Global ETD Search

11	Stanovení charakteristik cyklostacionárního detektoru signálu OFDM. / Assignment of the OFDM signal cyclostationary detector behaviour. Lehocký, Jiří January 2012 (has links) Master’s thesis belongs to the Cognitive radio network sphere. These networks utilize frequency spectrum more effectively than networks used in present radio communications. The Cognitive radio concept makes coexistence of classic and cognitive radio networks possible. Attention is aimed at spectrum sensing as the key task of the Cognitive radio. Main properties of the cyclostationary detector, as the detector, that reaches high probability of the detection at a very low signal to noise ratio with apriori knowledge of the transmitted signal's cyclic frequency, are examined in this paper. The OFDM signals, that inherit cyclostationarity from cyclic prefix, used in the real systems have been chosen for testing the properties of the detector. The influences of decimation and multipath propagation on the probability of detection are quantitatively expressed. The optimal values for the weights of the multicycle detector are determined.
12	Analýza přenosu mobilního digitálního rozhlasového vysílání / Analysis of the transmission in the mobile digital audio broadcasting Kresta, Daniel January 2016 (has links) This thesis deals with an analysis of a system called Digital Audio Broadcast and describes its mathematical model created in MATLAB program. In the first part basic blocks of a transmitter and a receiver are analyzed along with their principles. Then different types of transmission channels for static, portable and mobile receivers are described. The second part contains description of the DAB mathematical model itself. Individual blocks are described in the order of the DAB signal path, from the transmitter through the transmission channel to the receiver side. In this part the graphical user interface is also described. In the final part the results of experimental measurements and simulations are presented.
13	Indoor 5G Positioning using Multipath Measurements Lidström, Andreas, Andersson, Martin January 2022 (has links) Positioning with high precision and reliability is considered as an important feature of new wireless radio networks such as 5G. In areas where satellite positioning is not available or is not reliable enough, 5G can work as an alternative. An example is inside factories where autonomous vehicles might need to be positioned in complex environments. This work aims to investigate if multipath propagation of radio signals can be exploited to improve indoor positioning. A 5G simulator that simulates the propagation of a reference signal in a factory environment is used. Distances corresponding to several paths between the user equipment (UE) and the transmission/reception point (TRP) can be estimated given the received reference signal. These distance estimates are used together with a partially known map of the environment to develop and evaluate the algorithms in this thesis. The developed multipath-assisted algorithms are based on two different target tracking methods, an extended Kalman filter (EKF) and a particle filter (PF). Both alternatives use a data association algorithm to determine how measurements should be paired with propagation paths. Both filters that exploit multipath propagation are shown to greatly improve positioning accuracy compared to a line-of-sight (LOS) based alternative. The multipath-assisted algorithms can achieve an accuracy below 0.9 m in 90 % of all cases in a complex environment, which is more than tenfold better than the LOS based alternative considered here. The PF also shows an ability to track a UE in a complex environment using very few TRPs, while the EKF and LOS based methods do not succeed in this case. / Positionering med hög precision och tillförlitlighet anses vara en viktigt funktion i nya trådlösa radionätverk som 5G. I områden där satellitpositionering inte är tillgängligt eller inte är tillräckligt pålitligt, kan 5G fungera som ett alternativ. Ett exempel är inuti fabriker där autonoma fordon kan behöva positionera sig i komplexa miljöer. Det här arbetet syftar till att undersöka om flervägsutbredning av radiosignaler kan utnyttjas för att förbättra positionering i inomhusmiljöer. En 5G-simulator som simulerar utbredningen av en referenssignal i en fabriksmiljö används. Avstånden för flertalet vägar från användarenheten till basstationen kan estimeras givet den mottagna referenssignalen. Dessa avståndsestimat används tillsammans med en delvis känd karta av miljön för att utveckla och utvärdera algoritmer i det här arbetet. De utvecklade flervägsutbredningsassisterade algoritmerna baseras på två olika målföljningsmetoder, ett utökat Kalmanfilter och ett partikelfilter. Båda alternativen använder en associeringsalgoritm för att bestämma hur avståndsmätningar ska paras ihop med utbredningsvägar. De två filtren som studeras i detta arbete ger en stor förbättring av positioneringen jämfört med ett alternativ som inte använder flervägsutbredning. De flervägsutbredningsassisterade algoritmerna uppnår en precision på under 0,9 m i 90 % av fallen i en komplex miljö, vilket är mer än tio gånger bättre än alternativet utan flervägsutbredning. Partikelfiltret visar också en förmåga till positionering med väldigt få basstationer, vilket de andra metoderna inte klarar av i den komplexa miljön. Multipath Propagation 5G Networks Target Tracking Sensor Fusion Positioning Particle Filter Kalman Filter Signal Processing Signalbehandling Control Engineering Reglerteknik Communication Systems Kommunikationssystem
