Terminal, method and system for performing combination service using terminal capability version

A method for providing a circuit switched (CS) service, a session initiation protocol (SIP)-based service, or a combination of the CS service and an IP multimedia subsystem (IMS), the method comprising:

• receiving, by a terminal, a terminal capability version of at least one target terminal;
• comparing, by the terminal, the received terminal capability version with a previously stored terminal capability version of the at least one target terminal to obtain a first comparison result;
• and
• sending a message for requesting for terminal capability information of the at least one target terminal from the at least one target terminal, if the received terminal capability version of the at least one target terminal is different from the previously stored terminal capability version of the at least one target terminal based on the first comparison result,
• wherein if the received terminal capability version of the at least one target terminal is the same as the previously stored terminal capability version of the at least one target terminal, then the requesting for the terminal capability information of the at least one target terminal from the at least one target terminal is bypassed, and the method proceeds with a CS or IMS process, and
• wherein the terminal capability version identifies a version of capabilities of the at least one target terminal, and
• wherein the terminal capability version of the at least one target terminal has a value in a user equipment capability version-XX (UCV-XX) form, where XX is a 2-digit hexadecimal number.

A method for providing a circuit switched (CS) service, a session initiation protocol (SIP)-based service, or a combination of the CS service and an IP multimedia subsystem (IMS), the method comprising:

• exchanging, by a first terminal, a capability version of the first terminal and a capability version of a second terminal during a session or connection with the second terminal,
• updating, by the first terminal, the terminal capability version of the first terminal if the first terminal's capability information is changed;
• transmitting, by the first terminal, an INVITE message for an IMS session setup or CS call setup message for a CS call between the first terminal and the second terminal, the INVITE message including the updated capability version of the first terminal or the CS call setup message including the updated capability version of the first terminal;
• comparing, by the second terminal, the received terminal capability version of the first terminal with a stored terminal capability version of the first terminal to obtain a comparison result;
• selectively performing, by the second terminal, a terminal capability information request procedure if the received terminal capability version of the first terminal is different from the exchanged terminal capability version of the first terminal based on the comparison result;
• and
• proceeding with the IMS session setup and a CS call setup without the second terminal performing the terminal capability information request procedure, if the comparison result indicates that the received terminal capability version of the first terminal is the same as the stored terminal capability version of the first terminal,
• wherein the terminal capability version of the first terminal and the second terminal has a value in a user equipment capability version-XX (UCV-XX) form, where XX is a 2-digit hexadecimal number.