UE initiate detach 30 s after after establishing 5G bearer and passing RACH procedure

5G NR
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1

Hi Experts,
I have issue with some NSA testing.
It happening after establish 5G bearer and pass RACH procedure.
Always after 30 seconds UE initiate detach.
Do you now what could be the problem beside equipment?
It is Qualcomm chipset.

2

Need some more details:

  1. Is it normal detach?
  2. Is the device hot during testing?
  3. Happening always?
3

Sure:

  1. Yes, switch off is the cause
  2. it is normal
  3. no if data are running on the DL
4

Switch Off detach is due to Flight mode toggle or SIM removed or switching off device.
Is the SIM stk misbehaving?

5

Thanks @RMatolia, that is helpful.
I just wanted to confirm that those 3 are the only possible causes.
Not sure about the sim but when it tried in the other device (Samsung) it failed with NSA attach in RACH procedure (no msg4).

Do you think that changing SIM could solve the issue?

6

Ideally NSA is AS procedure, Detach is MM procedure and shouldn’t be related.
Trying with another SIM can clear whether it can be SIM or STK related issue.
If still it persists, please check which module sends the message towards MM to initiate Detach request.

7

LTE chipset initiate deregister.

8

If you have access to UE logs, can you check which client is sending the detach power off req to CM module?

9

No, unfortunately I don’t have it.
What are you suspecting?

10

I would check the APN parameter mismatch in this case first.
If there is such mismatch between initial APN req and configured APNs, then UI will trigger detach.
Another case would be that, if the APN type is set to IPV6 only & IPV6 address allocation is not done (router solicitation messages not answered etc), then UE will trigger detach.
There could be other reasons too from other clients, it’s hard to pin point without UE log.

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