Method for supporting carrier sensing in wireless access system supporting unlicensed band, and device supporting same
The present invention relates to methods for supporting carrier sensing in a wireless access system supporting an unlicensed band, and devices supporting same. A method for supporting carrier sensing in a wireless access system supporting an unlicensed band, according to an embodiment of the present invention, comprises the steps of: selecting a backoff counter value for performing carrier sensing; performing carrier sensing in a serving cell (S-cell) until the backoff counter value reaches a predetermined threshold value; when the backoff counter value reaches the predetermined threshold value, transmitting data in a transmission opportunity (TXOP) interval; receiving a reception state feedback indicating whether the transmitting of data is success, collision or error; and resetting the backoff counter value on the basis of the reception state feedback, wherein the S-cell can be configured in an unlicensed band.
1. A method for performing carrier sensing by a base station in a wireless access system supporting an unlicensed band, the method comprising:
selecting a backoff counter value for performing a carrier sensing procedure, based on a contention window size;
decreasing the backoff counter value based on a determination that the unlicensed band is an idle state while performing the carrier sensing procedure in the unlicensed band;
transmitting downlink data based on the backoff counter value being equal to 0;
obtaining a hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback for the downlink data;
and
adjusting the contention window size based on the HARQ-ACK feedback,
wherein the adjusting of the contention window size comprises:
initializing the contention window size or decreasing the contention window size when the HARQ-ACK feedback includes an acknowledgement (ACK) signal for the downlink data;
increasing the contention window size when the HARQ-ACK feedback includes a negative acknowledgement (NACK) signal for the downlink data; and
maintaining the contention window size and changing a modulation and coding scheme (MCS) level when the HARQ-ACK feedback includes neither the ACK signal nor the NACK signal.
2. The method of claim 1 ,
wherein the downlink data is transmitted via the unlicensed band, and
wherein the HARQ-ACK feedback is received via a licensed band.
3. The method of claim 1 , wherein the carrier sensing procedure is performed in a carrier sensing unit interval.
4. The method of claim 3 ,
wherein the carrier sensing unit corresponds to 1 orthogonal frequency division multiplexing (OFDM) symbol unit, a half OFDM symbol unit, or a 1/N OFDM symbol unit, and
wherein N corresponds to a natural number.
5. The method of claim 4 , wherein the unlicensed band is determined to be in the idle state when it is determined that the last n number of consecutive sections in the N number of 1/N OFDM symbol units are idle.
6. A base station performing carrier sensing in a wireless access system supporting an unlicensed band, the base station comprising:
a transmitter;
a receiver; and
a processor,
wherein the processor is configured to:
select a backoff counter value for performing a carrier sensing procedure, based on a contention window size;
decrease the backoff counter value based on a determination that the unlicensed band is an idle state while performing the carrier sensing procedure in the unlicensed band;
control the transmitter to transmit downlink data based on the backoff counter value being equal to 0;
obtain a hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback for the downlink data from; and
adjust the contention window size based on the plurality of HARQ-ACK feedback,
wherein the processor is further configured to:
initialize the contention window size or decreasing the contention window size when the HARQ-ACK feedback includes an acknowledgement (ACK) signal for the downlink data;
increase the contention window size when the HARQ-ACK feedback includes a negative acknowledgement (NACK) signal for the downlink data; and
maintain the contention window size and change a modulation and coding scheme (MCS) level when the HARQ-ACK feedback includes neither the ACK signal nor the NACK signal.
7. The base station of claim 6 ,
wherein the downlink data is transmitted via the unlicensed band, and
wherein the HARQ-ACK feedback is received via a licensed band.
8. The base station of claim 6 , wherein the carrier sensing procedure is performed in a carrier sensing unit interval.
9. The base station of claim 8 ,
wherein the carrier sensing unit corresponds to 1 orthogonal frequency division multiplexing (OFDM) symbol unit, a half OFDM symbol unit, or a 1/N OFDM symbol unit, and
wherein N corresponds to a natural number.
10. The base station of claim 9 , wherein the unlicensed band is determined to be in the idle state when it is determined that the last n number of consecutive sections in the N number of 1/N OFDM symbol units are idle.