Energy consumption of IoT devices: An accurate evaluation to better predict battery lifetime

LoRa to say Long Range is one of the Low Power Wide Area Network technologies suitable for Internet of Things due to its low power consumption. In this paper we evaluate the energy consumption of a LoRa network using the LoRaWAN protocol which is based on the pure Aloha access method. We define a reference scenario (scenario 0), which consists in neglecting the energy consumption related to the different states of the end-devices after transmission of a packet that does not require downlink acknowledgment and then we compare this scenario 0 to scenario 1, scenario 2 and scenario 3. Indeed the scenario 1 consists in considering the states of the end-devices after transmission in uplink of a packet without acknowledgment, in the evaluation of the energy consumption. However, scenario 2 takes into account the different states of the end-devices in scenario 1 with an acknowledgment on the first reception window. While in scenario 3 the acknowledgment is done on the second reception window always taking into account the end-devices states. The simulation results with the LoRaSim tool have shown that the network energy consumption (NEC) increases significantly when considering the different states of the end-device after uplink transmission of a packet without acknowledgment, but also that the increase of the NEC related to end-device states is even more important if packets are acknowledged. Thus for a rigorous evaluation of the NEC, it is important to take into account the states of the end-device after transmission of a packet but also the eventual acknowledgments in order to better predict the battery lifetime.