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Implementation of the channel equalization algorithms used in FMT modulation
Krejča, Libor ; Krajsa, Ondřej (referee) ; Šilhavý, Pavel (advisor)
The objective of Diploma thesis is design of analysis tool for equalizers used in FMT modulation. The model of transmission channel was designed for simulations with FMT. The transmission path is modeled by test loop, which corresponds to DSL line. For this reason, some principles of DSL technology is described in the thesis. The principles of multicarrier modulation are introduced in first part. The multicarrier modulation with filter bank (FMT) is described in detail.The different methods of design the fiter bank are given and compared. Channel equalization are introduced in second part. The attention was focused on minimum mean square error filtering (MMSE). Decision feedback channel equalizer (DFE) is extended from linear MMSE equalizer. DFE equalizers were programmed in analysis tool. For computation of equalizer coeficients was used also equalizers based on adaptive algorithms and MMSE. The last part describes the results of DFE equalizers used in communication system with FMT modulation. Analysis tool was programmed in MATLAB with a graphical user interface. It allows to show mean square error, signal-to-noise ratio and transmission speed dependence on delay between original and distorted signal. Signal-to-noise ration is displayed also in individual subchannels and users can display mean square error dependence on different orders of DFE filters.
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Security provisions of VoIP traffic in Open source PBX
Chalás, Jaroslav ; Daněček, Vít (referee) ; Šilhavý, Pavel (advisor)
Main goal of creating the Open Source project and GPL licence are free sources and applications available for a wide public. Competent communities are responsible for support and upgrade of Open source based applications and softwares, which are created on a voluntary bases. Due to this fact an implementation depends on plenty others publicly available libraries and applications, which sometimes complicate the installation process itself. Successfully created VoIP connection is two-phase based process. Signalization is necessary in the first place, which might be supported with H.323 or SIP. After call parameter negotiation – voice codec, cipher code, ports etc, the second phase takes over to transfer voice. Theoretical part of this thesis describes SIP, H.323, MGCP, RTP and IAX protocols, as well as secure ways of signalization and voice stream part of the call. These might be SIPS, SRTP, ZRTP and IPsec. In thesis Open Source Asterisk PBX is well described, when mentioning its options, features and community support. I put near options available for particular releases and introduce attacks and abuses which are possible to perform on the VoIP system in general, together with available, no cost and working tools to perform the attacks with. Practical part focuses on possibilities to generate experimental attacks on individual systen parts with exact definition of what the consequences are. Based on the overall analyse of achieved results I conclude three solutions as autoinstallation linux packages. These „deb“ packages consist of specific Asterisk release required to meet the security needs, ready-to-test configuration and guide to follow with correct options to set. Final security possibilities requires hardening on application layer, where Iptables takes its part. „Linux firewall“ as some express Iptables are configured to reflect VoIP system parameters and protect from DoS attacks.
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Control unit of the hoisting ramp
Špát, Pavel ; Šilhavý, Pavel (referee) ; Číž, Radim (advisor)
This work deals with the design of DC motor control for a hoisting platform which is supplied by the 12 V battery. The selection of control element is described here where suitability of a microcontroler usage and integrated logical circuits for this connection are compared for suitability. It also describes selection of sensors for sensing position of the hoisting platform where the mechanical switches, optical sensors and Hall probe are compared. This work also deals with the practical design of control. Each block of equipment and its function is described in this work. The functional prototype is the result of this work. The schematics, DPS proposal and plans of parts placement of the whole equipment are in the enclosure.
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Turbo codes and their applications
Ploštica, Stanislav ; Krajsa, Ondřej (referee) ; Šilhavý, Pavel (advisor)
This Diploma thesis aims to explain the data coding using turbo codes. These codes belong to the group of error correction codes. We can reach the high efficiency using these codes. The first part describes process of encoding and decoding. There are describes parts of encoder and decoder. Principle of encoding and decoding demonstrate a simple example. The end of this part contains description of two most frequently used decoding algorithms (SOVA and MAP). The second part contains description of computer program that was made for using as teaching aid. This program was created in Matlab GUI. This program enables to browse error correction process step by step. This program contains graphic interface with many options and display results. In the third part is described program created in Matlab Simulink that was implemented into the TMS320C6713 kit and there is description of measuring procedure. For verification of efficiency of turbo codes was measured any parameters. Some of these parameters are: number of decoding iterations, generating polynoms and using of puncturing. The last part contains measured value and result evaluation.
