5G NR: Scheduling Requests

 

What Happens when UE keeps sending Scheduling Requests but there is no response from network ?
 
When a UE transmits a Scheduling request to get UL grant, it starts a timer based on the configured value of the IE sr-ProhibitTimer in schedulingRequestConfig.
When the sr-ProhibitTimer expires UE transmits another SR, and if there is no response from network then UE waits again for sr-ProhibitTimer to expire and sends SR again.
A UE cannot keep sending SR indefinitely as it incurs a Data stall if there is no response from network.
So Network configures an IE sr-TransMax in schedulingRequestConfig which limits the max number of SR attempts a UE can make.     

Now what happens after max SR transmissions ?
- UE releases PUCCH resources .
- Starts RACH Procedure (i.e RACH with YL)DATA_ARRIVAL)
- NW reconfigures PUCCH resources
- NW reconfigures SR Configuration.