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Quality of service support in unix-like operating system for communication in WiFi networks
Mizera, Josef ; Komosný, Dan (referee) ; Novotný, Vít (advisor)
Diploma thesis is focused on the supporting of Quality of Services in wireless networks, especially in the Linux operation systems. The topic is connected not only with OS, but also with the wireless standard, which supports QoS in wireless networks called IEEE 802.11e. QoS is needed especially for time-consuming data transfers in real time. The theoretical part deals with the theoretical analysis of the issue of the QoS support. There are described parameters, which occurred in quality of services support. This section also deals with the division of services that are used to transmit data across computer networks. It also describes the QoS support in wireless networks according 802.11e, its implementation and methods of accessing a medium with a without possibility of traffic. This part is followed by a description of QoS support in UNIX operating systems. The chapter describes how is the QoS support designed in these operating systems. There are also characterized concrete tools which are used for control the data flow in the operating systems using Linux. At the end the theoretical part deals with different types of queues and methods used in linux OS. In the practical part of the thesis, there are various designed topologies and scenarios to verify the functionality of QoS support in wireless networks using a Unix system. These chapters show the results of different tests at selected transmission data streams that are sensitive to transmission time. There is also verified cooperation of QoS support between devices operating on the network and data link layers. The output of this work is to design a laboratory exercise for the subject Network Architecture. This exercise is focused on familiarization with the QoS support functionality in wireless networks and in Unix-like operating systems. This chapter also describes the devices and programs that are needed to measure this task. The last part of the chapter describes the procedure for the preparation of the measuring station. For this laboratory task, there is an inserted manual in the annex.
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Design of new V/I and I/V converters for the measurement of current-mode filters
Jarník, Lukáš ; Polák, Josef (referee) ; Langhammer, Lukáš (advisor)
This master’s thesis deals with problems of analog differential converters, which are used in measuring circuits working in the current mode. The aim of this thesis is to propose a new voltage to current and current to voltage converter, that should influence measured frequency properties as little as possible. Commercial active elements are use to design converters. Active components are compared on the basis of properties as bandwidth and slew rate. Designed converters are simulated in Orcad PSpice program. Converters, of the best behavior are practically implemented and measured. Measured and simulated values are compared.
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Classification of transmission channels based on speech signal analysis
Báňa, Josef ; Sysel, Petr (referee) ; Atassi, Hicham (advisor)
The thesis examines the impact of VoIP transmission channel characteristics on speech parameters. It seeks ways of emulating properties of a selected VoIP transmission channel and creating a network emulation environment. Several scripts have been created in the Matlab development environment and used to modify and divide a continuous recording into parts identical to the original speeches, before passing through the transmission channel. Subsequently a database of speech recordings is created, as affected by selected characteristics - jitter, bandwidth, loss. Within these databases, symptoms are sought as the most evident characteristics of the transmission channel. Using correlation, symptoms are selected that are best suited for automated determination of the properties of transmission channel characteristics such as jitter, loss and bandwidth.
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Analysis of delay dependence of modern communication services and channels, QoS optimization
Rozman, Jiří ; Szőcs, Juraj (referee) ; Endrle, Pavel (advisor)
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.
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Design and realisation of microwave directional coupler
Nejedlý, Miroslav ; Motl, Milan (referee) ; Dvořák, Radek (advisor)
The diploma thesis deals with microwave directional coupler. The paper presents some of the microwave directional coupler and an analysis of bifurcations. The paper also discussed the various techniques of bifurcations and the bandwidth to which they are making. Proposal is implemented in two selected directional couplers and determining their size. They also performed using the selected simulation program selected two bifurcations. Furthermore, these couplers are made on the perimeter of the analyzer is verified by their actions and are verified by the actual parameters of the coupler.
