975 research outputs found
Indoor wireless communications and applications
Chapter 3 addresses challenges in radio link and system design in indoor scenarios. Given the fact that most human activities take place in indoor environments, the need for supporting ubiquitous indoor data connectivity and location/tracking service becomes even more important than in the previous decades. Specific technical challenges addressed in this section are(i), modelling complex indoor radio channels for effective antenna deployment, (ii), potential of millimeter-wave (mm-wave) radios for supporting higher data rates, and (iii), feasible indoor localisation and tracking techniques, which are summarised in three dedicated sections of this chapter
Time domain analysis of partial discharges envelope in medium voltage XLPE cables
Partial discharge (PD) analysis has been widely used to detect premature degradation of power cables. Although there are recognized techniques for PD analysis, there is still lack of knowledge about measuring and modeling this phenomenon.
This paper proposes a new model based on time domain parameters of the PD signal envelope. The proposed variables (time duration, and rising and falling slopes of the envelopes), together with conventional PD analyses focused on PD amplitude and phase resolved patterns, will provide a better understanding of this phenomenon. Based on this model, a new technique to reshape the PD signal envelope is also proposed that compensates the negative effect of dispersion in the location techniques that estimate the time of arrival (TOA).
Experimental results were obtained in the lab, where a power cable has been artificially damaged in order to produce PD. To this end, a specific PD on-line acquisition system has been developed. In the first set of experiments, we illustrate how the cable attenuates and disperses the PD signal envelope. In the second one, we show how the proposed variables are useful to distinguish among different types of PD sources. Finally, an accurate estimation of the PD source location is achieved by measuring the time of arrival of the PD signal envelopes at both cable ends, and reshaping one of the signals captured. This technique improves the accuracy of the estimated location of the PD sources, both in simulation and in experimental results
Spatial Identification Methods and Systems for RFID Tags
DisertaÄnĂ prĂĄce je zamÄĆena na metody a systĂ©my pro mÄĆenĂ vzdĂĄlenosti a lokalizaci RFID tagĆŻ pracujĂcĂch v pĂĄsmu UHF. Ăvod je vÄnovĂĄn popisu souÄasnĂ©ho stavu vÄdeckĂ©ho poznĂĄnĂ v oblasti RFID prostorovĂ© identifikace a struÄnĂ©mu shrnutĂ problematiky modelovĂĄnĂ a nĂĄvrhu prototypĆŻ tÄchto systĂ©mĆŻ. Po specifikaci cĂlĆŻ disertace pokraÄuje prĂĄce popisem teorie modelovĂĄnĂ degenerovanĂ©ho kanĂĄlu pro RFID komunikaci. DetailnÄ jsou rozebrĂĄny metody mÄĆenĂ vzdĂĄlenosti a odhadu smÄru pĆĂchodu signĂĄlu zaloĆŸenĂ© na zpracovĂĄnĂ fĂĄzovĂ© informace. Pro ĂșÄely lokalizace je navrĆŸeno nÄkolik scĂ©nĂĄĆĆŻ rozmĂstÄnĂ antĂ©n. Modely degenerovanĂ©ho kanĂĄlu jsou simulovĂĄny v systĂ©mu MATLAB. VĂœznamnĂĄ ÄĂĄst tĂ©to prĂĄce je vÄnovĂĄna konceptu softwarovÄ definovanĂ©ho rĂĄdia (SDR) a specifikĆŻm jeho adaptace na UHF RFID, kterĂĄ vyuĆŸitĂ bÄĆŸnĂœch SDR systĂ©mĆŻ znaÄnÄ omezujĂ. DiskutovĂĄna je zejmĂ©na problematika prĆŻniku nosnĂ© vysĂlaÄe do pĆijĂmacĂ cesty a poĆŸadavky na signĂĄl lokĂĄlnĂho oscilĂĄtoru pouĆŸĂvanĂœ pro smÄĆĄovĂĄnĂ. PrezentovĂĄny jsou tĆi vyvinutĂ© prototypy: experimentĂĄlnĂ dotazovaÄ EXIN-1, mÄĆicĂ systĂ©m zaloĆŸenĂœ na platformÄ Ettus USRP a antĂ©nnĂ pĆepĂnacĂ matice pro emulaci SIMO systĂ©mu. ZĂĄvÄreÄnĂĄ ÄĂĄst je zamÄĆena na testovĂĄnĂ a zhodnocenĂ popisovanĂœch lokalizaÄnĂch technik, zaloĆŸenĂœch na mÄĆenĂ komplexnĂ pĆenosovĂ© funkce RFID kanĂĄlu. Popisuje ĂșzkopĂĄsmovĂ©/ĆĄirokopĂĄsmovĂ© mÄĆenĂ vzdĂĄlenosti a metody odhadu smÄru signĂĄlu. Oba navrĆŸenĂ© scĂ©nĂĄĆe rozmĂstÄnĂ antĂ©n jsou v zĂĄvÄru ovÄĆeny lokalizaÄnĂm mÄĆenĂm v reĂĄlnĂœch podmĂnkĂĄch.The doctoral thesis is focused on methods and systems for ranging and localization of RFID tags operating in the UHF band. It begins with a description of the state of the art