## 5 Results and Discussion
### Intra-Cluster Communication
#### 5.1.1 Comparison of Residual Energy  
In this experiment, the residual energy of each node was compared to assess the energy efficiency of the proposed intra-cluster communication scheme, which utilises a cluster-head rotation approach. Figure 10 illustrates the comparison of the residual energies of nodes during intra-cluster communication, contrasting the proposed rotation method (Figure 10a) with the traditional rotation method (Figure 10b) for a cluster consisting of three nodes. The traditional rotation method demonstrates a rapid depletion of energy, with the first node in the cluster exhausting its energy after 194 cycles of data transmission. The last node in the cluster depletes its energy after 360 cycles. This disparity in energy depletion imposes limitations on the cluster's lifetime and coverage, with a notable impact on first node death scale, thereby reducing stability. In contrast, the proposed cluster-head rotation scheme significantly extends the lifespan of the network. The first node's energy depletion is delayed until 298 cycles, with the nodes exhibiting converging behaviour in their energy consumption. This convergence indicates improved stability and more efficient utilisation of available energy, thereby prolonging the network's operation. Figure 11 presents results consistent with those observed in Figure 10, demonstrating the effectiveness of the proposed cluster-head rotation scheme as the number of nodes in the cluster increases to five. These results validate the scalability of the proposed method, confirming that it can efficiently manage energy consumption across larger clusters while maintaining balanced energy utilisation and extended network lifetime. The experiments conducted with clusters of nodes \(n=3\) and \(n=5\) were specifically chosen to illustrate the scalable and adaptable behaviour of the proposed cluster-head rotation method across different network sizes. These two configurations effectively represent small and moderately sized clusters, which are typical in many HWSN-based IoT applications. By focusing on these scenarios, the experiments provide a clear demonstration of the method's capacity to manage energy efficiently and extend network lifetime within smaller-scale deployments, where resource constraints are critical. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameter** & **Value** \\ \hline Number of nodes (\(n\)) & 3 and 5 \\ \hline Range of heterogeneous initial energies of nodes & (0.05\(-\)0.2) J \\ \hline Total energy of nodes in a cluster & 0.5 J \\ \hline Range of heterogeneous packet size (\(l\)) & (1000\(-\)8000) bits \\ \hline Total data transmitted by nodes in a cluster & 20,000 bits \\ \hline Electronic circuitry (\(E_{elc}\)) & 50 nJ/bit/m\({}^{2}\) \\ \hline Amplifier energy for free space (\(e_{fs}\)) & 10 pJ/bit/m\({}^{2}\) \\ \hline Amplifier energy for multipath (\(e_{mp}\)) & pJ/bit/m\({}^{4}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Simulation parameters. The choice of \(n=3\) and \(n=5\) is sufficient for assessing the proposed method's performance because they offer a simplified testing ground. These cluster sizes allow for detailed observation of energy consumption patterns and the benefits of the proposed rotation scheme in a controlled environment. The results show significant improvements in energy management, as seen through the extended network lifespan and balanced energy utilisation, even as the cluster size increases from three to five nodes. It is clear that these results can easily be extended to other cluster sizes. Additionally, these experiments serve as an initial demonstration of the proposed method's scalability. The consistent outcomes across both configurations suggest that the proposed approach can maintain energy efficiency and stability, even as the network scales up. This lays the groundwork for the full-scale network simulations presented in subsequent sections, where larger and more complex network topology of full networks is examined.