Scheduling Request
SR is a special Physical Layer message for UE to ask Network to send UL Grant (Downlink Control Information Format 0_0 /0_1) so that UE can transmit PUSCH. Putting it other way, SR is an Uplink Physical Layer message from UE to Network, saying
“I have some data to send to you. Would you send me some Grant for me to send the data ?“.
How does scheduling work? How does timing work as well?
https://www.sharetechnote.com/html/5G/5G_TimingAdvance.html
In time domain, 5G allocation can be done in mini-slot, one slot, or even multiple slots allocation.