Wireless communication method and wireless communication terminal in high density environment including overlapped basic service sets

1. A wireless communication terminal that communicates wirelessly, the terminal comprising:

a transceiver; and

a processor,

wherein the processor is configured:

to receive a first PLCP Protocol Data Unit (PPDU) including a trigger frame through the transceiver, wherein the trigger frame triggers an uplink multiuser PPDU transmission of one or more wireless communication terminals in a first Basic Service Set (BSS) which is overlapped with a second BSS including the wireless communication terminal,

to receive a physical layer header of a second PPDU which is transmitted in response to the trigger frame, wherein the physical layer header of the second PPDU comprises a spatial reuse field indicating a parameter, wherein the parameter is determined based on a magnitude of interference acceptable by a wireless communication terminal which transmits the first PPDU when receiving the second PPDU, and a transmission power of the first PPDU,

when predetermined conditions are met, to transmit a third PPDU while the second PPDU being transmitted and not to set a network allocation vector based on the trigger frame, wherein the predetermined conditions include that a transmission power of the third PPDU is below than a value which is determined based on a received signal strength of the first PPDU and the parameter, and a BSS color indicated by the physical layer header of the second PPDU is equal to a BSS color indicated by a physical layer header of the first PPDU, wherein the value of the parameter is a value normalized over a 20 MHz frequency bandwidth, and

when at least one of the predetermined conditions is not met, to determine whether a channel through which the third PPDU to be transmitted is idle by using a static Clear Channel Assessment (CCA) threshold value as a reference value and transmit the third PPDU according to whether the channel is idle while the second PPDU being transmitted,

wherein the static CCA threshold value is used for determining whether a channel is idle when the wireless communication terminal is receiving a PPDU transmitted from the second BSS.

2. The wireless communication terminal of claim 1 , wherein the trigger frame comprises a field indicating the parameter.

3. The wireless communication terminal of claim 1 , when the predetermined conditions are met, wherein the processor is configured to determine whether the channel through which the third PPDU to be transmitted is idle by using an overlapped BSS CCA threshold value and reduce a backoff counter by a predetermined time period when the channel is idle,

wherein the overlapped BSS CCA threshold is for a PPDU which is transmitted from a BSS overlapped with the second BSS,

wherein the backoff counter is a reference value used for channel access to the channel in an existing backoff procedure.

4. The wireless communication terminal of claim 3 , wherein the static CCA threshold is higher than the overlapped BSS CCA threshold.

5. An operation method of wireless communication terminal that communicates wirelessly, the method comprising:

receiving a first PLCP Protocol Data Unit (PPDU) including a trigger frame, wherein the trigger frame triggers an uplink multiuser PPDU transmission of one or more wireless communication terminals in a first Basic Service Set (BSS) which is overlapped a second BSS including the wireless communication terminal,

receiving a physical layer header of a second PPDU which is transmitted in response to the trigger frame, wherein the physical layer header of the second PPDU comprises a spatial reuse field indicating a parameter, wherein the parameter is determined based on a magnitude of interference acceptable by a wireless communication terminal which transmits the first PPDU when receiving the second PPDU, and a transmission power of the first PPDU,

when predetermined conditions are met, transmitting a third PPDU while the second PPDU being transmitted and not setting a network allocation vector based on the trigger frame, wherein the predetermined conditions include that a transmission power of the third PPDU is below than a value which is determined based on a received signal strength of the first PPDU and the parameter, and a BSS color indicated by the physical layer header of the second PPDU is equal to a BSS color indicated by a physical layer header of the first PPDU, wherein the value of the parameter is a value normalized over a 20 MHz frequency bandwidth, and

when at least one of the predetermined conditions is not met, determining whether a channel through which the third PPDU to be transmitted is idle by using a static Clear Channel Assessment (CCA) threshold value as a reference value and transmit the third PPDU according to whether the channel is idle while the second PPDU being transmitted,

wherein the static CCA threshold value is used for determining whether a channel is idle when the wireless communication terminal is receiving a PPDU transmitted from the second BSS.

6. The method of claim 5 , wherein the trigger frame comprises a field indicating the parameter.

7. The method of claim 5 , wherein the transmitting the third PPDU when the predetermined conditions are met comprises determining whether the channel through which the third PPDU to be transmitted is idle by using an overlapped BSS CCA threshold value and reducing a backoff counter by a predetermined time period when the channel is idle,

wherein the overlapped BSS CCA threshold is for a PPDU which is transmitted from a BSS overlapped with the second BSS,

wherein the backoff counter is a reference value used for channel access to the channel in an existing backoff procedure.

8. The method of claim 7 , wherein the static CCA threshold is higher than the overlapped BSS CCA threshold.