Modeling of transitions in received power for an urban V2I scenario. - In: Focus on linking antennas and propagation with the automotive and 5G industries, (2021), insges. 5 S.
In this contribution, we investigate how changes in received power for a vehicle to infrastructure (V2I) communication scenario in an urban environment can be modeled. Significant changes are not only observed for line of sight (LoS) to none line of sight (NLoS) transitions but also when the mobile station travels from a narrow street onto a crossroad and other maneuvers, even with no LoS being present. To model these transitions, in terms of received power, we propose a variant of an arctangent function. We fit the model to different exemplary transitions, which were found in channel sounding data collected in a V2I measurement campaign. We discuss the results in terms of quality of fit and the estimated parameters.
https://doi.org/10.23919/EuCAP51087.2021.9411370
Advances on the detection of landmines and IEDs in Colombia using UWB GPR and machine learning techniques. - In: Focus on linking antennas and propagation with the automotive and 5G industries, (2021), insges. 4 S.
In this paper we present the latest results of a research program on the use of ground penetrating radar and machine learning-based algorithms for humanitarian demining in Colombia. We describe the experimental setup developed, which includes a polarimetric GPR-UWB unit, a radar positioning system, and a control unit. We describe as well a soil characterization campaign and an IED classification technique based on Support Vector Machine.
https://doi.org/10.23919/EuCAP51087.2021.9411214
Cost-effective measurement methods to investigate RF leakages in UHF RFID e-Kanban racks. - In: Focus on linking antennas and propagation with the automotive and 5G industries, (2021), insges. 4 S.
In this paper, we present cost-effective techniques to assess shielding performance of RFID Kanban racks equipped with UHF RFID readers. This includes a self-developed positioner, made from roof battens and stepper motors, which positions a tag in a vertical area around each side of the rack to sense the radio frequency (RF) distribution emitted from the reader. For the measurements on the shelves, we sticked 30 tags on a foam board in a 20 cm grid to detect leakages on the horizontal planes. The overall material cost is less than 50 € and we made the documentation and control software publicly available.
https://doi.org/10.23919/EuCAP51087.2021.9411416
Wave-physical factors determining the link quality in ITS-G5 studied with field-operational tests. - In: Focus on linking antennas and propagation with the automotive and 5G industries, (2021), insges. 5 S.
Even though vehicular communication systems have been rolled out in road, they remain a prominent field of research and development. The functional and operational safety of vehicle-to-X system demands reliable and efficient methods for verification and validation, based on their functional principles and underlying wave-physical phenomena. To test such systems in virtual environment, we have undertaken empirical studies of the communication channel, to analyze parameters like distance and sight conditions in a rich multipath environment. This paper describes the results and conclusions derived from a set of field-operational tests along a track, with modules operating with ITS-G5. While the results confirm the expectation that field-operational tests aren't reproducible on a quantitative level, we have gained insight into fundamental constraints on the channel parameters and approaches towards emulation in virtual environment. Employing omni-directional roof-mounted antennas, we have observed reliable communication links for ranges up to 250 meters, independent of sight conditions.
https://doi.org/10.23919/EuCAP51087.2021.9411275
Characterization of slow and fast fading in V2I channels for smart cities. - In: Focus on linking antennas and propagation with the automotive and 5G industries, (2021), insges. 5 S.
A vehicle to X (V2X) propagation channel corresponds to a wideband channel that means a receiver (Rx) able to resolve multipath components. In contrast to a narrow band channel, multipath components are indistinguishable at the receiver and seen as a single composite signal, thus fading approximation has been assumed as the Rayleigh fading. It is interesting to see how the fading is characterized in V2X applications because the channel corresponds to the wideband and it can not be assumed to follow wide sense stationary uncorrelated scattering (WSSUS) assumption due to inherent mobility. The aim of this paper is to characterize and study slow fading and fast fading variations of each tap, which is selected from measurement data. This investigation pertains to three various scenarios, which are omnidirectional antenna, two antennas faced directly to each other and two antennas faced away from each other. In each scenario, LOS and two different NLOS categories are studied.
https://doi.org/10.23919/EuCAP51087.2021.9411001
Projection-OTA, over-the-air testing by reconfigurable reflecting structures. - In: Focus on linking antennas and propagation with the automotive and 5G industries, (2021), insges. 5 S.
The bottleneck in OTA testing electrically large equipment is the large number of sources required for sufficient angular density. That is, if the sources are active. In that case, high-bandwidth, high-frequency equipment with excellent stability, processing power, and configurability is needed per antenna element. The costs of scaling up the current MIMO OTA configuration to higher frequencies and/or large equipment is prohibitive. In case passive radiators are used, the maximum control speed is determined by the maximum expected Doppler frequency. Such performance is order of magnitudes cheaper, even for large numbers of elements. In this contribution, we will present a new OTA concept that uses passively radiating reconfigurable structures and is inherently bi-directional. The concept that we call Projection-OTA, accommodates test objects in FR1 that are electrically large to very large and shows good prospects for emulating beam dynamics for testing 5G NR in FR2. Whether such passive structures will be made up by reflect arrays, meta-surfaces, or even intelligent surfaces is to be determined. We will discuss the prospects and limitations of this concept.
https://doi.org/10.23919/EuCAP51087.2021.9411326
Joint communication and radar sensing: an overview. - In: Focus on linking antennas and propagation with the automotive and 5G industries, (2021), insges. 5 S.
