# Survey on Wireless Technology Trade-Offs for the Industrial Internet of Things
## 5 Discussions
This result is also reflected in the predicted battery lifetime shown in Figure 5. Given a sufficiently large battery of 2000 mAh, the lifetime of Wi-Fi HaLow is expected to be above 10 years for a 10-min transmission interval, without battery replacement. For 802.15.4g, battery life expectancy is under 3 years in the same scenario. For the long-range contenders, it is under a year, as shown in Figure 5(b), except the LoRaWAN SF7 that can live up to 7.5 years (cf. Figure 5(a)). The compared configurations of 802.15.4g and 802.11 ah do not represent the best case scenario regarding energy consumption, as both technologies are configured to use low data rates. However, the chosen settings result in similar coverage range. In a line-of-sight scenario, 802.15.4g FSK-50 reaches a good PDR up to 700 m, while FSK-200 goes up to 420 m [62]. For 802.11 ah [63], MCS10 (150 kbps) has a range of 700 m to more than 1000 m. For a higher data rate, 802.15.4g will achieve better energy efficiency but it's achievable range would be very different from that of MCS10 of 802.11 ah. Similarly, 802.11 ah will achieve better energy efficiency for higher data rates (MCS10 represents the lowest possible data rate and thus the worst case). Figure 6 illustrates the benefits of low power modes in the design of a technology. As shown in the Figure, the lifetime of LoRaWAN devices is much higher than that of NB-IoT. Power consumption of LoRaWAN devices in transmission (TX)/reception (RX) mode is the dominant factor of the overall consumption, considering the very low power consumption in the idle/sleep mode (cf. Table 4). This results in a large difference in lifetime between LoRaWAN devices that use SF7 and SF12. The difference between SF7 and SF12 is especially large when the transmissions are frequent. The rarer the transmissions, the smaller the difference between SF7 and SF12 as idle/sleep time prevails and the TX/RX time becomes less significant in comparison to the idle/sleep time. The larger difference in battery lifetime between NB-IoT MCS9 and MCS4 occurs due to the better efficiency of MCS9 which reflects not only in data TX/RX but also in signaling between the transmissions which adds up to the difference. The difference between MCS9 and MCS4 also reduces as the traffic interval increases, similarly as the difference between spreading factors of LoRaWAN. \begin{table}
\begin{tabular}{c c c c} \hline  & **IEEE 802.15.4g** & **IEEE 802.11 ah** & **LoRaWAN** & NB-IoT \\ \hline
**Radio module** & Atmel AT86 RF215 & SEMTECH SX1272 & uBlox SARA N210 \\
**TX power (dBm)** & 14 & 23 & 20 \\
**Power (mA)** & 28/62/628/0.03 & 11.2/125/0.0015/0.0001 & 46/220/6/0.003 \\
**Technology-specific** & 113 slots @ 40 ms per frame & 4096 ms beacon interval & no repetitions & RRC: 10 s, DRX: 0 s, \\
**parameters** & 2-PSK—100 kHz (50 kbps) & MCS 10 —1 MHz (150 kbps) & no ACK & PSM: TI s \\
0.33\% DIO and EB probability & 1 RAW group, 1 slot & no repetitions \\
**Payload size** & 104 bytes & 12 bytes \\
**Microcontroller** & ARM Cortex M3 @ 32 MHz (3.38 mA power consumption) & \\ \hline \end{tabular}  
* Frequency Shift Keying (PSK); Enhanced Beacon (EB); DODAG Information Object (DIO); Destination Oriented Directed Acyclic Graph (DODAG); Modulation and Coding Scheme (MCS); Restricted Access Window (RAW); Radio Resource Control (RRC); Power Saving Mode (PSM); Transmission Interval (TI); Discontinuous Reception (DRX)  
\end{table} 
Table 4: Technology-specific parameters for energy consumption simulations. NB-IoT has higher data rate than LoRaWAN, thus it is more efficient in terms of TX/RX. However, the NB-IoT hardware is less efficient in terms of energy consumption in all four modes, so LoRaWAN becomes more energy efficient relative to NB-IoT. Higher data rates of NB-IoT cannot compensate for the energy efficiency of LoRaWAN in the evaluated scenarios. It is important to note that the shelf life also affects the battery life.