Patent ID: 8639820

Claim:
A method for transmitting information in a wireless communication system to perform a combined service between terminals having different communication environments, the method comprising: receiving, by a CSI (Combined Circuit-Switched and IMS) application server, from an IMS (Instant Messaging Service) terminal incapable of performing communications over a circuit-switched (CS) domain, a request message for a CS call setup with a CSI (Combined Circuit-Switched and IMS) terminal that supports communications over both the CS domain and a packet-switched (PS) domain; sending, by the application server to the CSI terminal via the CS domain during the CS call setup, a first message including radio environment capability information of the IMS terminal on behalf of the IMS terminal, wherein the application server adds the radio environment capability information of the IMS terminal to a header of the first message; receiving, by the application server, a second message including a radio environment capability information of the CSI terminal sent by the CSI terminal in response to the first message, wherein the radio environment capability information of the CSI terminal indicates whether the CS domain and the PS domain are simultaneously supported; and sending, by the application server, a response message to the IMS terminal.