Enhancement of vision-based 3D reconstruction systems using radar for smart farming. - In: 2022 IEEE International Workshop on Metrology for Agriculture and Forestry, (2022), S. 155-159
Digital field recordings are central to most precision agriculture systems since they can replicate the physical environment and thus monitor the state of an entire field or individual plants. Using different sensors, such as cameras and radar, data can be collected from various domains. Through the combination of radio wave propagation and visible light phenomena, it is possible to enhance, e.g., the optical condition of a fruit with internal parameters such as the water content. This paper proposes a method to correct sensor errors to perform data fusion. As an example, we observe a watermelon with camera and radar sensors and present a system architecture for the visualization of both sensors. For this purpose, we constructed a handheld platform on which both sensors are mounted. In our report, the radar is analyzed in terms of systematic and stochastic errors to formulate an angle-dependent mapping function for error correction. It is successfully shown that camera and radar data are correctly assigned with a watermelon used as a target object, demonstrated by a 3D reconstruction. The proposed system shows promising results for sensor overlay, but radar data remain challenging to interpret.
https://doi.org/10.1109/MetroAgriFor55389.2022.9964699
Analysis of wireless radio channel measurement data using machine learning. - Ilmenau. - 75 Seiten
Technische Universität Ilmenau, Masterarbeit 2022
Die Erfassung und Bewertung der Eigenschaften des Funkkanals ist für die Entwicklung eines drahtlosen Kommunikationssystems unerlässlich. Die Merkmale, die den Kanal am genauesten charakterisieren können, werden durch die Verarbeitung durch die Verarbeitung von Daten aus Funkkanalmessungen ermittelt. Die nach der Verarbeitung generierten Parameter können je nach den Bedingungen in verschiedene Szenarien unterteilt werden. Um komplexere zugrundeliegende Muster zu finden, werden in dieser Arbeit auch unüberwachtes maschinelles Lernen auf Funkkanalmessdaten verwendet. Hier wird die Struktur mit Hilfe von RIMAX und large-scale Parameterdatensätzen untersucht. Zunächst wird die Kombination verschiedener Datenvorverarbeitungs- und Clustering-Techniken untersucht, und eine solche Kombination wird anhand der Bewertungsmetriken ausgewählt. Dann wird sie für beide Datensätze auf jede Messfahrt einzeln, auf eine Kombination von einigen Messfahrten und auf alle Messfahrten angewendet. Anschließend werden die Daten daraufhin untersucht, ob die ermittelten Muster mit einer bestimmten Umgebung übereinstimmen. Der Vergleich der Ergebnisse derselben Messfahrten ermöglicht es, die Auswirkungen der Verwendung verschiedener Datensätze zu untersuchen. In dieser Arbeit wurde festgestellt, dass die Muster des unüberwachten maschinellen Lernalgorithmus für einige Ergebnisse von der Umgebung beeinflusst wurden.
One-Dimensional Convolutional Neural Network for Detection and Mitigation of DDoS Attacks in SDN. - In: Machine learning for networking, (2022), S. 11-28
In Software-Defined Networking (SDN), the controller plane is an essential component in managing network traffic because of its global knowledge of the network and its management applications. However, an attacker might attempt to direct malicious traffic towards the controller, paralyzing the entire network. In this work, a One-Dimensional Convolutional Neural Network (1D-CNN) is used to protect the controller evaluating entropy information. Therefore, the CICDDoS2019 dataset is used to investigate the proposed approach to train and evaluate the performance of the model and then examine the effectiveness of the proposal in the SDN environment. The experimental results manifest that the proposed approach achieves very high enhancements in terms of accuracy, precision, recall, F1 score, and Receiver Operating Characteristic (ROC) for the detection of Distributed Denial of Service (DDoS) attacks compared to one of the benchmarking state of the art approaches.
Comparison of angle-dependent scattering of convoluted and straight microwave absorbers. - In: AMTA 2022 proceedings, (2022), insges. 6 S.
