EV2X mobility support for mode 3.5/RSU scheduled mode

1. A method for managing an operation mode implemented by a first user equipment (UE) in device-to-device communication, comprising:

transmitting, by the first UE, a request message to a base station to indicate the first UE is switching from a base station scheduling mode to a peer UE scheduling mode;

receiving, by the first UE, an acknowledgment message from the base station indicating a state change to allow the peer UE scheduling mode, wherein the acknowledgement message includes a resume identifier for resuming the base station scheduling mode; and

maintaining a connection state with the base station while in the peer UE scheduling mode based at least in part on the acknowledgment message.

2. The method according to claim 1 , further comprising:

receiving, by the first UE from a second UE, an allocation of resources for the device-to-device communication for the first UE, wherein the resources are allocated using a direct communication interface between the first UE and the second UE, a sidelink interface between the first UE and the second UE, or any combination thereof.

3. The method according to claim 2 , further comprising:

performing, by the first UE, a handover from the second UE to a third UE to continue the peer UE scheduling mode.

4. The method according to claim 3 , wherein the handover comprises:

sending, by the first UE, another request message to the base station including an identifier of the third UE to the base station.

5. The method according to claim 2 , wherein the second UE comprises a roadside unit (RSU).

6. The method according to claim 1 , further comprising:

determining, by the first UE, that the first UE is within an area identified by an area identifier; and

transmitting, by the first UE, a resume message to the base station to indicate the first UE is switching from the peer UE scheduling mode to the base station scheduling mode.

7. The method according to claim 6 , wherein the area identifier includes a list of identifiers, among which at least one identifier of the list of identifiers is announced by a second UE allocating resources for the device-to-device communication for the first UE.

8. The method according to claim 6 , wherein the area identifier includes an identifier announced by the base station.

9. The method according to claim 6 , wherein the resume message includes the resume identifier.

10. The method according to claim 1 , further comprising:

receiving, by the first UE, an area identifier from the base station, the area identifier indicating an area in which the peer UE scheduling mode is allowed.

11. The method according to claim 1 , further comprising:

performing, by the first UE, a handover from the base station to another base station; and

maintaining, by the first UE, the peer UE scheduling mode.

12. The method according to claim 1 , further comprising:

determining, by the first UE, a priority of device-to-device communication traffic in the peer UE scheduling mode based on an application that is being handled by the first UE.

13. The method according to claim 1 , wherein the resume identifier comprises an index for the first UE's stored context information.

14. The method according to claim 1 , wherein the request message is a radio resource control message or a medium access control message.

15. The method according to claim 1 , wherein the device-to-device communication comprises vehicle-to-everything (V2X) communication.

16. A first user equipment (UE) to manage an operation mode of the first UE in device-to-device communication, comprising:

a processor;

memory coupled with the processor, the processor configured to

transmit a request message to a base station to indicate the first UE is switching from a base station scheduling mode to a peer UE scheduling mode; and

receive an acknowledgment message from the base station indicating a state change to allow the peer UE scheduling mode, wherein the acknowledgement message includes a resume identifier for resuming the base station scheduling mode; and

maintain a connection state with the base station while in the peer UE scheduling mode based at least in part on the acknowledgment message.

17. The first UE according to claim 16 , wherein the peer UE scheduling mode comprises:

a second UE allocating resources for the device-to-device communication for the first UE, wherein the resources are allocated using a direct communication interface between the first UE and second UE, or a sidelink interface between the first UE and the second UE, or any combination thereof.

18. The first UE according to claim 17 , wherein the processor is further configured to:

perform a handover from the second UE to a third UE to continue the peer UE scheduling mode.

19. The first UE according to claim 17 , wherein the request message includes an identifier for the second UE.

20. The first UE according to claim 16 , wherein the processor is further configured to:

determine that the first UE is within an area identified by an area identifier; and

transmit a resume message to the base station to indicate the first UE is switching from the peer UE scheduling mode to the base station scheduling mode.

21. The first UE according to claim 20 , wherein the area identifier includes an identifier announced by the base station.

22. The first UE according to claim 16 , wherein the processor is further configured to:

perform a handover from the base station to another base station; and

maintain the peer UE scheduling mode.

23. The first UE according to claim 16 , wherein the processor is further configured to:

determine a priority of device-to-device communication traffic in the peer UE scheduling mode based on an application that is being handled by the first UE.

24. The first UE according to claim 16 , wherein the resume identifier comprises an index for the first UE's stored context information.

25. The first UE according to claim 16 , further comprising receiving an area identifier from the base station, the area identifier indicating an area in which the peer UE scheduling mode is allowed.

26. An apparatus for managing an operation mode of a user equipment (UE) in device-to-device communication, comprising:

means for sending a request message to a base station to indicate the UE is switching from a base station scheduling mode to a peer UE scheduling mode;

means for receiving an acknowledgment message from the base station indicating a state change to allow the peer UE scheduling mode, wherein the acknowledgement message includes a resume identifier for resuming the base station scheduling mode; and

means for receiving an area identifier from the base station, the area identifier indicating an area in which the peer UE scheduling mode is allowed; and

means for maintaining a connection state with the base station while in the peer UE scheduling mode based at least in part on the acknowledgment message.

27. A method for managing an operation mode of a first user equipment (UE) in device-to-device communication implemented by a base station, comprising:

receiving, by the base station, a request message from the first UE to indicate the first UE is switching from a base station scheduling mode to a peer UE scheduling mode;

transmitting, by the base station, an acknowledgment message to the first UE indicating a state change to allow the peer UE scheduling mode, wherein the acknowledgement message includes a resume identifier for resuming the base station scheduling mode; and

maintaining, by the base station, a connection state of the first UE while the first UE is in the peer UE scheduling mode based at least in part on the received request message.

28. The method according to claim 27 , further comprising:

performing, by the base station, at least one type of authorization of the peer UE scheduling mode based on an identifier for a second UE.

29. The method according to claim 28 , wherein performing the at least one type of authorization comprises:

increasing or decreasing, by the base station, resources allocated to the second UE for peer UE scheduling mode operation.

30. The method according to claim 28 , wherein the request message includes the identifier for the second UE.