# Robust Clustering Routing Method for Wireless Sensor Networks Considering the Locust Search Scheme
## 5 Experiments and Simulation
### Network Lifetime  
The network lifetime analyzes the evolution of the alive and dead nodes in every round. This evolution is illustrated in Figures 2 and 3, respectively, where the graphics represent the obtained simulation results for all comparison methods. Figure 2 shows how many alive sensor nodes remain in the network in every round, while Figure 3 reveals the number of accumulated dead nodes in each round. From the graphics, it is clear that the proposed scheme outperforms the protocols in comparison since it manages to maintain more alive nodes in every round than the other methods. In other words, the proposed scheme manages to further reduce the number of nodes out of energy compared to the other protocols in every round.  
Contemplating the attained outcomes, the proposed method manages to extend the network's lifetime more than the protocols in comparison. The LS-II scheme can reach such results because it can automatically build the optimal number of clusters to stabilize the power load and extend the network lifetime. Moreover, the proposed protocol can change the network configuration in each round to increase the sensors' lifetime and reduce the power expenditure.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Protocol** & **Parameter** & **Value** \\ \hline GWO & \(a\) (linearly decreased from 2 to 0) & [2,0] \\ LEACH & \(p\) (the percentage of CHs) & 0.05 \\ LS-II & \(q\) (the number of best individuals considered for the social phase) & 10 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Setting parameters of the methods in comparison.  
Figure 2: Alive nodes’ evolution.  
The simulation of the network lifetime is also illustrated in Figure 4, where the cluster configuration selected by the proposed scheme for different periods is shown. Figure 4a-d show the optimal cluster configuration in rounds 1, 5, 11, and 15, respectively. The figure exemplifies the clusters' formation given the set of cluster heads chosen by the proposed method in distinct rounds. In the figure, it can be appreciated that the number of cluster heads can change from one round to another. Similarly, the number of clusters and the size of every cluster can be different. Furthermore, the figure shows the nodes that have died over time and how they are excluded from the clustering-transmission-reception process.  
Figure 4: Wireless sensor network clustering evolution: (**a**) cluster configuration in round 1, (**b**) in round 5, (**c**) in round 11, and (**d**) in round 15.  
Figure 3: Dead nodes’ evolution.  
In Figure 4, the base station is placed at the center of the sensing area and symbolized with a gray color diamond marker. On the other hand, normal sensor nodes are represented as gray color circles, while cluster heads are indicated with gray color squared markers. In contrast, dead sensor nodes are illustrated with black color circles. Regarding the communication links, every normal sensor node that belongs to a specific cluster has a connection line to its cluster head identified by a particular line style, which is a dotted line. Similarly, the communication between every cluster head and the base station is represented with a dashed line. Finally, a simple line represents the communication link of every normal sensor node that is not part of a cluster and transmits directly to the base station.