Method and apparatus for changing coverage enhancement/repetition level used for radio link monitoring in wireless communication system

1. A method for performing, by a user equipment (UE), a radio link monitoring (RLM) in a wireless communication system, the method comprising:

configuring a repetition level for the RLM;

performing a first RLM measurement based on the configured repetition level;

detecting a radio link failure (RLF) by the first RLM measurement based on the configured repetition level;

based on that the configured repetition level is smaller than a maximum repetition level, configuring the maximum repetition level, which is supported by a network, as the repetition level for the RLM, after the RLF is detected;

performing a second RLM measurement based on the maximum repetition level;

determining that a network is in range that a scheduling of user traffic to the UE is possible based on that in-sync is detected based on the second RLM measurement, which has been performed based on the maximum repetition level; and

starting a random access procedure to reconfigure the repetition level for the RLM, based on that the network is determined to be in the range,

wherein the UE requires coverage enhancement,

wherein the repetition level is related to a repetition of a physical downlink control channel (PDCCH) or an enhanced PDCCH (EPDCCH), and

wherein for each repetition level, a different frequency location is used for the PDCCH or the EPDCCH.

2. The method of claim 1 , wherein the configured repetition level is related to the maximum repetition level configured for PDCCH transmission, EPDCCH transmission or machine-type communication (MTC) PDCCH (MPDCCH) transmission.

3. The method of claim 1 , wherein the first RLM measurement or the second RLM measurement is performed based on a bundled PDCCH or a bundled EPDCCH.

4. The method of claim 1 , further comprising:

transmitting a result of the first RLM measurement or the second RLM measurement to the network.

5. The method of claim 4 , wherein the result of the first RLM measurement or the second RLM measurement is transmitted based on each repetition level.

6. The method of claim 4 , wherein the result of the first RLM measurement or the second RLM measurement is transmitted based on a lowest repetition level where an in-sync is detected.

7. The method of claim 4 , wherein the result of the first RLM measurement or the second RLM measurement is transmitted based on the configured repetition level for the RLM.

8. The method of claim 4 , wherein the result of the first RLM measurement or the second RLM measurement is transmitted based on the maximum repetition level configured for PDCCH transmission, EPDCCH transmission or machine-type communication (MTC) PDCCH (MPDCCH) transmission.

9. The method of claim 1 , wherein the UE detects that the network is in range, when the RLF is avoided by the second RLM measurement based on the maximum repetition level.

10. The method of claim 1 , further comprising:

validating the RLF for the maximum repetition level when the configured repetition level is smaller than the maximum repetition level.

11. A user equipment (UE) for performing a radio link monitoring (RLM) in a wireless communication system, the UE comprising:

a memory;

a transceiver; and

a processor connected with the memory and the transceiver, wherein the processor is configured to:

configure a repetition level for the RLM;

perform a first RLM measurement based on the configured repetition level;

detect a radio link failure (RLF) by the first RLM measurement based on the configured repetition level;

based on that the configured repetition level is smaller than a maximum repetition level, configure the maximum repetition level, which is supported by a network, as the repetition level for the RLM, after the RLF is detected;

perform a second RLM measurement based on the maximum repetition level;

determine that a network is in range that a scheduling of user traffic to the UE is possible based on that in-sync is detected based on the second RLM measurement, which has been performed based on the maximum repetition level; and

start a random access procedure to reconfigure the repetition level for the RLM, based on that the network is determined to be in the range,

wherein the UE requires coverage enhancement,

wherein the repetition level is related to a repetition of a physical downlink control channel (PDCCH) or an enhanced PDCCH (EPDCCH), and

wherein for each repetition level, a different frequency location is used for the PDCCH or the EPDCCH.

12. The UE of claim 11 , wherein the configured repetition level is related to the maximum repetition level configured for PDCCH transmission, EPDCCH transmission or machine-type communication (MTC) PDCCH (MPDCCH) transmission.

13. The UE of claim 11 , wherein the first RLM measurement or the second RLM measurement is performed based on a bundled PDCCH or a bundled EPDCCH.

14. The UE of claim 11 , wherein the UE detects that the network is in range, when the RLF is avoided by the second RLM measurement based on the maximum repetition level.

15. The UE of claim 11 , wherein the processor is further configured to:

validate the RLF for the maximum repetition level when the configured repetition level is smaller than the maximum repetition level.