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Automatic Attendant application using Asterisk PBX
Benýšek, Jiří ; Krajsa, Ondřej (referee) ; Kovář, Petr (advisor)
Application of IP telephony is still more and more popular. This technology is designed for large companies as well as for home or office use. If customer needs to use advanced features of the private branch exchanges, he had to purchase more expensive solutions than common equipment. These professional products may be replaced by open source solutions, which can fully replace them. Private branch exchange Asterisk is one example of these products. Bachelor’s thesis is focused on IP telephony, treats of basic principles and network protocols used by this service. This thesis then describes the public branch exchange Asterisk, its possibilities for use in call centers and administration of call queues using this PBX. After theoretical analysis, this thesis deals with installation and configuration of this PBX. It includes installation of necessary operating system, additional packages containing necessary libraries and modules needed for correct function of the PBX. Configuration of Asterisk such as creation of user accounts of SIP protocol and dialplan is described in the next chapter and then all of these functions are tested. Achieved practical results are presented in the last chapter of this bachelor’s thesis.
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Virtual serial port and its safety conversion to Ethernet
Pokorný, Michal ; Krajsa, Ondřej (referee) ; Koutný, Martin (advisor)
Bachelor´s thesis try to find a solution to make virtual serial port and its safe transfer on Ethernet. Nowdays communications channels don't offer appropriate security of a whole communication. Therefore it depends on get-togethers, in order to realize this security themselves.This means ensure reliable data transfer, these data from among get-togethers encrypt in order to appropriate attacher be unable to read them in real - time, eventually to change them. As a result this Bachelor thesis is the application, which, except transfer between virtual serial port and Ethernet, insure authentication among get - togehthers communication and cipher transfer among them. As an encryption algorithm is used algorithm AES. It is concerned symmetrical cipher, which ciphers data after pages about size 128 byte.
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Thermostat for biological experiments
Štens, Radovan ; Krajsa, Ondřej (referee) ; Chmelař, Milan (advisor)
Master's thesis deals with a design of the thermostat for biological experiments considering 2l of volume, with capability of setting up required temperature between 20-40 degree Celsius and related accuracy of measurement +/- 1 degree Celsius. Following chapters are one by one described and properly explained from possible ways of measuring temperature to final implementation. Result of the thesis presents necessarily calculations, discussion of module's performance modeling, schematics together with PCB's design and the list of components. Neither the question of software nor possibilities of realization is neglected.
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Billing system and call monitoring for PBX Asterisk
Depiak, Petr ; Šilhavý, Pavel (referee) ; Krajsa, Ondřej (advisor)
This master's thesis is focused on developement of billing system with the options of monitoring individual calls for software exchange Asterisk. Billing of calls is adaptible with the help of group of individual rules, consisting of tariff impulses, numerical prefix, with help of outgoing trunk and cost of the billed unit. The first part of this work is focused on instalation, configuration and preparation of individual components of the billing system. In this work is explained the architecture of the billing system and highlighted the purpose of work of the model database. Next we focused on the purpose and the principal system invidual function of the system including solution. At last there is a simple manual to operate the system with the help of created web interface.
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Optimization of data communication over high-voltage lines
Minárik, Peter ; Krajsa, Ondřej (referee) ; Mlýnek, Petr (advisor)
The thesis deals with analysis of the PLC (Power Line Communication) system for data communications through powerlines. In the introduction describes the technology of data transmission through the energy network and is divided into categories corresponding with the explanation of the various specifications and features. Different types of coding, affecting the transmitted signal interference and modulation techniques used in a PLC are also described. The practical part is made up of telecommunications network model with transmission channel realized as additive white noise. The model can setup different types of modulation and coding in relate with the signal to noise ratio and bit error rates. The individual blocks settings are described in detail. The model was simulated. The results of simulation are displayed and evaluated at the end of work.
