## 4 Performance Evaluation of the Navigation Algorithm through the M&S Software  
The performance evaluation was performed for the GPS only navigation system and a multi-radio integrated navigation system under the navigation warfare environment through the proposed M&S software. The measurement errors of the navigation systems in the performance evaluation were assumed to be white noise Gaussian and their standard deviations are listed in Table 5.  
The reference trajectory of the vehicle is shown in Figure 13. The jammer was located in the left of the trajectory, 38.096521 degrees of latitude, 126.576012 degrees of longitude and 300 m of altitude, as shown in Figure 13. The jammer was set to start its operation at 1600 s and end at 3500 s via the navigation warfare scenario parameter setting window, shown in Figure 11. It could be seen that the navigation warfare occurred during the operation of the vehicle. The location and start point of the jammer are shown in Figure 13. For the multi-radio integrated navigation system, the weighted least squares method was used. The weights were determined from the measurement error statistics listed in Table 5. It was assumed that the jammer influenced only the GPS signals. When the J/S (jammer to signal power ratio) was larger than 40 dB, the measurement was not available, since the signals could  
Figure 12: GUI for measurements, signal sources, navigation results and navigation warfare situation. \begin{table}
\begin{tabular}{c c} \hline \hline
**Navigation System** & **Measurement Error (1 \(\sigma\))** \\ \hline GPS & 3 m \\ KNSS & 10 m \\ eLoran & 10 m \\ Loran-C & 100 m \\ DME & 340 m \\ VOR & 1.5\({}^{\circ}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Measurement error of navigation system. not be tracked in this environment. When the J/S was less than 40 dB, the measurement error caused by the jammer was added to the measurement. The performance evaluation was performed for 0, 10, 30, 50, and 100 W of jammer power in the navigation warfare environment. For 0, 10, 30, 50, and 100 W of jammer power, the number of satellites in view are shown in the upper graph of Figure 14. The distance from the vehicle to the jammer is shown in the lower graph of Figure 14. It could be seen that the number of satellites in view decreased from 1600 s when the jammer started its operation. At the time around 2750 s, when the distance from the vehicle to the jammer was the shortest, the number of the satellites in view was the least. It could be observed from these test results that the GPS measurement error due to the jammer to the navigation warfare scenario was well modeled. The position errors of GPS only navigation and the multi-radio integrated navigation system are shown in Figures 15-18 for the cases of 0 and 50 W of jammer power. In the case of the GPS  
Figure 14: Variations of the number of satellites in view and distance between vehicle and jammer. Figure 13: Reference trajectory for performance evaluation. only navigation, it was regarded that the normal navigation outputs could be obtained only when PDOP (position dilution of precision) was less than 10. The position errors are shown in Figures 15 and 16 when there was no jammer. The performance of the multi-radio integrated navigation system in Figure 16 was similar to that of the GPS only navigation when the GPS was available. This can be easily expected since the measurements of GPS are more accurate than those of other navigation systems, as in Table 5. The position errors for the case of 50 W of jammer power are shown in Figures 17 and 18. It can be seen from Figure 17 that the position error increased from the time when the jammer started, and the navigation outputs were not obtained from the time when the number of satellites in view was less than four (Figure 14). It can also be seen that the navigation results could be obtained from the time of 3470 s when the number of satellites in view became more than four.