Seamless Mobility Management In IMS

IMS (IP Multimedia Subsystem) is a new network architecture for providing multimedia service in the next generation wireless networks. 3GPP has chosen SIP to be the signaling protocol in IMS. Although SIP can realize VoIP and multimedia communication successfully, it has problems in dealing with mobility. At present, IMS can only support nomadic mobility but not seamless mobility. So, we should work out a new solution to support seamless mobility in IMS, which can improve customers' experience of real-time service in IMS and provide support for various kinds of mobility.Currently, Mobile IP and SIP are the prevalent protocols used to provide mobility management. Mobile IP works on network layer. It can maintain the connection on transport layer and higher layer by assigning one constant IP address for mobile node. SIP is an application layer protocol, which can create, modify and terminate the multimedia session between IP users. SIP can also provide mobility management for kinds of mobility. However, both Mobile IP and SIP have problems dealing with mobility, we should integrate Mobile IP and SIP to provide better mobility management in IMS. In this paper, we proposed a new cross-layer mobility management solution based on Mobile IP and SIP. In the proposed solution, we introduce a cross-layer module between home agent and S-CSCF, which can realize information exchange between network layer and application layer. Through the cross-layer module, the binding update message received by home agent can be translated and forwarded to S-CSCF to trigger the registration procedure in IMS. So the signaling between mobile node and home network can be reduced dramatically. In addition, Mobile IP and SIP can also provide mobility management on its own, so the mobile node which dose not support cross-layer mobility management can be processed by either of the two protocols. In the end, we analyzed three mobility management solutions proposed in this paper theoretically and made simulation based on our analysis. The simulation results demonstrated that the cross-layer mobility management solution has smaller handoff delay and introduces lower signaling overhead to the network compared with the other two solutions. So we can conclude that our proposed cross-layer mobility management solution can provide better mobility management for real-time service in IMS and has good scalability.