A Predictive Digital Twin for Integrity Monitoring of Multi-Source Positioning Navigation & Timing (PNT) Systems

Although GNSS is able to provide reliable PNT services for most of our daily applications, they are vulnerable to unintentional interference, intentional jamming, and malicious spoofing, especially for DoD-related applications. On the battlefield, PNT utilizing any single GNSS service becomes unreliable. To overcome this shortcoming, a family of more robust methods was proposed to enhance the reliability of PNT services by exploiting multiple sources for navigation. The digital twin (DT) for integrity monitoring of multi-source PNT (MS-PNT) system developed in phase I provides a realistic software testbed to support the testing and validation of integrity monitoring methods for MS-PNT systems. In the phase II project, receiver autonomous integrity monitoring (RAIM) methods will be developed at all processing stages of the GNSS receiver. Specifically, a PRN code phase-based integrity monitoring method will be developed by analyzing results from the receiver’s code tracking loop. A Doppler shift-based integrity monitoring method will be developed, which uses the evaluated patterns of Doppler shifts in the GNSS sigal channels induced by the receiver’s movement for integrity monitoring.  Bit and data frame synchronization-based PNT integrity monitoring methods will be developed, which are based on the bit and frame synchronization results of the GNSS receiver. The pseudo-range-based PNT integrity monitoring and receiver kinematic state estimation-based integrity monitoring will also be developed. The developed PNT monitoring functions will be integrated to offer greatly enhanced performance against various types of PNT spoofing attacks. In addition, the digital twin will also be used to generate data in various spoofing attack scenarios to support the machine learning based integrity monitoring. The use of explainable artificial intelligence (xAI) in the machine learning process will also be investigated. Finally the developed integrity monitoring methods will be implemented in hardware receivers, e.g., Software Defined Radio (SDR), for testing and performance evaluation with real GNSS signals and spoofing attacks.