# Modeling the Energy Performance of LoRaWAN
## 6 Conclusions  
In this paper, we have modeled the energy consumption of a Class A LoRaWAN end-device transmitting data messages periodically, considering impact of unacknowledged and acknowledged transmission, DRs, frame payload size and BER. Performance parameters have been end-device average current consumption and lifetime, and energy cost of data delivery. The models have been developed based on measurements performed on prevalent LoRaWAN hardware. For BER = 0, acknowledged transmission reduces LoRaWAN end-device average current consumption. This happens because an acknowledgment may be sent in the first receive window, whereas unacknowledged transmission involves two receive windows and a larger average current consumption than a transmission acknowledgment in the first receive window. Note that the quantitative difference between energy consumption in acknowledged and unacknowledged  
Figure 22: Impact of message payload, \(l_{pay}\), on the energy cost of data delivery, assuming a dense LoRaWAN network, for, \(\alpha=0.4\) J and DR = 5.  
transmission for BER = 0 may be platform-specific. In fact, in contrast with the behavior observed with the platform used in this work, the end-device hardware platform might stay in a low consumption mode (e.g., such as the sleep state) during the interval between the first and the second receive windows. On the other hand, for a non-negligible BER, acknowledged transmission leads to greater current consumption than unacknowledged transmission, due to message retries. For a notification period of 5 min, DR5 leads to a current consumption lower than that of DR0 by a maximum factor of 2.8, whereas a 1-byte frame payload size reduces current consumption by up to a maximum factor of 1.59. For the same notification period, using DR6 (which is not mandatory as per the LoRaWAN specification), current consumption decreases by a factor of 3.18, compared to using DR0. Non-zero BER up to \(10^{-3}\) may increase current consumption by up to one order of magnitude in acknowledged transmission. Current consumption differences due to the settings considered tend to decrease with the notification period, since sleep current consumption then becomes dominant. An end-device running on a 2400 mAh battery and sending one message every 5 min can achieve a 1-year lifetime. As the notification period increases, the theoretical end-device lifetime tends asymptotically to roughly 6 years under the conditions considered. However, from our state of the art analysis, we conclude that current LoRaWAN hardware is not as well optimized as that of other low-power technologies. In the latter, sleep current in the order of (or even below) 1 \(\upmu\)A is common, which allows multiyear device lifetimes with a button cell battery, of 1 order of magnitude less capacity than the one considered in this study. In contrast, current batteries used for LoRaWAN hardware have a larger size and weight, which in turn has an impact on the physical dimensions and weight of current LoRaWAN devices and limits applicability of current LoRaWAN devices for domains where such dimensions are relevant, such as wearables. Finally, the energy cost per delivered bit of maximum-sized frame payload transmission is roughly two orders of magnitude lower than the one obtained for the short payload of 1 byte per frame. An end-device operating as a sensor will thus benefit significantly from accumulating readings and sending them at the highest notification period possible. For non-zero BER up to \(10^{-3}\), acknowledged transmission increases the energy cost of data delivery by up to roughly one and two orders of magnitude, for DR0 and DR5, respectively. This work was supported in part by the European Regional Development Fund (ERDF) and the Spanish Government through project TEC2016-79988-P, AEI/FEDER, UE. L.C. developed the analytical models and studied configuration of the hardware used. [PERSON] performed current consumption measurements and contributed to producing evaluation results.