Robust Time Synchronization Methods for Future APNT

Kurzfassung

The paper deals with concepts and methods to provide a robust time synchronization algorithm for a network of ground stations, which provide an APNT (Alternative Positioning, Navigation and Timing) service. Besides the concept to synchronize the stations to an external GNSS time scale such as GPS, Galileo or EGNOS or with the use of a geostationary satellite, the concept to generate an internal timescale by a composite clock algorithm is investigated. Using the calculated time offsets relative to the composite clock offset, the ground station signals are synchronized, to mitigate the clock related error of the pseudo range measurements. As discussed within the paper, the application of a composite clock algorithm requires a measurement network, whose network graph is connected. The robustness of a ring network is studied by simulation of clock feared events of time and frequency offset steps and the performances are evaluated in terms of Required Navigation Performance (RNP).