Fast and Secure Session Mobility in IMS-based Vertical Handover Scenario

In this paper, the make-before-break handover method is basically considered in order to reduce the SIP (session initiation protocol) session restoration delay due to the interface switching during WiFi-to-3G vertical handover under IMS (IP multimedia subsystem). Actually, the session restoration delay in WiFi-to-3G handover scenario can be dramatically reduced by performing IMS registration and session re-setup beforehand via WiFi link before actual vertical handover. However, the proper SA (security association) setup scheme between MH (mobile host) and P-CSCF (proxy call session control function) should be developed for the successful pre-authenticated registration since the IP address bound to 3G interface has to be used instead of the IP address bound to WiFi interface as the source IP address of the packets that the MH generates. In this paper, we have enhanced SIP header in order to solve this kind of IP address-mismatch problem. That is, a SA setup scheme is proposed for pre-authenticated registration in WiFi-to-3G handover scenario. We also define IMS handover delay as the sum of authenticated registration delay and session re-setup delay occurring under IMS-based vertical handover. We finally show that this delay reduced by the proposed scheme is acceptable enough to provide delay-sensitive real-time services. Moreover, the modification is deployed only at MH and P-CSCF, which is independent of other party’s network as well as the CSCFs in MH’s HN (home network).