# A Novel Adaptive Cluster Based Routing Protocol for Energy-Harvesting Wireless Sensor Networks
## 2 Adaptive Hierarchical-Clustering-Based Routing Protocol for EH-WSNs
### HCEH-UC Routing Algorithm
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Initial- Energy** & **LEACH** & **LEACH-C** & **CEEC** & **HUCL** & **SEED** & **NEHCP** & **HCEH-UC** \\ \hline
0.25 & 336 & 347 & 1500 & 1775 & 2012 & 2500 & 2573 \\
0.5 & 621 & 740 & 2675 & 3120 & 4200 & 4912 & 5145 \\
0.75 & 844 & 946 & 4088 & 4512 & 5312 & 6075 & 7713 \\
1 & 1133 & 1336 & 4912 & 5587 & 7500 & 8300 & 10,280 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: MLC under a different initial energy. the cluster head or the data-transmission node, and the exhausted node would switch into sleep mode and implement energy harvesting when the energy is insufficient. Therefore, uninterrupted target coverage can then be accomplished based on energy harvesting. Take a complete cycle from the residual energy curve for specific analysis. The example cluster contains six nodes, including nodes 10, 11, 12, 13, 14, and 33. In the first stage, node 10 of the cluster serves as the cluster head node, nodes 11, 12, 13, and 14 serve as data-transmission nodes, and node 33 enters sleep mode due to insufficient energy and performs energy harvesting. At this stage, the energy of node 10 drops rapidly, nodes 11, 12, 13, and 14 drop slightly, and the energy stored in node 33 rises steadily. In the second stage, node 11 would be selected as the cluster head based on the remaining energy and node information through the cluster-head-selection mechanism proposed in this paper. Cluster head node 10 would switch into sleep mode and collect energy due to the insufficient energy. Nodes 12, 13, 14, and node 33, which has completed energy storage, would serve as the data-transmission nodes until the energy of node 11 reaches a low level. When the energy harvesting of node 10 is completed, node 11 would switch into sleep mode and the successor cluster head node would be re-elected; thus, the third stage and the following stage can start. The energy consumption of cluster head nodes is relatively high, and the energy consumption of non-CH nodes is relatively slow. When the energy storage is insufficient, the node switches into a sleep node to accomplish energy harvesting. The simulation results prove that the algorithm proposed in this paper can control the number of nodes in the sleep mode for one cluster within a reasonable range through the reasonable adjustment of the communication mode of nodes. Therefore, uninterrupted target coverage would be accomplished based on energy harvesting. ## 4 Conclusions

This paper proposes an energy harvesting-based routing algorithm for uninterrupted WSN target coverage. Firstly, based on the proposed hierarchical clustering algorithm, the nodes can accomplish environment-adaptive clustering based on the distance between each other, which can reduce the energy consumption of data transmission inside the cluster and optimize the topological relationship of the network. A cluster head selection mechanism is then proposed based on three crucial aspects of energy harvesting, including the residual energy of nodes, the data-transmission energy model, and the energy collection needed to form an advanced HCEH-UC routing protocol. Finally, the distributed communication mode and topological relationship of the node cluster that is formed can be adaptively determined through the alternative operating-recharging mode of the cluster head node. Therefore, an energy harvesting-based, uninterrupted target coverage can be accomplished. In order to verify the proposed HCEH-UC routing algorithm, comparison simulations were conducted in terms of the improved clustering algorithm and the energy harvesting-based, uninterrupted target coverage algorithm. Compared with the conventional routing algorithm, the simulation results proved the effectiveness of the proposed HCEH-UC routing algorithm. The research was funded by the National Natural Science Foundation of China, grant number 61674100. **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable.