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Perceptual Omnidirectional Image Quality: Subjective Ratings by Diverse User Aspects
Šimka, Marek ; Polak, Ladislav
This paper deals with an unconventional experiment of subjective quality assessment of omnidirectional images. Within the subjective tests with 36 volunteers, the study was carried out in terms of different aspects of each user. Based on the assessments of 100 images by each respondent, it offers a new source of results for further investigation and development of virtual reality (VR) content or quality of experience (QoE). It focuses on the subjective ratings of various types of users such as people using dioptric glasses, with VR experience, or users with vision impairments. The output is thus the results of the subjective scores, including an analysis of their correlations with several objective quality metrics. The initial results of this work suggest that, for example, subjects with corrected vision using dioptric glasses exhibit similar subjective perceptions of the quality of omnidirectional images as average respondents without visual impairment.
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Mapping and analyzing of signal coverage of 4G/5G mobile networks
Baránek, Michal ; Polák, Ladislav ; Kufa, Jan
This paper addresses the enhanced measurement of signal coverage, capacity, and reliability in mobile networks, particularly with the growing prevalence of 4G and 5G technologies. Given the escalating importance of these networks in everyday activities, there arises a demand for open-source solutions to evaluate and enhance their performance effectively. The objective of this research is to analyze gathered data to pinpoint areas necessitating network enhancements and to develop opensource software and hardware solutions for extracting essential performance metrics (KPIs) from 4G/5G networks. The proposed system offers an interface for assessing network performance and signal coverage, enabling cost-efficient measurements across diverse environments.
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Measurement of the DVB-T2-based MISO Signal influenced by I/Q-errors in the OFDM Modulator
Buchta, Simon ; Polák, Ladislav
The Second Generation Digital Video Broadcasting Terrestrial (DVB-T2) system stands out as the most advanced system among the second generation DVB standards. Among others, it supports the multiple-input single-output (MISO) transmission technique to enhance terrestrial TV broadcasting. This paper focuses on a performance study of the DVB-T2 system utilizing the MISO technique for various fixed transmission scenarios, which are modeled by different transmission channel models. Additionally, it considers imperfections of the transmitter, due to errors in the Orthogonal Frequency-Division Multiplexing (OFDM) modulator. To facilitate this study, a laboratory measurement workstation with an appropriate measurement methodology is established. The proposed concept enables the interchangeability of measurement equipment and set-top-boxes (STBs).
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Laboratory exam for visual quality analysis of compressed images
Sedlák, Ondřej ; Kufa, Jan (referee) ; Polák, Ladislav (advisor)
This bachelor's thesis deals with the evaluation of the visual quality of compressed still images. The theoretical part provides an overview of current standards for image compression and describes methods for evaluating the quality of a compressed image. Compression algorithms are categorized by method and the key formats that will be used in the experimental section are highlighted. Emphasis is also placed on objective and subjective evaluation methods, providing a robust framework for evaluating the performance of compression codecs. The practical part focuses on the application of selected compression and quality assessment methodologies, comparison of individual results and proposal of a procedure for the processing of a laboratory task.
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Stereo ADC and DAC converter for audio
Koiš, Christopher ; Polák, Ladislav (referee) ; Kratochvíl, Tomáš (advisor)
This bachelor's thesis deals with the problem of designing a programmable digital sound processor with its input connected to a device, such as a personal computer or a mobile phone, and an output intended for headphones. One segment of this thesis handles digital filters, specifically FIR and IIR filters. The MATLAB environment was used to design the filters shown in this thesis. Furthermore, the buses SPI, I2C and I2S that are used on the device are described. The parameters of individual functional blocks are summarized, and the designed circuit schematic are displayed in this thesis. In the practical part of this thesis a prototype printed ciruit board was designed and its' electrical parameters were measured and processed. Finally, the last part of this thesis describes the inner workings of the program that the microcontroller executes.
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Measurement of the SISO/MISO Signal in the DVB-T2 System
Buchta, Šimon ; Kratochvíl, Tomáš (referee) ; Polák, Ladislav (advisor)
Tato bakalářská práce je zaměřena na měření a analýzu televizního signálu druhé generace digitálního pozemního vysílání (DVB-T2), zahrnujíc různé přenosové techniky a chyby, jež mohou vznikat v tzv. OFDM modulátoru. Pro tento účel bylo navrženo a zrealizováno měřící pracoviště. První část práce je věnována zkoumání a následnému zhodnocení výsledků měření reálného DVB-T2 signálu vysílaného v České republice. Druhá část této práce se zaměřuje na měření signálu DVB-T2 s odlišnou konfigurací, na příklad užití MISO přenosové techniky a přídání vlivu chyb v OFDM modulátoru a výkonového nevyvážení mezi vysílači. Tyto konfigurace jsou zkoumány v různých kanálových modelech pro fixní a mobilní příjem. Získané výsledky jsou zkoumány nejen z pohledu konvenčních objektivních parametrů (MER, BER), ale také z pohledu použitých měřících přístrojů a přijímačů (set-top-boxů).
