One research focus of the group is the development of positioning methods for terrestrial radio systems, which include standardized systems in the field of mobile radio, WiFi or UWB as well as dedicated in-house developments.
We exploit the radio signals of these systems for position and orientation estimation of mobile terminals as well as the agents of a swarm for the exploration of extraterrestrial celestial bodies such as the Moon or Mars. In particular, cooperative methods are used for this purpose. With such cooperative positioning methods, mobile units, for example the rovers of a swarm, establish a decentralized self-organized and densely meshed radio network. With the help of time-of-flight measurements of the radio signals exchanged between the mobile units, the distances between mobile units, and thus their position, are determined. In addition to position and orientation estimation, our methods enable both intra-swarm communication and temporal synchronization of all swarm units.
For multipath propagation environments, the group develops methods that do not suppress multipath propagation but exploit it specifically for position estimation. With the principle "Channel-SLAM" we consider multipath propagation as the sum of radio links with direct line-of-sight between so-called virtual transmitters and a receiver. Since the positions of these virtual transmitters are needed to estimate the receiver position, but are usually not known, they are estimated together with the receiver position using “Simultaneous Localization and Mapping (SLAM)”.
Another research focus of the is the development and testing of future digital communication and navigation methods in the VHF and C-band for marine applications. The focus is on the integration of communication and navigation in one system. The group is significantly involved in the development of the navigation component “R-Mode” for the maritime “VHF Digital Exchange System (VDES)”. Furthermore, methods to reduce interference between maritime radio systems, for example VDES and AIS, are designed.
For research and development in the field of terrestrial radio communication and navigation technologies, methods from information- and estimation theory, computer-aided simulations as well as experimental setups are used. The basis for the research work is a deep understanding of the propagation characteristics of electromagnetic signals. To this end, we perform extensive channel measurements and use the measurement data to build suitable models for capturing the electromagnetic wave propagation properties for the application environments of our radio communication and navigation technologies.
Zur Forschung und Entwicklung im Bereich terrestrischer Kommunikations- und Navigationsverfahren werden Methoden sowohl aus der Informations- bzw. Schätztheorie, computergestützte Simulationen als auch experimentelle Aufbauten verwendet. Grundlage für die Forschungsarbeiten ist ein tiefes Verständnis der Ausbreitungseigenschaften elektromagnetischer Signale. Dazu führen wir umfangreiche Kanalmessungen durch und erstellen aus den Messdaten geeignete Modelle zur Erfassung der elektromagnetischen Wellenausbreitungseigenschaften für die Anwendungsumgebungen unserer Verfahren.
In detail, the research topics include
Positioning using terrestrial radio systems
Cooperative positioning methods, in particular based on signal propagation time measurements between mobile terminals
Decentralized positioning for swarm navigation
Positioning methods using multipath propagation (Channel-SLAM)
Combination of our algorithms with complementary positioning technologies, e.g. GNSS and inertial sensors
Development of methods for future maritime communication and navigation systems in VHF and C-band
Channel measurements and modeling for terrestrial and maritime environments
Channel-SLAM bei Mehrwegeausbreitung von Signalen
Werden die elektromagnetischen Wellen eines Senders auf dem Weg zum Empfänger abgelenkt, z.B. durch Gebäude oder Wasseroberflächen, spricht man von Mehrwegeausbreitung. Diese wird mit dem Verfahren "Channel-SLAM" nicht unterdrückt, sondern gezielt zur Positionsbestimmung ausgenutzt.
Funksignale werden zur Positions- und Orientierungsschätzung von mobilen Endgeräten sowie den Agenten eines Schwarms genutzt - beispielsweise zur Erkundung extraterrestrischer Himmelskörper wie Mond und Mars. Damit bauen die mobilen Einheiten (z.B. Rover oder Drohnen) ein dezentral selbstorganisiertes und eng vermaschtes Funknetzwerk auf. Damit ist auch sowohl die Kommunikation innerhalb eines Schwarms als auch die zeitliche Synchronisation aller Schwarmeinheiten möglich.
