5G NR (New Radio) has been developed to operate in two distinct bands; sub-6 GHz (3GPP 38.101-1 FR1), and mmWave (3GPP 38.101-2 FR2). Each band may operate in either FDD or TDD duplex mode. A band may be a supplementary downlink-only (SDL) or uplink-only (SUL) band used to provide additional capacity in the respective direction.
Due to the range of frequencies in use 5G NR uses four different Subcarrier Spacing (SCS) modes; 15, 30, and 60 kHz for sub-6 GHz (FR1) bands; 60 and 120 kHz for mmWave (FR2) bands. Channel bandwidths vary based on SCS, with many only supporting a 5 MHz channel width with an SCS of 15 kHz.