Hello experts, I’ve been investigating this topic for quite some time now. I constantly get RRC Reestablishment Request instead of RRC Reconfiguration Complete for HO. Can anyone point out what’s wrong with the content of RRC Reconfiguration message
Note that for some UEs, I am getting successful HO
reconfig and ue capability are attached
reconfig.txt (31.2 KB)
capability.txt (106.8 KB)
Do you have a pcap?
Unfortunately, I am not authorized to share it for privacy concerns
Can you describe a bit more the scenario, like what service you were doing. What messages were shared before this situation happened?
UE is initially connected to Cell PCI 20, then A3 event received in RAN, then triggered NG HandoverRequired to PCI 30. Handover was accepted by target cell, RRC Reconfiguration in attached file is the one sent by source to the UE to move to target cell. But, instead of RRCReconfigurationComplete, UE is sending ReestablishmentRequest to target
Is this N2 or Xn? PCI 20 and PCI 30 are cells from same gnb? do you see the ngap messages?
I believe that even though you received the RRCReconfiguration for HO from source cell, at some point of the NGAP or XNAP procedure something went wrong. But to know what it was, you must have NGAP or XNAP pcap or some kind of trace. Because you receive RRCReestablishmentRequest, this means since the HO was not done then maybe your signal starts to degrade. Any how I can be wrong so more detail needed.
They are from different gNBs, Everything was OK only up to missing RRCReconfigurationComplete to target cell, hence no Handover Notify:
Note that the whole exact procedure and gnb setting (src and target) are working with a few UE models, and only has some issue with 2 other UE models
Do you know if it’s N2 or Xn interface HO?
Nevermind I already saw in callflow it’s N2
Can you please check inside the HandoverCommand message the IE id-PDUSessionResourceReleaseList , check if it exists and if it indeed exist then open it and open by PDUSessionID IE and inside look for something that has a name like “Handover Preparation Unsuccessful Transfer”, inside this you will find the IE Cause, open it and see what is the cause code.
So if everything it’s ok , a possibility of the new cell not being able to sync on RACH exist, look the following picture in point 9.
Maybe that’s why no RRCReconfigurationComplete.
No Unsuccessful Transfer. Everything goes well up until step 9, where the UE does not perform RACH to target until T304 expired. We notice this since the UE eventually triggered RACH to Target but with RRCReestablishmentRequest.
You may try to increase timer t304 then, how about radio conditions for the other cell at that moment? any UL interference not letting the rach procedure to happen? Also release version of the UE’s with problem versus a UE doing it correctly. No more ideas for the moment.
What is the ReestablishmentCause??
reconfiguration-Failure
Hello,
Thank you for the solution, This is very helpful for me.