## 3 Charging-Aware Multi-Mode Routing Protocol
### Charging-Aware Multi-Mode Routing Protocol (CMRP)
The RICA is designed to reduce the propagation delay of the PEGASIS and is tried to make two groups of sensors transfer data at the same time. Therefore, its LDR value approximately 1.5-times that of the PEGASIS+. The MSTP devotes its efforts on reducing energy consumption on data propagation. It makes multiple sensors to transfer data at the same time so that the LDR is higher than 0.7. The CMRP takes advantage of the MSTP to reduce the energy consumption for extending the operation time of the energy-lacking sensors. Sensors with moderate energy resource use the ring-based method to reduce the energy consumption and propagation delay. Sensors with plenty of energy resource use the cluster-based method to reduce the propagation delay. Thus, the CMRP has the best value on LDR. ## 5 Conclusions

A charging-aware multi-mode routing protocol based on the charging status of sensors is proposed for data gathering. CMRP is designed for the scenario that sensors can replenish their energy. Sensors with plenty of energy select the routing methods which introduce shorter propagation delay time and the sensors with less energy apply the routing method that consumes less energy. The next propagation target of CMRP considers both the charging status of the sensors and the distance to the sink. Simulation results show that the proposed CMRP can reduce energy consumption and shorten the propagation delay at the same time. The life-delay rate of the CMRP is better than all the other evaluated method. In future work, the gradually changed sunlight coverage can be used so that the CMRP can be applied to the scenario that sensors have different charging rate. **Funding:** This research received no external funding. **Conflicts of Interest:** The author declares no conflict of interest. ## References

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\begin{tabular}{c c c c c c} \hline \hline
**Protocols** & **Number of Nodes** & **100** & **125** & **150** & **175** & **200** \\ \hline LEACH & 0.047318 & 0.041506164 & 0.037179 & 0.034871 & 0.036515 \\ PEGASIS & 0.064274 & 0.053254316 & 0.044155 & 0.039632 & 0.036429 \\ PEGASIS+ & 0.284873 & 0.294922576 & 0.289819 & 0.28729 & 0.272922 \\ RICA & 0.43765 & 0.416311686 & 0.426872 & 0.414078 & 0.384849 \\ MCC & 0.565505 & 0.558406847 & 0.565445 & 0.555464 & 0.543804 \\ CMRP & 0.892515 & 0.911723311 & 0.946629 & 0.961023 & 0.949263 \\ MSTP & 0.723171 & 0.739505321 & 0.764615 & 0.762257 & 0.791184 \\ \hline \hline \end{tabular}
\end{table} 
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