# Efficient Node Deployment of Large-Scale Heterogeneous Wireless Sensor Networks
## 6 Performance Evaluation
### Results and Discussion  
The suggested deployment method was evaluated with respect to network lifespan and coverage ratio under various number of mobile nodes, number of sensor nodes, and initial deployment strategies of mobile nodes. 1. Network Lifetime Evaluation  
Here, a set of experiments is conducted to evaluate whether the improved coverage is worth the trade-off in energy consumption which in turn negatively affect the network lifetime. In this set, the performance of the proposed deployment algorithm is evaluated in terms of network lifetime compared to the deployment algorithms in [6; 13]. The first experiment studies the variation of network lifetime with a different number of mobile nodes. This experiment varies the percentage number of mobile nodes from 10% to 50% of the overall network nodes. The total number of sensor nodes in the network is set to 90. Figure 8 shows the variation of network lifetime to the percentage of the mobile node. As seen in Figure 8, the proposed deployment algorithm gives the best improvement in the network lifetime over other algorithms. It employs the nodes' available energy, movement energy, and movement distance to decide each mobile node's new location. Meanwhile, the comparison indicates that the deployment algorithm in [13] gives the worst performance since it does not consider nodes' residual energy when selecting which node to move. Still, it attempts to select only the nodes with the shortest movement distance. On the other hand, the deployment algorithm in [6] does not employ the movement distance, but it selects only nodes with the lowest movement distance. In the second experiment, the proposed algorithm's performance is evaluated under different sensor nodes compared to the algorithms in [6,13]. This experiment varies the number of sensor nodes from 90 to 130 nodes while setting mobile nodes' percentage at 30%. Figure 9 shows the variation of network lifetime with a different number of sensor nodes. From this figure, it can be observed that the proposed algorithm greatly increases the network lifetime in comparison to previous algorithms. In the last experiment of this set, the proposed algorithm's performance is evaluated with different initial deployment strategies of mobile nodes. We select four strategies for the initial deployment of mobile nodes, listed in Table 6, to evaluate their effects on the network deployment. We refer to these strategies as strategy 1-4, respectively. In this experiment, the number of sensor nodes and the percentage number of mobile nodes is set to 90 and 30%, respectively. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Values** \\ \hline Network size & 300 m \(\times\) 300 m \\ Number of sink nodes & 1 \\ Maximum number of retransmission & 4 \\ Packet size & 50 byte \\ Data rate & 19.2 Kbps \\ Frequency & 868 MHz \\ Transmission power & 0 dBm \\ Maximum transmission range & 200 m \\ Path loss exponent & 3 \\ Shadow fading variance & 4 \\ Noise power & \(-\)141 dBm \\ Reference distance & 1 m \\ \(\lambda\) & 15 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Simulation environment parameters [8,27]. Figure 8: Influence of increasing percentage of mobile nodes on network lifetime. according to the percentage of mobile nodes. As clearly seen, the proposed algorithm provides better coverage ratio compared to the deployment algorithm in [13]. However, the deployment algorithm's main goal in [6] is to improve network coverage, while the primary purpose of the proposed algorithm is to achieve the trade-off between coverage improvement and energy consumption. So, based on these results, we can say that the proposed algorithm achieves the suitable trade-off between the coverage improvement and the network lifetime. On the other hand, the deployment algorithm in [6] cannot get such a reasonable trade-off since it has the lowest coverage ratio. The second experiment of this set is conducted to evaluate the proposed algorithm's performance regarding the coverage ratio against the number of sensor nodes.