Method and apparatus for call connection

The method according to claim wherein after the called terminal sends the first response message and before the ringing message is sent, the method further comprises:

• receiving a voice bearer setup message from the called core network device, wherein the voice bearer setup message is used for requesting to set up a voice bearer in the second communication standard with the called terminal;
• setting up a voice bearer with the called terminal according to the voice bearer setup message;
• and
• sending a voice bearer setup complete message to the called core network device, wherein the voice bearer setup complete message is used for indicating that a voice bearer is set up between the called terminal and the called core network device.

A call method, wherein the method is applied to a called terminal, and the method comprises:

• receiving a session invite from a calling terminal, wherein the session invite is used for requesting to set up a voice call with the called terminal;
• sending a request response message to the calling terminal, wherein the request response message is a response to the session invite and is used for indicating that the called terminal has received the session invite-message;
• receiving an update message from a called core network device;
• starting a first timer after receiving the update message;
• receiving, by the called terminal, a handover command in during the first timer, wherein the handover command is used for notifying the called terminal to hand over from a first communication standard to a second communication standard;
• handing over, by the called terminal, from the first communication standard to the second communication standard according to the handover command;
• sending, by the called terminal, a second response message to the called core network device when the called terminal receives, during the first timer, a voice bearer setup message from the called core network device after handing over from the first communication standard to the second communication standard and a voice bearer is set up between the called terminal and the called core network device after the voice bearer setup message is received, wherein the second response message is a response to the update message, the second response message is used for indicating that the called terminal has received the update message, the second response message carries a second parameter, the second parameter indicates that a voice bearer is set up between the called terminal and the called core network device, and the voice bearer setup message is used for requesting to set up a voice bearer in the second communication standard with the called terminal;
• and
• sending a ringing message after the called terminal sends the second response message, wherein the ringing message is used for notifying the calling terminal that the called terminal has started ringing.