VPL Parameter Determination for Improved Performance of Advanced RAIM

Advanced Receiver Autonomous Integrity Monitoring (ARAIM) helps ensure the integrity of vertical guidance using multi-constellations and new civil signals [1]. Among Global Navigation Satellite System (GNSS) error sources, signal-in-space (SIS) range error, which includes satellite ephemeris and clock errors, is most significant because combinations of signals on multiple frequencies are used to remove ionospheric errors, which are dominant in single-frequency operations. In order to ensure the integrity of ARAIM, an integrity parameter a is proposed to be broadcast by air navigation service providers. This a parameter is an inflation factor applied to broadcast URAs to ensure that SIS range errors are bounded to the required level of integrity. Based on a comprehensive analysis of SIS error characteristics, this paper determines the a parameter for subgroups of satellites that have similar error behavior and for individual satellites to lower the conservatism of the computed protection levels. Three different grouping scenarios (a single value of a for all satellites, one value of a for each satellite block type, and one value of a for each satellite) were used to determine a. The performance for each scenario was evaluated by performing ARAIM availability simulations. The simulation results demonstrated the performance improvements from grouping satellites into block types compared to the case of using a single value of a for all satellites. In particular, applying one value of a for each satellite gave significantly higher availability than other scenarios. This benefit gets more evident when the Gaussian tail behaviors of SIS error distributions differ across satellites.