Method for channel access in wireless communication system and apparatus for performing same

1. A method of performing channel access on an unlicensed band by a user equipment in a wireless communication system, the method comprising:

sensing a carrier of an unlicensed band for receiving a downlink signal; and

receiving the downlink signal when power detected by sensing the carrier is less than an energy detection threshold that is configured by a base station,

wherein the energy detection threshold is configured to be equal to or less than a maximum energy detection threshold determined by the base station,

wherein when a different radio access technology (RAT) sharing the carrier is able to exist, the maximum energy detection threshold is determined adaptively to a bandwidth of the carrier using a decibel value of a ratio between a reference bandwidth and the bandwidth of the carrier,

wherein the maximum energy detection threshold is configured to be equal to or greater than a first power value which is a sum of a lower bound of the maximum energy detection threshold for the reference bandwidth and the decibel value, and

wherein the first power value is obtained by a first equation ‘−72+10*log 10(BWMHz/20 MHz) [dBm]’, where ‘20 MHz’ of the first equation corresponds to the reference bandwidth, ‘BWMHz’ corresponds to the bandwidth of the carrier represented in a unit of MHz, ‘10*log 10(BWMHz/20 MHz)’ corresponds to the decibel value, and ‘−72’ corresponds to the lower bound of the maximum energy detection threshold for the reference bandwidth represented in a unit of dBm.

2. The method of claim 1 , wherein the maximum energy detection threshold is configured to be equal to or greater than a second power value which is determined in consideration of a difference between the decibel value and maximum transmit power of the base station set for the carrier.

3. The method of claim 2 , wherein the second power value is obtained by a second equation ‘min{Tmax, Tmax−TA+(PH+10*log 10(BWMHz/20 MHz)−PTX)} [dBm]’, where ‘Tmax’ of the second equation corresponds to ‘10*log 10(3.16288*10−8/BWMHz)’, ‘TA’ corresponds to a constant predefined according to a type of the downlink signal, ‘PH’ corresponds to 23 dBm, ‘20 MHz’ corresponds to the reference bandwidth, ‘BWMHz’ corresponds to the bandwidth of the carrier represented in a unit of MHz, ‘10*log 10(BWMHz/20 MHz)’ corresponds to the decibel value, and ‘PTX’ corresponds to the maximum transmit power of the base station set for the carrier.

4. The method of claim 3 , wherein the maximum energy detection threshold is determined to be a greater value among the first power value obtained by adding the decibel value to −72 dBm, and the second power value.

5. The method of claim 3 ,

wherein when the downlink signal contains a physical downlink shared channel (PDSCH), the ‘TA’ is configured as 10 dB and

wherein when the downlink signal contains a discovery signal but does not contain the PDSCH, the ‘TA’ is configured as 5 dB.

6. The method of claim 3 , wherein when the different RAT sharing the carrier does not exist, the maximum energy detection threshold does not exceed Tmax+10 dB.

7. The method of claim 1 ,

wherein the downlink signal is transmitted via at least one licensed-assisted access secondary cell (LAA SCell) operating based on LAA and

wherein the sensed carrier corresponds to a carrier at which the at least one LAA SCell resides.

8. A user equipment performing channel access on an unlicensed band, the user equipment comprising:

a processor to sense a carrier of an unlicensed band for receiving a downlink signal; and

a receiver to receive the downlink signal when power detected by sensing the carrier is less than an energy detection threshold that is configured by a base station,

wherein the energy detection threshold is configured to be equal to or less than a maximum energy detection threshold determined by the base station,

wherein when a different radio access technology (RAT) sharing the carrier is able to exist, the maximum energy detection threshold is determined adaptively a bandwidth of the carrier using a decibel value of a ratio between a reference bandwidth and the bandwidth of the carrier,

wherein the maximum energy detection threshold is configured to be equal to or greater than a first power value which is a sum of a lower bound of the maximum energy detection threshold for the reference bandwidth and the decibel value, and

wherein the first power value is obtained by a first equation ‘−72+10*log 10(BWMHz/20 MHz)’ of the first equation corresponds to the reference bandwidth, ‘BWMHz’ corresponds to the bandwidth of the carrier represented in a unit of MHz, ‘10*log 10(BWMHz/20 MHz)’ corresponds to the decibel value, and ‘−72’ corresponds to the lower bound of the maximum energy detection threshold for the reference bandwidth represented in a unit of dBm.

9. The user equipment of claim 8 , wherein the maximum energy detection threshold is configured to be equal to or greater than a second power value which is determined in consideration of a difference between the decibel value and maximum transmit power of the base station set for the carrier.

10. The user equipment of claim 9 , wherein the second power value is obtained by a second equation ‘min{Tmax, Tmax−TA+(PH+10*log 10(BWMHz/20 MHz)−PTX)} [dBm]’, wherein ‘Tmax’ of the second equation corresponds to ‘10*log 10(3.16288*10−8/BWMHz)’, where ‘TA’ corresponds to a constant predefined according to a type of the downlink signal, ‘PH’ corresponds to 23 dBm, ‘20 MHz’ corresponds to the reference bandwidth, ‘BWMHz’ corresponds to the bandwidth of the carrier represented in a unit of MHz, ‘10*log 10(BWMHz/20 MHz)’ corresponds to the decibel value, and ‘PTX’ corresponds to the maximum transmit power of the base station set for the carrier.

11. The user equipment of claim 10 , wherein the maximum energy detection threshold is determined to be a greater value among the first power value obtained by adding the decibel value to −72 dBm and the second power value.

12. The user equipment of claim 10 ,

wherein when the downlink signal contains a physical downlink shared channel (PDSCH), the ‘TA’ is configured as 10 dB and

wherein when the downlink signal contains a discovery signal but does not contain the PDSCH, the ‘TA’ is configured as 5 dB.

13. The user equipment of claim 10 , wherein when the different RAT sharing the carrier does not exist, the maximum energy detection threshold does not exceed Tmax+10 dB.