Code multipath analysis of Galileo FOC satellites by time-frequency representation

Abstract

Galileo is currently in full operational capability (FOC) phase with 18 FOC satellites. The purpose of this paper is to investigate the multipath performance of Galileo FOC signals E1, E5a, E5b, and E5. With the advent of FOC satellites, assessing the multipath behavior of Galileo FOC signals is becoming one of the greatest interests for the user’s community. In fact, the reduction of multipath has been one of the main criteria on which the Galileo signals have been designed. We analyzed data over three different days from six International GNSS Service (IGS) stations located at different latitudes, for all visible Galileo satellites. This is one of the first studies to present experimental results for the multipath of Galileo signals transmitted by FOC satellites since they started to operate in 2015. Code multipath was estimated using code-minus-carrier (CMC) and pseudorange multipath (MP) methods. The study involves a comparison with the GPS signals, showing results of multipath performance as function of satellite elevation. A time-frequency representation, based on the use of continuous wavelet transform (CWT), was performed to rigorously account for the presence of multipath. The expectations of FOC satellites to lead to a multipath reduction have been verified: the E5 signal shows the highest suppression of multipath as compared to the other Galileo and GPS signals and it is almost independent from the satellite elevation. An assigned FOC satellite showed a lower frequency multipath compared to a GPS satellite at the same azimuth and elevation, which is in line with a lower Galileo satellite elevation rate.