Availability assessment of dual-frequency GNSS based aviation applications under ionospheric scintillation

Abstract

One of the most severe disruptions of Global Navigation Satellite System (GNSS) based aviation applications is caused by ionospheric scintillation. Under the scintillation, the GNSS signal intensity can drop below a certain threshold which event is referred to as deep fading, enough to lose the signal. In extreme cases, this leads to multiple signal loss which reduces the number of satellites available for use, consequently, degrades the navigation availability. This scintillation impact can be mitigated by using dual-frequency GNSS signals which decreases the chance of complete satellite loss. In the use of signals in different frequencies, satellite loss occurs only when the signal losses in different signals overlap, mostly due to their concurrent deep fading. Hence, to assess the benefit from the use of dual-frequency signals under scintillation, it is necessary to consider the correlation level between their deep fades. This thesis proposes new approaches on fading process model which can generate correlated fading processes on dual-frequency signals. Using high rate GPS L1/L5 dual-frequency measurements obtained from equatorial regions, the characteristics of deep fades are analyzed and utilized to construct the correlated fading process model. The availability simulations are assessed by considering scintillation impacts from correlated deep fades in the perspective of future GNSS aviation architectures. The results verified the availability improvement from aviation applications supporting dual-frequency GNSS over existing single-frequency systems. Also, new aviation receiver performance standards for dual-frequency GNSS based aviation applications were proposed by studying parametric analysis according to two parameters

probability of loss-of-lock and reacquisition time, which depends on the receiver tracking performance. This thesis can be used to evaluate the performance of GNSS-based aviation applications under various scintillation scenarios. Furthermore, this research can be extended to Multi-Constellation, Multi-Frequency (MCMF) based systems to guarantee aviation performance under severe scintillation.