Abstract: Aimed at the rcregistration procedure of user who has registered in IMS(IP Multimedia Subsystem) , an improved fast r}registration method was proposed. As a registering user's UE(User Equipment) has known the address information of S-CSCF(Serving-Call Session Control Function) in home network, the delay of r}registration can be decreased effectively by carrying routing information of S-CSCF and transferring the REGISTER message from P-CSCF(Proxy-Call Session Control Function) in visited network to S-CSCF in home network directly. Analysis result shows that the improved fast rcregistration mechanism is better than the standard rcregistration procedure and some improved procedure proposed by other researchers. Furthermore, the fast rcregistration procedure has minor change to IMS network and can be realized easily.

Key words: IMS, SIP, Registration, Re-registration