The increasing complexity and sensitivity of wireless communication systems enforce the requirements for test environments such as anechoic chambers. The minimum achievable level of interference between desired signal and scattered copies is essentially determined by the reflectivity of the installed absorbers, emphasizing the importance of thoroughly characterizing the scattering behavior of absorbers. In this paper, the scattering off absorbers with different geometric shapes, namely convoluted, pyramidal, wedge, and flat, is investigated using a numerical unit-cell model. To verify the simulation model, the angle-dependent reflectivity of the convoluted absorbers was measured at different angles-of-incidence between 2GHz and 18GHz. The numerical results agree well with the measured reflectivity at representative angles-of-incidence, validating the numerical model and revealing the expected increase in reflectivity for increasing beam tilts. Further, it becomes apparent that the performance of all shapes decreases similarly at oblique incidence. These results contribute to build a comprehensive database on the angle- and frequency-dependent reflectivity of absorbers, in order to develop a consistent data body, e.g., for modelling anechoic environments.
https://doi.org/10.23919/AMTA55213.2022.9955000
Emulation of LTE link scenarios reproducibly derived from field-operational tests. - In: AMTA 2022 proceedings, (2022), insges. 6 S.
Virtual drive tests using the over-the-air/vehicle-in-the-loop method are becoming an essential part of testing vehicular radio systems. Different approaches ask which link scenarios and channel environments are relevant and should be tested. This paper deals with the systematic evaluation of field-operational tests and the implementation of virtual drive tests of LTE communication links focussing on the performance of the radio link close to the edges of the radio cells, which are identified as a relevant testing scenario. For this purpose, three test drives were performed on each of two test tracks. Close to cell edges the available data throughput is as much as a factor of 10 lower than the maximum available data throughput along the test track and reduced approximately by half compared to the average data throughput in the cell center. Instead of trying to recreate the entire test drive with high accuracy, this approach focusses on recreating the critical parts of a test drive in the laboratory, as these are the most likely to cause radio link failure in real operation. Therefore, the physical parameters in terms of serving signal strength and level of interfering signals were transferred to a wired virtual test, and the data rate was examined again. Despite some systematic differences between real drive test and virtual drive test, which could be clearly identified, it was possible to reproduce the behavior at the cell edge very precisely with deviations smaller than 5 %.
https://doi.org/10.23919/AMTA55213.2022.9954989
Analytical and experimental studies of ground reflections on bi-static radar signal propagation. - In: AMTA 2022 proceedings, (2022), insges. 6 S.
Progressing towards highly automated and connected vehicles, radar systems have evolved into reliable assistance systems for environmental perception, for a wide spectrum of traffic scenarios, and with them, accurate angle-dependent descriptions of reflectivities and scattering centers of traffic participants and road users. Depending on the electrical size of the radar object, the influence of possibly unwanted ground reflections can be significant in radar cross-section measurements. This paper presents an analytical model based on the transmitter, receiver, and single or multiple scattering center positions, that takes into account the geometric reflections at the ground floor and calculates the resulting interference. Considering also the bi-static crosstalk between the transmit and receive antennas, six different propagation paths are obtained, which differ in path delay and attenuation. Subsequent validation measurements in a semi-anechoic automotive antenna test facility confirm the analytical approach very well. Existing discrepancies between the single scattering center model and the measurements with a metal sphere could be corrected by a closer look at the position of the scattering center. Final measurements on realistic bicyclist dummies show that the model is also reliably applicable to extended radar targets.
https://doi.org/10.23919/AMTA55213.2022.9954954
Recovery under side constraints. - In: Compressed sensing in information processing, (2022), S. 213-246
This chapter addresses sparse signal reconstruction under various types of structural side constraints with applications in multi-antenna systems. Side constraints may result from prior information on the measurement system and the sparse signal structure. They may involve the structure of the sensing matrix, the structure of the non-zero support values, the temporal structure of the sparse representation vector, and the nonlinear measurement structure. First, we demonstrate how a priori information in the form of structural side constraints influence recovery guarantees (null space properties) using ℓ1-minimization. Furthermore, for constant modulus signals, signals with row, block, and rank sparsity, as well as non-circular signals, we illustrate how structural prior information can be used to devise efficient algorithms with improved recovery performance and reduced computational complexity. Finally, we address the measurement system design for linear and nonlinear measurements of sparse signals. To this end, we derive a new linear mixing matrix design based on coherence minimization. Then, we extend our focus to nonlinear measurement systems where we design parallel optimization algorithms to efficiently compute stationary points in the sparse phase-retrieval problem with and without dictionary learning.
