Esta dissertação descreve os métodos, medidas e análises feitas para otimizar a rede de comunicação de dados do Instituto de Física de São Carlos. As tecnologias e protocolos utilizados na rede são apresentados. Especial atenção é dada a análise do desempenho de VLANs utilizando inicialmente o protocolo LANE no núcleo ATM da rede. Neste caso a rede é composta de switches ATM e ATM-Ethernet. Medidas comparativas foram realizadas com a utilização da tecnologia Fast Ethernet no backbone, que possui uma capacidade de transmissão relativamente próxima da ATM de 155Mbps. Melhores resultados obtidos com a implementação de sub-redes maiores, reduzindo em um numero menor de sub-redes, são discutidos e apresentados. Análises estatísticas baseadas apenas no tempo de resposta da rede são apresentados para avaliar o desempenho das alterações efetuadas nas configurações da rede. Mesmo que o tráfego tenha aumentado muito durante esses anos e que vários serviços tenha sido agregados a esta rede, foi possível adequar o desempenho as novas necessidades beneficiando-se da evolução tecnológica que os equipamentos de rede de dados trouxeram ao IFSC. / This work describes the methods, measures and analyses performed aiming to optimize the data communication network from the Physics Institute of Sao Carlos as well as the technologies and protocols used in the network recently. Special care is given to the analysis of the VLANs performance using, initially, the LANE protocol over ATM which has its core based on pure ATM and ATM-Ethernet switches. Comparative measures had been carried out using a backbone working on a Fast Ethernet technology, which seems to have a very close transmission rate from the ATM 155Mbps. This work also discusses best results acquired with the implementation of larger networks reducing the number of subnetworks, statistical analyses based on time delay of the network in order to evaluate the performance of the changes made on its configuration. Even though the traffic from the Institute has been increased over these years and several services have been added to the network, it was completely possible to adapt the performance to the needs, using the benefits of the technological evolution which the network equipments had brought to the Institute.

Wireless communication systems are increasingly deployed by family, businesses, government and SOHO users because of the freedom wireless communications afford, simplicity of installation and ease of use. Along with its rapid development, the security problem in wireless communication network has attracted more and more attention. It has been estimated that the IEEE 80.211 standard is susceptible to attacks both on data content and user authentication, such as eavesdropping, spoofing and Denial of Service. These attacks are due to the standard's inherent flaws and space signal sharing caused by the omni-directional antenna it usually uses. In recent years, few studies have been undertaken which examine the use of the smart directional antenna to mitigate the security risks in mobile wireless computing networks. One of the major reasons is the antenna size, as portability is a key requirement. Due to the dielectric-material embedding and FDTD optimal design technology, a smart antenna with controllable directionality can now achieve an overall volume reduction of 80%. This has promise for application in the wireless security realm. This thesis provides a conventional background in wireless computing networks and security theory. In addition, security level definition, program in Matlab™ and corresponding experimental results are provided. To show the effectiveness of improving security in WLAN with the use of a smart directional antenna, this thesis proposes a model for predicting electromagnetic environments using a directional transmission antenna based on the Finite Element method. To validate the numerical results, a new experimental method (using Network Stumbler software) to measure the signal strength in different locations is introduced. Results from experiments using the two methods are consistent. The latter method gives the users the possibility of using a laptop (with an appropriate wireless card, software and roguing around) to detect the real-time signal strength in different locations instead of using expensive measure apparatus. Such an advantage can be valuable for the efficient implementation of indoor wireless networks for security purposes. Finally, it contributes a security solution using DE-ESMB and DE-ESPAR smart antennas in WLAN. Through these simulated and experimental results, one can conclude that the security performance in WLAN can be greatly improved by using smart directional antenna. There are five chapters in this thesis: Chapter 1 introduces the wireless communication network. Information about architecture, topology and popular wireless standards is presented in this chapter. Chapter 2 investigates the security problem in IEEE 802.11 Standards. Recent improvements in security, and their limitations, are also included. This problem is investigated by performing laboratory experiments, including a real attack on 802.11 Standards and packet capture experiments using AiroPeek NX software. Chapter 3 describes the useful parameters of smart directional antennas, and then presents the security level definition in WLAN. Simple software in Matlab™ to determine the security level according to the beamwidth of the adopted antenna is also introduced. Chapter 4 is the important part of this thesis. Simulation results of signal strength in different locations using FEMLAB™ are presented, which are consistent with the follow-up experimental results carried out in a typical office area. This chapter also describes the final security solution using the newly-designed DE-ESMB and DE-ESPAR directional antennas. Chapter 5 is a summary of the thesis. It presents the conclusions and suggests area of future research for improving the security level using smart antennas in WLAN.