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Automation of measurement of disturbance influence on xDSL technologies
Röszler, Pavel ; Číž, Radim (referee) ; Šilhavý, Pavel (advisor)
This work focuses on interference of DSL transmission, measurement and testing with Spirent noise generator and injection unit. Deals with proposition of automated measurement of transmission bit rate dependency on wireline lenght and noise type and level. In theoretical part are described ADSL technology and noise types. Following part focuses on measurement setup and description of wireline simulator units E414 and 8234, gene- rator DLS-5800 a injection unit DLS-5410DC by Spirent company. Main part describes generator and injection unit control software and remote control commands, which are used for automated measurement. There are also described xDSL Measure tool software, which is using for automated measurement with wireline simulators and upgrade, which implements remote communication with generator a injection unit, for remote control and automatic changing noise types generated at the output.
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Multitone Modulation Implemented via Filter Bank
Krajsa, Ondřej ; Vlček, Čestmír (referee) ; Róka, Rastislav (referee) ; Šilhavý, Pavel (advisor)
The work is focused on multitone modulation implemented by filter banks, which are alternative modulations to DMT and OFDM modulations. The paper describes the two proposed modulation schemes, non-overlapped FMT and half-overlapped FMT. This modulations utilize the benefits of implementing FFT algorithm in conjunction with a bank of polyphase filters that are derived from the prototype filter. To design the prototype filter a Matlab tool is developed. For both modulations the simulation models were created for xDSL systems and for wireless transmission channel. Non-overlapped FMT modulation proved to be a suitable modulation scheme for channels with narrowband interference and sharp edges in the transmission function of the channel. It was allowed by perfect separation of each subchannel and with preserving the orthogonality between subchannels using the FFT algorithm and utilization of appropriate filters. Half-overlapped FMT modulation allows as well as the DMT modulation optimal utilization of provided transmittion band, because the power spectral density of the signal is flat. But it is not suitable for transmission channels with roughly shaped by changes in the transmission function and narrowband interference. Optimization implementations were designed using parallel processing on the DSP Texas Instruments TMS320C67x series. It thus achieved almost ten-fold reduction in computational complexity. In FMT modulation both options ensure increased signal to noise ratio and thus allow the use of constellation diagrams with a large number of signal elements with the same transmit power and also higher transmission speed.
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Data acquisition by Zigbee wireless technology
Kubíček, Lukáš ; Šilhavý, Pavel (referee) ; Koutný, Martin (advisor)
The bachelor thesis deals with a ZigBee wireless technology and focuses on the potential use in the sensor networks. This thesis addresses both the structure and basic properties of ZigBee standard and possible use of this application in practice. The main part of this work is implementation of the sensor networks using ZigBee development kit of Jennic company. As an example of the practical use of ZigBee technology this network is connected to a computer in which data is collected from each sensor using the database and then through a PHP script presented on the Internet. Problem solving in this thesis focuses primarily on the simplicity and universality of the resulting applications.
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Automation of measurement of transmission properties of DSL modems
Pokorný, Lukáš ; Šedý, Jakub (referee) ; Šilhavý, Pavel (advisor)
The work deals with transmission parameters of DSL systems and software development for the automated measurement. The first part is devoted to the transmission medium and modulation techniques. The following describes the detailed functions and features of ADSL2+ modems. Integral part of the work is the overview of the ITU test methodology, together with parameters of test loops and types of interference. Within the automation of measurement are described used Spirent simulators DSL414E and DLS8234 and important communication commands. The practical part is devoted to designing applications for control simulators and software for automated measurement. For implementation of algorithms and creation of graphical interface is used C++ programming language. Finally the results of measuring the transmission properties of ADSL and VDSL systems executed by created application are presented.
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