14	Evaluation of Bluetooth 5.1 as an Indoor Positioning System / Utvärdering av Bluetooth 5.1 som ettInomhus Lokaliserings System Andersson, Philip, Persson, Linus January 2020 (has links) There is a high demand for Indoor Positioning Systems (IPS) due to the wide application possibilities. The main issue for localization by wireless signals in an indoor environment is the multipath propagation problem. Multipath propagation occurs when signals reflects and refract from an object, changing the signals characteristics. Today there is no IPS that can balance the cost, accuracy, and complexity. In January 2019 Bluetooth released a new standard, Bluetooth Low Energy (BLE) 5.1, which enables the ability to measure the Angle of Arrival (AoA) of an incoming signal. The purpose of this thesis is to mitigate the disturbances caused by multipath propagation by conducting a case study. This was done by designing systems that combine different positioning techniques with sensor fusion and evaluating them based on power efficiency, execution time and precision. Two wireless localization techniques were evaluated, trilateration and triangulation, which are based on Received Signal Strength Indication (RSSI) and AoA respectively, along with an Inertial Measurement Unit (IMU). An Extended Kalman Filter EKF was used to fuse the sensor data. The system with the best overall performance uses the AoA signals and a multipath mitigation technique. The system with AoA and IMU had a similar performance but has an overall higher complexity due to the added IMU component. The RSSI system could not satisfy the requirement of precision. / Det finns en stor efterfrågan på inomhus positionssystem (IPS) tack vare de många möjliga tillämpningarna. Det största problemet för inomhuslokalisering med trådlösa signaler i inomhusmiljö är flervägsutbredningsproblemet. Felvägsutbredning inträffar när signaler reflekterar och bryts på ett objekt, och ändrar dess karaktär. Idag finns det inga IPS som kan balansera kostnaden, noggrannhetoch komplexitet. I januari 2019, släppte Bluetooth en ny standard, Bluetooth Low Energy (BLE) 5.1, som gör det möjligt att mäta ankomstvinkeln (AoA) för en inkommande signal. Syftet med denna avhandling är att minska störningarna orsakade av flervägsutbredning genom att utföra en fallstudie. Detta gjordes genom att designa system som kombinerar olika positioneringstekniker med sensor fusion och utvärdera dessa med avseende på energieffektivitet, exekveringstid och precision. Två trådlösa lokaliseringstekniker utvärderades, trilaterering och triangulering, som är baserade på mottagen signalstyrka indikation RSSI och AoA respektive, tillsammans med en tröghetssensor (IMU). Ett Utökat Kalman-Filter (EKF) användes för att kombinera data. Systemet med den överlag bästa prestandan använder AoA-signaler och en teknik för att dämpa flervägsutredningen. Systemet med AoA och IMU hade liknande prestanda men den totala komplexiteten ökade med att lägga till en IMU komponent. RSSI systemet var inte tillräckligt tillfredsställande med avseende på precisionskraven. Indoor Positioning System AoA RSSI IMU Sensor Fusion Multipath Propagation Inomhus positioneringssystem AoA RSSI IMU Sensor Fusion Flervägsutbredning Engineering and Technology Teknik och teknologier
15	Odhad parametrů přenosového kanálu pro systémy CDMA / Channel estimation in CDMA systems Kadlec, Petr January 2009 (has links) 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.
16	Simulace vícecestného šíření vícestavových modulací / Simulation of multipah propagation of multistate modulations Polák, Ladislav January 2009 (has links) The diploma thesis Simulation of Multipath Propagation of Multistate Modulations is focused on the development of an appropriate algorithm in MATLAB environment, which is capable to simulate the impact of the multipath propagation on received signal (error rate) on the basis of given parameters of the transmission channels. Mechanisms and characteristics of the wave propagation in communication environment, types of digital modulations and their most important parameters are described in the first part of this thesis. The second part is focused on the simulation itself. Created GUI (Graphical User Interface) is able to display constellation diagrams of transmitted and received signals, as well as their bit error rate. It is also possible to compare these data with the data of signal, which is passed by a non-fading channel.
17	Channel Probing for an Indoor Wireless Communications Channel Hunter, Brandon 13 March 2003 (has links) (PDF) The statistics of the amplitude, time and angle of arrival of multipaths in an indoor environment are all necessary components of multipath models used to simulate the performance of spatial diversity in receive antenna configurations. The model presented by Saleh and Valenzuela, was added to by Spencer et. al., and included all three of these parameters for a 7 GHz channel. A system was built to measure these multipath parameters at 2.4 GHz for multiple locations in an indoor environment. Another system was built to measure the angle of transmission for a 6 GHz channel. The addition of this parameter allows spatial diversity at the transmitter along with the receiver to be simulated. The process of going from raw measurement data to discrete arrivals and then to clustered arrivals is analyzed. Many possible errors associated with discrete arrival processing are discussed along with possible solutions. Four clustering methods are compared and their relative strengths and weaknesses are pointed out. The effects that errors in the clustering process have on parameter estimation and model performance are also simulated. multipath multipath propagation propagation environment indoor propagation indoor multipath indoor multipath propagation channel probing channel probing indoor wireless communications channel indoor wireless communications indoor wireless communications wireless communications wireless communications channel MIMO SISO multiple input multiple output single input single output antenna diversity antenna diversity antenna array channel modeling modeling model wireless propagation clustering methods clustering algorithms clustering parameter estimation parameter channel matrix h matrix ray tracing point spread function psf deconvolution clean algorithm clean algorithm antenna pattern network analyzer temporal pattern 2.4 ghz system 6 ghz system channel capacity capacity estimate channel capacity estimate propagation environment scattering transfer matrix matrix water filling solution water filling method water filling Saleh Valenzuela Saleh and Valenzuela Model arrival time of arrival angle of arrival direction of arrival arrival amplitude arrivals antenna positioner data simulations measurements angle of departure direction of departure correlation convolution errors error CFA CFAD constant false alarm constant false alarm detection signal signal dependent clutter clutter returns transmitter transmit receive receiver transmit antenna receive antenna spatial correlation system PSF system point spread function mapping fuzzy c-means clustering fuzzy clustering c-means clustering c-means fuzzy k-means euclidean distance time amplitude delay performance prediction performance prediction errors fuzzy weighted distance method rectangular method weighted rectangular method statistics statistical statistical model Electrical and Computer Engineering

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