What is difference between BSR and Scheduling Request?

Hi Experts,
What is difference between BSR and Scheduling Request?
As per understanding both sent by UE in uplink to get UL grants.

If scheduling request can be used for UL grants, then what use of BSR?

SR (Scheduling request) is use to notify the eNB that there is data to transmit at the UE RLC/PDCP. So eNB grant some minimum resources to UE.

With these resources UE start transmitting UL data, where MAC header consist of MAC CE , indicating BSR. By reading BSR then eNB keep giving grant to UE as long as there is BSR.

So in short, BSR cannot be sent in uplink unless UE have some UL grant. And to get UE UL grant, UE has to send SR

4 Likes

Ok, thanks!
Sso first SR will be used then BSR, is it correct?

Yes, correct.