## 3 Results and Discussion
The B3 signal has the smallest SICB corrections. The SICB corrections on the same frequency are very consistent for satellites with the same orbit type, and the differences among them are usually at a level of several centimeters. To pursue high accuracy, we still establish the SICB correction model for each satellite rather than IGSO-type or MEO-type satellites [10; 11]. Figure 8: RMS statistics of high- and low-frequency components in the time series of MP combinations at station SGG1. Figure 7: MP combination time series at station SGG1 on 13 July 2016. The red, green and blue lines refer to the MP combination time series for the code observations on the B1, B2 and B3 frequencies, while the black, cyan and magenta lines refer to the corresponding series for the three new navigation signals, namely B1C, B2a and B2b. Figure 11 provides the estimated correction model parameters for BDS-3S satellites. In conjunction with the results shown in Figure 10, we can conclude that the SICB corrections for BDS-3S satellites are much smaller than those for BDS-2 satellites, and are usually confined to 0.1 m. It is interesting to notice that the SICB corrections on B3 frequency at elevations larger than 20\({}^{\circ}\) for C31 and at elevations larger than 40\({}^{\circ}\) for C32 are strongly elevation dependent, while the corresponding SICB corrections at other elevations are unstable due to the effects of the larger receiver CMN. We can deduce that the SICB corrections for the two legacy signals of all BDS-3S IGSO satellites depend on the elevations, although the elevation-dependent characteristics of SICB corrections with a small range of variance  
Figure 10: SICB correction model as a function of elevations on B1, B2 and B3 frequencies for each BDS-2 MEO and IGSO satellite. Figure 9: RMS statistics of code multipath and noises against satellite elevation angles at stations SGG1 and XIA1. are severely contaminated by the receiver CMN for some cases. As to the BDS-3S MEO satellites, the estimated SICB corrections on the B1 frequency also seem to be elevation dependent. However, the SICB values of these satellites are different at the same elevation angles with different azimuth angles [20]. Thus, the established elevation-dependent SICB correction model for the B1 and B3 signals of BDS-3S MEO satellites is not applicable, as will be demonstrated in the following. The abnormal fluctuation of SICB corrections for the BDS-3S satellites at low elevations can be attributed to the larger CMN. To validate the effectiveness of our SICB correction model, the SICB corrections are added to the original code observations to reform the MP combinations. Figure 12 illustrates the distribution of MP combination time series with application of SICB corrections for BDS-2 IGSO satellites. Datasets from 58 stations spanning 32 days are used. For the purpose of comparison, the distribution of original MP combination time series is also presented in this figure. It is clearly seen that both the uncorrected and corrected MP combinations are approximately normally distributed, but the expectations of the former ones show a slight deviation from zero. Compared with the original MP series, the MP series with SICB corrections account for larger percent of smaller errors. In each panel, the RMSs of MP series are also provided. The RMS values of corrected MP series are reduced by 7%, 6% and 2% over the uncorrected MP series on the B1, B2 and B3 frequencies, respectively. The corresponding results for BDS-2 MEO satellites are shown in Figure 13. The benefits from the SICB correction for IGSO satellites are smaller than those for MEO satellites. The decrease in RMS values for the corrected MP series over the uncorrected MP series is 18%, 14% and 5% on the three frequencies, respectively. Figure 12 involves 11.5, 11.5 and 5.4 million epoch-wise MP values for B1, B2 and B3 frequencies, respectively, while the corresponding numbers are 3.7, 3.7 and 2.1 million for the three frequencies in Figure 13, respectively.