Abstract: Two authentication procedures arc essential when mobile station registers to the IMS network; the GPRS access authentication and the IMS authentication. Both of the authentication procedures perform the protocol AKA. Almost all of the operations are the same, which increase the register procedure delay. As a result, it is very inefficient.This paper investigated the performance of IMS registration procedure and proposed an optimized scheme in IMS registration procedure based on previous study. We through the interaction between SGSN and HSS completed the registration procedure between mobile station and network, which avoids the bandwidth waste when authentication fails. The result of data analysis illustrates that the performance of this optimized registration scheme is better than the primitiveone.

Key words: IMS, Registration, Authentication, Optimization