# A Novel Adaptive Cluster Based Routing Protocol for Energy-Harvesting Wireless Sensor Networks
###### Abstract
To optimize the energy-efficient routing protocol based on these widely-used classic protocols, a centralized energy efficient distance (CEED) routing protocol [16] is proposed to establish the chain among the specifically formed CHs to evenly distribute the energy consumption of all sensor nodes. In [17], a BS-centralized energy regulation has been added to the LEACH protocol to form the LEACH-centralized (LEACH-C) protocol, which can avoid nodes with low energy being selected as the cluster head. A parallel communication structure is designed for the PEGASIS protocol in [18] to reduce the transmission delay caused by the chain-based routing protocol. However, the stored energy of the node would inevitably be exhausted and cause a coverage hole. Thus, the EH technology [19] is an excellent option to guarantee uninterrupted coverage [20] of the network. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Protocol** & **Structure** & **Feature** \\ \hline Low-energy & & \\ adaptive & & The cluster head nodes compress data received from the \\ clustering & & respective cluster and send an aggregated packet to the base \\ hierarchy & & station in order to reduce the amount of transmission data \\ (LEACH) [13] & & \\ LEACH- & & \\ centralized & & head, thus prolonging the maximum lifetime coverage \\ (LEACH-C) [17] & & \\ Power-efficient & & \\ gathering in & & \\ sensor & & \\ information & & \\ systems & & nearest-neighbor principle \\ (PEGASIS) [15] & & \\ Centralized & & \\ energy efficient & & \\ distance & & \\ (CEED) [16] & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Comparison of the conventional routing protocols. In the EH-WSNs, each sensor node possesses the ability to capture energy from the environment into its own rechargeable battery, such as wind, solar, and thermal energy [21]. For the whole-energy management of WSNs, uninterrupted coverage can be accomplished when the amount of energy harvesting is more than or equal to the energy consumption [22]. Therefore, the MLC of WSNs not only depends on EH efficiency, but also the energy consumption [23]. The WSN node can not perform data transmission in the energy-harvesting phase, so the energy-efficient protocol should be redefined for the EH network to deal with the variable information routing and the inoperative nodes [24]. In [25], a novel energy-harvesting clustering protocol (NEHCP) is proposed based on the hierarchical clustering routing protocol. The collected data are aggregated and transmitted to the base station under uncontrollable ambient resources based on EH technology. The energy-efficient protocol was improved by the Euclidean distance matrix reconstruction method in [26], which could solve the intermittent energy shortage caused by the imbalance between harvested and demanded energy in EH-WSNs. Although the energy can be harvested, these research achievements prove that energy-consumption optimization remains an important problem in EH-WSNs. As mentioned above, the cluster-based and the chain-based routing protocol possess the ability to accomplish the energy-efficient WSNs through the optimization of the data transmission. However, the node in EH-WSNs would be inoperative in the EH phase, as the disabled node may completely analyze the chain-based routing if the distance between the last node and the next node is beyond the communication distance. Thus, for the routing protocol design for EH-WSNs, the cluster-based routing protocol has become the research focus because of the independent node assignment and the robust cluster reconstruction. In the cluster-based routing protocol of EH-WSNs, the node-clustering method and the management of CHs remain the essential problems. In [27], a triangular, fuzzy-based, spectral cluster routing (TF-SCR) mechanism is proposed, considering the MLC of WSNs and the reliability of data transmission. The spectral clustering method is adopted to accomplish the residual-energy-based node clustering.