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FM Coincidence Detector - Laboratory Equipment
Mlčoch, Jiří ; Urbanec, Tomáš (referee) ; Baran, Ondřej (advisor)
This work is aimed at an analysis of frequency demodulation, design, simulation, and construction of a coincidence demodulator. Chapter 1 explains the basic characteristics of frequency modulated (FM) signals and provides an overview of the required signal bandwidth, the signal spectrum, and the signal-to-noise ratio after demodulation. Chapter 2 describes each type of FM demodulator separately, and it includes all significant types of demodulator for FM radio broadcast. The function of the coincidence demodulator and its characteristics are explained in detail. Chapter 3 contains a theoretical solution of the phase shift network. Calculated values of the circuit elements are verified by simulation with a view to the total harmonic distortion of the demodulator output signal. Chapter 4 describes the front-end circuit of the receiver. Here, the filter design and the mixer circuit description are provided. The final part of the thesis presents the applicable laboratory task.
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Laboratory device focused on the switched capacitor circuits
Urban, Lukáš ; Šotner, Roman (referee) ; Petržela, Jiří (advisor)
This Master`s thesis is focused on through acquaintance of principles of the function circuits with switched capaticors and posibility of their application mainly in frequency filters or signal generators. The origin of the switched capacitor circuits is mentioned at the beginning of the work. There are references to the first scientific work and scientists who have dealt with this issue. Maxwell`s idea: lossy element (resistor) replace with lossless element (switched capacitor) in electric circuit, is further described. In the next chapter of this work are listed types of switching capacitors and their use in simple RC filters and in structures of inverted or noninverted integrators and their application in more complex higher order filters. The advantages and disadvantages of SC circuits versus circuit composed of discrete components are shown. It is also listed a simple low-pass switched RC filter implemented with analogue multiplexer 4053. Using the LTC1043 integrated circuit, which structure and properties are described and analyzed in detail in the work, the 1st order aktive or pasive low and high pass filters were designed and subsequently simulated in the computer simulator OrCAD PSpice v.10. Another chapter deals with the integrated circuits higher order filters, structure and properties of the integrated filter LTC1060 are further analyzed here. Except this IC there are mentioned integrated filters commercially less available from the corporations Linear Technology and Maxim. The main objective of thesis was to propose and establish laboratory device and laboratory measurment focused on the switched capacitor circuits. The laboratory device has been designed with integrated circuits LTC1043 and LTC1060, which is demonstrated by using passive and active integrator, 2nd order band-pass and 4th order band-pass with Chebyshevovou approximation.
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Design of circular polarized antenna for 2.4 GHz
Hase, Michal ; Lukeš, Zbyněk (referee) ; Láčík, Jaroslav (advisor)
In this thesis, I introduce two types of circularly polarized rectangular microstrip antennas at 2.44 GHz. First type has direct fed and the second has two inputs for fed. In first case is used a stub to make the frequency with minimum return loss and equal to the frequency with minimum axial ratio. In second case is use the power splitter to divide the wave in to two lines with phase shift 90° for feeding the patch. In this thesis is described, how to get the best results of Axial Ratio.
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Measuring of data communication parameters in computer networks
Šeda, Pavel ; Hošek, Jiří (referee) ; Skořepa, Michal (advisor)
Master‘s thesis is focused on basic characteristics of data transmissions in computer networks. In forepart I digestedly described basic characteristics computer networks, metods of their measurement and valuation. Computer networks type LAN as well as wireless computer networks Wifi, are mentioned. In second part I realized my own proposition of basic characteristics measurement. This proposition is used for SW applications development. Main goal of these applications is measurement of packet delay, packet jitter, paket loss and available bandwidth. I described details of SW applications and realized measurement of real computer networks in the end.
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Methods for measuring the bit rate on the Internet
Pilčík, Jan ; Mišurec, Jiří (referee) ; Zeman, Václav (advisor)
Due to a signifikant development of computer networks in the last few years the demands for measurement of network metrics increased. This master´s thesis is dealing with standards for testing and test techniques used for the measurement of network metrics. Further it compares the existing free accessible measurement tools and metrics measures them. Finaly the thesis draws up a web application for measurement of the basic network metrics.
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