Method for a configuration error management for a sidelink radio bearer and device therefor

1. A method for a User Equipment (UE) operating in a wireless communication system, the method comprising:

receiving a plurality of Device to Device (D2D) packets via a sidelink radio bearer;

counting erroneous D2D packets among the plurality of D2D packets;

detecting configuration error for the sidelink radio bearer if a number of the counted erroneous D2D packets is equal to or larger than a threshold;

starting a timer when the configuration error for the sidelink radio bearer is detected;

generating a configuration error recovery request including an identifier of the sidelink radio bearer;

transmitting the configuration error recovery request to a network or a peer UE directly connected to the UE via the sidelink radio bearer;

stopping the timer and re-establishing a Radio Link Control (RLC) entity and a Packet Data Convergence Protocol (PDCP) entity of the sidelink radio bearer according to configuration information received in response to the configuration error recovery request, when the configuration information is received before the timer is expired; and

transmitting a recovery fail indicator to the network or the peer UE when the configuration information is not received before the timer is expired.

2. The method according to claim 1 ,

wherein the UE counts only consecutive erroneous D2D packets when the erroneous D2D packets are counted.

3. The method according to claim 1 ,

wherein the counted erroneous D2D packets are received consecutively if the configuration error is detected.

4. The method according to claim 1 , wherein the counted erroneous D2D packets are received within a predefined time period.

5. The method according to claim 1 ,

wherein the erroneous D2D packets are counted in only the RLC entity, only the PDCP entity or both of the RLC entity and the PDCP entity.

6. The method according to claim 1 ,

wherein D2D packets of the plurality of D2D packets are counted as the erroneous D2D packets in one of following cases:

when header decompression failure occurs in the PDCP entity of the sidelink radio bearer;

when a PDCP Protocol Data Unit (PDU) that contains reserved or invalid values is received in the PDCP entity of the sidelink radio bearer; or

when a RLC PDU that contains reserved or invalid values is received in the RLC entity of the sidelink radio bearer.

7. The method according to claim 1 ,

wherein the threshold is configured independently for each sidelink radio bearer, or commonly for all sidelink radio bearers.

8. The method according to claim 1 ,

wherein the threshold is received from the network or the peer UE.

9. The method according to claim 1 ,

wherein threshold information is received in at least one of Radio Resource Control (RRC) signal, PDCP signal, RLC signal, Medium Access Control (MAC) signal, or PHYsical (PHY) signal.

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

releasing the RLC entity and the PDCP entity of the sidelink radio bearer when the configuration error for the sidelink radio bearer is detected.

11. The method according to claim 1 ,

wherein the identifier of the sidelink radio bearer includes at least one of a Source ID, a Target ID or a LCID.

12. A User Equipment (UE) for operating in a wireless communication system, the UE comprising:

a Radio Frequency (RF) module; and

a processor operably coupled with the RF module and configured to:

receive a plurality of Device to Device (D2D) packets via a sidelink radio bearer;

count erroneous D2D packets among the plurality of D2D packets;

detect configuration error for the sidelink radio bearer if a number of the counted erroneous D2D packets is equal to or larger than a threshold;

start a timer when the configuration error for the sidelink radio bearer is detected;

generate a configuration error recovery request including an identifier of the sidelink radio bearer;

transmit the configuration error recovery request to a network or a peer UE directly connected to the UE via the sidelink radio bearer;

stop the timer and re-establish a Radio Link Control (RLC) entity and a Packet Data Convergence Protocol (PDCP) entity of the sidelink radio bearer according to configuration information received in response to the configuration error recovery request, when the configuration information is received before the timer is expired; and

transmit a recovery fail indicator to the network or the peer UE when the configuration information is not received before the timer is expired.

13. The UE according to claim 12 ,

wherein the UE counts only consecutive erroneous D2D packets when the erroneous D2D packets are counted.

14. The UE according to claim 12 ,

wherein the counted erroneous D2D packets are received consecutively if the configuration error is detected.

15. The UE according to claim 12 ,

wherein the counted erroneous D2D packets are received within a predefined time period.

16. The UE according to claim 12 ,

wherein the erroneous D2D packets are counted in only the RLC entity, only the PDCP entity or both of the RLC entity and the PDCP entity.

17. The UE according to claim 12 ,

wherein D2D packets of the plurality of D2D packets are counted as the erroneous D2D packets in one of following cases:

when header decompression failure occurs in the PDCP entity of the sidelink radio bearer;

when a PDCP Protocol Data Unit (PDU) that contains reserved or invalid values is received in the PDCP entity of the sidelink radio bearer; or

when a RLC PDU that contains reserved or invalid values is received in the RLC entity of the sidelink radio bearer.