Integrating LEO Satellite Signal Doppler Measurements and DME/VOR for enhanced GNSS-Free Positioning and Fault Detection

The International Civil Aviation Organization (ICAO) has introduced the concept of Performance-Based Navigation (PBN) to improve the safety and efficiency of navigation operations. This framework imposes stringent requirements on the accuracy and integrity of navigation systems. However, in western regions of China, the coverage of Distance Measuring Equipment (DME) and VHF Omnidirectional Range (VOR) stations is insufficient. Additionally, Global Navigation Satellite System (GNSS) performance is significantly degraded under conditions such as electromagnetic interference and ionospheric anomalies, which reduce the number of visible satellites and deteriorate geometric distribution. To address these limitations, a novel scheme is proposed that leverages Low Earth Orbit (LEO) satellites as a reliable complement to DME and VOR for navigation in GNSS-denied scenarios. The proposed approach constructs a tightly integrated positioning model by combining Doppler shift measurements from LEO satellites, distance information from DME, and azimuth data from VOR. A Kalman filter is employed for integrated navigation, with observation noise weighting to enhance positioning accuracy. Additionally, fault detection is performed using a multiple-hypothesis solution separation (MHSS) method to calculate the protection level and ensure system integrity. To reduce computational complexity, the method aggregates subsets of data from co-orbital LEO satellites and co-located DME and VOR stations. Simulation results demonstrate that the LEO/DME/VOR integrated navigation approach significantly expands coverage, improves the computational efficiency of the MHSS-based integrity monitoring.