## 4 Active Systems
### Active Radios Powered by Coin Cell Batteries  
Due to their power consumption and characteristics, BLE, LoRa, and SigFox have been used in multiple IoT applications. BLE has a lower power consumption and higher data rates but presents a shorter distance of communication when compared with LoRa and SigFox. This difference makes BLE more suitable for applications that require high levels of data transmission or a higher communication frequency. LoRa and SigFox are preferable for applications requiring long distances. As both technologies have very similar energy profiles, only LoRa is studied in this context. Besides this distinction, the following lines explore the possibility of developing a real application scenario using BLE or LoRa communications powered by a coin cell battery. The application would be on an agriculture farm that requires environmental monitoring (e.g., atmospheric temperature and relative humidity) each 5 min, corresponding to 20 messages per hour. For higher-range applications, the BLE packet structure takes 376 us before transmitting its data unit. As it contains the payload, the data unit size depends on the amount of data being transmitted, which for the required application can be considered to be 16 bytes (8 bytes for atmospheric temperature and 8 for relative humidity) [138]. In this condition, the transmitting message would take approximately 1.7 ms as detailed in Figure 20.  
By its side, based on [139], a LoRa packet using a SF = 7 and a payload of 16 bytes would take approximately 40 ms. Increasing the SF to achieve the maximum distance can increase the packet duration up to 1.2 s. For further calculations SF = 7 is considered. Figure 21 illustrates the LoRa package. To compare the technologies, technical information from Nordic Semiconductor nRF52810 [123] and Microchip RN2483 [136] was collected from datasheets. Both devices were considered to be equipped with the same sensor (SHTC3 from Sensirion), consuming 0.5 uA [140], and supplied by the same battery Panasonic BR2032 which has 200 mA h for a nominal voltage of 3 V.  
The BLE nRF52810 chip consumes 7.5 mA when transmitting and 0.6 uA when in sleep mode. On the other hand, the LoRa RN2483 chip uses 39 mA when transmitting and 1.6 uA when in sleep mode. Using the coin cell battery and the predefined energy profile (transmitting 20 messages per hour) it is possible to estimate how long each solution could operate in a real scenario. Figure 21: LoRa Packet Structure-SF = 7, BW = 125 kHz, CRC = 0 and Payload = 16 bytes. Data from source [139]. Figure 20: BLE Packet Structure-Payload = 16 bytes. Data from source [138]. Using the total packet time information, Equation (1) calculates the time each technology spends in active and sleep mode. \[ \begin{split} BLE_{Tx}=1.7\,\mathrm{ms}\times 20\,\mathrm{messages}=34\, \mathrm{ms}\,\mathrm{h}^{-1}=0.034\,\mathrm{s}\,\mathrm{h}^{-1}\\ BLE_{Sleep}=3600\,\mathrm{s}-0.034\,\mathrm{s}\approx 3600\, \mathrm{s}\,\mathrm{h}^{-1}\end{split}  \tag{1}\]  
\[ \begin{split} LoRa_{Tx}=40\,\mathrm{ms}\times 20\,\mathrm{messages}=800\, \mathrm{ms}\,\mathrm{h}^{-1}=0.80\,\mathrm{s}\,\mathrm{h}^{-1}\\ LoRa_{Sleep}=3600\,\mathrm{s}-0.8\,\mathrm{s}\approx 3599.2\, \mathrm{s}\,\mathrm{h}^{-1}\end{split} \]  
Using the values calculated in Equation (1) it is possible to calculate the average consumption of each device. The results are presented in Equation (2)  
\[ \begin{split} BLE_{ChargeConsumet}=BLE_{Tx}\times 7.5\, \mathrm{mA}+BLE_{Sleep}\times 0.0006\,\mathrm{mA}+0.0005\,\mathrm{mA}=0.0012\, \mathrm{mA}\,\mathrm{h}^{-1}\\ LoRa_{ChargeConsumet}=LoRa_{Tx}\times 39\,\mathrm{mA}+LoRa_{Sleep} \times 0.0016\,\mathrm{mA}+0.0005\,\mathrm{mA}=0.0108\,\mathrm{mA}\, \mathrm{h}^{-1}\end{split}  \tag{2}\]  
The following Equation (3) calculates how much time can each technology operate powered by a single coin battery with a electric charge of \(200\,\mathrm{mA}\,\mathrm{h}\). \[