This paper provides an overview of recent developments in Joint Communication and Radar Sensing (JCRS) systems and networks. Our discussion will focus on radio system and network architectures that can be used for JCRS and on approaches to select, generate and process waveforms suitable for both communication and sensing. In addition, advantages and challenges of assembling a network out of several JCRS nodes are addressed. Finally, we give an outlook to possible applications of JCRS networks, which we see in autonomous driving and low altitude air traffic control.
https://doi.org/10.23919/EuCAP51087.2021.9411178
Realistic emulation of GNSS testing scenarios using 3D wave field synthesis in an OTA testbed. - In: Focus on linking antennas and propagation with the automotive and 5G industries, (2021), insges. 5 S.
While traditional testing methods as conducted and open field tests have their limitations in terms of realism and repeatability of the scenario's conditions, Over-the-Air (OTA) testing enhances the way that GNSS and mobile communications systems with integrated antennas are tested, since it provides the freedom to accurately emulate an impinging wave with arbitrary polarization and direction radiated from any source/reflection such as GNSS satellites and terrestrial base stations. Therefore, real world scenarios can be precisely reproduced with total control of the environment's conditions. In this context, this paper describes the process to implement full polarimetric 3D Wave Field Synthesis (WFS) in an OTA testbed, from the principle to characterize the electromagnetic (EM) field in three dimensions to the system calibration and correspondent verification measurements inside the anechoic chamber, which will provide a deeper insight on the quality and reliability of the EM field for testing purposes.
https://doi.org/10.23919/EuCAP51087.2021.9411259
TRICE: a channel estimation framework for RIS-aided millimeter-wave MIMO systems. - In: IEEE signal processing letters, ISSN 1558-2361, Bd. 28 (2021), S. 513-517
We consider the channel estimation problem in point-to-point reconfigurable intelligent surface (RIS)-aided millimeter-wave (mmWave) MIMO systems. By exploiting the low-rank nature of mmWave channels in the angular domains, we propose a non-iterative Two-stage RIS-aided Channel Estimation (TRICE) framework, where every stage is formulated as a multidimensional direction-of-arrival (DOA) estimation problem. As a result, our TRICE framework is very general in the sense that any efficient multidimensional DOA estimation solution can be readily used in every stage to estimate the associated channel parameters. Numerical results show that the TRICE framework has a lower training overhead and a lower computational complexity, as compared to benchmark solutions.
https://doi.org/10.1109/LSP.2021.3059363
Erklärbarkeit und Transparenz maschineller Entscheidungsprozesse zur Performancesteigerung bildbasierter Inspektionsprozesse im automatisierten Faserverbundleichtbau. - Ilmenau. - 136 Seiten
Technische Universität Ilmenau, Bachelorarbeit 2021
Der Einsatz von automatisierten Faserlegeprozessen in der Luft- und Raumfahrtindustrie hat in den letzten Jahren stark zugenommen. Prominente Anwendungsbeispiele für die automatisierte Fertigung von großflächigen Bauteilen aus Kohlefaserverbundswerkstoffen sind der A380 oder die B787. Dabei wird in der Qualitätssicherung zunehmend auch maschinelles Lernen in bildbasierten Inspektionsprozessen eingesetzt, um Herstellungskosten und Fertigungsdauer zu verringern. Ein solches Qualitätssicherungssystem (QSS) ist in der Großbauteile in Fiber Placement Technologie-Forschungsplattform des Deutschen Zentrums für Luft- und Raumfahrt realisiert, an der der automatisierte Faserverbundleichtbau und bildbasierte Inspektionsprozess in großem Maßstab erforscht wird. Transparenz des Inspektionsprozesses und Vertrauen in das QSS sind grundlegende Voraussetzungen für dessen Verwendung. Um das Verhalten des maschinellen Lernens in der Anwendung nachvollziehbar zu gestalten, ist auf dem Gebiet der Explainable Artificial Intelligence eine Vielzahl neuer Verfahren hervorgebracht worden. In dieser Bachelorarbeit sind solche Erklärbarkeitsverfahren für eine Support Vector Machine und ein Convolutional Neural Network am Beispiel von Höhenprofilscans von typischen Faserlegefehlern aus dem Faserlegeprozess betrachtet worden. Dahingehend ist eine umfassende Literaturrecherche durchgeführt worden. Anhand von Kriterien aus der Literatur ist eine Auswahl für den Anwendungsfall geeigneter dekompositorische und pädagogische Erklärbarkeitsverfahren herausgearbeitet worden. Zur Untersuchung der Erklärbarkeit einer SVM ist zuerst ein für die vorliegenden Bilddaten geeigneter Merkmalsraum ermittelt worden. Anschließend ist die Eignung der Erklärbarkeitsverfahren empirisch validiert worden. Zudem sind die Erklärbarkeitsverfahren vor dem Hintergrund der Performancesteigerung und der Steigerung der Transparenz des QSS untersucht worden. Es konnte eine algorithmische Transparenz der SVM für vier der sechs Klassen mit dem pädagogischen Verfahren TREPAN hergestellt werden, während das dekompositorische Verfahren RulExSVM durch ungenügende Treue gegenüber der SVM als ungeeignet bewertet wurde. Die Erklärungen der Verfahren smooth Integrated Gradients, Guided Grad-CAM und DeepSHAP beinhalten Information über zur Klassifikation wichtige Bildpunkte. Sie erlauben damit Schlussfolgerungen über das Verhalten des CNNs. Es wurden zudem in Versuchen potenzielle systematische Unzulänglichkeiten des untersuchten CNNs identifiziert.