# On the Energy Performance of Iridium Satellite IoT Technology
## 6 Comparison with Other IoT Technologies  
In order to assess the energy performance results obtained in the previous section from a broader perspective, this section compares the energy performance of Iridium satellite IoT technology with that of prominent long-range terrestrial IoT technologies such as LoRaWAN or Sigfox. The two latter technologies offer a communication link range typically 1-2 orders of magnitude lower than the Iridium one. While energy performance of a given technology depends on how the technology is configured, and on how it is implemented on real hardware, this section aims to explore the energy performance of the different communication technologies on representative examples using reasonably common settings.  
Figure 11 depicts the lifetime of a 2400 mAh-battery-operated device sending a message (carrying a 12-byte payload) for different values of \(T\) and for \(p\) = 0, for Iridium, Sigfox, and LoRaWAN. In all cases, an ideal line-of-sight channel has been assumed. In addition, a single user was assumed (i.e., there was no interference from other users). For Sigfox and LoRaWAN, the calculations were performed by using published energy models and device settings for operation in the 868 MHz band [20; 21]. More specifically, for the Sigfox evaluation, radio configuration (RC) number 1 (i.e., RC1) and unidirectional data message transmission were assumed [21]. In RC1, the uplink and downlink bit rate for RC1 was 100 bit/s. For the LoRaWAN evaluation, the sender device belonging to Class A, and data rate (DR) 0, which corresponds to spreading factor (SF) 12 and a bit rate of 250 bit/s, has been used [20]. Under the considered conditions, and due to spectrum access regulations, both LoRaWAN and Sigfox need to enforce a duty cycle below 1%. Note that Iridium satellite IoT technology is also assumed to be duty cycled in this study, since for feasibility and for a practical battery lifetime, the IoT device must return to sleep mode after message transmission.  
Figure 10: Energy cost vs. T, for several message payload sizes and \(p\) values. Dashed curves represent the energy cost values for \(p\) = 0.1 for the payload sizes illustrated with the same color.  
For a fair comparison of the asymptotic device lifetime (which is independent of communication activity), the same battery capacity and asymptotic sleep current have been assumed for all three considered technologies. Note that while the transmission power used by the Iridium device was 32 dBm, the transmit power considered in the Sigfox and LoRaWAN energy models used were 14 dBm and 11 dBm, respectively. These transmit power settings stem from the need to comply with European regulations on the frequency bands used by Sigfox and LoRaWAN (which limit transmit power to 14 dBm).  
As shown in Figure 11, as \(T\) increases, device battery lifetime becomes less dependent on the communication technology, since sleep intervals become dominant. However, as \(T\) decreases, the device lifetime for Iridium becomes significantly lower than that achieved for LoRaWAN and Sigfox (e.g., by factors of 7.8 and 5.8 for \(T\) = 10 min, respectively). Such a difference cannot only be attributed to the transmission power of the Iridium device, which leads to a current consumption of up to 45.8 mA (Figure 4), since the current consumption in transmit state for the LoRaWAN and Sigfox devices is 82.8 mA and 27.5 mA, in their respective energy models. There are two main contributors to Iridium device energy consumption underperformance: (i) the current consumption penalty introduced by its supercapacitor, especially when the device returns to sleep mode after communication activity, and (ii) the large processing and communication overhead, which corresponds to 6.0 s (for a nominal transmission time of 2.72 s for a 340-byte user payload) during which the device consumes a significant amount of current.