In this phase service triggering functions carry out in 3G domain, however WiFi is able to add some advance and combinational services to the existing services in 3G domain in order to enrich the existing services for the clients. Finally, in the last phase as depicted in Fig.8, the IMS overlay will be deployed completely. S-CSCF in WiFi domain localizes the clients when they register for IMS services and invokes the services for them when they request. SIP based services will be implemented in this phase in IMS overlay of WiFi domain. In this phase in both of bearer and signaling level WiFi is independent of 3G and can connect to the rest of the network directly.