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Channel estimation in CDMA systems
Kadlec, Petr ; Prokopec, Jan (referee) ; Kejík, Petr (advisor)
The subject of this work deals with the problem of channel estimation for CDMA systems. This method of multiple access when individual users share the same full bandwidth simultaneously and are differentiated with any of pseudorandom sequences, is now the most perspective method. That is proved by its wide implementation in mobile networks of the third generation and higher systems. This work describes basic theory principles of spread spectrum, above all DS-CDMA (Direct Sequence-CDMA) and furthermore some phenomena of radio wireless channel that affect changes in transmitted signal in its way from transmitter to receiver. Terms of fading, multipath propagation, loss, refraction, scattering of the wave and Rice and Rayleigh probability density functions are mentioned. The third chapter deals with yet known and used capabilities of channel estimation. Differences, advantages and disadvantages of so-called blind estimation or training-based estimation are discussed. Two algorithms: LS method and sliding correlator are analyzed in more detail. There is also description of their simulations in Matlab and some results of these simulations are discussed. The last chapter deals with comparison of main characteristics and achievable accuracy of wireless channel impulse response estimation by both methods, and their possible utilization in real live.
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Simulation of UMTS system
Predajňa, Martin ; Prokopec, Jan (referee) ; Kejík, Petr (advisor)
The bachelor’s thesis deals with modeling of UMTS system in downlink. It is focused on signal processing in physical layer and observes BER depending on parameters of model of real environment by setting different interruption. Basic architecture of UMTS system, channel coding and multiplexing of transport channels to physical channels is described in this thesis. Radio frame structure for downlink dedicated physical data channel is also described there. Using of pseudorandom sequences in CDMA systems and their properties are key parameters for observation of BER. Simulation uses single-user model in basic band, which enables to observe the influence of noise and narrowband jamming. These channel properties have impact on BER, which is used for evaluation of UMTS system. The orthogonality of sequences is influenced by multi access interference so detection of required signal (which uses correlation properties of spreading sequences) is limited.
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Active probes PMS in UMTS-TDD network
Doskočil, Ladislav ; Kejík, Petr (referee) ; Hanus, Stanislav (advisor)
This essay contains basic information about the UMTS system, teach-in with the programming language C++, succinct description of some technologies used by internet, specifically protocol TCP/IP, HTML and PHP language, which relate to this project. Included is also an introduction to databases systems and brief description SQL language and MySQL database system. The last part of this work describes the system design of the Active probes PMS for network monitoring and results of experimental measuring.
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T-Speed Test for UMTS System
Šmíd, Jan ; Kejík, Petr (referee) ; Hanus, Stanislav (advisor)
The thesis deals with adding new parts to program for measuring data rates in mobile communications. New program parts are used for analyzing web pages and HTTP protocol, recieving position data from GPS reciever and for creating automated measuring sequences.
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Uninterruptible power supply for Robotics
Kejík, Petr ; Ligocki, Adam (referee) ; Burian, František (advisor)
This Bachelor thesis deals with the design and construction of a DC power supply unit with the possibility of battery backup power. The device in intended as an uninterruptible power supply for robotic devices. Thanks to its modularity it can also be used to power other small appliances and it can be easily expanded with more functions. In the designed configuration, the device contains two identical output modules, which together provide four independent power outputs. The power output voltages are adjustable in the range of 3–20 V, with a maximum considered continues current of 6 A. Digital control of modules and monitoring of critical parameters is procured through two Atmel ATmega32U4 microcontrollers placed on separate main board. Configuration and communication with the device it self is done via a local user interface (display and keyboard) and USB port (virtual seriál interface). Main power supply is provided by means of an external commercial DC power source producing voltage in the range of 30–38 V. Backup operation is secured from a 24V lead-acid battery, which is also recharged in normal conditions
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Wireless data collection form engine control units
Procházka, Miroslav ; Kejík, Petr (referee) ; Prokopec, Jan (advisor)
This thesis deals with implementation of a wireless interface for a module providing communication between computer and electronic control unit of an automobile. The 802.11 standard, wireless network structures and MAC sublayer were described. The thesis suggests selection of the most suitable WLAN module, testing of module's features used and the WLAN module implementation. Modifications for the next device version were developed and programs for device operation were implemented.
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Automatic Detection of a Vessel Mooring at an Anchor Buoy in LPWAN Networks
Kejík, Petr ; Klusáček, Stanislav (referee) ; Kopečný, Lukáš (advisor)
This Master’s thesis deals with the design and construction of a maintenance-free unit for the detection of vessel mooring to an anchor buoy. The unit is powered by a battery with the possibility of running from another alternative source of power, in this particular case a solar panel. For wireless communication, the unit uses LoRa and NB-IoT technologies working in the LPWAN networks. During the designing phase, emphasis is placed on aspects such as maintenance-free duty, minimal consumption and the possibility of mounting on any type of buoy. The thesis also deals with the mechanical design of the device and design of the prototype of the detection element. The work is created in a cooperation with Netlia IoT s.r.o., which mainly deals with the custom production of devices using smart sensors and LPWAN communication technologies.
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Uninterruptible power supply for Robotics
Kejík, Petr ; Ligocki, Adam (referee) ; Burian, František (advisor)
This Bachelor thesis deals with the design and construction of a DC power supply unit with the possibility of battery backup power. The device in intended as an uninterruptible power supply for robotic devices. Thanks to its modularity it can also be used to power other small appliances and it can be easily expanded with more functions. In the designed configuration, the device contains two identical output modules, which together provide four independent power outputs. The power output voltages are adjustable in the range of 3–20 V, with a maximum considered continues current of 6 A. Digital control of modules and monitoring of critical parameters is procured through two Atmel ATmega32U4 microcontrollers placed on separate main board. Configuration and communication with the device it self is done via a local user interface (display and keyboard) and USB port (virtual seriál interface). Main power supply is provided by means of an external commercial DC power source producing voltage in the range of 30–38 V. Backup operation is secured from a 24V lead-acid battery, which is also recharged in normal conditions
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