in the field of RFID positioning with short extension to the area of modeling and prototyping of such systems. After a brief specification of dissertation objectives, the thesis overviews the theory of degenerate channel modeling for RFID communication. Details are given about phase-based ranging and direction of arrival finding methods. Several antenna placement scenarios are proposed for localization purposes. The degenerate channel models are simulated in MATLAB. A significant part of the thesis is devoted to software defined radio (SDR) concept and its adaptation for UHF RFID operation, as it has its specialties which make the usage of standard SDR test equipment very disputable. Transmit carrier leakage into receiver path and requirements on local oscillator signals for mixing are discussed. The development of three experimental prototypes is also presented there: experimental interrogator EXIN-1, measurement system based on Ettus USRP platform, and antenna switching matrix for an emulation of SIMO system. The final part is focused on testing and evaluation of described positioning techniques based on complex backscatter channel transfer function measurement. Both narrowband/wideband ranging and direction of arrival methods are validated. Finally, both proposed antenna placement scenarios are evaluated with real-world measurements.
A Hybrid Indoor Location Positioning System
Indoor location positioning techniques have experienced impressive growth in recent years. A wide range of indoor positioning algorithms has been developed for various applications. In this work a practical indoor location positioning technique is presented which utilizes off-the-shelf smartphones and low-cost Bluetooth Low Energy (BLE) nodes without any further infrastructure. The method includes coarse and fine modes of location positioning. In the coarse mode, the received signal strength (RSS) of the BLE nodes is used for location estimation while in the fine acoustic signals are utilized for accurate positioning. The system can achieve centimeter-level positioning accuracy in its fine mode. To enhance the systemâs performance in noisy environments, two digital signal processing (DSP) algorithms of (a) band-pass filtering with audio pattern recognition and (b) linear frequency modulated chirp signal with matched filter are implemented. To increase the systemâs robustness in dense multipath environments, a method using data clustering with sliding window is employed. The received signal strength of BLE nodes is used as an auxiliary positioning method to identify the non-line-of-sight (NLoS) propagation paths in the acoustic positioning mode. Experimental measurement results in an indoor area of 10 m2 indicate that the positioning error falls below 6 cm
Realization Limits of Impulse-Radio UWB Indoor Localization Systems
In this work, the realization limits of an impulse-based Ultra-Wideband (UWB) localization system for indoor applications have been thoroughly investigated and verified by measurements. The analysis spans from the position calculation algorithms, through hardware realization and modeling, up to the localization experiments conducted in realistic scenarios. The main focus was put on identification and characterization of limiting factors as well as developing methods to overcome them
Communication Subsystems for Emerging Wireless Technologies
The paper describes a multi-disciplinary design of modern communication systems. The design starts with the analysis of a system in order to define requirements on its individual components. The design exploits proper models of communication channels to adapt the systems to expected transmission conditions. Input filtering of signals both in the frequency domain and in the spatial domain is ensured by a properly designed antenna. Further signal processing (amplification and further filtering) is done by electronics circuits. Finally, signal processing techniques are applied to yield information about current properties of frequency spectrum and to distribute the transmission over free subcarrier channels
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