## 4 Simulation Analysis
### Simulation and Result Analysis
#### 4.2.2 INS+LEO2-Satellite Alternate Switching Ranging Integrated Navigation Algorithm  
The experimental research object and the navigation satellite system are the same as the standard INS+LEO2-satellite integrated navigation positioning algorithm. The research scenario uses INS combined with two satellites in the SpaceX satellite system to achieve integrated navigation and positioning of the aircraft by alternately switching between the two satellites. Specifically, the research scenario is first divided according to the difference in the satellite orbital surface and phase, into two research sub-scenarios. These are (1) INS+LEO2-satellites on the same orbital surface alternately switching ranging, integrated navigation, and positioning, and (2) INS+LEO2-satellites on the adjacent orbital surface, alternately switching ranging, integrated navigation and positioning. Then in each research sub-scenario, considering that the time for the LEO satellite to pass the zenith is very short (about several min to 10 min [37]), carrier users inevitably have to switch between different LEO satellites (generally between beams) to ensure continuous navigation and positioning services. It is worth mentioning that switching also brings many benefits. On the one hand, in a military scenario, a certain extent of anti-interference ability can be guaranteed, and the shorter the switching time, the less likely interference is. On the other hand, switching between beams can avoid bandwidth occupied for a long time, and therefore bandwidth resources can be fully utilized and waste avoided. However, this is a beam resource management and optimization issue, and we will not consider it here. Both short and long switching times have advantages and disadvantages. Frequent switching will increase the processing pressure and power consumption of the receiver, and will also affect the ICN communication function. A longer switching time can ensure the operation of navigation and positioning functions without affecting ICN communication functions. However, a longer switching time will also cause an increase in the final navigation and positioning error, due to the cumulative error of the INS, affecting the location service. Therefore, in actual projects, trade-offs should be made according to actual needs. As an experimental analysis, we examined the navigation and positioning effects under alternate intervals of 5 s, 10 s, 30 s and 60 s, at the same time, using the standard INS+LEO2-satellite as a reference, and simulate them together. (1) Same orbits surface Based on the fundamental principle that the altitude angle of the satellite cannot be lower than \(10^{\circ}\), we selected two satellites on the same orbital surface that are always visible on the trajectory of the carrier. This experiment simulated two satellites, numbered 233 and 245 on the V orbital surface of the SpaceX satellite system, and named satellites #1 and #2 respectively. The final simulation result is shown in Figure 4.  
In Figure 4, one satellite provides the true ranging value on the same orbital surface, and the other satellite provides the virtual ranging value. We find that this algorithm can effectively improve the INS error and suppress its divergence through different switching time intervals. It is more effective in improving the position error and velocity error; the attitude error improvement in the north and up direction also received good results. Judging from the final trajectory, the longitude, latitude and altitude errors were very small. To quantitatively analyze the algorithm's performance on the same orbital surface, we used the mean and standard deviation as evaluation indicators. We calculated statistics from the final navigation trajectory errors, and the results are shown in Table 4.  
Figure 4: Error curve of the INS+LEO2-satellite alternate switching ranging integrated navigation algorithm based on the same orbital surface.