The latest field of research is considering an alternative means for positioning, navigation and timing (APNT). With aeronautical navigation relying more and more on the use of global satellite navigation systems (GNSS) and its augmentation systems (SBAS, GBAS) air traffic becomes more vulnerable to outages of the service, e.g. due to large scale interference. Legacy ground navigation aids, such as NDB, VOR and possibly DME and ILS will be decommissioned over the next several years to save costs.
One of the concepts under investigation is the use of a new digital aeronautical communications link (L-DACS) for ranging. Together with knowledge about the precise location of the transmitting antennas on the ground a position solution can be computed. This, however, requires synchronization of the ground stations with very high accuracy. Furthermore, several performance requirements concerning accuracy, integrity and continuity have to be met in order to support a sufficiently high level of service when in use.
The DLR is currently investigating the capabilities of L-DACS based ranging and is deriving requirements on ground station siting, specifications of the navigation quality and levels of service provided.