How to decide which attach type shall use when UE set “IMS PS Voice preferred and CS Voice as secondary”?

Question

In TS 23.221 7.2a, there is a note describe that "Whether to perform combined EPS/IMSI attach/combined TA/LA Update or EPS attach/TAU for the case of "IMS PS Voice preferred" is to be evaluated in each release of the specifications.", but I can not find any information about that.

Answer 1

Four mode of operations are defined as following :
- PS mode 1 of operation: the UE registers only to EPS services, and UE's usage setting is "voice centric";
- PS mode 2 of operation: the UE registers only to EPS services, and UE's usage setting is "data centric";
- CS/PS mode 1 of operation: the UE registers to both EPS and non-EPS services, and UE's usage setting is "voice centric"; and
- CS/PS mode 2 of operation: the UE registers to both EPS and non-EPS services, and UE's usage setting is "data centric".

As per your question statement, I think CS/PS mode 2 of operation is applicable since in this mode "IMS based voice service" has higher preference than "CS based voice".

Comments

Thank you for your reply. Is there any spec mention about it? Because 23.221 said that it is evaluated by each spec.