R) communication, as a part of Intelligent Transportation System (ITS), over multi-channel wireless networks is also modelled and analysed in this thesis. In this respect, through proposing a novel mathematical model, the connectivity level which an arbitrary vehicle experiences during its packet transmission with a RSU is also investigated.

This work deals with programs designed to manage data networks and to their use in managerial practice. The purpose is to explain how these programs contribute to a systemic understanding of managed network and system thinking. All these methods are applied on example of two largest wireless ISP companies in South Bohemia. The dissertation explains the issue of making mental models of the managed network, which concerns specially managers of ISP companies. The work is not an administrator view at programs for network management, but rather a management view and instructions how to use these programs in management decisions to solve complex problems and future development of managed network.

This research involves the design, development, and theoretical demonstration of models resulting in integrated misbehavior resolution protocols for ad hoc networked devices. Game theory was used to analyze strategic interaction among independent devices with conflicting interests. Packet forwarding at the routing layer of autonomous ad hoc networks was investigated. Unlike existing reputation based or payment schemes, this model is based on repeated interactions. To enforce cooperation, a community enforcement mechanism was used, whereby selfish nodes that drop packets were punished not only by the victim, but also by all nodes in the network. Then, a stochastic packet forwarding game strategy was introduced. Our solution relaxed the uniform traffic demand that was pervasive in other works. To address the concerns of imperfect private monitoring in resource aware ad hoc networks, a belief-free equilibrium scheme was developed that reduces the impact of noise in cooperation. This scheme also eliminated the need to infer the private history of other nodes. Moreover, it simplified the computation of an optimal strategy. The belief-free approach reduced the node overhead and was easily tractable. Hence it made the system operation feasible. Motivated by the versatile nature of evolutionary game theory, the assumption of a rational node is relaxed, leading to the development of a framework for mitigating routing selfishness and misbehavior in Multi hop networks. This is accomplished by setting nodes to play a fixed strategy rather than independently choosing a rational strategy. A range of simulations was carried out that showed improved cooperation between selfish nodes when compared to older results. Cooperation among ad hoc nodes can also protect a network from malicious attacks. In the absence of a central trusted entity, many security mechanisms and privacy protections require cooperation among ad hoc nodes to protect a network from malicious attacks. Therefore, using game theory and evolutionary game theory, a mathematical framework has been developed that explores trust mechanisms to achieve security in the network. This framework is one of the first steps towards the synthesis of an integrated solution that demonstrates that security solely depends on the initial trust level that nodes have for each other.

This Master´s thesis deals especially with exploration of the handover process and with searching for ways of in?uencing this process. The goal of this thesis is to create tools for recording of access point utilization and in?uence the handover of wireless clients based on the obtained data. An access point with open ?rmware, which allows low-level management, was necessary for practical tests. First chapter deals with a survey of current o?er of open ?rmware available for access points and then the appropriate candidate for this thesis is chosen – the OpenWRT project. Second chapter deals with the con?guration of OpenWRT system and basic settings of the chosen wireless router – TP-Link TL-WR1043ND. Next chapter deals with analysis of the handover process in wireless networks. Information obtained by this analysis is used during the creation of the graphic application. The fourth chapter presents the basics of Microsoft Native Wi-Fi API and introduces basic functions used by this API. Those functions were used during the creations of the application. Last two chapters present the created graphic application. The ?fth chapter deals with the application design and examination of its functionality and used functions. Last chapter then documents usability of the application in real environment.

The purpose of this project is to build a wireless sensor network for measuring temperature and relative humidity in hop drying facility. This is a monitoring device, consists of several sensor units and one control and display unit. Display unit coordinates a whole network and can display data on LCD or download collected data to PC. Sensor unit measures a relative humidity, temperature, battery voltage and transmits data to display unit. Units contain a transceiver which operates in ISM band 868 MHz. Circuits are driven by 8-bits microcontroller Freescale.

The main aim of this thesis is to familiarize with options of services using real-time data transfer in wireless networks. Theoretical part presents wireless network based on IEEE 802.11 standard and its practical use. Large part is focuses on 802.11e standart, that provides support for quality of service in wireless networks. Furthemore this thesis deals with transport and applicaton protocols supporting multimedia streaming over computer network. Second chapter is focused on analyzing real computer network with purpose in measuring parametrs influencing quality of service such as bandwith, delay, jitter and loss. Last part deals with the design of wireless network in OPNET Modeler enviroment with focus on simulating parameters that influence quality of service.