Method for performing random access procedure by terminal in wireless communication system supporting unlicensed band and terminal for performing same

1. A method of performing a random access procedure by a user equipment (UE) in a wireless communication system supporting an unlicensed band, the method comprising:

performing a first channel access procedure for transmitting a random access channel (RACH) preamble in the unlicensed band during a first time unit;

when the first channel access procedure succeeds, transmitting the RACH preamble based on a first configuration during the first time unit; and

when the first channel access procedure fails, performing a second channel access procedure for transmitting the RACH preamble in the unlicensed band during a second time unit and transmitting the RACH preamble based on a second configuration during the second time unit depending on whether the second channel access procedure succeeds.

2. The method of claim 1 , wherein a first transmission power configuration and a first beam configuration included in the first configuration are set to be equal to a second transmission power configuration and a second beam configuration included in the second configuration, respectively.

3. The method of claim 1 , wherein when a predetermined number or more of channel access procedures including the first channel access procedure fail before the second access procedure is performed, a first beam configuration included in the first configuration is set to be different from a second beam configuration included in the second configuration.

4. The method of claim 3 , wherein the first and second channel access procedures are performed based on the first and second beam configurations, respectively.

5. The method of claim 1 , wherein a transmission power value in a first transmission power configuration included in the first configuration is set to be higher than that in a second transmission power configuration included in the second configuration,

wherein an energy detection (ED) threshold value in a first ED threshold configuration included in the first configuration is set to be lower than that in a second ED threshold configuration included in the second configuration, and

wherein the number of repetitions in a first RACH repetition configuration included in the first configuration is set to be lower than that in a second RACH repetition configuration included in the second configuration.

6. The method of claim 1 , wherein when the first and second time units are included within a channel occupancy time (COT) occupied by a base station, each of the first and second channel access procedures corresponds to a channel access procedure for determining whether a channel is idle during a predetermined time for the unlicensed band.

7. The method of claim 6 , wherein the first and second time units are preconfigured by the base station.

8. The method of claim 6 , wherein the UE expects to receive a response message for the RACH preamble within a predetermined time window from a time when the RACH preamble is transmitted.

9. The method of claim 8 , wherein the predetermined time window is set to be longer than a time window for the RACH preamble configured for a licensed band.

10. The method of claim 8 , wherein the response message corresponds to a random access response (RAR) message.

11. The method of claim 1 , further comprising, when the UE succeeds in one of the first and second channel access procedures, transmitting information on a channel occupancy time (COT) occupiable by the UE to a base station.

12. The method of claim 1 , wherein the first and second time units correspond to first and second slots, respectively.

13. A user equipment (UE) for performing a random access procedure in a wireless communication system supporting an unlicensed band, the UE comprising:

a transmitter;

a receiver; and

a processor connected to the transmitter and the receiver,

wherein the processor is configured to:

perform a first channel access procedure for transmitting a random access channel (RACH) preamble in the unlicensed band during a first time unit;

when the first channel access procedure succeeds, transmit the RACH preamble based on a first configuration during the first time unit; and

when the first channel access procedure fails, perform a second channel access procedure for transmitting the RACH preamble in the unlicensed band during a second time unit and transmit the RACH preamble based on a second configuration during the second time unit depending on whether the second channel access procedure succeeds.

14. The UE of claim 13 , wherein the UE communicates with at least one of a mobile terminal, a network and an autonomous vehicle.