## 3 Results and Discussion  
The data sets from 60 globally distributed stations are adopted for analysis, as shown in Figure 6. The Multi-GNSS Experiment (MGEX) stations, which are marked in red and green, are all able to track signals on B1 and B2 frequencies for BDS-2 satellites. The green ones can also track the BDS-2 B3 signal. Both yellow and blue points refer to the international GNSS Monitoring and Assessment System(iGMAS) stations. The yellow ones have the capability of offering both B1/B2/B3 BDS-2 and B1/B3 BDS-3S tracking, while the blue ones are capable of tracking the B1, B2 and B3 signals of BDS-2 satellites. The station SGG1 located in Wuhan University and the iGMAS station XIA1, which are marked in black, can track all available signals for BDS-3S and BDS-2 satellites, except for B2 BDS-2 tracking at station XIA1. The analysis period spans a week from 7 to 13 July 2016 at station SGG1, two weeks from 2 to 15 September 2016 at station XIA1, and 32 days from 15 August to 15 September 2016 at other stations. Figure 7 shows the time series of MP combinations of each BDS-2 and BDS-3S satellite at station SGG1 on 13 July 2016. We use the carrier phase observations on the B3 frequency to form the MP combinations for the code observations on the B1 and B1C frequencies, while the carrier phase observations on the B1 frequencies are used to form the B2, B3, B2a and B2b MP combinations. The MP combination time series of the B1C signal for C32 are not presented because of frequent gross errors. For the BDS-2 GEO satellites, the MP series contain apparent bias variations, which can reach up to 2 m on B1 and B2 frequencies, due to the severe ground multipath effects. Bias variations can also be observed in MP series from BDS-2 MEO and IGSO satellites, but with less fluctuation and smaller amplitude. With regard to BDS-3S satellites, no significant bias variations can be noticed, except for the C31. The MP series of C31 on the B1 frequency show systematic long-term variations, especially for the period 18:15-24:00 (Figure 7). For further analysis, the root mean square (RMS) statistics of the high- and low-frequency components in the time series of MP combinations for each BDS-2 and BDS-3S satellite on each frequency are provided in Figure 8. We can separate the high- and low-frequency components in MP series using wavelet decomposition and reconstruction. We employ the Symlet wavelet \"sym5\". The datasets from SGG1 on 7-13 July 2016 are adopted. The long-term changes, namely SICB variations, are mainly reflected by the low-frequency components, while the code multipath and noise (CMN) errors are mainly contained in the high-frequency components. The magnitude of phase multipath and noise (PMN) errors is very small, and thus they can be ignored. Actually, partial multipath effects will be also included in the low-frequency components, especially for the BDS-2 GEO satellites. Due to the presence of SICB, the RMSs of the low-frequency components are relatively larger for BDS-2 satellites,  
Figure 6: Geographical distribution of 60 stations. Both the red and green points refer to the MGEX stations, and can offer B1/B2 and B1/B2/B3 BDS-2 tracking, respectively. Both the yellow and blue points refer to the iGMAS stations, and the former are able to offer both B1/B2/B3 BDS-2 and B1/B3 BDS-3S tracking, while the latter can only offer B1/B2/B3 BDS-2 tracking. The black points refer to the stations with the capability of tracking the new navigation signals. The stations indicated by the station name will be used as illustrations in the manuscript. especially for the BDS-2 GEO satellites, the RMSs of which are enlarged by the severe ground multipath effects. For the new navigation signals and the legacy signal B3 of BDS-3S satellites, the RMSs of the low-frequency components are all smaller than 2.5 cm. Regarding the low-frequency components on B1 frequency for BDS-3S satellites, the corresponding RMS values are 7.2, 5.4, 3.1 and 4.1 cm for C31, C32, C33 and C34, respectively.