NB-IoT focuses specifically on indoor coverage, low cost, long battery life, and high connection density. NB-IoT uses a subset of the LTE standard, but limits the bandwidth to a single narrow-band of 200kHz. It uses OFDM modulation for downlink communication and SC-FDMA for uplink communications.[5][6][7][8][9] IoT applications which require more frequent communications will be better served by LTE-M, which has no duty cycle limitations operating on the licensed spectrum.
In March 2019, the Global Mobile Suppliers Association (GSA) announced that over 100 operators had either NB-IoT or LTE-M networks.[10] This number had risen to 142 deployed/launched networks by September 2019.[11]