Optimization of RAIM Based on Dual-Frequency Dual-Constellation INS Integrated Navigation System

The development of the global navigation satellite system (GNSS) has enabled the implementation of receiver autonomous integrity monitoring (RAIM) for precision approach with vertical guidance in civil aviation. Considering the most challenging threat—constellation-wide threat, an integrity monitoring system for dual-frequency dual-constellation (DFDC)/inertial navigation system (INS) integrated navigation is designed. To enhance integrity performance, we employ the augmented state method for nominal unmodeled bias in pseudo-range measurement and the optimal allocation method for continuity budget. Based on civil aviation standards requirements, the vertical protection level (VPL) availability distribution and static station experiment are presented for different integrity monitoring algorithms. The simulations demonstrate that the constellation-wide threat significantly affects integrity performance, and DFDC/INS integrity monitoring significantly improves integrity performance compared to the single-constellation solution. Furthermore, for the VPL availability, the augmented state method and optimization of allocation method increase the availability percentage by 3.08 and 3.59% and average VPL by 5.62 and 5.13 m, respectively. Finally, for the static station, vertical accuracy and effective monitor threshold (EMT) satisfy the localizer performance with vertical guidance down to 200 feet (LPV-200) requirements for civil aviation.