Advanced Message Generation Facility For Future Gnss Broadcasting

The Advanced Message Generation Facility (AMGF) is a software tool developed to support the assessment of future GNSS navigation message dissemination strategies aimed at enhancing user level performances, such as availability of positioning, timing or authentication services at the user level. Concepts like the dissemination of messages in "broadcast-target pairing mode" are studied, where satellites can act as "broadcast" satellites, transmitting data also for other satellites called "target", contrary to typical dissemination of current GNSS systems that disseminate from each SV the data of the broadcasting satellite.. This paper describes one of the main modules integrated in the AMGF, the Navigation Message Mechanization Logic (NMML). The NMML emulates a component of the Message Generation Facility (MGF) of future GNSS ground system and it is capable to identify in run-time the satellites that shall act as "broadcast", transmitting data also for other satellites called "target". Three innovative mechanization modes are already supported by the tool; however, being designed with a high level of flexibility, it can be upgraded to integrate any future GNSS system level logic. The NMML tool integrates a Geometric Core that is used to compute a matrix of potential broadcast/target couples based on the satellite footprints intersection areas. A heuristic algorithm has been defined for the broadcast-target pairing that is able to trade-off two different objectives: to maximize the number of times that all SVs are assigned as targets and to minimize the number of times that broadcast-target pairs are re-configured by the system to avoid frequent uploads from the Uplink Stations to the SVs. The algorithms have been simulated with Galileo constellations scenario to assess a set of system level key performance indicators retained of value in the analysis of the performance of different dissemination strategies.