Method and device for requesting RRC connection

1. A method for a radio resource control (RRC) connection by a user equipment (UE) in a wireless communication system, the method comprising:

receiving, from a first cell, a resume ID for resumption of the RRC connection and a list of cells in which the resume ID is valid;

selecting a second cell;

receiving, from the second cell, system information including information representing whether or not the second cell supports an RRC connection resume for re-establishment;

determining whether or not the resume ID is valid for the second cell, based on the list of cells and the information included in the system information,

wherein, based on (i) the second cell not being included in the list of cells and (ii) the information representing that the second cell supports the RRC connection resume for re-establishment, the UE determines that the resume ID is valid for the second cell; and

based on whether or not the resume ID is valid for the second cell, transmitting an RRC connection resume request message or an RRC connection re-establishment request message to the second cell,

wherein, based on determining that the resume ID is valid for the second cell, the RRC connection resume request message including the resume ID is transmitted to the second cell, and

wherein, based on determining that the resume ID is not valid for the second cell, the RRC connection re-establishment request message including (i) a cell radio network temporary identifier (C-RNTI) of the second cell and (ii) an ID of the first cell is transmitted to the second cell.

2. The method of claim 1 , wherein after a radio link failure (RLF), a handover failure, a reconfiguration failure, or a security check failure occurs, the second cell is selected by the UE.

3. The method of claim 1 , wherein the UE communicates with at least one of a mobile terminal, a network or autonomous vehicles other than the UE.

4. The method of claim 1 , wherein, based on (i) the second cell not being included in the list of cells and (ii) the information representing that the second cell does not support the RRC connection resume for re-establishment, the UE determines that the resume ID is not valid for the second cell.

5. The method of claim 1 , wherein, based on the second cell being included in the list of cells, the UE determines that the resume ID is valid for the second cell.

6. The method of claim 1 , further comprising:

receiving a validity timer for the resume ID,

wherein the UE determines whether the resume ID is valid for the second cell based on the validity timer.

7. The method of claim 6 , further comprising:

initiating the validity timer,

wherein, based on the validity timer not expiring, the UE determines that the resume UE ID is valid for the second cell.

8. The method of claim 7 , wherein, based on the resume ID being received from the first cell, the validity timer is initiated.

9. The method of claim 1 , wherein the first cell is a source cell of the UE, and the second cell is a cell selected or a cell reselected by the UE.

10. The method of claim 1 , further comprising:

resuming all suspended signaling radio bearers (SRBs) and all suspended data radio bearers (DRBs) after transmitting the RRC connection resume request message.

11. The method of claim 1 , further comprising:

resuming only all suspended signaling radio bearers (SRBs) after transmitting the RRC connection re-establishment request message.

12. A UE configured for a radio resource control (RRC) connection in a wireless communication system, the UE comprising:

a memory;

a transceiver; and

a processor connecting between the memory and the transceiver,

wherein the processor is configured to

control the transceiver to receive, from a first cell, a resume ID for resumption of the RRC connection and a list of cells in which the resume ID is valid;

select a second cell;

control the transceiver to receive, from the second cell, system information including information representing whether or not the second cell supports an RRC connection resume for re-establishment;

determine whether or not the resume ID is valid for the second cell based on the list of cells and the information included in the system information,

wherein, based on (i) the second cell not being included in the list of cells and (ii) the information representing that the second cell supports the RRC connection resume for re-establishment, the UE determines that the resume ID is valid for the second cell; and

based on whether or not the resume ID is valid for the second cell, control the transceiver to transmit an RRC connection resume request message or an RRC connection re-establishment request message to the second cell,

wherein, based on determining that the resume ID is valid for the second cell, the RRC connection resume request message including the resume ID is transmitted to the second cell, and

wherein, based on determining that the resume ID is not valid for the second cell, the RRC connection re-establishment request message including (i) a cell radio network temporary identifier (C-RNTI) of the second cell and (ii) an ID of the first cell is transmitted to the second cell.

13. The UE of claim 12 , wherein after a radio link failure (RLF), a handover failure, a reconfiguration failure, or a security check failure occurs, the second cell is selected by the UE.

14. The UE of claim 12 , wherein the UE communicates with at least one of a mobile terminal, a network or autonomous vehicles other than the UE.

15. The UE of claim 12 , wherein, based on (i) the second cell not being included in the list of cells and (ii) the information representing that the second cell does not support the RRC connection resume for re-establishment, the UE determines that the resume ID is not valid for the second cell.

16. The UE of claim 12 , wherein, based on the second cell being included in the list of cells, the UE determines that the resume ID is valid for the second cell.

17. The UE of claim 12 , wherein the processor is further configured to:

control the transceiver to receive a validity timer for the resume ID,

wherein the UE determines whether the resume ID is valid for the second cell based on the validity timer.

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

initiate the validity timer,

wherein, based on the validity timer not expiring, the UE determines that the resume ID is valid for the second cell.

19. The UE of claim 18 , wherein, based on the resume ID being received from the first cell, the validity timer is initiated.

20. The UE of claim 12 , wherein the first cell is a source cell of the UE, and the second cell is a cell selected or a cell reselected by the UE.