# A Hybrid Scheme for Disaster-Monitoring Applications in Wireless Sensor Networks
## 6 Performance Evaluation
### Clustering Performance  
The proposed clustering method was compared with the pLEACH algorithm using the same radio model and simulation parameters. The message sizes sent by the sound-monitoring, seismic monitoring, and picture-monitoring nodes to the cluster head in each round were 5, 15, and 25 kB. The initial energies of the sound-, seismic, and picture-monitoring nodes were 2 J, 3 J, and 5 J, respectively. The other simulation parameters of the proposed model are listed in Table 3.  
In HT-MAC, \(T_{trutch}\), the residual working time as a cluster head, is the variable that determines which node is the cluster head. We assume that a sensor node gains \(l\) bits of sensing data in time \(t_{sc}\); thus, \(P_{sc}\) the mean power of sensing and calculation for this node is  
\[P_{sc}=\frac{lE_{sc}}{t_{sc}}, \tag{28}\]  
where \(E_{sc}\) is the energy consumption for sensing and calculating this type of node. If a sensor node aggregates \(k\) bits of data and relays them to a base station at a distance \(d\) in time \(t_{ar}\), \(P_{ar}\) is the mean power of the data aggregation and relay as a cluster head:  
\[P_{ar}=\frac{kE_{DA}+kE_{Tx}(k,d)}{t_{ar}}. \tag{29}\]  
Through clustering simulations, the number of alive nodes for pLEACH and HT-MAC are is in Figure 8. At the same number of rounds, HT-MAC had more live nodes than pLEACH. Owing to the uneven energy consumption, pLEACH started to experience node energy exhaustion at over 847 rounds. However, HT-MAC did not experience node energy exhaustion until more than 1227 rounds. After experiencing a rapid decline, the number of live HT-MAC nodes gradually stabilized at approximately 1700 rounds. When the number of members in a cluster decreases, the energy consumption of the cluster head for relaying decreases significantly. A similar phenomenon was observed with pLEACH.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Description** & **Symbol** & **Value** \\ \hline Energy consumption of short distance transmission & \(\varepsilon_{fg}\) & 10 pJ/bit/m\({}^{2}\) \\ Energy consumption of long distance transmission & \(\varepsilon_{mp}\) & 0.0013 pJ/bit/m\({}^{4}\) \\ Energy consumption for digital coding, modulation, filtering, and spreading of the signal & \(E_{dec}\) & 50 nJ/bit \\ Energy for data aggregation & \(E_{DA}\) & 5 nJ/bit/signal \\ Energy for sound-sensing and calculating & \(E_{sc-gau}\) & 50 pJ/bit \\ Energy for picture-sensing and calculating & \(E_{sc-pic}\) & 5 nJ/bit \\ Energy for seismicity-sensing and calculating & \(E_{sc-sci}\) & 3 nJ/bit \\ \hline \hline \end{tabular}
\end{table}
Table 3: Simulation parameters of clustering performance.  
Figure 8: Number of nodes alive over time.  
The total amount of data received at the base station during the network lifetime is shown in Figure 9. This shows that the amount of received data increases smoothly at the beginning for HT-MAC and pLEACH. After 847 rounds, HT-MAC received significantly more data at the base station than the pLEACH algorithm, and the growth of the data received by pLEACH became slower. The data received by HT-MAC also become slower after 1227 rounds, but HT-MAC still receives much more data than the pLEACH algorithm, and it perseveres longer.