Method and system for call setup

1. A method for setting up a call for a user equipment, comprising:

receiving, by the user equipment, a measurement configuration message that specifies a set of measurement events corresponding to poor signal quality between the user equipment and a packet-switched network;

initiating, by the user equipment, a first call setup process for setting up the call using the packet-switched network;

sending, by the user equipment, a measurement report when one of the set of measurement events occurs while performing the first call setup process;

starting a timeout timer when sending the measurement report;

terminating the first call setup process after sending the measurement report that indicates poor signal quality between the user equipment and the packet-switched network; and

sending, by the user equipment in response to the timeout timer reaching a predetermined value, a service request to begin a second call setup process for setting up the call for the user equipment using a circuit-switched network after terminating the first call setup process.

2. The method according to claim 1 , wherein the set of measurement events comprises at least one of:

a first event where a signal strength from a base station that communicatively connects the user equipment and the packet-switched network becomes less than a first threshold;

a second event where a signal strength from a neighboring base station becomes better than a second threshold; and

a third event that is a combination of at least the first event and the second event.

3. The method according to claim 1 , further comprising:

receiving a termination message after sending the measurement report, the termination message indicating termination of the first call setup process without requesting the user equipment to perform retry attempts; and

sending the service request in response to receiving the termination message.

4. The method according to claim 1 , further comprising:

receiving a termination message after sending the measurement report, the termination message indicating termination of the first call setup process without requesting the user equipment to perform retry attempts; and

sending the service request in response to an earlier one of receiving the termination message and/or the timeout timer reaching the predetermined value.

5. The method according to claim 1 , further comprising:

receiving, by the user equipment, an invite message that indicates initiation of the first call setup process;

receiving a cancellation message after sending the measurement report, the cancellation message indicating termination of the first call setup process;

receiving a service notification message after receiving the cancellation message, the service notification message indicating initiation of the second call setup process; and

sending the service request in response to receiving the service notification message.

6. The method according to claim 1 , further comprising:

sending, by a base station that communicatively connects the user equipment and the packet-switched network, the measurement configuration message to the user equipment;

receiving, by the base station, the measurement report from the user equipment; and

determining whether to terminate the first call setup process and to begin the second call setup process based on at least the measurement report from the user equipment and call status of the user equipment.

7. The method according to claim 6 , further comprising:

receiving, by the base station, a create bearer request from an Internet Protocol Multimedia Subsystem (IMS); and

sending, by the base station to the IMS in response to the create bearer request, a create bearer response that indicates a determination result of whether to terminate the first call setup process and to begin the second call setup process.

8. A user equipment, comprising:

a transceiver configured to communicate with a packet-switched network and a circuit-switched network; and

a controller configured to:

receive, through the transceiver, a measurement configuration message that specifies a set of measurement events corresponding to poor signal quality between the user equipment and a packet-switched network;

initiate a first call setup process for setting up the call using the packet-switched network;

send, through the transceiver, a measurement report when one of the set of measurement events occurs while performing the first call setup process;

start a timeout timer when sending the measurement report;

terminate the first call setup process after sending the measurement report that indicates poor signal quality between the user equipment and the packet-switched network; and

send, through the transceiver in response to the timeout timer reaching a predetermined value, a service request to begin a second call setup process for setting up the call for the user equipment using the circuit-switched network after terminating the first call setup process.

9. The user equipment according to claim 8 , wherein the set of measurement events comprises at least one of:

a first event where a signal strength from a base station that communicatively connects the user equipment and the packet-switched network becomes less than a first threshold;

a second event where a signal strength from a neighboring base station becomes better than a second threshold; and

a third event that is a combination of at least the first event and the second event.

10. The user equipment according to claim 8 , wherein the controller is further configured to:

receive a termination message after sending the measurement report, the termination message indicating termination of the first call setup process without requesting the user equipment to perform retry attempts; and

send the service request in response to receiving the termination message.

11. The user equipment according to claim 8 , wherein the controller is further configured to:

receive a termination message after sending the measurement report, the termination message indicating termination of the first call setup process without requesting the user equipment to perform retry attempts; and

send the service request in response to an earlier one of receiving the termination message and/or the timeout timer reaching the predetermined value.

12. The user equipment according to claim 8 , wherein the controller is further configured to:

receive, by the user equipment, an invite message that indicates initiation of the first call setup process;

receive a cancellation message after sending the measurement report, the cancellation message indicating termination of the first call setup process;

receive a service notification message after receiving the cancellation message, the service notification message indicating initiation of the second call setup process; and

send the service request in response to receiving the service notification message.

13. A communication system, comprising:

a service network; and

a user equipment configured to communicate with the service network, wherein

the service network is configured to send a measurement configuration message that specifies a set of measurement events corresponding to poor signal quality between the user equipment and a packet-switched network of the service network;

the user equipment is configured to:

receive the measurement configuration message;

initiate a first call setup process for setting up the call using the packet-switched network;

send a measurement report when one of the set of measurement events occurs while performing the first call set-up process;

start a timeout timer when sending the measurement report;

terminate the first call setup process after sending the measurement report that indicates poor signal quality between the user equipment and the packet-switched network; and

send, in response to the timeout timer reaching a predetermined value, a service request to begin a second call setup process for setting up the call for the user equipment using a circuit-switched network after terminating the first call setup process.

14. The communication system according to claim 13 , wherein the user equipment is further configured to:

receive a termination message after sending the measurement report, the termination message indicating termination of the first call setup process without requesting the user equipment to perform retry attempts; and

send the service request in response to receiving the termination message, and the service network is further configured to:

receive the measurement report from the user equipment;

determining whether to terminate the first call setup process and to begin the second call setup process based on at least the measurement report from the user equipment and call status of the user equipment; and

send the termination message indicating termination of the first call setup process to the user equipment when the first call setup process is determined to be terminated.

15. The communication system according to claim 13 , wherein the user equipment is further configured to:

receive a termination message after sending the measurement report, the termination message indicating termination of the first call setup process without requesting the user equipment to perform retry attempts; and

send the service request in response to an earlier one of receiving the termination message and the timeout timer reaching the predetermined value.

16. The communication system according to claim 13 wherein

the user equipment is further configured to:

receive an invite message that indicates initiation of the first call setup process;

receive a cancellation message after sending the measurement report, the cancellation message indicating termination of the first call setup process;

receive a service notification message after receiving the cancellation message, the service notification message indicating initiation of the second call setup process; and

send the service request in response to receiving the service notification message, and

the service network is further configured to:

receive the measurement report from the user equipment;

determining whether to terminate the first call setup process and to begin the second call setup process based on at least the measurement report from the user equipment and call status of the user equipment; and

send the cancellation message and the service notification message when the first call setup process is determined to be terminated.

17. The communication system according to claim 13 , wherein the service network comprises:

an Internet Protocol Multimedia Subsystem (IMS); and

a base station that is configured to receive a create bearer request from the IMS, and send a create bearer response that indicates a determination result of whether to terminate the first call setup process and to begin the second call setup process to the IMS in response to the create bearer request.