Is there any IE UE indicates to network for support of EPS Fall Back?

RAN
1

Hi Experts.

Is there any IE UE indicates to network for support of EPS Fall Back?

2

Hmmm…shouldn’t this be mandatory for all UEs?

What do you expect a UE that is not able to do EPS fallback?

How should it behave?

3

I mean how network come to know UE support EPSFB or not.

Is there any indication from UE to network for EPSFB?

4

I think UE send UECapabiltyInformtion-NR Capability with VoiceOverNR flag set as FALSE.

Then it will do an EPS fallback whenever a voice is attempted.

5

IE UE indicates to network for support of EPS Fall Back
IE UE indicates to network for support of EPS Fall Back876×567 127 KB

6

Is it for EPSFB?

Seems it is for R16. Is it not from rel15?

I’ve seen same in specs but not sure is it required.

To indicate support of EPSFB.

7

Some more details with 3gpp reference: :point_down:

voiceEpsFbPossible=true Whether EPS fallback is assumed possible.

When Redirection for Voice EPS Fallback IE is not included from core network (AMF node), the IE is assumed set to possible.
The IE Redirection for Voice EPS Fallback is indicated over NGAP from core network. This IE controls whether it is possible to perform EPS fallback or not. This IE is optional, and this attribute is used to define the behaviour when this IE is not indicated from core network.
This attribute should be false if core network supports CR S2-2007918 for NGAP in 3GPP TS 38.413 Rel-16.

Specification: 3GPP TS 38.413
Takes effect: Next usage.

The explanation above will answer you doubts for R15 ad R16 both.