UE specific RRC message

Hi Experts.

MIB is transmitted over PBCH so it’s like broadcast group message.

But SIB is on PDSCH. Does that make this RRC message UE specific?

For UE specific message, it requires UE specific identifier.

SIB is broadcasted with Si-rnti which is common for all UEs.

Thansk alot!

I wonder why SIB not transmitted on pbch type channel rather than pdsch.

Sib1 is transmitted over pdsch but it’s still broadcasted with DCI containing SI-rnti meant for all UEs.

Because info transferred on pbch i.e mib demands light weight data so it can be decoded very quickly as pbch is also accompanied with synchronization signals PSS/SSS. It there were more information like sib1 it would take more time for ue to get synchronized quickly. Hence only very important info is delivered via MIB and rest is delivered via sib1 followed by sib2

…and remaining sibs

If you’ve noticed there are very limited resources for pbch and hence not all information can be captured in pbch.