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Implementing of GSM modem in PBX Asterisk
Benýšek, Jiří ; Krajsa, Ondřej (referee) ; Šilhavý, Pavel (advisor)
Short Message Service (shortly SMS) is the most widely used type of communication systems. The main advantages are that allow a fast exchange of messages between devices, a very good availability through GSM and a reasonable price. Nowadays the SMS service support has expanded to include other technologies such as a service of the information navigation and the remote connection. The master‘s thesis concentrates on the Short Message Service, deals with basic principles and statements using by this service. The topic of the thesis is software PBX Asterisk and its possibility of SMS implementation, especially verification of SMS processing goes through the PSTN. After the basic introduction the master‘s work deals with the installation and configuration of the server. The main focus is on an installation of the operating system with an additional pack including necessary libraries and modules for a correct working of the server. The following section is paying attention to the Asterisk server configuration, especially a hardware card installation which is necessary for a connection with analog telephones, done by Bluetooth connections, set up user’s profiles of the SIP protocol and create a dial plan. This is followed by a verification of SMS option of the implementation and communication with GSM modem which is used as a gate for an exchange SMS between PSTN and GSM network. The last chapter of this master‘s thesis comes with the aimed results.
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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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Design and development of application for position monitoring
Kovář, Petr ; Šilhavý, Pavel (referee) ; Krajsa, Ondřej (advisor)
The aim of the master’s thesis was to implement in the C++ language a software solution of the localization of the mobile phone with Symbian OS in the GSM network. The intended purpose of this solution would be especially the phone localization in the case of its theft or loss. A familiarization with the development process of the Symbian platform and understanding the features of the Symbian version of the C++ language preceded the realization itself, because the Symbian C++ has an original style of the memory manipulation and error handling. The Symbian C++ basic principles and its features used in the implemented software are described in the second chapter of the text part, the first chapter deals with the history and version structuring of the Symbian OS. In the third part of the text is described the created software. The realized solution consists of three parts – server application PhoneLocServer for a mobile device, client application PhoneLocClient for a PC and the web-located part. The server was developed for the Symbian OS in the C++ language in the IDE Carbide.c++ and was tested in the S60 3rd edition SDK MR emulator and on the real device Nokia N73. It is a GUI-less application running in the background, which is run automatically after a smartphone start-up. It controls the incoming SMS over the socket listening and the messages addressed to itself processes before a user can notice them. The control messages body is comprised of a prefix, which identifies them, a password, a sending period value and a state to which application should change. After the receiving of the control SMS server verifies the SMS sender through the use of his telephone number and the password. It compares these values with the data stored for the given IMEI on the web server. If the verification succeeds, the server runs a timer with the period known from the control SMS and on the callback of this timer are transferred the data describing current phone location and state via HTTP protocol to the web server. The GSM localization method “Cell ID” is used for the location determination. After the client user asks for the start of loading the data, he must answer the password and the observed phone’s IMEI and he is verified through the use of the web server again. If the verification succeeds, the periodic download of the server data starts and from the first downloaded file is found out the upload period. Download then continues till the time the client detects the end of sending by the server part or till the client user stops the download himself. The client was developed in the C++ language in the C++ Builder environment. It requires a Windows OS and internet connection for its right function. The web server mediates communication between the server and the client, stores the data for user verification and makes possible the server-side upload by the help of a simple PHP script. In all the used web server directories is present the .htaccess file to improve its security, e.g. it denies the directory listing in a web browser.
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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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Wireless Network Security
Sedlák, Břetislav ; Krajsa, Ondřej (referee) ; Lambertová, Petra (advisor)
Master thesis focuses on wireless network security. The thesis is divided in two parts. First part describes today’s used standards and their components, topology and security methods as stealth SSID, MAC addresses filtration, WEP, WPA and WPA2. The last three methods are described in detail. In second part there are realized attacks on above described methods of security. There are described attacks on WEP as KoreK chopchop attack, fragment attack, attack FMS, KoreK and attack PTW. Then is described the dictionary attack on passphrase by WPA/WPA2 with PreShared Key authentication obtaining, precomputed hash tables for faster passphrase finding and for using more core procesors during dictionary browsing. The last attack describes obtaining of keystream used for encrypting of frames by WPATKIP and then sending custom data to client. It is described how to carry out each attack and how to protect against them.
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