How we know UE added Scell in carrier aggregation? Is there any message or IE to check?

Question

I have a 3 part question
1) How does the EnodeB know if the user equipment supports carrier aggregation or not?
2) If a UE does not support carrier aggregation does it mean it’s a Release 9 or lesser compliant UE?
3) If the answer to question 2 is yes , then how does the UE not supporting carrier aggregation(release 9 or lesser UE) decode a DCI message sent from a EnodeB that is currently supporting LTE A(Release10) , as the DCI message (say DCI format 0) contains extra bits?

Answer 1

Hi Gnanendra, I have not worked directly into Carrier -Aggregation but have some thoughts which I can share.
1. RRC Connection Reconfiguration message which is sent from eNodeB to UE, carries secondary cell information.
2. RRC Connection reconfiguration complete message is an indication that tells UE has accepted the configuration.
3. For the carrier aggregation, PUCCH format1b (extended version) and PUCCH format 3 are used. If you have doubt whether UE has setup for CA or not, please check the PUCCH format for HARQ ACK/NACK. PUCCH format 1b is used when UE is using 2 carriers while PUCCH format 3 is used when more than 1 secondary cells are being used for carrier aggregation.

This is my view to find out the solution of your problem.
I expect If someone has working experience on this feature can provide better answer.

Answer 2

Vimal is correct. Please look for following.
RRCConnectionReconfiguration-v1020-IEs ::= SEQUENCE {
sCellToReleaseList-r10 SCellToReleaseList-r10 OPTIONAL, -- Need ON
sCellToAddModList-r10 SCellToAddModList-r10 OPTIONAL, -- Need ON
nonCriticalExtension SEQUENCE {} OPTIONAL -- Need OP
}