In NR, the downlink scheduler is responsible for dynamically controlling the device(s) to transmit to.
Each of the scheduled devices is provided with a scheduling assignment including information on the set of time–frequency resources upon which the device’s DL-SCH is transmitted.
Scheduler depends on the specific scheduling strategy -
Channel conditions at the device, including spatial-domain properties
Buffer status of the different data flows
Priorities of the different data flows, including the amount of data pending retransmission
gNB use CSI reports to measure the channel quality in the time, frequency, and spatial domains.
YouTube: :
5G NR Scheduler - YouTube