Method and apparatus for handling circuit switched calls at a user equipment
A method at a user equipment including detecting that a circuit switched (CS) call has been requested at the user equipment; if a most recent registration attempt or registration update attempt with a network of a first radio access technology (RAT) resulted in an abnormal state, registering with a network of a second RAT; and initiating the CS call with the network of the second RAT.
1. A method at a user equipment comprising:
detecting that a voice call has been requested at the user equipment;
determining that a registration attempt or registration update attempt with a network of a first radio access technology (RAT) is in an abnormal state;
after determining that a last successful network registration information matches current registration information received from a network of a second RAT, registering with the network of the second RAT, wherein the registering with the network of the second RAT is in a form of a second registration update; and
initiating the voice call with the network of the second RAT.
2. The method of claim 1 , wherein the voice call is initiated after the registering with the network of the second RAT is completed.
3. The method of claim 1 , wherein the first RAT is a packet switched only RAT.
4. The method of claim 1 , further comprising sending a service request to the network of the second RAT.
5. The method of claim 1 , wherein the registration attempt with the network of the first RAT is in an abnormal state due to a radio link failure or a radio resource control connection release.
6. The method of claim 5 , wherein the abnormal state is based on a reject cause indicating an identifier is unknown in a visitor location registry.
7. The method of claim 1 , further comprising checking whether the registering is successful, and if not ending the process.
8. The method of claim 1 , further comprising checking whether the registering is successful, and if not proceeding back to registering with the network of the second RAT.
9. The method of claim 1 , wherein the first RAT is an evolved-universal terrestrial radio access (E-UTRAN) RAT.
10. The method of claim 1 , wherein the second RAT is a global system for mobile communications (GSM) RAT or universal terrestrial radio access network (UTRAN) RAT.
11. The method of claim 1 , wherein determining that a last successful network registration information matches current registration information received from the network of the second RAT comprises determining that a tracking area code of the last successful network registration matches a tracking area code in a broadcast message from the network of the second RAT.
12. A user equipment comprising:
a communications subsystem; and
a processor;
wherein the communications subsystem and the processor cooperate to:
detect that a voice call has been requested at the user equipment;
determine that a registration attempt or registration update attempt with a network of a first radio access technology (RAT) is in an abnormal state;
after determining that a last successful network registration information matches current registration information received from a network of a second RAT, register with the network of the second RAT, wherein the registering with the network of the second RAT is in a form of a second registration update; and
initiate the voice call with the network of the second RAT.
13. The user equipment of claim 12 , wherein the voice call is initiated after the registering with the network of the second RAT is completed.
14. The user equipment of claim 12 , wherein the first RAT is a packet switched only RAT.
15. The user equipment of claim 12 , further comprising sending a service request to the network of the second RAT.
16. The user equipment of claim 12 , wherein the registration attempt with the network of the first RAT is in an abnormal state due to a radio link failure or a radio resource control connection release.
17. The user equipment of claim 16 , wherein the abnormal state is based on a reject cause indicating an identifier is unknown in a visitor location registry.
18. The user equipment of claim 12 , wherein the communications subsystem and the processor further cooperate to check whether the registering is successful, and if not, performing one of:
ending the process; or
proceeding back to registering with the network of the second RAT.
19. The user equipment of claim 12 , wherein the first RAT is an evolved-universal terrestrial radio access (E-UTRAN) RAT.
20. The user equipment of claim 12 , wherein the second RAT is a global system for mobile communications (GSM) RAT or universal terrestrial radio access network (UTRAN) RAT.
21. A non-transitory computer-readable medium for storing instruction code which, when executed by a processor of a user equipment cause the user equipment to:
detect that a voice call has been requested at the user equipment;
determine that a registration attempt or registration update attempt with a network of a first radio access technology (RAT) is in an abnormal state;
after determining that a last successful network registration information matches current registration information received from a network of a second RAT, register with the network of the second RAT, wherein the registering with the network of the second RAT is in a form of a second registration update; and
initiate the voice call with the network of the second RAT.