## 5 Simulations and Discussions
### Evaluation of Detection Capability
Considering the polar region boundary latitude, the link delay range of AOLs is about 4-12 ms. At the same time, we set up a satellite-ground communication link and obtain the link distance range between the satellite and the ground station through simulation, as shown in Figure 19. Without considering the weather and other complex factors, the link delay range between the satellite and ground station is about 3-10 ms. The transmission delay can be expressed as \(Dly_{trans}\), as shown in Equation (8), where \(Size_{data}\) represents the size of the transmission data and \(Tr\) represents the transmission rate of the channel. \[Dly_{trans}=Size_{data}/Tr \tag{8}\]  
According to different transmission frequencies and communication bandwidth, \(Tr\) varies from tens of K to tens of Mbps. Generally speaking, the frequency and bandwidth of the inter-satellite link, data uplink, and data downlink are different. For example, the  
Figure 18: The link propagation delay of IOLs and AOLs. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**NS**} & **SN (Extra** & **GN (Extra** & **SGN (Extra Overhead)** & **SGN (Extra Overhead)** \\ \cline{2-5}
**PT** & \(K\times GR+N\times M\times GRT\) & 0 & 0 & 0 \\ \hline
**DT** & \(K\times CR+N\times M\times CRT\) & \(P\times\) (\(GR+GRT\)) & \(q\times GRT\) & \(p\times(GR+GRT)+r\times GRT\) \\ \hline \hline \end{tabular}
\end{table} 
Table 8: The computing overhead of the proposed framework in different situations. inter-satellite link of the MILSTAR satellite system uses 60 GHz mmWave communication with a 2.16 GHz bandwidth, and the uplink frequency and downlink frequency are about 44 GHz and 20 GHz, respectively [35; 36]. For the convenience of evaluation, the transmission rates of inter-satellite link, data uplink, and data downlink in this example are set to 3 Mbps, 2 Mbps, and 1 Mbps, respectively. At the same time, in the framework proposed in this paper, the five types of process files involved in the DHRP routing protocol are transmitted and stored in the form of \(txt\). The size of each file, the required number of files in the satellite network, inter-satellite link transmission delay, uplink transmission delay, and downlink transmission delay are shown in Table 9, and Figure 20 contains five curves that correspond to the five types of process files involved in the DHRP routing protocol. Each curve shows the change in the transmission delay of one file with the transmission rate. To evaluate the additional communication time cost of the detection and protection framework proposed in this paper, we take the DHRP routing protocol as an example to obtain the total routing convergence time under the NS, SN, GN, and SGN situations, respectively, as shown in Figure 21.  
Under the normal situation (NS), the total routing convergence time consists mainly of the following parts: the time for collecting inter-satellite link delay (_Link delay obtaining_), the maximum delay for PS to obtain the LSA of the current orbit satellite (_LSAs to PS_), the S-LSA exchange time between PS of different orbits (_S-LSA exchange_), and the maximum delay for PS to distribute route tables for satellites in the orbit (_RT distribution_). Due to the uncertainty in PS selection in the satellite network, we consider the optimal and worst  
Figure 19: The distance range of a satellite–ground communication link. \begin{table}
\begin{tabular}{l l l l l l} \hline \hline  & **POS** & **LSA** & **S-LSA** & **RIB** & **RT** \\ \hline Size (B) & 17 & 26 & 368 & 1868 & 432 \\ \hline The number of files in PT & 66 & 66 & 6 & 6 & 66 \\ \hline The inter-satellite link transmission delay (ms) & - & 0.07 & 0.98 & - & 1.16 \\ \hline The uplink transmission delay (ms) & - & - & - & - & 1.73 \\ \hline The downlink transmission delay (ms) & 0.14 & 0.21 & - & 14.94 & 3.46 \\ \hline \hline \end{tabular} Note: “-” means that the proposed framework doesn’t need to consider this delay.  
\end{table} 
Table 9: Transmission delay of different files. case of S-LSA switching.