T-RAIM Approaches: Testing with Galileo Measurements.

Area of Science:

• Satellite Navigation Systems
• Timing Integrity Monitoring
• Signal Processing

Background:

• Critical timing applications depend on Global Navigation Satellite System (GNSS) signals.
• Existing GNSS systems lack integrity information specifically for timing.
• GNSS integrity data may not be timely or account for local signal interference.

Purpose of the Study:

• To develop and evaluate autonomous integrity monitoring algorithms for GNSS timing.
• To address the need for timely and localized timing integrity.
• To assess algorithm performance under various signal conditions.

Main Methods:

• Implementation and testing of three Timing Receiver Autonomous Integrity Monitoring (T-RAIM) algorithms: Forward-Backward (FB), Danish, and Subset.
• Application of algorithms to both Position Velocity and Timing (PVT) solutions and time-only scenarios with known receiver coordinates.
• Validation through tests with identical receivers in open-sky and obstructed environments.

Main Results:

• T-RAIM algorithms demonstrated significant benefits in frequency error and Allan Deviation (ADEV) under degraded signal conditions.
• Knowledge of receiver coordinates enhances the performance of integrity algorithms due to increased redundancy.
• A minor increase in execution time was noted when employing T-RAIM algorithms.

Conclusions:

• Local computation of timing integrity using T-RAIM algorithms is a viable solution to bridge the gap in GNSS timing integrity.
• The proposed T-RAIM algorithms effectively improve timing performance in challenging environments.
• Receiver coordinate knowledge is vital for optimizing T-RAIM algorithm effectiveness.