What are the reason Blocked Call Caused "SIP invite failure" in VoLTE?

Hi Experts.

I’m new in VoLTE.
During Drive test we faced blocked Call during inital → one blocked cayse is “Dial serving stop” and other Blocked cause is “SRVCC handover fail”. What are the reason of these caused?

What are the reason Blocked Call Caused" SIP invite failure" in VoLTE?

Did you get this message in DL from P-CSCF after sending SIP INVITE in UL?
After how much time from SIP INVITE you get " SIP invite failure"?

We received “Log Configuration Modified” msg just before call blocked.

Could you please describe signaling failure of that event ?

Do you mean SIP message code?

Registration failure is one cause.

Can you please post here what SIP message you get from IMS in case of failure after UE sends SIP INVITE?

No SIP INVITE Request.

In my case, I am getting this message when analysing block VoLTE call.

So you say UE is not sending SIP INVITE?

MO UE is not sending SIP INVITE?

Or MT UE is not receiving SIP INVITE?

These are some sample snaps:

SIP 503 Errors (in your case service unavailable are IMS issue).

All 5xx codes are server internal errors, have nothing to do with the UE, you need to contact IMS Core engineers.

:point_up: This one also you have to check with IMS engineers what is it that core doesn’t like and send this message SIP CANCEL in DL

Is it normal to have RSSI values in the -60s or -70s?

Is that occurring during register SIP msg?

It is happening during VoLTE call initiation.

I think there is a routing problem between UE ← → CSCF.

Do you have E2E trace?

So it means Core end issue?

Exactly.

In my case it was 487.