NB-Fi devices typically operate in unlicensed ISM bands, which vary in different countries according to their national radio regulations. However, the NB-Fi transceiver can operate in the frequency ranges of 430-500 MHz and 860-925 MHz, that allow using it on either the licensed or unlicensed spectrum.
NB-Fi devices use the 50 kHz bandwidth for Uplink messages and the 100 kHz bandwidth for Downlink messages, which are only small channels inside the allowed license-free ISM bandwidth. The width of one NB-Fi frequency channel starts from 50 Hz, so up to one thousand of NB-Fi channels can be accommodated simultaneously within the operating bandwidth.
The ISM radio bands are portions of the radio spectrum reserved internationally for industrial, scientific and medical (ISM) purposes other than telecommunications.