Resource Block Definition
One NR Resource Block (RB) contains 14 symbols in time domain and 12 sub-carriers in frequency domain similar to LTE. In LTE resource block bandwidth is fixed to 180 KHz but in NR it is not fixed and depend on sub-carrier spacing.
NR Channel Bandwidth
The NR is expected to work with 100 MHz channel bandwidth for lower bands < 6 GHz and 400 MHz channel bandwidth higher bands in mmWave ranges. NR is designed to provide higher bandwidth efficiency reaching to 99% which was about 90% in LTE (10% was wasted in guard band). Another different the NR has w.r.t. LTE is that it does not reserved any D.C. sub-carrier for up-link and down-link.
Each numerology has defined minimum and maximum number of resource block and having knowledge of one resource block bandwidth one can calculate minimum and maximum channel bandwidth.
Table below shows the same calculation for minimum and maximum channel bandwidth consider lower band and higher band. The bandwidths shown here includes the guard band bandwidth also.
Maximum Number of Resource Block after Guard band
3GPP 38.101 has specified maximum transmission bandwidth configuration for each UE channel and sub-carrier spacing provided in below table. The resource block number shown are after removing guard band from channel bandwidth and maximum bandwidth considered is 100 MHz