Method for performing an attach procedure when mint service is supported

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

upon selecting a public land mobile network (PLMN) for a disaster roaming in an evolved packet system (EPS), performing an attach procedure with an attach type set to “disaster roaming attach”;

transmitting capability information indicating a support of a minimization of service interruption (MINT)-EPS during the attach procedure;

receiving a response message,

wherein if the response message is an attach accept message, the attach accept message includes at least one a disaster roaming wait range and a disaster return wait range, and

wherein if the response message is an attach reject message, the attach reject message includes a cause value set to “disaster roaming for the determined PLMN with disaster condition not allowed”;

starting a first timer based on a first random number which is generated within the disaster roaming wait range;

starting a second timer with a second random number value which is generated with the disaster return wait range; and

upon expiry of the second timer based on the disaster return wait range, not starting the second timer with the disaster return wait range again until the UE selects any PLMN for a disaster roaming service.

2 . The method of claim 1 ,

wherein while the first timer is running, the UE does not initiate an attach procedure on a selected public land mobile network (PLMN), except if the UE needs to request a packet data network (PDN) connection for an emergency bearer service.

3 . The method of claim 1 ,

wherein while the second timer is running, the UE does not initiate a registration procedure on a selected first PLMN, except if the UE needs to request an emergency protocol data unit (PDU) session in which case the UE initiates a registration procedure.

4 . The method of claim 1 , further comprising:

upon expiration of the first timer, if the UE does not have a PDN connection for an emergency bearer service, performing an attach procedure for a disaster roaming service if still camped on a selected PLMN.

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:

upon selecting a public land mobile network (PLMN) for a disaster roaming in an evolved packet system (EPS), performing an attach procedure with an attach type set to “disaster roaming attach”;

transmitting capability information indicating a support of a minimization of service interruption (MINT)-EPS during the attach procedure;

receiving a response message,

wherein if the response message is an attach accept message, the attach accept message includes at least one a disaster roaming wait range and a disaster return wait range, and

wherein if the response message is an attach reject message, the attach reject message includes a cause value set to “disaster roaming for the determined PLMN with disaster condition not allowed”;

starting a first timer based on a first random number which is generated within the disaster roaming wait range;

starting a second timer with a second random number value which is generated with the disaster return wait range; and

upon expiry of the second timer based on the disaster return wait range, not starting the second timer with the disaster return wait range again until the UE selects any PLMN for a disaster roaming service.

6 . The UE of claim 5 ,

wherein while the first timer is running, the UE does not initiate an attach procedure on a selected public land mobile network (PLMN), except if the UE needs to request a packet data network (PDN) connection for an emergency bearer service.

7 . The UE of claim 5 ,

wherein while the second timer is running, the UE does not initiate a registration procedure on a selected first PLMN, except if the UE needs to request an emergency protocol data unit (PDU) session in which case the UE initiates a registration procedure.

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

upon expiration of the first timer, if the UE does not have a PDN connection for an emergency bearer service, performing an attach procedure for a disaster roaming service if still camped on a selected PLMN.

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:

upon selecting a public land mobile network (PLMN) for a disaster roaming in an evolved packet system (EPS), performing an attach procedure with an attach type set to “disaster roaming attach”;

transmitting capability information indicating a support of a minimization of service interruption (MINT)-EPS during the attach procedure;

receiving a response message,

wherein if the response message is an attach accept message, the attach accept message includes at least one a disaster roaming wait range and a disaster return wait range, and

wherein if the response message is an attach reject message, the attach reject message includes a cause value set to “disaster roaming for the determined PLMN with disaster condition not allowed”;

starting a first timer based on a first random number which is generated within the disaster roaming wait range;

starting a second timer with a second random number value which is generated with the disaster return wait range; and

upon expiry of the second timer based on the disaster return wait range, not starting the second timer with the disaster return wait range again until the UE selects any PLMN for a disaster roaming service.

10 . The semiconductor chipset of claim 9 ,

wherein while the first timer is running, the UE does not initiate an attach procedure on a selected public land mobile network (PLMN), except if the UE needs to request a packet data network (PDN) connection for an emergency bearer service.

11 . The semiconductor chipset of claim 9 ,

wherein while the second timer is running, the UE does not initiate a registration procedure on a selected first PLMN, except if the UE needs to request an emergency protocol data unit (PDU) session in which case the UE initiates a registration procedure.

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

upon expiration of the first timer, if the UE does not have a PDN connection for an emergency bearer service, performing an attach procedure for a disaster roaming service if still camped on a selected PLMN.