Integrity and Performance of a Commercial VDES R-Mode Testbed with Synchronization Monitoring

Ronald Raulefs, Markus Wirsing

Peer Reviewed

Abstract:	This research is motivated by the escalation of GNSS interference and spoofing incidents recently observed in the Baltic Sea, a threat underscored by a joint call from the IMO, ITU, and ICAO in March 2025 urging member states to protect the GNSS spectrum and accelerate the development of resilient PNT solutions. As a consequence, the IMO’s Maritime Safety Committee (MSC), during its recent 111th session, tasked the Sub-Committee on Navigation, Communications and Search and Rescue (NCSR) with developing a performance standard for R-Mode receivers at its upcoming 13th session. This paper details the experimental setup and initial field results of a maritime VDES R-Mode (VHF Data Exchange System Ranging Mode) testbed established in the Baltic Sea. The infrastructure includes three VDES R-Mode base stations deployed along the coast and east of Ruegen. For precise synchronization, each base station is equipped with an atomic clock that is observed and tracked by an external 10 MHz reference source. The same has been also installed on a vessel to determine the position. Furthermore, all VDES R-Mode base stations have additionally receivers enabling them to operate as monitoring stations for observing by coupler the very same base station as well as the other base stations within the area and the network. The study utilizes commercially available base stations in conjunction with a receiver based on a Software Defined Radio. To evaluate the positioning performance, various tracking algorithms were tested: a family of Kalman Filters and an outlier-robust particle filter. The data presented represents the first field testing results obtained in motion using this configuration of commercial base stations and an SDR-based VDES R-Mode receiver.
Published in:	Proceedings of the ION 2026 Pacific PNT Meeting April 13 - 16, 2026 Hilton Waikiki Beach Honolulu, Hawaii
Pages:	465 - 473
Cite this article:	Raulefs, Ronald, Wirsing, Markus, "Integrity and Performance of a Commercial VDES R-Mode Testbed with Synchronization Monitoring," Proceedings of the ION 2026 Pacific PNT Meeting, Honolulu, Hawaii, April 2026, pp. 465-473. https://doi.org/10.33012/2026.20598
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