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Programmable attenuator for laboratory measurement
Husslik, Tomáš ; Šimka, Marek (referee) ; Polák, Ladislav (advisor)
This thesis deals with the design of a programmable attenuator with digital control. The main objective of the work is to design and create an attenuator with a nominal impedance of 50 , providing adjustable attenuation in the range of 0 to 40 dB, functioning within a bandwidth of 1 to 2 500 MHz. Control of the proposed attenuator is facilitated by a microcontroller that manages the settings of an integrated circuit attenuator. Furthermore, the attenuator features a basic user interface. A PCB was designed for the attenuator and subsequently manufactured. The device was then assembled and its key parameters were measured.
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Testing the response of operating systems to different IPv6 flows
Ruiner, Michal ; Polák, Ladislav (referee) ; Jeřábek, Jan (advisor)
The aim of the thesis is to create an array of virtual machines and research their response to the IPv6 protocol. Another significant part is to utilize the provided tool for generating and sniffing IPv6 traffic and verify its correct functionality. For such purpose, the GNS3 open-source software is selected. A~reader is familiarized with the concepts of virtualization, GNS3 functionality and various methods of software testing together with the implemented practical models. The IPv6 protocol is introduced in detail as well as the packet format, address types and several IPv6 protocols useful for the thesis. The practical part is discussed in the Numerical results chapter. The topology is established and connectivity verified using IPv4. Configuration of static IPv6 addresses is performed on the devices as well as configuration of router to distribute particular prefixes. 5 testing scenarios are proposed that increase the input load to the tool in sense of higher number of addresses for the 3 different modes - passive, active and aggressive. 3 scripts were developed. Performance testing script measures utilization of computational resources. The other 2 scripts perform packet capturing and further analysis to compare the results of proposed scripts with provided tool. The comparison is done utilizing passive and aggressive modes. Active mode is used to observe the response of various operating systems to different IPv6 flows. Specifically, multiple Windows 10 builds, Linux distributions, Windows XP, 7, 11, macOS and Android.
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AI-based classification of RF signals
Turák, Samuel ; Ulovec, Karel (referee) ; Polák, Ladislav (advisor)
Táto práca sa zameriava na klasifikáciu rádiofrekvenčných (RF) signálov založenú na hlbokom učení. Pre tento účeľ, tri neuronové siete sú vybrané a prezentované: Konvolučná Neurónová Sieť (CNN), Sieť s Bránovými Rekurentnými Jednotkami (GRU), Konvolučná Hlboká Neurónová Sieť s Bránami (CGDNN). Všetky sú trénované a vyhodnotené na viacerých datasetoch, ovplyvnené rôznymi RF rušeniami, pre klasifikáciu rôznych bezdrátových štandardov. Signály v jednotlivých datasetoch boli vytvorené pomocou aplikácie Wireless Waveform Generator v programu MATLAB. Jeden verejne dostupný dataset na klasifikáciu modulácie je takisto testovaný na modeloch. Použité prístupy k predspracovaniu dát, tréningu modelov a vyhodnoteniu modelov sú implementované v programovacom prostredí Python s využitím knižníc ako Scikit-learn a Keras. \mbox{Získané výsledky} sú prehľadne prezentované a diskutované.
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Mapping and analyzing signal coverage in 4G/5G mobile networks
Baránek, Michal ; Jeřábek, Jan (referee) ; Polák, Ladislav (advisor)
Tato práce se zabývá s pokročilým měřením kapacity a spolehlivosti v mobilních sítích, zejména s rozšířeným přijetím technologií 4G a 5G. Vzhledem k tomu, že se tyto sítě stávají stále více nedílnou součástí každodenního života, existuje potřeba efektivních řešení pro hodnocení a optimalizaci jejich výkonu. Primárním cílem této práce je vyvinout cenově dostupná softwarová a hardwarová řešení schopná extrahovat základní klíčové ukazatele výkonu (KPI) z mobilních sítí 4G/5G. Navrhovaný systém si klade za cíl poskytnout uživatelům přístupný nástroj pro hodnocení výkonu sítě, pokrytí signálem v konkrétních oblastech a prediktivní modely pro budoucí kapacitu sítě. Tyto funkce jsou prezentovány prostřednictvím uživatelsky přívětivého grafického rozhraní (tzv. GUI), které umožňuje přímočará a cenově výhodná měření ve venkovním i vnitřním prostředí.
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