## 4 Performance Evaluation
### Simulation Result
On this basis, our further proposed NCS fully considers the spatial correlation among nodes, and thus is able to satisfy the coverage rate threshold with fewer monitoring nodes, so the ERG-NCS has the longest network lifetime, and simultaneously achieves a high PDR with a high network lifetime. Table 4 gives the network lifetime of these algorithms with different numbers of nodes, the underlined value is the highest lifetime for each node number. The network lifetime of ERG-NCS is improved by an average of 3.27 times over AMSG and 4.03 times over RTG, which is due to the high number of nodes in a large-scale sensor network, which makes this gain especially effective after scheduling nodes to work. In addition, the lifetime of ERG-NCS is also improved by an average of  
Figure 8: Network PDR with different number of sensor nodes. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Nodes Number** & **500** & **600** & **700** & **800** \\ \hline ERG-NCS & 0.9357 & 0.9409 & 0.9573 & 0.9683 \\ ERG-DGS & 0.9172 & 0.9237 & 0.9458 & 0.9508 \\ AMSG-DGS & 0.6161 & 0.6683 & 0.7100 & 0.7447 \\ RTG-DGS & 0.6308 & 0.7045 & 0.7558 & 0.7801 \\ ERG & 0.8501 & 0.8644 & 0.8838 & 0.8968 \\ AMSG & 0.5734 & 0.6281 & 0.6630 & 0.6976 \\ RTG & 0.6245 & 0.6677 & 0.7148 & 0.7374 \\ \hline \hline \end{tabular} The underlined value is the highest PDR for each node number.  
\end{table} 
Table 3: The algorithms’ network PDR with different number of sensor nodes. 15.57% and 35.79% over AMSG-DGS and RTG-DGS, which results from the high efficiency of the NCS algorithm. Figure 10 demonstrates the network PDR with different communication radii. When the communication radius increases, the node has more next-hop nodes to choose from, and thus it has more paths to choose from, which betters the network communication environment, so the PDR increases with the communication radius. The ERG is able to repair the broken paths, and the PDR of ERG is not affected by communication radius as much as AMSG and RTG, and it can be said that ERG's robustness is superior to that of the AMSG and RTG. In addition, the differences of these algorithms remain consistent with Figure 8.  
Figure 11 measures the network lifetime with different communication radii. As mentioned earlier, as the communication radius increases, the communication environment of the entire network becomes better and packets are more likely to be transmitted back to the sink successfully through multiple hops, so the energy consumption of the RTG and AMSG networks increases with the increase in the communication radius, thus leading to a decrease in the network lifetime. For the ERG algorithm, when the network communication environment is not good, it also repairs the links and saves the energy of the broken links, thus it does not change significantly due to the change in the communication radius, which further demonstrates that ERG is very robust and ERG-NCS is able to maintain a high network lifetime all the time. Generally, as the communication radius of sensor nodes increases, although the communication environment of the network becomes better, it aggravates the node energy consumption and the network lifetime will decrease, but ERG-NCS has better robustness, which means that it has a strong dynamic adjustment ability, and the network lifetime decreases not obviously, so in the figure it has an optimal communication radius of 120 m, and at this time, it has the highest packet delivery rate and the lowest network latency, and the network lifetime is almost unaffected. Next, the variation in network energy consumption, number of alive nodes, network coverage, throughput, and PDR with the number of rounds is explored for the same nodes distribution scenario with the number of nodes being 600, communication radius being 100 m, and coverage rate threshold being 0.9. From Figure 12, it can be seen that due to the difference in the number of monitoring nodes selected by different algorithms, each monitoring node creates a path by single hop or multiple hops.