Decentralised secure handover in IMS-based networks
International Journal of Ad Hoc and Ubiquitous Computing
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VoIP over WLAN (VoWLAN) gradually has become a popular application with the fast maturing of both WLAN and Voice over IP (VoIP) technology. However there exists one problem that heavily affects the satisfaction of the users which is that the mobility of the mobile host (MH) can disrupt or even intermittently disconnect an ongoing real-time session. Therefore the issue of how to reduce the handover delay gets more and more important. This paper proposes a Network-Initiated SimUltaneouS mobility (NISUS) mechanism to facilitate terminal mobility with the session initiation protocol (SIP) in Voice over 3GPP-WLAN. We design the E2E tunnel state model running on the packet data gateway (PDG) referring to the CAMEL concept. The NISUS is triggered at the PDG by detecting the state transition of the E2E tunnel state model that represents the occurrence of a handover. Then the PDG sends the handover request to notify the Mobility Server (MS) to perform a third party call control (3PCC) and a third party registration on behalf of the MH in parallel for session re-establishment. With the help of the MS we ensure the lost signaling messages could be correctly re-sent to moving hosts. Moreover the Master-Slave Determination procedures derived from H.245 are proposed for the MS in order to handle the racing conditions fairly when two MSs involved in a simultaneous mobility issue 3PCC calls respectively at about the same time. We demonstrate the NISUS works well in the simultaneous and non-simultaneous movement cases. Analytical results show that the handover delay can be improved significantly by using the NISUS compared with the mobile-initiated simultaneous/non-simultaneous mobility. Copyright © 2010 John Wiley & Sons, Ltd.