Research Roundup: Using UAVs as GNSS satellites

Real-time real-world testbed for new signals

By Daniel S. Maier, Thomas Kraus, Daniela E. Sánchez, Ronny Blum and Thomas Pany, Universität der Bundeswehr München

This research paper presents an update of the authors’ real-time real-world testbed for new GNSS signals. It includes experience gained in setting up an airborne pseudolite, UAVlite, to analyze the code- and phase-ranging performance and to test navigation message authentication schemes.

UAVlites transmit GNSS-like signals free from any local transmitter multipath, in contrast to ground-based transmitters. A software-defined radio allows easy broadcast of new navigation signals, which can be tested in real environments.

Purpose. To improve GNSS signals, it is important to test and analyze signal performance under various conditions and harsh environments. This is done mainly with computer simulation. However, a simulation always relies on assumptions and simplifications of a real-world problem.

Therefore, the authors are developing a flexible, cost-efficient and highly adjustable test system, usable for real test scenarios. With this system, researchers can investigate GNSS signal structures, range performance, authentication methods, channel coding and signal behavior under foliage, blockage, jamming, spoofing and other interferences.

Testbed Setup. Key elements include a UAVlite, two ground stations and a composite binary offset carrier signal. The system has demonstrated decimeter code-range accuracy and millimeter phase-range accuracy. Performance of a Galileo Open Service Navigation Message Authentication implementation was also analyzed.

The testbed has potential in the field of signal analysis and optimization, especially in multipath, channel coding, authentication or robustness against jamming, spoofing or other interference for existing GNSS signals, and for developing potential new GNSS signals.

This paper was presented at ION-GNSS+ 2018. See www.ion.org/publications/browse.cfm.