Is there any case UE can send C-RNTI MAC CE to eNB in case of contention based RACH?

Question

As UE has valid C-RNTI , can eNodeB confirms same previous RNTI to UE on occasion of successful re-establishment?

Answer 1

Hi sripathi ,

Yes UE can send MAC CRNTI CE in contention based RACH. The following scenario UE can send.

1. If UE's reached MAX SR count then UE will rach to get uplink grant. In this case to delete the temp-CRNTI UE will send MAC CRNTI CE .

2. If UE is out of UL sync the to get Ul sync UE will do RACH . In this case also UE will send MAC CRNTI CE to delete the temp-CRNTI.

3. In case of contention based hand over, UE will send MAC CRNTI CE to target ENb to delete the temp -CRNTI.

I dont think so UE will send MAC CRNT CE in case of contention free rach.

Comments

Thanks alot Jaganathan. I have two more doubts here, Please explain..

1. At what scenarios UE experience UL Sync Loss?
2. What is meant by contention based handover as you mentioned?

Thanks for your help..

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Hi sripathi,

contention based hand over means If target ENb didn't give preambles to do hand over rach , then UE has to do contention based rach on target ENB.

If UE's is fast moving then UE will go out of UL sync very soon. In these case UE will do rach to get in the sync

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What are the indications at UE side for UL Sync loss?

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If UE is not having any UL & DL transmission and TAT is expired but UE didn;t receive TAT MAC CE form Enb means it is UL sync loss..