Towards Re-Creating Real-World Ionospheric Scintillation Events in a Spirent Simulator-Based Robust PNT Test Framework

摘要

The robust Position, Navigation and Timing (PNT) market, especially safety critical applications (e.g. Space-Based/Ground-Based Augmentation Systems (SBAS/GBAS) for Global Navigation Satellite Systems (GNSS)), have shown a growing concern regarding degraded accuracy, precision and availability of GNSS-based systems caused by ionospheric scintillation. Testing the resiliency of such systems to scintillation is thus imperative to ensure their reliable operation under scintillation conditions. However, conventional test paradigms for GNSS devices are not adequate given the nature of scintillation threats to GNSS. As such, there is a current need to simulate realistic ionospheric scintillation environments within test frameworks aimed at improving the resilience of GNSS-based PNT systems. This paper proposes a unique approach to modelling realistic ionospheric scintillation effects on GPS signals within a Spirent GNSS simulator. In contrast to statistical models, the method uses historical data to generate empirical models for amplitude and phase scintillation across a grid of latitude and local time for a given location. Scintillation strengths experienced by each satellite in view are then derived from the model, which is used as a guidance to implement real-world scintillating RF profiles to desired satellites within the Spirent simulator-based Robust PNT test framework. The RF profiles are extracted from historical raw data, and represent different strengths of amplitude/phase scintillation. The profiles are selected from data collected between 2004 and 2013 from two scintillation-rich sites at low and high latitudes – Cape Verde and Tromso, respectively. The proposed technique will enable receivers to be tested at any location and time, with the added flexibilities of selecting different combinations of scintillation profiles (for a given set of satellites), and the selection of satellites for which scintillation is implemented. The ability to replay real, observed phenomena as proposed in this paper is expected to present the best opportunity for developers, integrators and users of GNSS systems to build up a picture of their systems’ resilience to ionospheric scintillation, and is likely to result in a much more effective risk assessment tool.