O principal objetivo deste trabalho é apresentar os aspectos de especificação e implementação dos serviços de transferência de arquivos desenvolvidos para duas redes locais, usadas em ambientes de automação industrial e de automação de escritório, respectivamente. São apresentados, inicialmente, alguns conceitos e os requisitos de especificação que devem ser satisfeitos por estes serviços. À luz desta caracterização, algumas especificações de serviços de transferência de arquivos para redes de computadores são estudadas e analisadas. De acordo com esta análise e com as tendências de padronização de redes de computadores usadas nas aplicações acima mencionadas, é escolhida uma especificação a ser tomada como base na implementação destes serviços. Estes serviços são especificados detalhadamente, considerando as características das redes locais utilizadas. Alguns aspectos de implementação da máquina de protocolo que presta os serviços especificados são discutidos, descrevendo-se o conjunto de processos que constituem tal máquina. Em seguida, são especificados os programas aplicativos desenvolvidos a partir destes serviços de transferência de arquivos, considerando-se os requisitos das aplicações envolvidas. Para avaliar o sistema implementado, alguns testes são definidos, visando verificar a operacionalidade, conformidade e desempenho deste sistema. Os resultados destes test6es são apresentados e discutidos. Finalmente, são feitas considerações sobre o sistema implementado e a especificação tomada como base. Como continuidade do presente trabalho, é sugerida a implementação de outros serviços utilizando a infra-estrutura criada pelo mesmo. / The main purpose of this work is to present aspects on the specification and the implementation of the file transfer services, developed for two local area networks used in manufacturing and office automation. Some concepts and the specification requirements for such services are initially presented. In the light of this introduction some specifications of file transfer services for computer networks are studied and analyzed. Based on this analysis and on the trends in computer networks standardization for the above mentioned applications, a specification is selected as the basis for the file transfer services. These services are then fully specified taking into account the characteristics of the target local area networks. Some implementation aspects of protocol machine which provides the specified services are discussed describes the processes that make up such machine. The application programs developed using these file transfer services are then described. Some tests are conceived the verify the functionalism, conformity and performance of the implemented system. The results of these tests are presented and discussed in some detail. Finally, some considerations on the implemented system and the specification used as basis are presented. As future work the implementation of other services using the framework created is suggested.

One of the major problems in the realization of ATM is traffic management, in particular, the resource allocation for an efficient network. Many approaches to the bandwidth management problems [2] and buffer management problems have been proposed. Boyer [IO] suggested a "Fast Bandwidth Reservation" protocol, while Turner [2] applied the same technique to the buffer allocation for the bursty traffic. In this thesis, we extend Turner's scheme in order to make it more efficient with respect to buffer allocation. We define a new parameter "Reduction Factor'', which has the potential of saving a significant amount of buffer space in a commonly shared pool of buffers. It is observed that the amount of savings depends upon the cell loss probability (CLP) bound on the network, Source Activity Probability (SAP) and number of connections supported by the network (N) at particular instant. The performance of the scheme is evaluated under various QoS requirements. It is seen that this scheme leads to approximately 38% of savings in the buffer space under certain circumstances. For supporting multimedia services, we also employ the scheme of partitioning the total buffer space. The results show that it leads to 10 % less savings as compared to single buffer scheme under certain conditions. As usage policing is very critical in this scheme, we outline a suitable mechanism and hardware implementation for Usage Parameter Control. The algorithm for acceptance of virtual circuit in the network is also described.

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.

Thesis (M.S.) -- Mississippi State University. Department of Electrical and Computer Engineering. / Title from title screen. Includes bibliographical references.

<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>

Control oriented local area networks (COLANs) are being installed in factories at an increasing rate. Traditionally, process control has operated with a master scheduler (computer) monitoring a number of points in a control grid. As the complexity of today's process control needs grow, the need to process information locally increases. Microcontrollers, networked with a master scheduler, can collect data from a locus of points and make decisions as to whether the master needs to be notified or not. By processing data locally, memory and execution time are freed up for the master scheduler. Task implementation becomes modular in nature, resulting in process control software that is easier to write, and maintain. This structure is the basis for COLAN V, a low cost, real-time, distributed control network developed at Oregon State University. COLAN V was used as the foundation for the creation of a multi-media presentation system. Six microcontrollers were networked together to remotely control the operation of projectors, projector screens, and lighting. Based on the application the master scheduler was replaced by a tape player. This allowed the storage of the audio part of the presentation on one track of the tape and the storage of the synchronized control signals on the other track. This distributed control network supplied a low cost solution to a need that was not addressed by the commercial market at any price. / Graduation date: 1992

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.

Channel access fairness and efficiency in capacity utilization are the two main objectives for Quality of Service (QoS) specific to Medium Access Control (MAC) protocols in computer networks. For bursty and unpredictable traffic in networks, fairness and efficiency involve a mutual tradeoff with the currently popular QoS mechanisms. We propose a QoS MAC framework for carrier sensing multiple access (CSMA) networks, that achieves fairness with improved efficiency through extensive state-keeping based on the MAC evolution. This CSMA with Implicit Scheduling through State-keeping (CSMA/ISS) framework involves the tracking of traffic arrival at active nodes, the nodes that need channel access frequently. It also involves implicit channel access grants to different active nodes according to their estimated queue backlogs and the fair scheduling requirements. These methods save channel capacity that may otherwise be required for disseminating the access requirements of various nodes, and their access rights according to fairness rules. A static, hierarchical, and weighted fair access scheme is designed in CSMA/ISS by allowing repeated rounds of access that are weighted fairly according to requirements. Weighted fairness across classes is achieved by invoking channel access for each traffic class in a round as many times as its weight. Within each class, all active nodes are allowed equal access through in-order channel access based on a looped list of active nodes. Although CSMA/ISS is proposed as a distributed control framework for efficiency, it may also be employed in central control protocols. It may also be adapted to different types of CSMA networks, both wireless and wired, by an appropriate choice of the underlying classical access mechanism. The CSMA/ISS framework was modeled and simulated as a QoS capable MAC protocol for a wired fully connected local network environment. We present the CSMA/ISS framework, the example implementation, and the results of performance evaluation of the example implementation. Significant performance improvements were observed, and the memory and processing trade-off was found to be low to moderate.

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.