## 3 Methodology
### Energy Profile of LoRa Sensor Nodes  
Each sensor node is characterized by an energy profile and LoRa parameters. The node's behavior is designed as specified by [70; 71; 72; 73], as presented in Table 3. The energy consumption model based on LoRa, which estimates the consumed power of different states of sensor nodes, is used. The default energy profile used in the simulation process, whose presentation is given in Section 4 of the paper, is based on the energy consumption of [54], due to its energy efficiency and application in conducted field measurements. Therefore, the energy consumption values of the selected transceiver listed in the specifications [54] are used. However, the simulations are not solely constrained to a single energy profile, since a comparison was made of the selected transceiver with other transceivers referenced in the literature relevant to the research area. The power consumption optimization in the selected scenarios is conducted by adopting specific power reduction settings of communication parameters. For instance, a reduction in the power consumption of the radio frequency (RF) mode is applied. As a result, it minimizes the total power consumption of sensor nodes since RF modules (for Tx and Rx) use considerable power. During the simulation process, different energy profiles are allocated to nodes, imitating various nodes, whereby the average values of energy consumption in different states are used. The different energy states of the simulated nodes are summarized in Table 3 according to sources in the cited literature and the technical report of the transceiver used in the conducted field measurements. A similar experiment has been conducted in [3], but there are differences between the energy profile in transmit and receive modes. As can be observed from Table 3, the power states that are considered are transmit, receive, sleep, and processing, as well as waking up and setting up the radio. The simulation process assumes that all nodes have an initial transmit power of 14 dBm, which conforms to the LoRaWAN specification. This power level, which corresponds to the low-power operation mode, enables lower energy consumption than the high-power operation mode, but also sufficient signal coverage of the area, which was previously proven by field measurements. Moreover, only the operations in the channels \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{5}{c}{**Energy Profile Used in the Analyses**} \\ \hline
**Sensor State** & \multicolumn{2}{c}{**Power [54]**} & \multicolumn{2}{c}{**Duration (ms) [70; 71; 73]**} \\ \hline Sleep & \multicolumn{2}{c}{4.95 \(\times\) 10\({}^{-3}\) mW} & \multicolumn{2}{c}{-} \\ \hline Processing & \multicolumn{2}{c}{19.14 mW} & \multicolumn{2}{c}{5 ms} \\ Tx prep. & \multicolumn{2}{c}{12.5 mW} & \multicolumn{2}{c}{40 ms} \\ Tx & 2 dBm & 7 dBm & 14 dBm & 17 dBm & 20 dBm \\  & 25 mW & 66 mW & 125 mW & 287 mW & 396 mW \\ Wait Rx1 & \multicolumn{2}{c}{4.95 \(\times\) 10\({}^{-3}\) mW} & \multicolumn{2}{c}{\(1\times 10^{3}\) ms} \\ Wait Rx2 & \multicolumn{2}{c}{4.95 \(\times\) 10\({}^{-3}\) mW} & \multicolumn{2}{c}{\(1\times 10^{3}\)-len (state Rx1)} \\ Rx prep. & \multicolumn{2}{c}{5.94 mW} & \multicolumn{2}{c}{3.4} \\ Rx1 & \multicolumn{2}{c}{37.95 mW} & \multicolumn{2}{c}{air\_time (DR = DR\_tx)} \\ Rx2 & \multicolumn{2}{c}{35.64 mW} & \multicolumn{2}{c}{air\_time (DR = 3)} \\ Rx post proc. & \multicolumn{2}{c}{5.94 mW} & \multicolumn{2}{c}{10.7} \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Energy profiles of the sensor nodes. required by the LoRaWAN specification are considered, i.e., 868.1 MHz, 868.3 MHz, and 868.5 MHz. As already proven, optimizing the LoRa parameters such as SF, CR, and payload size are crucial in reducing the sensor node's consumed energy. A spreading factor SF12 should be used in the second receive window [70]. However, in this work, a confirmed message was sent with SF10. A lower spreading factor results in a faster reception, yielding lower energy consumption at the node.