Method and apparatus for offload operation of the idle mode in a cellular device

1. A method of a first device, the method comprising:

entering an idle mode of a cellular radio interface;

performing a proximity connection with a second device using a proximity radio interface;

transmitting an offload request message to the second device; and

receiving an offload accept response message from the second device in response to the offload request message if a registered public land mobile network (PLMN) of the second device is same as a registered PLMN of the first device.

2. The method of claim 1 , further comprising:

transmitting an idle mode offload request message to a cellular network, wherein idle mode offload request message includes UE identity; and

receiving an idle mode offload response message in response to the idle mode offload request message.

3. The method of claim 1 , further comprising:

receiving, from the second device, non-access stratum (NAS) context container using the proximity radio interface to update NAS information of the first device if the first device detects an event to update the NAS information; and

updating the NAS information of the first device.

4. The method of claim 1 , further comprising:

receiving, from the second device, a context transfer container using the proximity radio interface if the second device detects an event trigger associated with the first device;

updating NAS context based on information included in the context transfer container; and

turning on the cellular radio interface.

5. The method of claim 4 , further comprising:

entering an active mode of the cellular radio interface; and

transmitting a response message to a cellular network if the event trigger is associated with page record for the first device.

6. A method of a second device, the method comprising:

performing a proximity connection with a first device using a proximity radio interface after the first device enters an idle mode of a cellular radio interface;

receiving an offload request message from the first device; and

determining whether a registered PLMN of the second device is same as a registered PLMN of the first device or not; and

transmitting, to the first device, an offload accept response message in response to the offload request message received from the first device if the registered PLMN of the second device is same as the registered PLMN of the first device.

7. The method of claim 6 , further comprising:

transmitting, to a cellular network, a tracking area update (TAU) request message for the second device and the first device if tracking area change is detected;

receiving a TAU accept message in response to the TAU request message, wherein the TAU accept message includes NAS information for the second device and the first device;

updating an NAS context for the second device; and

creating the NAS context associated with the first device.

8. The method of claim 7 , further comprising:

transmitting, to the first device, a NAS context container using the proximity radio interface to update the NAS information of the first device.

9. The method of claim 6 ,

transmitting, to the first device, a context transfer container using the proximity radio interface if the second device detects an event trigger associated with the first device.

10. The method of claim 6 , further comprising:

verifying the registered PLMN of the second device; and

deciding an offload operation requested by the first device based on the verified registered PLMN.

11. A first device comprising:

a transceiver configured to:

transmit signals to a second device and a cellular network; and

receive signals from the second device and the cellular network, wherein the transceiver comprises a proximity radio interface and a cellular radio interface; and

a processor configured to:

enter an idle mode of a cellular radio interface;

perform a proximity connection with the second device using a proximity radio interface;

transmit an offload request message to the second device; and

receive an offload accept response message from the second device in response to the offload request message if a registered PLMN of the second device is same as a registered PLMN of the first device.

12. The first device of claim 11 , wherein the processor is further configured to:

transmit an idle mode offload request message to the cellular network, wherein the idle mode offload request message includes UE identity; and

receive an idle mode offload response message in response to the idle mode offload request message.

13. The first device of claim 11 , wherein the processor is further configured to:

receive, from the second device, a non-access stratum (NAS) context container using the proximity radio interface to update NAS information of the first device if the second device detects an event to update the NAS information; and

updating the NAS information of the first device.

14. The first device of claim 11 , wherein the processor is further configured to:

receive, from the second device, a context transfer container using the proximity radio interface if the second device detects an event trigger associated with the first device;

updating NAS context based on information included in the context transfer container; and

turn on the cellular radio interface.

15. The first device of claim 14 , wherein the processor is further configured to:

enter an active mode of the cellular radio interface; and

transmit a response message to a cellular network if the event trigger is associated with page record for the first device.

16. A second device comprising:

a transceiver configured to:

transmit signals to a first device and a cellular radio interface; and

receive signals from the first device and the cellular radio interface, wherein the transceiver comprises a proximity radio interface and a cellular radio interface; and

a processor s configured to:

perform a proximity connection with the first device using a proximity radio interface after the first device enters an idle mode of a cellular radio interface;

receive an offload request message from the first device;

determine whether a registered PLMN of the second device is same as a registered PLMN of the first device or not; and

transmit, to the first device, an offload accept response message in response to the offload request message received from the first device if the registered PLMN of the second device is same as the registered PLMN of the first device.

17. The second device of claim 16 , wherein the processor is further configured to:

transmit, to the cellular radio interface, a tracking area update (TAU) request message for the second device and the first device if tracking area change is detected;

receive a TAU accept message in response to the TAU request message, wherein the TAU accept message includes NAS information for the second device and the first device;

update an NAS context for the second device; and

create the NAS context associated with the first device.

18. The second device of claim 17 , wherein the processor is further configured to transmit, to the first device, a NAS context container using the proximity radio interface to update the NAS information of the first device.

19. The second device of claim 16 , wherein the processor is further configured to transmit, to the first device, a context transfer container using the proximity radio interface if the second device detects an event trigger associated with the first device.

20. The second device of claim 16 , wherein the processor is further configured to:

verify the registered PLMN of the second device; and

decide an offload operation requested by the first device based on the verified registered PLMN.