Is there a 3GPP mentioning that if there is no TAU update UE cannot initiate a service?

Specs & Protocol Testing
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21

This is about causing multiple TAUs, IMS call failure can be inside TAU response.

22

Sorry, but the topic is why VoLTE call not initiated.

I should see rrc requests for sip invite.

23

For that i asked for the mm cause value if included in TAU accept or EPS bearer id for ims.

Even in case rrc conn rel with tau load balancing, call initiated during TAU pending state may not be initiated, so asking for that part.

24

If there is only ebi 5, probably this is data bearer and not IMS, thus no IMS calls?

25

TAU is done on default bearer.

EBI-5 probably is default bearer.

26

In that case as there is no IMS bearer, thus no IMS calls are initiated.

27

Does TAU need to include list of all bearers?

28

Yes, all bearers have to be negotiated with NW in TAU, if EPS bearer is missing, the bearer is dropped.

29

24.301 clause 5.3.3.1

Not exactly UE cannot initiate service, but EPS bearer active flag related info.

31

Hello,
I suggest to make testing from another UE handset for same purpose, Am not sure whether same UE had successfully made a VoLTE call, when in not in TAC border. This point is important as we are not aware as you yourself testing, or you are only instructing someone for the test.

As some other fellow also mentioned, VoLTE is enabled on TAC level from MME side, pls verify the VoLTE is enabled on respective TAC.

Only TAU procedure does not setup any bearer, complete procedure is over NAS layer (provided TAU not happening when UE is in already active session mode)

Another aspect is, why CSFB did not happen when UE tried making voice call? Hope UE is not data centric, could be checked from Attach request.
OR CSFB was not enabled for the network (very less likely as still many UE do not support VoLTE).

Thank you.

1 Like
32

I have seen this happening similar case…during testing…in some university…in korea…in live network…
likely to be happening if RAN neighbor isn’t set properly on network side. so UE’s trying best to camp by TAU but Network isn’t accepting it because eNB to eNB there’s proper neighbor setup…maybe you found sweet spot where they need wireless engineer to figure out neighbor list…

33

wait i left sarcastic comment previously. Sorry for that…ya…likely neighbor isn’t set correctly.