Circularly polarized embedded patch antenna array for automotive 5G satellite communications. - Ilmenau. - 73 Seiten
Technische Universität Ilmenau, Masterarbeit 2022
Die V2X-Kommunikation ist der am weitesten fortgeschrittene Anwendungsbereich der 5G Low Earth Orbit (LEO) Satellitentechnologie. Die Nachfrage nach einer extrem hohen Datenrate führt zu einer höheren Betriebsfrequenz, was die Kommunikationsverbindungen anfällig für Verluste macht. Um atmosphärischen und Polarisationsverlusten zu widerstehen, werden für die Satellitenkommunikation häufig zirkular polarisierte Antennen mit hoher Verstärkung verwendet. In dieser Arbeit wurde eine eingebettete kompakte zirkular polarisierte Antenne mit niedrigem Profil für die 5G LEO-Satellitenkommunikation für Automobilanwendungen entwickelt. Zunächst werden einige aktuelle Entwicklungen im Bereich der Automobil-Antennen untersucht und der Bedarf an einer zirkular polarisierten Mikrostreifen-Patch-Antenne vorweggenommen. Der erste Schritt auf dem Weg zu einer effektiven Satellitenkommunikation besteht darin, das Link-Budget zu ermitteln. Die Berechnung des Link-Budgets zeigt, dass eine Antenne mit moderatem Gewinn von 15 dBi für die Benutzerausrüstung zusammen mit einer Satellitenantenne mit hohem Gewinn (40 - 50 dBi) eine Uplink-Datenrate von 3,24 Mbit/s bietet. Um den geforderten Gewinn zu erreichen, wurde eine 4x4 zirkular polarisierte Patch-Antennengruppe implementiert, wobei die Kompaktheit der Gruppe beibehalten wurde. Die möglichen Einflussparameter wurden entsprechend dem Designziel optimiert. Die optimierte Array-Antenne bietet einen maximalen simulierten Gewinn von 15 dBi bei einer Frequenz von 28 GHz und eine sehr große Impedanzbandbreite von 4 GHz, was sie gegenüber anderen Antennen, die bei einer ähnlichen Frequenz arbeiten, neuartig macht. Die simulierte Bandbreite des Achsverhältnisses beträgt 720 MHz und die Kreuzpolarisationsunterscheidung (XPD) liegt bei 25 dB, was auf die Polarisationsreinheit in Breitseitenrichtung hinweist. Außerdem wurde die simulierte Antenne im Antennenmesslabor der TU-Ilmenau hergestellt und gemessen. Um den Effekt der Kunststoffeinbettung zu untersuchen, wurde die Antenne in den Heckspoiler eines modernen Autos eingebettet und gemessen. Der gemessene Gewinn der eingebetteten Antenne beträgt 12,1 dBi bei 28 GHz. Die Impedanzbandbreite beträgt mehr als 4 GHz und die Bandbreite des Achsverhältnisses liegt bei etwa 900 MHz. Abschließend wurden die simulierten und die gemessenen Ergebnisse verglichen, und es wird auf mögliche zukünftige Implementierungen hingewiesen.
Virtuelle Sensorvalidierung für automatisiertes und vernetztes Fahren. - In: Automobiltechnische Zeitschrift, ISSN 2192-8800, Bd. 124 (2022), 11, S. 58-62
https://doi.org/10.1007/s35148-022-1505-0
Virtual sensor validation for automated and connected driving. - In: ATZ worldwide, ISSN 2192-9076, Bd. 124 (2022), 11, S. 54-57
https://doi.org/10.1007/s38311-022-1405-7