# Energy Consumption Model for Sensor Nodes Based on LoRa and LoRaWAN
## 7 Conclusions  
Energy consumption is one of the most constraining requirements for design and implementation of communicating sensors. In this paper, we present an optimized energy model for sensor nodes using LoRa/LoRaWAN technologies. This model allows the analysis of different LoRaWAN modes and scenarios for a specific Internet of Things application based on LoRaWAN Class A. In fact, to evaluate the energy consumption of the sensor node, we proposed different LoRaWAN scenarios. We concluded that receiving a transmission acknowledgment consumes an energy amount which reduces the sensor node lifetime. Then, the proposed energy model was evaluated using different LoRaWAN modes: this mode must be optimized to minimize the dissipated energy by the communicating sensor.  
The developed model also allows studying the impact of the hardware and the software choices into the node autonomy. We showed through numerical results that the consumed energy changes with different LoRa/LoRaWAN parameters such as spreading factor, coding rate, payload size and bandwidth. Optimizing these parameters is very important to reduce the energy consumption of the sensor node.  
The microcontroller operating frequency plays important role in optimizing the sensor node lifetime. Increasing the microcontroller frequency has an effect on the consumed energy which reduces the sensor node autonomy.  
Besides, we showed through the optimization study that there is a trade-off between the LoRaWAN communication range, the spreading factor and the transmission power. This optimization study is very interesting to choose and configure LoRa/LoRaWAN parameters. In fact, the increase of transmission power is more interesting in terms of consumed energy per useful bit than the increase of spreading factor.  
Finally, to show the real application case of our energy model, we considered a connected sensor for IoT applications. A specific application is discussed in this paper which is the monitoring of high voltage electrical network pylons. Using the proposed energy model, the energy consumption of LoRaWAN Class A and the sensor node lifetime can be estimated taking into account an acknowledgment transmission.  
Figure 22: Total energy consumption for different microcontroller frequencies (**a**), Battery life (**b**) (Mode 3, Scenario 2).  
In future works, this energy model could be used in power management algorithms for communicating sensor powered by energy harvesting sources in order to maximize the sensor node lifetime.  
**Author Contributions:** [PERSON] and [PERSON] developed the energy model for the sensor node. [PERSON], [PERSON] and [PERSON] studied LoRa/LoRaWAN characteristics and developed corresponding results. [PERSON] and [PERSON] contributed to results evaluation. All authors participated to write and correct the paper.  
**Funding:** This research received no external funding.  
**Acknowledgments:** This work was funded by a resourcing project CEA Tech in the region of Pays de la Loire, in partnership with IETR laboratory, CEA Letai and Eolane. I would like to acknowledge the CEA project managers: [PERSON] and [PERSON] and the IETR members [PERSON] and [PERSON] for their appreciative helps and supports.  
**Conflicts of Interest:** All authors declare no conflict of interest.