Method and user equipment for resetting PLMN attempt counters in a tracking area update procedure for disaster roaming

1 . An operation method of user equipment (UE), comprising:

maintaining a list of public land mobile network (PLMN)-specific attempt counters for a determined PLMN with disaster condition for the UE supporting a minimization of service interruption (MINT)-evolved packet system (EPS);

generating a tracking area update request message;

setting an EPS update type in the tracking area update request message to a disaster roaming update, corresponding to the disaster roaming service;

inserting the determined PLMN with disaster condition into the tracking area update request message in response to initiating a tracking area update procedure with the EPS update type set to the disaster roaming update; and

resetting a PLMN-specific attempt counter of a first PLMN for the determined PLMN with disaster condition, in response to receiving a tracking area update accept message from the first PLMN for the disaster roaming service,

wherein the determined PLMN with disaster condition is inserted into the tracking area update request message, when the UE has determined the determined PLMN with disaster condition, and when an additional globally unique temporary identifier (GUTI) is included in the tracking area update request message and does not contain a valid GUTI mapped from a 5G-GUTI which was previously assigned.

2 . The method of claim 1 , further comprising:

determining whether the UE supports the MINT-EPS.

3 . The method of claim 1 , further comprising:

resetting the PLMN-specific attempt counter of the first PLMN for the determined PLMN with disaster condition, if an attach accept message is received from the first PLMN and if the attach accept message is for the disaster roaming service.

4 . The method of claim 1 , wherein the determined PLMN with disaster condition is inserted into the tracking area update request message, if the UE has determined the determined PLMN with disaster condition, and if an additional GUTI is not included in the tracking area update request message and an EPS mobility identity does not contain a valid GUTI mapped from a 5G-GUTI which was previously assigned.

5 . A user equipment (UE), the UE comprising:

at least one processor; and

at least one computer memory operably connectable to the at least one processor and storing instructions that, when executed by the at least one processor, perform operations comprising:

maintaining a list of public land mobile network (PLMN)-specific attempt counters for a determined PLMN with disaster condition if the UE supports a minimization of service interruption (MINT)-evolved packet system (EPS) is supported;

generating a tracking area update request message;

setting an EPS update type in the tracking area update request message to a disaster roaming update, if the tracking area update request message is for the disaster roaming service;

inserting the determined PLMN with disaster condition into the tracking area update request message if the UE initiates a tracking area update procedure with the EPS update type set to the disaster roaming update; and

resetting a PLMN-specific attempt counter of a first PLMN for the determined PLMN with disaster condition, if a tracking area update accept message is received from the first PLMN and if the tracking area update accept message is for the disaster roaming service,

wherein the determined PLMN with disaster condition is inserted into the tracking area update request message, if the UE has determined the determined PLMN with disaster condition, and if an additional globally unique temporary identifier (GUTI) is included in the tracking area update request message and does not contain a valid GUTI mapped from a 5G-GUTI which was previously assigned.

6 . The UE of claim 5 , wherein the operations further comprise:

determining whether the UE supports the MINT-EPS.

7 . The UE of claim 5 , wherein the operations further comprise:

resetting the PLMN-specific attempt counter of the first PLMN for the determined PLMN with disaster condition, if an attach accept message is received from the first PLMN and if the attach accept message is for the disaster roaming service.

8 . The UE of claim 5 , wherein the determined PLMN with disaster condition is inserted into the tracking area update request message, if the UE has determined the determined PLMN with disaster condition, and if an additional GUTI is not included in the tracking area update request message and an EPS mobility identity does not contain a valid GUTI mapped from a 5G-GUTI which was previously assigned.

9 . A semiconductor chipset, comprising:

at least one processor; and

at least one memory capable of storing instructions and being connected electrically to the at least one processor operably,

wherein operations, performed when the instructions are executed by the at least one processor, includes:

maintaining a list of public land mobile network (PLMN)-specific attempt counters for a determined PLMN with disaster condition if the UE supports a minimization of service interruption (MINT)-evolved packet system (EPS) is supported;

generating a tracking area update request message;

setting an EPS update type in the tracking area update request message to a disaster roaming update, if the tracking area update request message is for the disaster roaming service;

inserting the determined PLMN with disaster condition into the tracking area update request message if the UE initiates a tracking area update procedure with the EPS update type set to the disaster roaming update; and

resetting a PLMN-specific attempt counter of a first PLMN for the determined PLMN with disaster condition, if a tracking area update accept message is received from the first PLMN and if the tracking area update accept message is for the disaster roaming service,

wherein the determined PLMN with disaster condition is inserted into the tracking area update request message, if the UE has determined the determined PLMN with disaster condition, and if an additional globally unique temporary identifier (GUTI) is included in the tracking area update request message and does not contain a valid GUTI mapped from a 5G-GUTI which was previously assigned.

10 . The semiconductor chipset of claim 9 , wherein the operations further comprise:

determining whether the UE supports the MINT-EPS.

11 . The semiconductor chipset of claim 9 , wherein the operations further comprise:

resetting the PLMN-specific attempt counter of the first PLMN for the determined PLMN with disaster condition, if an attach accept message is received from the first PLMN and if the attach accept message is for the disaster roaming service.

12 . The semiconductor chipset of claim 9 , wherein the determined PLMN with disaster condition is inserted into the tracking area update request message, if the UE has determined the determined PLMN with disaster condition, and if an additional GUTI is not included in the tracking area update request message and an EPS mobility identity does not contain a valid GUTI mapped from a 5G-GUTI which was previously assigned.