Timing advanced receiver autonomous integrity monitoring augmented by BDSBAS

Abstract Global Navigation Satellite System (GNSS) provides sufficiently accurate and affordable time and frequency information for Timing and Synchronization (T&S) equipment, which is widely used in modern infrastructures such as 5G, small cells, and data centers. However, ensuring the integrity of GNSS timing faces challenges due to the inherent vulnerability of GNSS signals and the complexity of user environments. This study introduces the Timing Advanced Receiver Autonomous Integrity Monitoring (T-ARAIM) algorithm, an enhanced version of T-RAIM, designed to fully leverage dual-frequency and multi-constellation signals, making it suitable for high-precision timing applications. The algorithm integrates Differential Frequency Multi-Constellation (DFMC) messages from the BeiDou Satellite-Based Augmentation System (BDSBAS), which provide satellite ephemeris corrections, clock corrections, and integrity parameters. The performance of the T-ARAIM algorithm augmented by BDSBAS is thoroughly validated and analyzed through simulation experiments, real-world experiments, and BDSBAS augmentation experiments. Simulation results indicate that when the receiver position is estimated, the coverage of T-ARAIM (availability greater than 99.9%) using GPS + BDS-3 reaches 37.2%, with further improvement to 54.3% upon fixing the Inter-Satellite Bias (ISB). In scenarios where the receiver position is fixed, T-ARAIM coverage can achieve 100% even with a single constellation. Real-world experiments utilizing raw observations from seven globally distributed GNSS stations reveal that fixing the receiver position reduces timing errors and time protection levels (TPL) by over 40%. Fixing the ISB does not affect the accuracy of the timing solution but slightly reduces TPL by about 2 ns. Fixing the receiver position and/or ISB increases observation redundancy, significantly improving T-ARAIM availability. The integration of BDSBAS augmentation information further improves the timing solution, with timing accuracy increasing by approximately 3.2% to 9.6% and T-ARAIM availability rising by about 4.1% to 14.6% when the receiver position is estimated. In fixed-position scenarios, the improvements in timing accuracy are more pronounced, approximately 12.0% to 25.3%, with T-ARAIM availability reaching 100%.