Evaluation of a real-time GBAS ground facility prototype and its user performance

To augment the GNSS aviation navigation service in the Taipei flight information region (FIR), we develop a GBAS ground facility prototype to facilitate the implementation and operation of a GBAS. We use all commercial off-the-shelf (COTS) components to build each GBAS reference station, the GBAS master station prototype and the GBAS user platform. The objectives of this work are 1) real-time operation of the GBAS ground facility prototype, 2) evaluation of the real-time GBAS user algorithm performance, and 3) assessment of GBAS signal anomaly detection. In the paper, we first discuss the real-time implementation of the GBAS ground facility prototype, including the hardware architecture of the reference stations and the master station and the associated software designs for data processes. We then describe the technical issues encountered and their solutions in detail. Both static and dynamic experiments are conducted to evaluate user performance using the corrections and integrity messages generated from the developed GBAS ground facility prototype. In experiments, we utilize both Ethernet and Wi-Fi to develop the data links from the reference stations to the master station as well as the communication channel between the user and the master station. The effects of data transmission latency and data drops on the system performance are analyzed in the paper as well. After the designs of the real-time GBAS ground facility prototype and the associated user platform are validated, the developed system is used as a test bed for assessing GBAS signal anomalies. Because Taiwan is in a low-latitude region, signal anomalies due to the ionosphere are the major concern related to GBAS implementation and operation. The impact of the local ionospheric activity on GBAS performance is also of interest in this paper. Finally, the detection mechanism for the GBAS signal anomaly due to the ionosphere is presented in this paper as well.