I found the following URL which describes the bandwidth used by 4G LTE.
Frequencies that can provide LTE:
Band 2 (1900 MHz)
Band 5 (850 MHz)
Band 4 (1700/2100 MHz)
Band 66 (Extension of band 4 on 1700/2100 MHz).
For LTE-M (CAT-M1), which bandwidth will be used? Thanks.