# Modeling the Energy Performance of LoRaWAN
## 4 Modeling LoRaWAN End-Device Current Consumption
### Unacknowledged Transmission  
Our first goal is modeling the average current consumption of an end-device in the unacknowledged approach, denoted \(I_{avg\_unACK}\). In order to determine this parameter, we first derive a profile of the different states traversed by the end-device, as well as the duration and the current consumed in each state. In order to realistically model the end-device behavior, and without loss of generality, we develop the model based on measurements from a real LoRaWAN testbed. The measurement setup is shown in Figure 5. We use the MultiConnect mDot platform from Multitech [29] as our reference end-device platform for the model, since it is a popular platform, and it is based on the also widely used SX1272 transceiver [33] (see Table 1). While other LoRaWAN end-device platforms might exhibit differences with the mDot platform (e.g., due to their internal architecture), we understand that our model captures the main states of a LoRaWAN end-device. On the other hand, it must be noted that the mDot platform offers low current consumption decrease (of \(\sim\)3%, and only in the transmit state) when the voltage applied is reduced from 5 V to 3.3 V, the latter being the lowest voltage that allows the device to operate [29]. However, other platforms may not offer the same current consumption stability as battery voltage decreases over time. In the measurements, the transmit power of the end-device is set to 11 dBm, which is the default value for this parameter. The gateway is a Kerlink LoRa IoT Station platform [40]. Both the end-device and the gateway are located in an indoor scenario, where the distance between the end-device and the gateway is 2 m. In the measurements, data messages carry a frame payload of the maximum size allowed for each DR in the EU band. We assume a periodic behavior for the LoRaWAN end-device, therefore we model its current consumption during one period. Each period comprises a data message transmission by the end-device (including the related procedures required to enable such transmission), otherwise the device is in sleep mode. Note that, for an end-device in unacknowledged transmission, current consumption is independent of the BER; that is, regardless of whether channel errors take place in the communication, the end-device will consume the same amount of energy for any transmission, since there will not be retransmissions in unacknowledged transmission. Time and current consumption measurement results provided in this section are obtained from several measurements for each tested configuration within a notification period. We found negligible differences within each set of measurements for each configuration. Figure 6 illustrates the current consumption profile of an unacknowledged transmission performed by the MultiConnect mDot LoRaWAN end-device configured to use DR0 (note that the states traversed and behavior observed are the same for all DRs, except for the duration of some intervals). Table 5 defines and describes the different states involved in an unacknowledged transmission, along with the variables that represent the duration and current consumption of each state. Initially, the end-device is in sleep mode, which is characterized by a current consumption three orders of magnitude below that of the rest of states. When the end-device starts the procedure to perform the transmission, it first wakes up (state 1), next the radio interface is prepared for activity (state 2), and then the end-device transmits the data unit via the radio interface (state 3). After the transmission, the end-device disables radio activity and waits (state 4) until it sets the radio into receive mode and remains in the same state for the duration of the first receive window (state 5). Since no incoming preamble is detected, the first receive window is closed, and the end-device waits (state 6) until the start of the second receive window.