BeiDou 3 signal quality analysis and its impact on users

Abstract

Nowadays, one can use four global navigation satellite systems (GNSS). Two of them are complete constellations (GPS, Glonass) and two (BeiDou, Galileo) are already providing initial services and will be finished in the near future. Additionally, satellite-based augmentation systems (SBAS) and regional systems like WAAS, EGNOS, GAGAN or QZSS complement the GNSS service. However, within all systems one can observe changes, modifications, and updates every year. This can be related to signal property changes, renewing satellites up to the implementation of completely new GNSS platforms in space. Especially, for safety critical applications using GNSS, like advanced receiver autonomous integrity monitoring (ARAIM) or ground-based augmentation systems (GBAS) the new or changed signal properties are of high interest and are crucial for integrity analysis. With the help of detailed information about the signal deformation and the received signal power it is possible to calculate realistic error bounds and consequently realistic protection level for these kinds of safety-critical applications. This paper will present signal analysis results based on observations of the new BeiDou 3 signals appeared in the last two years. After a brief introduction of the measurement facility the basic analysis of the quality of the signals in spectral and modulation domain is introduced. This covers the transition from BeiDou 2 up to BeiDou 3 including the test and validation phase in the beginning of BeiDou 3. Based on captured in-phase and quadrature (I/Q) sampleswe will give a detailed overview on the BeiDou 3 satellite payload characteristics including signal deformation analysis. The paper will assess how such imperfections will influence the pseudo-range measurements and consequently provide the capability for error analysis with respect to safety-critical applications. We will show the dependency of tracking biases depending on different receiver configuration. Using the German Aerospace Center ´s (DLR) precise calibrated measurement facility, we will also present an analysis of the transmitted satellite signal. Considering the measured power in relation to the boresight angle of the satellite one get a cut through the antenna pattern of the satellite and can assess the antenna symmetry properties. Examples for different satellites will be presented.