Methods for selecting radio access technology (RAT) modes in wireless communication devices

1. A method performed by a wireless communication device for selecting a radio access technology (RAT) mode, the method comprising:

determining location information of the wireless communication device;

identifying a public land mobile network (PLMN) based on the location information;

obtaining a subscriber identity module (SIM) preferred list from a SIM based on a current operating mode;

when the identified PLMN is present in the obtained SIM preferred list, identifying one or more first access technology (AccTech) recorded in the SIM preferred list corresponding to the identified PLMN;

when the identified PLMN is absent in the SIM preferred list, identifying one or more second AccTech supported by the current operating mode; and

determining the RAT mode based on the one or more first AccTech or the one or more second AccTech.

2. The method as claimed in claim 1 , wherein the location information includes tracking area identity (TAI) information, routing area identification (RAI) information and location area identity (LAI) information which are extracted from evolved packet system location information (EPSLOCI), packet system location information (PSLOCI) and location information (LOCI), respectively.

3. The method as claimed in claim 1 , wherein the determining the location information includes one of:

reading EPSLOCI either from a SIM or a flash memory when a User Services Identity Module (USIM) is not changed; or

reading the EPSLOCI from a new USIM and invalidating the EPSLOCI from the flash memory when the USIM is changed.

4. The method as claimed in claim 1 , wherein the determining the location information includes reading PSLOCI or LOCI from a Subscriber Identity Module (SIM).

5. The method as claimed in claim 1 , further comprising;

adding at least one remaining supported AccTech to the stored RPLMN AccTech based on whether location update status information is valid.

6. The method as claimed in claim 1 , wherein the SIM preferred list comprises a home public land mobile network (HPLMN) selector with access technology, a user controlled PLMN selector with access technology, and an operator controlled PLMN selector with access technology.

7. The method as claimed in claim 1 , wherein the deriving derives the RPLMN using a last registered RAT and domain information when the validating is unsuccessful.

8. The method as claimed in claim 1 , wherein the selecting the RAT mode comprises:

checking whether an EPS update status is valid and long-term evolution (LTE) is supported;

selecting the RAT mode as LTE when the EPS update status is valid and long-term evolution (LTE) is supported;

checking whether a GMM/MM update status is valid and universal mobile telecommunications system (UMTS) is supported when the EPS update status is not valid or long-term evolution (LTE) is not supported;

selecting the RAT mode as UMTS when the GMM/MM update status is valid and universal mobile telecommunications system (UMTS) is supported; and

selecting the RAT mode as global system for mobile communication (GSM) when the GMM/MM update status is not valid and universal mobile telecommunications system (UMTS) is not supported.

9. The method as claimed in claim 5 , wherein the selecting the RAT mode is based on the current operating mode and in a priority order from highest to lowest of (i) LTE, (ii) UMTS and (iii) GSM.

10. The method as claimed in claim 8 further comprising:

searching for an RPLMN using stored frequencies on a next highest priority RAT if the wireless communication device receives a rejection or if registration fails on a highest priority RAT.

11. A wireless communication device for selecting a radio access technology (RAT) mode, the wireless communication device comprising:

a memory; and

at least one processor configured to

determine location information of the wireless communication device,

identify a public land mobile network (PLMN) based on the location information,

obtain a subscriber identity module (SIM) preferred list from a SIM based on a current operating mode,

when the identified PLMN is present in the obtained SIM preferred list, identifying one or more first access technology (AccTech) recorded in the SIM preferred list corresponding to the identified PLMN,

when the identified PLMN is absent in the SIM preferred list, identifying one or more second AccTech supported by the current operating mode, and

determining the RAT mode based on the one or more first AccTech or the one or more second AccTech.

12. The wireless communication device as claimed in claim 11 , wherein the location information includes tracking area identity (TAI) information, routing area identification (RAI) information and location area identity (LAI) information which are extracted from evolved packet system location information (EPSLOCI), packet system location information (PSLOCI) and location information (LOCI), respectively.

13. The wireless communication device as claimed in claim 11 , wherein the at least one processor is configured to:

read EPSLOCI either from a SIM or a flash memory when a User Services Identity Module (USIM) is not changed; and

read the EPSLOCI from a new USIM and invalidate the EPSLOCI from the flash memory when the USIM is changed.

14. The wireless communication device as claimed in claim 11 , wherein the at least one processor is configured to read PSLOCI or LOCI from a Subscriber Identity Module (SIM).

15. The wireless communication device as claimed in claim 11 , wherein the at least one processor is further configured to add at least one remaining supported AccTech to the stored RPLMN AccTech based on whether location update status information is valid.

16. The wireless communication device as claimed in claim 11 , wherein the SIM preferred list comprises a home public land mobile network (HPLMN) selector with access technology, a user controlled PLMN selector with access technology, and an operator controlled PLMN selector with access technology.

17. The wireless communication device as claimed in claim 11 , wherein the at least one processor is further configured to derive the RPLMN using a last registered RAT and domain information when the validation is unsuccessful.

18. The wireless communication device as claimed in claim 11 , wherein the at least one processor is configured to:

check whether an EPS update status is valid and long-term evolution (LTE) is supported;

select the RAT mode as LTE when the EPS update status is valid and long-term evolution (LTE) is supported;

check whether a GMM/MM update status is valid and universal mobile telecommunications system (UMTS) is supported when the EPS update status is not valid or long-term evolution (LTE) is not supported;

select the RAT mode as UMTS when the GMM/MM update status is valid and universal mobile telecommunications system (UMTS) is supported; and

select the RAT mode as global system for mobile communication (GSM) when the GMM/MM update status is not valid and universal mobile telecommunications system (UMTS) is not supported.