This document studies how services to the end user should be delivered and managed regardless of how the user accesses the services (e.g. using CS or IMS) and to ensure a consistent user experience. The services in scope include but are not restricted to:

• Conversational voice and video services
• Messaging services
• Supplementary Services as applied to the above.

For each of the above types, the service features that should be supported when accessing the service via CS or IMS using any appropriate access type are described. Also, how each service will behave when transferring between domains is described. The work will also consider how to support existing ("traditional") services while allowing new, innovative services to be provided to the end user using the enhanced capabilities of the IMS. It will cover possible migration paths from where services are provided on both CS and IMS to IMS Call and Service Control. Also, this work will consider roaming and call handling, interaction with legacy terminals, and the provision of user state and location for services accessed via CS or IMS and for services transferred between them.