Signal deformation fault monitors for dual‐frequency GBAS

Abstract

This paper proposes a new dual-frequency signal deformation fault monitor which can effectively reduce the time delay at the Ground-Based Augmentation System (GBAS) airborne user from the airborne filter initialization to the time when it incorporates ground corrections and user measurements for navigation, assuring the system integrity at the same time. The new monitor is applied together with the existing Honeywell signal deformation monitor and Code-Carrier Divergence monitors to protect the airborne users against the signal deformation faults. In addition, the probability of missed detection of the monitors are assessed for the GBAS Approach Service Types (GAST) F, which supports the Category (CAT) II and III precision approaches based on the multi-frequency and multi-constellation. As a result, the proposed monitor together with the Honeywell and the CCD monitors is able to assure the system integrity for all fault cases within the threat space. The result also shows that the addition of the proposed monitor can reduce the time delay by 80% and moreover, it can even reduce the recommended time delay below 50 second. Consequently, it can avoid the unnecessary delays for the use of newly available satellites at the airborne.

Analysis on the Impact of Different Time Constants of Smoothing Filter on Compliance of Ranging Source Monitors in Dual-Frequency GBAS

“…The green shade indicates the monitor satisfies the requirement and the red shade indicates the noncompliant results. Except for the case of in GPS L1 and Galileo E1c signals, the proposed SQM solution in [6] can successfully protect the GBAS system and user against the signal deformation faults which are within the threat space. For GPS L5 and Galileo E5a signal, we can observe that the required is smaller than those for GPS L1 and Galileo E1c.…”

“…And for the L1/L5 carrier phase, it is set from -0.005 m/s to +0.005 m/s with 0.0005 m/s interval according to [4]. As stated in [6], the magnitude of the maximum differential range error depends on the relative time ( ) of the airborne filter initialization time ( ) to the fault onset time ( ). Therefore, the assessment is conducted for various values for the airborne filter initialization time as shown in Table 2.…”

“…Therefore, the assessment is conducted for various values for the airborne filter initialization time as shown in Table 2. For the signal deformation fault, the SQM solution proposed in [6], which uses the ENAC CCD monitor [4], Honeywell SQM [5] and ENAC DF-Innovation monitor [6], is adopted. The signal distortion is generated in chip-level for GPS L1 C/A signal according to the ICAO standards [2].…”

“…Previously, the ENAC has proposed the dual-frequency CCD monitor to protect airborne users against the dualfrequency CCD faults [4]. In addition, the combination of the conventional Honeywell Signal Quality Monitor (SQM) [5], ENAC DF-Innovation monitor [6] and ENAC CCD monitors have been proposed to deal with the signal deformation fault. Using these solutions for the CCD and signal deformation faults, the compliance of the PMD is determined for various time constants at the airborne carrier smoothing filter.…”

Characterization of Real Multi-Correlator Outputs for SQM Performance Evaluation

“…In order to protect a Civil Aviation user from a Hazardous Misleading Information (HMI) created by a non -nominal GNSS signal distortion [1], specific monitors, called Signal Quality Monitors, are implemented in SBAS (Satellite Based Augmentation System) [4], [6] and GBAS (Ground Based Augmentation System) [8], [9] systems. These monitors are based on the combining of different correlator outputs computed by the fixed SBAS/GBAS reference station receiver in order to detect the presence of signal distortions on the correlation function.…”