057 - Development of advanced VDES-R user technologies for alternative PNT

057 - Development of advanced VDES-R user technologies for alternative PNT


VDES (VHF Data Exchange System) aims at digitalising maritime communications and enable the introduction of new capabilities for a variety of maritime use cases, such as AIS and Search and Rescue. It is also being considered to support alternative PNT with a dedicated ranging capability, the so-called R-mode or VDES-R, which is currently being investigated. The initiative is supported by IALA (International Association of Marine Aids to Navigation and Lighthouse Authorities, previously known as International Association of Lighthouse Authorities).

Through activities in Element 1 and 3, NAVISP is carrying out activities towards resilient PNT solutions for maritime applications. Investigations carried under Element 3 MARRINAV activity have confirmed VDES-R as a very relevant alternative source of PNT information, in combination with GNSS and eLoran. The VDES-R capabilities could be further enhanced by leveraging advanced user technologies, which would work around the limited bandwidth allocated to VDES channels and benefit accuracy and integrity performance, and security. This is foreseen, for instance, by tailoring advanced positioning and signal processing techniques to VDES-R, such as carrier phase positioning, advanced multipath mitigation, channel and antenna diversity processing. Additionally, ranging signals can potentially be used in combination with the bidirectional data channel in order to enhance resilience against spoofing attacks.

Initial guidelines and recommendations for VDES via satellite (VDE-SAT) are emerging. According to ITU – M.2092: ‘Due to the frequency used, it is likely that VDE-SAT will consist of LEO or MEO satellites. VDE-SAT could also consist of hosted payloads on spacecraft in such orbits’.

In the framework of ESA’s Open Space Innovation Platform (OSIP), the ANGELOS study is preliminary investigating the concept of using R-mode for VDE-SAT based, in particular, on a Low Earth Orbit (LEO) constellation using CubeSats. Detailed analyses are required to address complementary technologies at user level for VDE-SAT.

The objectives of this activity are to:

  • investigate and prove the concepts of novel user segment technologies allowing enhanced positioning with VDES (accuracy, integrity, security) and complement ongoing VDES investigations to improve APNT capabilities for coastal use cases;
  • analyse synchronisation/timing issues for R-Mode;
  • assess compatibility with a VDE-SAT service provided from MEO or LEO satellites.

The tasks to be performed include:

  • identification of relevant use cases and scenarios (e.g. involving an hybrid terrestrial/satellite VDES)
  • study of enhanced architectures, techniques and technologies, small to very small form factor VHF antenna, advanced signal processing for multipath mitigation and carrier phase tracking, positioning leveraging carrier phase of VDES signals;
  • implementation of the identified solutions into breadboards to prove the concept of those user technologies in trials representative of different use cases and scenarios;
  • execution of field trials, and benchmarking with state of the art (conventional VDES R-mode, GNSS, eLoran)

The main results of the activity will provide:

  • breadboards implementing the proof-of-concept of VDES-R user technologies (e.g. user terminal with antenna, RF, baseband and navigation algorithms).
  • results from field trials (demonstration and benchmarking)
  • recommendations and roadmaps for follow-on activities.