Radio link failure processing method and apparatus therefor

1. A method for communicating by a user equipment (UE) supporting a dual-connectivity communication system, the method comprising:

determining whether a radio link with a first base station fails;

transmitting to a second base station a message indicating that the radio link with the first base station fails when the radio link with the first base station is determined as failed;

receiving data from the second base station without releasing the radio link with the first base station after the message indicating that the radio link with the first base station fails is transmitted to the second base station;

determining whether the radio link with the first base station fails during a predetermined time after transmitting the message; and

transmitting data to the first base station when the radio link with the first base station is determined as successful.

2. The method of claim 1 , further comprising:

receiving a message indicating that a radio link with the UE is released from the second base station to the first base station; and

releasing the radio link with the first base station when the radio link with the first base station is determined as failed.

3. The method of claim 1 , wherein the message indicating that the radio link with the first base station fails is a measurement report message.

4. The method of claim 1 , wherein the predetermined time is determined by the first base station.

5. The method of claim 1 , wherein the message indicating that the radio link with the first base station fails further includes information about a position of the UE.

6. A user equipment (UE) supporting a dual-connectivity communication system, the UE comprising:

a transceiver configured to transmit and receive data; and

at least one processor configured to:

determine whether a radio link with a first base station fails,

control the transceiver to transmit, to a second base station, a message indicating that the radio link with the first base station fails when the radio link with the first base station is determined as failed,

receive data from the second base station without releasing the radio link with the first base station after the message indicating that the radio link with the first base station fails is transmitted to the second base station,

determine whether the radio link with the first base station fails during a predetermined time after transmitting the message, and

transmit data to the first base station when the radio link with the first base station is determined as successful.

7. The UE of claim 6 , wherein the at least one processor is further configured to:

control to receive, from the second base station, a message indicating that the radio link with the first base station is released, and

release the radio link with the first base station when the radio link with the first base station is determined as failed.

8. The UE of claim 6 , wherein the message indicating that the radio link with the first base station fails is a measurement report message.

9. The UE of claim 6 , wherein the predetermined time is determined by the first base station.

10. The UE of claim 6 , wherein the message indicating that the radio link with the first base station fails further includes information about a position of the UE.

11. A method for communicating by a first base station in a dual-connectivity communication system, the method comprising:

receiving, from a second base station, a message indicating that a radio link between a user equipment (UE) and the first base station fails;

determining whether the radio link with the UE fails depending on whether a message is received from the second base station indicating that the radio link between the UE and the first base station is recovered within a predetermined time after receiving the message without releasing the radio link with the UE in response to receiving, from the second base station, the message indicating that the radio link between the UE and the first base station fails; and

transmitting, to the second base station, a message indicating transmission of data to the first base station when the radio link with the UE is determined as successful.

12. The method of claim 11 , further comprising:

transmitting, to the second base station, a message indicating that the radio link with the UE is released; and

releasing the radio link with the UE when the radio link with the UE is determined as failed.

13. The method of claim 11 , wherein the message indicating that the radio link between the UE and the first base station fails is a measurement report message.

14. The method of claim 11 , wherein the predetermined time is determined by the UE.

15. The method of claim 11 , wherein the message indicating that the radio link between the UE and the first base station fails further includes information about a position of the UE.

16. A first base station in a dual-connectivity communication system, the first base station comprising:

a transceiver configured to transmit and receive data; and

at least one processor configured to:

control to receive, from a second base station, a message indicating that a radio link between a user equipment (UE) and the first base station fails,

determine whether the radio link with the UE fails depending on whether a message is received from the second base station indicating that the radio link between the UE and the first base station is recovered within a predetermined time after receiving the message without releasing the radio link with the UE in response to receiving, from the second base station, the message indicating that the radio link between the UE and the first base station fails, and

control to transmit, to the second base station, a message indicating transmission of data to the first base station when the radio link with the UE is determined as successful.

17. The first base station of claim 16 , wherein the at least one processor is further configured to:

control to transmit, to the second base station, a message indicating that the radio link with the UE is released, and

release the radio link with the UE when the radio link with the UE is determined as failed.

18. The first base station of claim 16 , wherein the message indicating that the radio link between the UE and the first base station fails is a measurement report message.

19. The first base station of claim 16 , wherein the predetermined time is determined by the UE.

20. The first base station of claim 16 , wherein the message indicating that the radio link between the UE and the first base station fails further includes information about a position of the UE.

21. The method of claim 1 , wherein the transmitting of the message indicating that the radio link with the first base station fails further comprises transmitting, to the second base station, the message indicating that the radio link with the first base station fails using a control signal transmission line with the second base station.

22. The method of claim 21 , further comprising:

switching a data transmission line from the first base station to the second base station after transmitting the message indicating that the radio link with the first base station fails,

wherein the receiving of the data from the second base station without releasing the radio link with the first base station further comprises receiving the data from the second base station using the data transmission line.

23. The method of claim 22 , further comprising:

transmitting, to the first base station, a radio link recovery message using the control signal transmission line with the first base station when the radio link with the first base station is determined as successful; and

switching the data transmission line from the second base station to the first base station after transmitting the radio link recovery message,

wherein the transmitting of the data to the first base station when the radio link with the first base station is determined as successful further comprises transmitting the data to the first base station using the data transmission line.

24. The UE of claim 6 ,

wherein, to control the transceiver to transmit the message indicating that the radio link with the first base station fails, the at least one processor is further configured to control the transceiver to transmit, to the second base station, the message indicating that the radio link with the first base station fails using a control signal transmission line with the second base station,

wherein the at least one processor is further configured to switch a data transmission line from the first base station to the second base station after transmitting the message indicating that the radio link with the first base station fails, and

wherein, to receive the data from the second base station without releasing the radio link with the first base station, the at least one processor is further configured to receive the data from the second base station using the data transmission line.

25. The UE of claim 24 ,

wherein the at least one processor is further configured to:

control the transceiver to transmit, to the first base station, a radio link recovery message using the control signal transmission line with the first base station when the radio link with the first base station is determined as successful, and

switch the data transmission line from the second base station to the first base station after transmitting the radio link recovery message, and

wherein, to transmit the data to the first base station when the radio link with the first base station is determined as successful, the at least one processor is further configured to transmit the data to the first base station using the data transmission line.

26. The method of claim 11 ,

wherein the receiving of the message indicating that the radio link between the UE and the first base station fails further comprises receiving, from the second base station, the message indicating that the radio link between the UE and the first base station fails using a control signal transmission line with the second base stations, and

wherein the message indicating the transmission of the data comprises an indication message indicating a switch of a data transmission line from second base station to the first base station.

27. The method of claim 26 , further comprising:

transmitting and receiving data with the UE using the data transmission line after transmitting the indicating message.

28. The first base station of claim 16 ,

wherein, to control to receive the message indicating that the radio link between the UE and the first base station fails, the at least one processor is further configured to control to receive, from the second base station, the message indicating that the radio link between the UE and the first base station fails using a control signal transmission line with the second base stations, and

wherein the message indicating the transmission of the data comprises an indication message indicating a switch of a data transmission line from second base station to the first base station.

29. The first base station of claim 28 , wherein the at least one processor is further configured to control the transceiver to transmit and receive data with the UE using the data transmission line after transmitting the indicating message.