<p>Wireless On-board diagnostics functionality, which is a future outlook to vehicle system </p><p>parameter analysis, enables measurements and controlling without the limitation of a physical </p><p>connector. Today every vehicle must by law provide the possibility to analyze engine and </p><p>emission related parameters (OBD II). The wireless connection requires a high security level </p><p>to prevent unauthorized communication establishment with the truck’s bus system. The aim </p><p>of the project is to make a survey of the available security mechanisms and to find the most </p><p>promising solutions. Furthermore, several usage scenarios and access right levels are </p><p>specified and a risk analysis of the whole system is made. The greatest challenge is the </p><p>specification and implementation of a proper key-exchange mechanism between the analyzing </p><p>device and the truck’s bus system, which is therefore carried out with the highest possible </p><p>level of awareness. Consequently several different concepts have been formulated based on </p><p>the different usage scenarios.</p>

As wireless devices become more common, the ability to position a wireless device has become a topic of importance. Accurate positioning through technologies such as the Global Positioning System is possible for outdoor environments. Indoor environments pose a different challenge, and research continues to position users indoors. Due to the prevalence of wireless local area networks (WLANs) in many indoor spaces, it is prudent to determine their capabilities for the purposes of positioning. Signal strength and time based positioning systems have been studied for WLANs. Direction or angle of arrival (AOA) based positioning will be possible with multiple antenna arrays, such as those included with upcoming devices based on the IEEE 802.11n standard. The potential performance of such a system is evaluated. The positioning performance of such a system depends on the accuracy of the AOA estimation as well as the positioning algorithm. Two different maximum-likelihood (ML) derived algorithms are used to determine the AOA of the mobile user: a specialized simple ML algorithm, and the space- alternating generalized expectation-maximization (SAGE) channel parameter estimation algorithm. The algorithms are used to determine the error in estimating AOAs through the use of real wireless signals captured in an indoor office environment. The statistics of the AOA error are used in a positioning simulation to predict the positioning performance. A least squares (LS) technique as well as the popular extended Kalman filter (EKF) are used to combine the AOAs to determine position. The position simulation shows that AOA- based positioning using WLANs indoors has the potential to position a wireless user with an accuracy of about 2 m. This is comparable to other positioning systems previously developed for WLANs.

Wireless On-board diagnostics functionality, which is a future outlook to vehicle system parameter analysis, enables measurements and controlling without the limitation of a physical connector. Today every vehicle must by law provide the possibility to analyze engine and emission related parameters (OBD II). The wireless connection requires a high security level to prevent unauthorized communication establishment with the truck’s bus system. The aim of the project is to make a survey of the available security mechanisms and to find the most promising solutions. Furthermore, several usage scenarios and access right levels are specified and a risk analysis of the whole system is made. The greatest challenge is the specification and implementation of a proper key-exchange mechanism between the analyzing device and the truck’s bus system, which is therefore carried out with the highest possible level of awareness. Consequently several different concepts have been formulated based on the different usage scenarios.

With the proliferation of mobile devices and the advance of audio/video coding technologies, there is an increasing demand to provide quality-of-service (QoS) guarantees for multimedia applications. A WLAN (wireless local are network) typically consists of an access point (AP) and a finite set of mobile stations. Since the AP is generally more powerful and less physical constraint than mobile stations, it is of great interest to consider the use of sectorized multi-beam antennas at the AP to boost the network throughput by exploiting the benefit of spatial reuse. IEEE 802.11 is current the de facto standard for WLANs. However, if we directly apply 802.11 to the WLAN with multi-beam AP without any modification, we will encounter many challenging problems. Although existing solutions modify the 802.11 DCF (distributed coordination function) to solve these problems, yet DCF does not provide any QoS support. On the basis of 802.11e HCCA (hybrid channel control access), in this thesis, we propose a novel MAC protocol, named MPCF (multi-beam AP-assisted point coordination function), which is not only backward compatible with DCF, but also supports QoS functionalities, including non-reversal prioritization, time-bounded reservation, admission control, and cross-layer rate adaptation for multimedia streaming. Simulation results show that, in terms of throughput, frame delay dropped rate, and energy throughput, MPCF significantly outperforms existing protocols even in imperfect beam-forming and mobility environments.

