GBAS RF Interference Detection Threshold Determination at Palermo Airport

The GNSS ranging signals have extremely low powers and are deeply buried into the noise at the antenna port of a navigation receiver. Because of this, the GNSS receivers are inherently vulnerable to the radio interference problem. Due to the utilization of the spread spectrum technology, some resistance to radio frequency interference (RFI) is provided by obtaining the processing gain after the PRN code dispreading. However, this amount of the resistance is not sufficient against strong radio interference that can distort the GNSS operation at large areas. Especially of large concern is the RFI problem in the GNSS applications with safety-critical content, such as aircraft landing with the help of a Ground Based Augmentation System (GBAS). Like in other safety-critical systems, any GBAS failure mode that may lead to misleading information for the user must be detected at a high level of confidence. The detection of the failure modes caused by the radio interference/jamming is in the focus of this paper. In the paper we propose and analyze the performance of three methods for detecting the corresponding types of interferers defined by the GBAS minimum operational requirements: continuous wave, wideband and pulsed interference. The methods have been developed keeping in mind the implementation with the out-of-shelf GBAS GPS receiver