## 3 Results and Discussion
### Performance of BDS-3 SAIM Based on On-Orbit Data
#### 3.1.1 Signal Power Monitoring  
Figure 5 shows the time series of the on-orbit signal power monitoring value of C30 and C34 satellites during 2021. It can be seen from the figures that the power monitoring values of the two satellites both have high stability. The standard deviations of the B1C and B2a signal power for the C30 satellite are 0.07 dBm and 0.12 dBm, respectively, and the standard deviations of the B1C and B2a signal power for the C34 satellite are 0.07 dBm and 0.04 dBm, respectively.  
Figure 5a shows that the power data of the C30 satellite has a long-term slow peak-to-peak fluctuation phenomenon, as the peak-to-peak value has changed from 0.3 dBm to 0.4 dBm, and the average value has also changed by about 0.05 dBm. This value is caused by the slight change in the temperature of the single machine caused by the operation of the satellite.  
Figure 6 shows the quantile and quantile (QQ) diagram of the SAIM power monitoring data of the C30 satellite. In this figure, the red line is the reference line of normal distribution and the blue curve is the distribution curve of the signal power monitoring data. The blue line is closer to the red curve, indicating that the monitoring data have an almost normal distribution.  
The distribution deviation of the B1C signal power monitoring data of the C30 satellite is 0.09 and the kurtosis is 2.66. The distribution deviation of the B2a signal power monitoring data of the C30 satellite is 0.01 and the kurtosis is 1.61. It can be seen that the signal power monitoring results of the B1C signals of the C30 satellite is almost normally distributed. Compared with the B2a signal, the distribution deviation of the B1C signal power monitoring data is close to a normal distribution, and the dispersion of the mean is smaller.  
We can see that the B2a signal is relatively sensitive, and the individual differences between different satellites are large. Generally, the integrity monitoring value is in a long-term relatively stable state. Due to the variation characteristics of the B2a signal of the C30 satellite over a long period of time, the normal distribution characteristics of its power monitoring data is relatively insignificant. However, considering the long-term drift of the data or the sensitivity of the existence of hardware existence, if the data is divided into multi-segment data analysis, it still conforms to the normal distribution characteristics. Therefore, in the follow-up integrity study, the drift characteristics and root causes of the integrity monitoring data should be fully analyzed.  
Figure 7 shows the QQ diagrams of the BIC signal and B2a signal power monitoring data of the C34 satellite. The distribution deviation of the BIC signal power monitoring data of the C34 satellite is \(-0.13\) and the kurtosis is 2.47. The distribution deviation of the B2a signal power monitoring data of the C34 satellite is \(-0.07\) and the kurtosis is 2.19. It can be seen from the figure that the normal distribution of the BIC and B2a signals' power monitoring data of the C34 satellite is obvious.  
Figure 5: SAIM monitoring values of B1C and B2a for (**a**) the C30 satellite and (**b**) the C34 satellite.  
The results show that signal power of BDS-3 SAIM has long-term stability and the variation in the monitoring data has an almost normal distribution in general.