## 5 Performance Analysis and Simulation
### Comparison of the Performance Simulation
#### 5.3.1 Comparison of Safety Period  
In each experiment, the network topology remains the same, and the SoN sends data packets to the SN at time interval T. The attacker traces back one hop every time he overhears a packet, and the simulation ends once the attacker captures the SoN. If the attacker does not overhead the data packet within the time interval T, he will roll back hop-by-hop along the tracking path until he returns to the \begin{table}
\begin{tabular}{c c} \hline \hline
**Scheme** & **Total Communication Overhead** \\ \hline EPUSBRF & \(\text{Hop}_{\text{EPUSBRFsum}}=\text{Hop}_{\text{PEUSBRF}}+\text{Hop}_{ \text{EPUSBRFc}}\) \\ RPBMP & \(\text{Hop}_{\text{RPBMPsum}}=\text{Hop}_{\text{RPBMP}}+\text{Hop}_{\text{ RPBMPc}}\) \\ Shortest path algorithm & \(\text{Hop}_{\text{Shortest}}=\text{Hop}_{\text{PShortest}}+\text{Hop}_{\text{ S,sink}}\) \\ NRSPS & \(\text{Hop}_{\text{PNRSPSsum}}=\text{Hop}_{\text{PSPS}}+\text{Hop}_{\text{ NRSPSc}}\) \\ NRDPS & \(\text{Hop}_{\text{PNRDPSsum}}=\text{Hop}_{\text{PDPS}}+\text{Hop}_{\text{ PNRDPSc}}\) \\ RSPS & \(\text{Hop}_{\text{RSPSsum}}=\text{Hop}_{\text{PSPSPS}}+\text{Hop}_{\text{ RPSSc}}\) \\ RDPS & \(\text{Hop}_{\text{PDPSsum}}=\text{Hop}_{\text{PDPS}}+\text{Hop}_{\text{ RDPSc}}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison of the total communication overhead. SN. If the attacker overhears a packet while returning to the SN, he moves to the packet sending node and continues listening and backtracking until the end of the experiment. It should be noted that the end condition of the experiment in this paper is that the attacker captures the SoN, that is, in a single experiment the panda does not disappear once it appears. If the safety period is greater than 1000, the scheme can ensure that the panda will not be captured by the attacker. **Experiment 1:** Comparison of the safety period of NRSPS and other three schemes  
According to the analysis in Section 5.1.3, the NRSPS scheme provides the shortest safety period among our proposed schemes. Therefore, in Experiment 1, we compare the safety period of the NRSPS scheme with that of the shortest path algorithm, EPUSBRF and RPBMP. The average safety period is obtained by repeating 100 experiments, as shown in Figure 10.  
It can be seen from Figure 10 that compared with the shortest path algorithm, EPUSBRF, and RPBMP, the average safety period of our proposed NRSPS scheme increases by 6.08 times, 3.57 times and 2.78 times, respectively. As the hop count between the SoN and the SN increases, the safety period of the four schemes increases. This is because the hop count that the attacker needs to backtrack increases correspondingly with the increase of hop count between the SoN and the SN. However, the safety period of each scheme in the experiment is less than 200, indicating that the SoN only sent less than 200 packets before being captured by the attacker. Therefore, although the safety period of NRSPS scheme improves compared with the shortest path algorithm, EPUSBRF, and RPBMP, it still cannot prevent the SoN from being captured by the attacker. **Experiment 2:** The effect of the number of phantom nodes on the safety period  
Since the NRSPS scheme cannot prevent the source node from being captured by the attacker, in Experiment 2, we consider increasing the number of PNs, and compare the safety period of the NRSPS scheme with that of the NRDPS scheme. The average safety period is obtained by repeating the experiment 100 times, as shown in Figure 11.  
It can be seen from Figure 11 that the safety period provided by our proposed NRDPS scheme is much larger than that of the NRSPS scheme. Compared with NRSPS, the average safety period of NRDPS increases by 7.62 times. This is because as the number of PNs increases, the hop count of the routing path increases accordingly, which leads to an increase in the hop count required by the attacker to backtrack.