Channel access method for carrying out transmission in unlicensed band, and device using same

A method of operating a base station of a wireless communication system, the method comprising:

• when the base station performs transmission of the DRS and non-unicast data which are multiplexed, selecting one of two channel access types according to whether both of two conditions are satisfied, wherein the two conditions include a first condition that a duration of the transmission of the DRS and non-unicast data which are multiplexed is 1 ms or shorter, and a second condition that a duty cycle of DRS transmission is 1/20 or less, wherein the two channel access types includes a first type and a second type, the first type is a channel access in which a random backoff is performed using a variable-size contention window (CW), and a size of the CW is determined according to a channel access priority class, and the second type is a channel access in which only LBT based on a single time interval is performed;
• performing the transmission according to the selected channel access type,
• when the base station performs the transmission of the DRS and non-unicast data which are multiplexed using the first type and the transmission is associated with a hybrid automatic repeat request (HARQ)-ACK feedback corresponding to the transmission, adjusting the size of the CW based on the HARQ-ACK feedback and performing the channel access using the first type with the adjusted size of the CW, and
• when the base station performs the transmission of the DRS and non-unicast data which are multiplexed using the first type and the transmission is not associated with HARQ-ACK feedback corresponding to the transmission, performing the channel access using the first type with a smallest value among CW size values allowed for the channel access priority class determining the size of the CW.

A user equipment of a wireless communication system, the user equipment comprising:

• a communication module;
• and
• a processor configured to control the communication module,
• wherein the processor is configured to:
• receive a DRS and non-unicast data which are multiplexed from a base station of the wireless communication system, wherein a channel access type used for a transmission of the DRS and non-unicast data which are multiplexed is selected among two channel access types according to whether both of two conditions are satisfied,
• wherein the two conditions include a first condition that a duration of the transmission of the DRS and non-unicast data which are multiplexed is 1 ms or shorter, and a second condition that a duty cycle of DRS transmission is 1/20 or less,
• wherein the two channel access types include a first type and a second type, the first type is a channel access in which a random backoff is performed using a variable-size contention window (CW), and a size of the CW is determined according to a channel access priority class, and the second type is a channel access in which only LBT based on a single time interval is performed,
• when the first type is used for the transmission of the DRS and non-unicast data which are multiplexed and the transmission is associated with a hybrid automatic repeat request (HARQ)-ACK feedback corresponding to the transmission, the size of the CW is determined based on the HARQ-ACK feedback, and
• when the first type is used for the transmission of the DRS and non-unicast data which are multiplexed and the transmission is not associated with HARQ-ACK feedback corresponding to the transmission, the size of the CW is a smallest value among CW size values allowed for the channel access priority class determining the size of the CW.