NB-IoT is considered a licensed low power wide area networks (LPWANs) technology supported by your local telecom operator. That means each device requires a SIM card and monthly or annual payments to your operator just like your cell phone. The benefit is that you don’t need to manage the infrastructure; you do not need to install your own base stations.
The key advantage of NB-IoT is the protocol is synchronous and designed to optimize the spectral usage and throughput of the network. This optimization for spectral utilization comes at the cost of compromised battery life and recurring costs (monthly or yearly).
Unlicensed LPWANs, such as LoRaWAN® and Weightless™ are optimal for longer battery lifetime. If sensor data is small and infrequent (one or twice a day), LoRaWAN could be the optimal choice being an asynchronous protocol. If data is larger and data transmissions must be acknowledged then Weightless stands alone as the option for a synchronous protocol for private networks.
The effect of asynchronous versus synchronous protocols has significant impact on the battery lifetime of sensors.
Semtech conducted a comparison using the T-Mobile NB-IoT network available in the U.S. The NB-IoT sensor consistently took more than 20 seconds of active time to negotiate a slot to communicate an 11-byte packet. The average current consumption over this 20 second period was 40mA. In comparison, sending the same 11-byte packet over LoRaWAN required an active time of only 1.6 seconds, with an average active current consumption of 6.4mA. This translates into greater than 50 times advantage in battery lifetime for LoRaWAN.
Take an example application: wireless, battery powered, pushbutton. A LoRaWAN-enabled pushbutton and an NB-IoT pushbutton each were equipped with a 600 maH battery. The LoRaWAN device could support roughly 70,000 button presses on a single battery, while the NB-IoT button could handle only about 2,000 button presses on a single battery. The difference is quite drastic.
When choosing a LPWAN technology, be sure to thoroughly review the application requirements. One size does not fit all.