scope:

This document specifies the architectural requirements for delivery of consistent IMS services to the user regardless of the attached access type (e.g. CS domain access, or IP-CAN).

Consideration is given to how to access IMS Services (see clause 22.4 of TS 22.101 [9]) while still allowing innovative services.

IMS control of Emergency calls that utilise TS12 are outside the scope of this specification in this release.

The scope of the specification includes: -

- Session establishment when using CS access for media transmission for an IMS service

- Support of Service continuity as specified in TS 23.237 [12]

- Access domain selection

- IMS control of services where the media is transported via the CS network (e.g. managing of mid-call services)

- Service data management

The solution is applicable for UE"s with or without ICS functionality, and is applicable for the following deployment scenarios:

- An operator who supports for their subscribers only UEs that have ICS functionality

- An operator who supports for their subscribers only UEs that do not have ICS functionality

- An operator who supports for their subscribers UEs which do and do not have ICS functionality (to different subscribers and the same subscribers) ensuring the coexistence of UEs that have and do not have ICS functionality.

- Inbound roaming subscribers on an operator's network that supports either the same or different ICS functionality that the inbound roaming subscriber is using, ensuring the coexistence of UEs that have and do not have ICS functionality.