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Analysis of Speech Signals in VoIP Transferred Over a Network Channel
Báňa, Josef
The article 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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The effect of optical fiber attenuation on the capacity of optical traces
Žák, Ondřej ; Škorpil, Vladislav (referee) ; Reichert, Pavel (advisor)
The essence of this thesis is the creation of complex insight on optic fibre attenuation. There is successive steps explained mechanism of optical attenuation and characterized its spectral dependence. We are describing primary elements of optical attenuation, its sorts and their own spectral dependence. Bachelor´s thesis is explaining requirements of transmission system to spectral characteristic optic fibre and influence of optic fibre attenuation on capacity of optical trace. Output of bachelor´s thesis is program solution of designed mathematical model for calcula-tion spectral dependence of optical attenuation. Program is realized in MATLAB and there is furthermore added version in Microsoft Office 1997-2003. Created program is able to ap-proximate points data obtained from measurement of optic fibre by using Lagrange interpola-tion polynomial and Rayleigh scatter interlay.
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Wideband antenna for the frequency range from 5 GHz to 10 GHz
Hebelka, Vladimír ; Oliva, Lukáš (referee) ; Řezníček, Zdeněk (advisor)
The design and manufacturing of a wideband bow-tie antennas for the frequency range from 5GHz to 10GHz are described on this thesis. In the first part of this thesis is decsribe a several type of bow-tie antennas. Next part provides the design of bow-tie antennas and optimalization in CST microwave studio software. At the end of the thesis are compare simulation results and measured results of bow-tie antennas.
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Monitoring of communication properties in Internet
Iľko, Pavol ; Červenka, Vladimír (referee) ; Komosný, Dan (advisor)
This thesis deals with measuring transmission parameters of the Internet network, in particular latency of ping, SSH protocol and bandwidth. The thesis is divided into a theoretical and a practical part. Theoretical part describes PlanetLab network, its brief history and contemporary projects. At the same time, tools for data mining from web pages are described. These information obtained from the theoretical part are used for creating PlanetLab nodes list and for programming applications which measure the network transmission parameters. Applications, list of nodes and obtained data are attached on DVD disc.
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Synthesis of the electronically reconfigurable frequency filters
Michalička, Filip ; Dvořák, Jan (referee) ; Langhammer, Lukáš (advisor)
This diploma thesis deals with design of reconection-less electronically reconfigurable filter structures which have single input and single output using unconventional active elements, which have ability to adjust one of their parameter e.g. gain or transconductance. The first part describes basic parameters of frequency filters, the division of filters by frequency transfer response and used circuit elements, their operational modes, the principle of reconnection-less electronically reconfiguration and the circuit design method MUNV. Second part describes all active elements used in the proposal of filters, their properties and the implementation using existing transistor-level models. The third part contains the design of three reconnection-less electronically reconfigurable filters and the simulations results obtained from simulation programs OrCAD Capture and PSpice. The obtained results were compared with theoretical behaviour. This part also contains results of these analyses: sensitivity, parasitic, Monte Carlo and temperature to determine the behaviour in varied cases.
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New solutions of converters for measurement of current-mode filters
Štork, Petr ; Kubánek, David (referee) ; Jeřábek, Jan (advisor)
This bachelor’s thesis describes some new solutions of differential converters that convert voltage to current and vice versa. Such converters are necessary for measurement of frequency filters in a current mode due to absence of instruments able to mesure signals with current as signal carrier. The goal is to design such converters that should influence gauged frequency properties in a current mode as little as possible. Converters will consist of operative amplifiers with current feedback. Converters designed this way are tested using simulations from PSpice programme, where particularly wideness of band of individual solutions is tested. Simulated solutions that are the most suitable ones are practicably re-enacted and gauged. These resuls of measurement and simulations are compared.
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Analysis of methods of measurement of fully-differential frequency filters
Kučera, Tomáš ; Kubánek, David (referee) ; Jeřábek, Jan (advisor)
This bachelor thesis focuses on measurements methods of differential frequency -selection filters with active elements in current mode. Firstly it describes differential frequency-selection filters in current mode and conversions from voltage to current mode. Next the thesis deals with measuring of particular voltage converters to differential current and back from differential current to voltage, which is an integral part for measurements of differential frequency-selection filters in current mode. For design of particular converters there was used program OrCAD there and subsequent simulation was executed in program PSpice.
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Implementation of Asterisk VoIP PBX
Schön, Martin ; Münster, Petr (referee) ; Szőcs, Juraj (advisor)
The thesis is divided into two parts, theoretical and practical. In theory, it analyzed the signaling protocols, the RTP protocol for data transmission, VoIP Asterisk PBX and security options. The practical part describes the installation of the Asterisk PBX, conducted demonstration call forwarding. PBX was associated with an LDAP directory server to manage users and ejabberd for text messaging protocol XMPP. It was configured translation SIP-Skype using the SiSky Gateway and with dialplan SIP-H.323 translation. The study was to develop Dialplan with IVR. It was measured bandwidth of the audio/video codecs in an encrypted/unencrypted connections.
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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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Detector of optical beam position
Lukáč, Vladimír ; Barcík, Peter (referee) ; Kolka, Zdeněk (advisor)
The bachelor's thesis deals with the design of an optical beam position detector with the required parameters. The aim was to select a suitable photodetector that captures light rays and converts them into photocurrent, to design photocurrent processing into a voltage signal with linear properties and specified parameters, to convert the analog form of the voltage signal into digital information with which a microcomputer or microcontroller can work. The analog part of the work is simulated in the program OrCAD PSpice, in which the functionality and correctness of the designs is confirmed. The digital part processes the voltage signal to the information of the used channel, its level displays this data on the display.
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