The Impact of GPS Modernization on Standalone User Performance and Integrity with ARAIM

Advanced RAIM, or ARAIM, extends and improves upon the traditional RAIM algorithm to detect and mitigate independent, multiple, and correlated GPS signal faults. While ARAIM depends on multiple redundant satellites in view and will perform best for multi-constellation users, the modernization of the GPS satellite constellation and Operational Control Segment provides a basis for future improvements in ARAIM availability for GPS-only users due to improved ranging accuracy and lower satellite fault probabilities. This paper quantifies the effects of GPS modernization to evaluate the capability of ARAIM for military dualfrequency (L1-L2) users. Different mixes of GPS satellite types (Blocks IIA, IIR, IIR-M, IIF, and III) are generated to represent future stages of GPS modernization, and different range-error and failure models are constructed for each satellite type. ARAIM simulation results show the performance improvements for military LPV precision approach users as modernization proceeds. In particular, a future constellation of GPS Block III satellites provides significantly higher availability of LPV accuracy and integrity than today's mix of satellites and late-generation Block II satellites. As modernization proceeds, it is likely that sufficient LPV availability will be obtainable from the GPS constellation alone.