# A Sigfox Energy Consumption Model
## 6 Conclusions  
This paper has presented analytical models that allow to evaluate the current consumption and the lifetime of a battery-enabled Sigfox device, as well as the energy cost of data delivery. The model, which has been derived based on measurements performed on real hardware, captures the impact of using uplink and downlink communication, the frame payload size, the uplink bit rate, and frame losses on the aforementioned energy performance parameters. The average current consumption decreases with the transaction period, with an asymptotic value equal to the sleep state current consumption. Differences among the considered options decrease as well with the transaction period. For low transaction periods, bidirectional communication increases current consumption by a factor up to \(\sim\)4. Current consumption is only affected by frame losses for bidirectional transactions. In those, since an uplink frame is sent thrice, the impact of frame losses becomes only relevant for very high FLR values, where the device awaits a downlink frame for the maximum receive window duration. Assuming a 2400 mAh battery, and the device model used in the study, the theoretical asymptotic device lifetime is 14.6 years. Similarly to the observations made for current consumption, differences between using bidirectional or unidirectional transactions are significant for low transaction periods. For an uplink bit rate of 100 bit/s, a 1-byte payload and a transaction period of 10 minutes, device lifetime is 1.49 years and 0.40 years for unidirectional transactions and for bidirectional transactions, respectively. Using an uplink bit rate of 600 bit/s (in regions where that is possible) increases device lifetime for low to moderate transaction periods. For a transaction period of 10 min, unidirectional transactions and a 1-byte payload, the device lifetime is 1.49 years and 2.57 years for uplink bit rates of 100 bit/s and 600 bit/s, respectively. The uplink frame payload size has a greater impact on the energy cost of data delivery than on the rest of performance parameters considered. Increasing the uplink frame payload size amortizes the energy consumed per delivered bit by a factor similar to the payload size increase. Using an uplink bit rate of 600 bit/s leads to remarkable energy cost savings (up to a factor of 1.84). Frame losses impact on the energy cost for rather high FLR values (of 0.5 or greater) for both unidirectional and bidirectional transactions, to a greater extent for the latter. The paper also evaluates the sensitivity of the current consumption model to \(I_{sleep}\) and \(I_{tx}\), two relevant parameters. Finally, energy harvesting sources have been considered as well, illustrating that \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Transaction**} & \multirow{2}{*}{**Energy Required (mJ)**} & **Outdoor Panel:** & **Indoor Panel:** \\  & & **Minimum \(T_{Period}\) (min)** & **Minimum \(T_{Period}\) (min)** \\ \hline
1-byte, unidirectional & 2.61 & 0.09 & 54.1 \\
12-byte, unidirectional & 4.56 & 0.14 & 94.7 \\
1-byte, bidirectional & 10.3 & 0.62 & 214.6 \\
12-byte, bidirectional & 12.6 & 0.65 & 261.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Energy required and minimum feasible \(T_{Period}\) for different types of transactions, for the two energy harvesting sources considered, and for an uplink bit rate of 100 bit/s. powerful ones allow the operation of the Sigfox device for the whole range of transaction types and periods considered in this paper, whereas more limited energy harvesting sources constrain the range of feasible transaction periods. **Author Contributions:** [PERSON] developed the analytical model. [PERSON] and [PERSON] performed current consumption measurements. [PERSON] and [PERSON] produced the evaluation results. [PERSON] analyzed the state of the art and contributed to the analytical model. All authors contributed to the design and writing of the paper, and to the analysis of results.