Method for transmitting/receiving wireless signal in wireless communication system and device therefor

1. A method for a wireless communication apparatus comprising a plurality of antennas to transmit and receive a wireless signal in an unlicensed band in a wireless communication system, the method comprising:

performing CCA(Clear Channel Assessment) using the plurality of antennas for a predetermined time duration in the unlicensed band;

wherein the performing CCA comprises:

obtaining a reference value based on energy sensing indicators (ESIs) measured through each of the plurality of antennas; and

determining whether the unlicensed band is in an idle state where the unlicensed band is unoccupied by other communication apparatuses, by comparing the reference value with a CCA threshold,

when the unlicensed band is determined as the idle state, transmitting the wireless signal through the unlicensed band; and

when the plurality of antennas is configured to a directional antenna, keeping a first difference the same as a second difference,

wherein the first difference is a difference between a CCA range and an interference range when the wireless signal is transmitted and received using the directional antenna,

wherein the second difference is a difference between the CCA range and the interference range when the wireless signal is transmitted and received using an omni-directional antennas.

2. The method of claim 1 , wherein the reference value is set as the largest, smallest, or average value among the ESIs measured through each of the plurality of antennas.

3. The method of claim 1 , wherein the reference value is set to a value no less than any of the ESIs measured through each of the plurality of antennas.

4. The method of claim 1 , wherein the CCA threshold is preset by higher-layer signaling.

5. The method of claim 1 , wherein, when a radiation condition related to a total radiated power value is set, an individual radiated power value for each beam direction when a plurality of beams are transmitted is determined as the total radiated power value divided by the number of beams.

6. The method of claim 1 , wherein, when a radiation condition related to a total radiated power value is set, an individual transmission bandwidth for each beam direction when a plurality of beams are transmitted is determined as the total system bandwidth divided by the number of beams.

7. The method of claim 6 , further comprising determining whether the radiation condition is met or not based on an average radiated power value obtained by averaging transmit power values of beams transmitted within a preset frequency region.

8. The method of claim 6 , wherein, while a plurality of candidate scheduling hypothesis sets are preset by higher-layer signaling, the size of the individual transmission bandwidth is indicated as one of the candidate scheduling hypothesis sets through a scheduling grant.

9. The method of claim 6 , wherein, when a periodic CSI (channel state information) feedback is performed, a CSI feedback reporting frequency granularity is set by taking into account the size of the individual transmission bandwidth.

10. The method of claim 6 , wherein, when CSI feedback is performed, a subband for CSI feedback is selected as one of pre-defined subband sets, and a PMI(pre coding matrix indicator) to be applied for the selected subband set is selected as one of pre-defined PMI sets.

11. The method of claim 1 , wherein, when a radiation condition related to a total radiated power value for each beam direction to be radiated during a specific time duration is set, the wireless signal is transmitted in the total radiated power value for each beam direction, but through different time resources.

12. The method of claim 11 , wherein the different time resources are indicated by a base station through a multi-subframe scheduling grant, or

wherein the different time resources are set through inter-cell cooperative signaling exchange.

13. The method of claim 11 , further comprising determining whether the radiation condition is met or not based on an average radiated power value obtained by averaging transmit power values of beams transmitted within a preset time.

14. A wireless communication apparatus for transmitting and receiving a wireless signal in an unlicensed band in a wireless communication system, comprising:

an RF(Radio Frequency) unit configured to transmit and receive a wireless signal,

wherein the RF unit includes a plurality of antennas; and

a processor functionally connected to the RF unit,

wherein the processor is configured to:

perform CCA (Clear Channel Assessment) using the plurality of antennas for a predetermined time duration in the unlicensed band;

wherein the perform CCA includes:

obtain a reference value based on energy sensing indicators (ESIs) measured through each of the plurality of antennas;

determine whether the unlicensed band is in an idle state where the unlicensed band is unoccupied by other communication apparatuses, by comparing the reference value with a CCA threshold,

transmit the wireless signal through the unlicensed band when the unlicensed band is determined as the idle state; and

when the plurality of antennas is configured to a directional antenna, keep a first difference the same as a second difference,

wherein the first difference is a difference between a CCA range and an interference range when the wireless signal is transmitted and received using the directional antenna,

wherein the second difference is a difference between the CCA range and the interference range when the wireless signal is transmitted and received using an omni-directional antennas.

15. The method of claim 1 , further comprising,

when the interference range is changed,

changing at least one of a sensitivity of the ESI, the CCA threshold and/or a transmission power of the wireless signal.