In which cases RAN will send RRC reestablishment reject instead of initiating reestablishment procedure?

RAN
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1

Hi all.

I have following question: UE had a radio link failure in 4G and sends reestablishment request.

But sometime UE gets in DL gets reestablishment reject.

My question is this one: in which particular cases RAN will send RRC reestablishment reject instead of initiating reestablishment procedure?

RRC reestablishment reject instead of initiating reestablishment procedure
RRC reestablishment reject instead of initiating reestablishment procedure1049×745 151 KB

2

When old cell doesn’t have UE context.

3

OK. So you mean missing neighbor or X2 down.

Any other case?

4

No…
Whenever UE will send RRCRestablishmentReq message on new cell with old C-RNTI.

New cell will try to fetch UE context from old cell.

Old cell doesn’t have UE context then UE will get RRC Reestablishment reject.

5

Check PCAP for reject reason.

Is it reconfig failure or some other?

6

There are case with “other failure” as cause.

But also there are cases with “handover failure”.

7
  1. Lack of UE context
    • either old cell deleted UE context
    • or new cell can not get UE contet from old cell
  2. Admission control fail in new cell for admitting new UE
  3. RRE do not contain last cell it was connected to
8

For this last case:

In RRE I see UE identity: C-RNTI,PCI and shortMAC-I

9

Yes, same thing.

10

Your reject is most probably due to lack of UE context.

11

OK, clear it is PCI of old cell inside UE identity.