Method and apparatus for supporting security in RRC inactive state in wireless communication system

1. A method performed by a wireless device in a wireless communication system, the method comprising:

receiving, from an anchor cell, a radio resource control (RRC) release message including (i) a suspend configuration and (ii) multiple security variables,

wherein the multiple security variables are mapped to multiple values of a security counter, respectively;

calculating a resumeMAC-I based on (i) a Physical Cell Identifier (PCI) of the anchor cell, (ii) a Cell-Radio Network Temporary Identifier (C-RNTI) used for the anchor cell, (iii) a cell ID of a target cell, and (iv) a specific security variable selected based on a value of the security counter; and

updating an inactive Radio Network Temporary Identifier (I-RNTI) of the wireless device, based on the specific security variable;

transmitting, to the target cell, an RRC resume request message including (i) the calculated resumeMAC-I and (ii) the updated I-RNTI; and

increasing the security counter, based on transmitting the RRC resume request message;

based on the security counter reaching a maximum trial value:

entering into an RRC idle state; and

performing a connection recovery procedure through a Non-access stratum (NAS) layer of the wireless device.

2. The method of claim 1 , wherein the method further comprises:

starting a security timer, upon receiving the RRC release message; and

increasing the security counter and restarting the security timer, whenever the security timer expires.

3. The method of claim 1 , wherein information on the value of the security counter is included in the RRC resume request message.

4. The method of claim 3 , wherein the information on the value of the security counter is forwarded to the anchor cell via the target cell.

5. The method of claim 1 , wherein the method further comprises, based on the security counter reaching the maximum trial value, setting the security counter to zero (0).

6. The method of claim 1 , wherein the method further comprises receiving information informing the wireless device whether i) to set the security counter to zero (0) or ii) to enter into an RRC idle state and performing a connection recovery procedure through a NAS layer, based on the security counter reaching the maximum trail value.

7. The method of claim 1 , wherein the method further comprises increasing the security counter, whenever receiving an RRC reject message as a response to the RRC resume request message.

8. The method of claim 1 , wherein the wireless device is in communication with at least one of a user equipment, a network, and/or autonomous vehicles.

9. A wireless device in a wireless communication system, the wireless device comprising:

a memory;

a transceiver; and

a processor, operably coupled to the memory and the transceiver, wherein the processor is configured to:

control the transceiver to receive, from an anchor cell, a radio resource control (RRC) release message including (i) a suspend configuration and (ii) multiple security variables,

wherein the multiple security variables are mapped to multiple values of a security counter, respectively;

calculate a resumeMAC-I based on (i) a Physical Cell Identifier (PCI) of the anchor cell, (ii) a Cell-Radio Network Temporary Identifier (C-RNTI) used for the anchor cell, (iii) a cell ID of a target cell, and (iv) a specific security variable selected based on a value of the security counter; and

update an inactive Radio Network Temporary Identifier (I-RNTI) of the wireless device, based on the specific security variable;

control the transceiver to transmit, to the target cell, an RRC resume request message including (i) the calculated resumeMAC-I and (ii) the updated I-RNTI; and

increasing the security counter, based on transmitting the RRC resume request message;

based on the security counter reaching a maximum trial value:

enter into an RRC idle state; and

perform a connection recovery procedure through a Non-access stratum (NAS) layer of the wireless device.

10. The wireless device of claim 9 , wherein the processor is further configured to:

start a security timer, upon receiving the RRC release message; and

increase the security counter and restart the security timer, whenever the security timer expires.

11. The wireless device of claim 9 , wherein information on the value of the security counter is included in the RRC resume request message.

12. The wireless device of claim 11 , wherein the information on the value of the security counter is forwarded to the anchor cell via the target cell.

13. The wireless device of claim 10 , wherein the processor is further configured to, based on the security counter reaching the maximum trial value, set the security counter to zero (0).

14. The wireless device of claim 10 , wherein the processor is further configured to control the transceiver to receive information informing the processor whether i) to set the security counter to zero (0) or ii) to enter into an RRC idle state and perform a connection recovery procedure through a NAS layer, based on the security counter reaching the maximum trial value.

15. A processor for a wireless device in a wireless communication system, wherein the processor is configured to:

control the wireless device to receive, from an anchor cell, a radio resource control (RRC) release message including (i) a suspend configuration and (ii) multiple security variables,

wherein the multiple security variables are mapped to multiple values of a security counter, respectively;

control the wireless device to calculate a resumeMAC-I based on (i) a Physical Cell Identifier (PCI) of the anchor cell, (ii) a Cell-Radio Network Temporary Identifier (C-RNTI) used for the anchor cell, (iii) a cell ID of a target cell, and (iv) a specific security variable selected based on a value of the security counter; and

control the wireless device to update an inactive Radio Network Temporary Identifier (I-RNTI) of the wireless device, based on the specific security variable;

control the wireless device to transmit, to the target cell, an RRC resume request message including (i) the calculated resumeMAC-I and (ii) the updated I-RNTI; and

control the wireless device to increase the security counter, based on transmitting the RRC resume request message;

based on the security counter reaching a maximum trial value:

control the wireless device to enter into an RRC idle state; and

control the wireless device to perform a connection recovery procedure through a Non-access stratum (NAS) layer of the wireless device.