Method for transmitting data in wireless communication system and apparatus therefor

1. A spatial reuse, SR, method of a first station, STA, associated with a first basic service set, BSS, in a wireless local area network, WLAN, system, the SR method comprising:

receiving an inter-BSS physical protocol data unit, PPDU, from an AP or a second STA associated with a second BSS different from the first BSS,

wherein the inter-BSS PPDU comprises a physical, PHY, preamble and an inter-BSS frame,

wherein a high efficiency signal, HE-SIG, A field of the PHY preamble comprises an SR indicator indicating whether SR is allowed;

executing a clear channel assessment, CCA, on a channel based on a CCA level which is a criterion by which a busy or idle state of the channel is determined when the SR indicator indicates that SR is allowed,

wherein, when the CCA level applied in a 20 MHz channel is set to a reference threshold value, the CCA level applied in a greater channel than the 20 MHz channel is calculated by adding a predetermined value to the reference threshold value; and

transmitting a signal through the channel when the channel is in the idle state as a result of the execution of the CCA,

wherein, when the PPDU is an UL PPDU, a first CCA level is applied to the CCA level, and

wherein, when the PPDU is a DL PPDU, a second CCA level smaller than the first CCA level is applied to the CCA level.

2. The SR method of claim 1 , wherein the HE-SIG A field further comprises an uplink, UL/downlink, DL, indicator indicating whether the inter-BSS PPDU is a DL PPDU transmitted by the AP or an UL PPDU transmitted by the second STA.

3. The SR method of claim 1 , wherein the CCA level is increased as the transmission power is decreased.

4. The SR method of claim 3 , wherein the CCA level applied in the greater channel is calculated by adding 3 dB to the reference threshold value whenever the bandwidth of the greater channel is twice larger than the 20 MHz channel.

5. The SR method of claim 4 , wherein the CCA level applied in the greater channel is determined according to an equation 1:

C 1= C 2+10*log( BW/ 20 MHz),  [Equation 1]

wherein C1 is the CCA level applied in the greater channel, C2 is the CCA level applied in the 20 MHz channel and BW is the bandwidth of the greater channel.

6. The SR method of claim 5 , wherein receiving the inter-BSS PPDU comprises:

receiving a PPDU; and

determining whether the received PPDU is the inter-BSS PPDU or not by using a BSS color or Medium Access Control, MAC, address in the PPDU.

7. A first station, STA, associated with a first basic service set, BSS, in a wireless local area network, WLAN, system, the first STA comprising:

a radio frequency, RF, unit configured to transmit and receive a radio signal; and

a processor configured to control the RF unit,

wherein the first STA is configured to:

receive an inter-BSS physical protocol data unit, PPDU, from an AP or second STA associated with a second BSS different from the first BSS,

wherein the inter-BSS PPDU comprises a physical, PHY, preamble and an inter-BSS frame,

wherein a high efficiency signal, HE-SIG, A field of the PHY preamble comprises an SR indicator indicating whether SR is allowed;

execute a clear channel assessment, CCA, on a channel based on a CCA level which is a criterion by which a busy or idle state of the channel is determined when the SR indicator indicates that SR is allowed,

wherein, when the CCA level applied in a 20 MHz channel is set to a reference threshold value, the CCA level applied in a greater channel than the 20 MHz channel is calculated by adding a predetermined value to the reference threshold value; and

transmit a signal through the channel when the channel is in the idle state as a result of the execution of the CCA,

wherein, when the PPDU is an UL PPDU, a first CCA level is applied to the CCA level, and

wherein, when the PPDU is a DL PPDU, a second CCA level smaller than the first CCA level is applied to the CCA level.

8. The first STA of claim 7 , wherein the CCA level is increased as the transmission power is decreased.

9. The first STA of claim 8 , wherein the CCA level applied in the greater channel is calculated by adding 3 dB to the reference threshold value whenever the bandwidth of the greater channel is twice larger than the 20 MHz channel.

10. The first STA of claim 9 , wherein the CCA level C1 applied in the greater channel is determined according to an equation 1:

C 1= C 2+10*log( BW/ 20 MHz),  [Equation 1]

wherein C1 is the CCA level applied in the greater channel, C2 is the CCA level applied in the 20 MHz channel and BW is the bandwidth of the greater channel.

11. The first STA of claim 10 , wherein the first STA is configured to:

receive a PPDU; and

determine whether the received PPDU is the inter-BSS PPDU or not by using a BSS color or (Medium Access Control), MAC, address in the PPDU.

12. The first STA of claim 7 , wherein the HE-SIG A field further comprises an/a uplink, UL/downlink, DL, indicator indicating whether the inter-BSS PPDU is a DL PPDU transmitted by the AP or an UL PPDU transmitted by the second STA.