It is a future trend to include the function of wireless networking in portable electronic devices, such as notebooks, tablet PC, PDA, mobile phone, and other information applicants. IEEE 802.11 is the most popular wireless LAN protocol that defines the functions in the medium access control (MAC) layer and physical layer. In this thesis, we design and implement a flexible and reusable soft IP (Intellectual Property) for wireless MAC that is compatible with AMBA system and can be used in SOC applications. The wireless MAC supports buffer descriptors, interrupt and DMA. The IP provides an AMBA-compatible interface for the host system bus, and provides a communication interface for the baseband processor in the physical layer.

<p>Användningen av trådlöst nätverk blev under början av 2000-talet mycket populärt bland privatpersoner, genom dess mobila fördelar, Tekniken medförde många fördelar, men också många nackdelar och frågan var hur många som verkligen hade blivit uppmärksammade på eller kände till dessa och därefter valt att skydda sina trådlösa nätverk.</p><p>Det främsta syftet med denna uppsats var därmed att undersöka på vilken nivå säkerhetsmedvetandet låg i samhället vid användning av trådlöst nätverk vid gällande tidpunkt. Vidare handlade det också om att reda ut gällande rättsläge , vid handlingar mot eller via ett trådlöst nätverk, och mäta hur utbredd säkerhetsanvändningen var bland trådlösa hemmanätverk. För att besvara detta utgick vi från ett positivistiskt och deduktivt synsätt, med kvalitativa intervjuer för att reda ut gällande rättsläge, pejling av trådlöst nätverk för att mäta säkerhetsläget och kvantitativa enkätintervjuer, för att få fram typer av säkerhetsmedvetande, bland användare av trådlöst hemmanätverk. Innehållet i alla intervjuer baserades på fastställd fakta kring trådlöst nätverk, risker med tekniken, riskförebyggande säkerhetsrutiner och Svensk lag.</p><p>Vi konstaterade slutligen att gällande rättsläge för närvarande var föråldrat och inte anpassat att hantera de risker som trådlöst nätverk hade medfört. Vidare visade resultatet på ökad säkerhetsanvändning bland trådlösa nätverk i samhället, och att det överlag var yngre användare som stod för denna ökning. Yngre användare visade sig även överlag ha ett högre säkerhetsmedvetande, än äldre, och då särskilt hög teknisk kunskap</p> / <p>The usage of Wireless local area networks (WLAN) became very popular amongst private citizens, during the beginning of the 21 century, because of its mobile advantages. The technology brought many advantages, but also many disadvantages and the question was how many had noticed or knew that these existed and afterwards had chosen to secure their WLAN.</p><p>The main purpose of this thesis was to examine the current level of security awareness, in the community, when using WLAN. Other goals were to investigate the current general legal context, about actions against or through a WLAN, and measure the widespread usage of security within WLAN. To answer this we used a positivistic and deductive approach, with qualitative interviews to sort out the current general legal context, Wardriving to find and measure the current state of security within WLAN's and quantitative questionnaires to find out the most common types of security awareness amongst users of WLAN. The content of all this was based on facts about the WLAN technology, the risks that comes with it, risk preventing security routines and the Swedish law.</p><p>Finally we established that the current general legal context was out-of-date and not adapted to handle the new risks that WLAN had brought. Further on the result also showed a increased usage of security amongst WLAN in the community and that the main reason for this was the younger WLAN owners. Younger users also turned out to have higher security awareness, than older users, and particularly very high technical knowledge.</p>

Thesis (M.S.)--Florida State University, 2003. / Advisor: Dr. Xin Yuan, Florida State University, College of Arts and Sciences, Dept. of Computer Science. Title and description from dissertation home page (viewed Apr. 7, 2004). Includes bibliographical references.

Thesis (M.S. in Computer Science)--Naval Postgraduate School, September 2003. / Thesis advisor(s): Geoffrey Xie, John Gibson. Includes bibliographical references (p. 75-76). Also available online.