MIP-based enhanced mid-session macro-mobility for IMS-controlled state-full applications

It is expected that mobile terminals will handover between heterogeneous networks in order to extend coverage or to get connectivity to faster and/or cheaper access technologies. Access and session control must be guaranteed when moving across different administrative domains so that operators can, e.g., block unauthorized visiting users. The 3GPP IP Multimedia Subsystem (IMS) is a platform standardized towards network-independent access and session control. The current IMS specifications do not allow for any change of the user's current IP address during an ongoing session, which prevents seamless mid-session macro handover. In this paper, we present the standard mechanisms that support access and session control in the IMS and how they interact with the UMTS access routers to implement the control. Then, we propose a MIP-based solution for mid-session macro handover that provides session continuity and considerably shortens the handover time as compared to the original SIP-based IMS procedures, while respecting the desired levels of authentication, authorization and QoS control expected by the operators.