T.0 General

23.2283GPPIP Multimedia Subsystem (IMS)Release 18Stage 2TS

This clause describes the main IP-Connectivity Access Network specific concepts that are used for the provisioning of IMS services over a Trusted WLAN (TWAN) access to EPC.

As IMS is accessed over EPC, most of the features defined in clause E for the case of EPC (and PDN connections/EPS bearers) apply in the case of a TWAN access, e.g. a P‑GW is used as an IP anchor point and IP-Connectivity Access Network bearers are provided by PDN connections and bearers.

Following specific considerations apply to the case of a TWAN access:

– The Mobility related procedures for EPS and TWAN access are described in TS 23.402 [82]

– TWAG/TWAP (refer to clause 16 of TS 23.402 [82]) are used to interface the access network and to control relevant PDN connectivity (over S2a) towards a P-GW.

– For a TWAN access, the way the notification of the loss of IP-CAN session for an UE is triggered within a TWAN is out of scope of 3GPP specifications.