A hybrid mobility mechanism for heterogeneous networks in IMS

IMS is the new approach adopted by 3GPP towards networks convergence. It was designed to be access independent and ubiquitous. IMS already provides personal mobility for nomadic users, but still needs to deal with service continuity within non 3GPP networks. In this paper we propose a novel hybrid mobility management scheme, based on tight cooperation between fast handovers for mobile IPv6 (FMIPv6) and session initiation protocol (SIP) to ensure an uninterrupted real-time service. Moreover, the new Media Independent Handover (MIH) service is integrated into the IMS architecture in order to perform intelligent and accurate horizontal and vertical handovers. The handover is managed in two phases. The first one or the fast phase is handled by FMIPv6 protocol to preserve as soon as possible packets of the ongoing communication. The second one or the slow phase is handled by the SIP protocol to optimize packet delivery route. By doing so, we exploit the benefits of both layer 3 and application mobility protocols to ensure a continuous session over the two networks without imposing new elements to the network. Through a comparison with other mobility mechanisms, we show in the analytic analysis that our hybrid scheme presents better results in terms of handover latency and packet loss.