## 4 Simulation and Analysis
### Acceptable URA and \(P_{\text{sat}}\)
# represents the different degrees of increase. Figure 4: The global availability coverage with different _URA_ and \(P_{\text{sat}}\). The solid markers indicate the baseline constellation of 24 GPS + 27 BDS. The hollow markers indicate the depleted constellation of 23 GPS + 26 BDS. Under the depleted constellation, _URA_ should better than 0.6 m with \(P_{\text{sat}}\) at \(10^{-3}\) and the required integrity risk at \(10^{-7}\). As revealed by the literature [7; 8; 9; 10; 11], \(P_{\text{sat}}\) for GPS and BDS ranged from \(10^{-5}\) to \(3.5\times 10^{-4}\), which indicated that the combination of GPS and BDS had the potential to satisfy the integrity risk requirement of LPV-200 concerning \(P_{\text{sat}}\). For the Galileo, greater attention should be paid to constellation faults because their probability, \(P_{\text{const}}\), is equal to or greater than that of single-satellite faults [8]. The representative SISRE values of 0.2-0.58 m and 2 m were demonstrated for Galileo and GLONASS [31; 32]. _URA_ can be empirically expressed as 1.5\(\times\) SISRE [24]. Consequently, the SIS performance of Galileo had the potential to support the integrity risk requirement of LPV-200. It was expected that the comparable integrity level could not be achieved by GLONASS unless _URA_ improved by 2.34 m and \(P_{\text{sat}}\) was constrained within \(10^{-3}\). Since the selection of the third group of parameters affected the integrity performance, acceptable _URA_ under a different third group of parameters needs to be considered. The effect of the third group on global integrity performance was analyzed. The selection of the third group of parameters was referenced from the requirement of LPV-200 and APV-II [33]. Acceptable _URA_ with a different third group of parameters has been shown in Table 4. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Third Group of**} & \multirow{2}{*}{**Coverage**} & \multicolumn{6}{c}{**Integrity Risk Requirement**} \\  & & & \(\mathbf{2\times 10^{-7}}\) & \(\mathbf{10^{-7}}\) & \(\mathbf{9\times 10^{-8}}\) & \(\mathbf{4.5\times 10^{-8}}\) & \(\mathbf{2\times 10^{-8}}\) & \(\mathbf{10^{-8}}\) \\ \hline \multirow{6}{*}{_URA_ (m)} & \multirow{2}{*}{\(8\times 10^{-6}\)} & 99.5\% & 1.04 & 0.96 & 0.94 & 0.88 & 0.78 & 0.70 \\  & & 95.0\% & 1.44 & 1.36 & 1.34 & 1.26 & 1.20 & 1.14 \\ \cline{2-10}  & \multirow{2}{*}{\(4\times 10^{-6}\)} & 99.5\% & 1.00 & 0.92 & 0.92 & 0.82 & 0.74 & 0.68 \\  & & 95.0\% & 1.40 & 1.32 & 1.30 & 1.24 & 1.16 & 1.10 \\ \cline{2-10}  & \multirow{2}{*}{\(10^{-4}\)} & 99.5\% & 1.04 & 0.98 & 0.96 & 0.90 & 0.80 & 0.72 \\  & & 95.0\% & 1.46 & 1.38 & 1.36 & 1.28 & 1.20 & 1.14 \\ \cline{2-10}  & \multirow{2}{*}{\(P_{\text{md}}\)} & \multirow{2}{*}{\(10^{-5}\)} & 99.5\% & 1.04 & 0.98 & 0.96 & 0.90 & 0.80 & 0.72 \\  & & 95.0\% & 1.46 & 1.38 & 1.36 & 1.28 & 1.20 & 1.14 \\ \cline{2-10}  & \multirow{2}{*}{\(20\)} & 99.5\% & / & / & / & / & / & / \\  & & 95.0\% & / & / & / & / & / & / \\ \cline{2-10}  & \multirow{2}{*}{\(30\)} & 99.5\% & 0.64 & 0.50 & / & / & / & / \\  & & 95.0\% & 1.08 & 0.98 & 0.98 & 0.90 & 0.80 & 0.74 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Acceptable _URA_ with different third group of parameters.