Method of supporting for uplink multi-user transmission in wireless area network system

A wireless device using a method of supporting for uplink multi-user (UL MU) transmission in a wireless local area network (WLAN) system, comprising:

• a transceiver transmitting and receiving a radio signal;
• and
• a processor connected to the transceiver, wherein the processor is configured
• transmit a control frame to an access point (AP) during a first duration,
• wherein the control frame includes an operating mode (OM) field having a first value,
• wherein the OM field has the first value when the UL MU MIMO transmission is resumed by the STA, and
• wherein the OM field has a second value when the UL MU MIMO transmission is suspended by the STA;
• determine whether a trigger frame soliciting the UL MU transmission is received during a second duration subsequent to the first duration,
• wherein the trigger frame includes:
• first information for identifying a plurality of STAs related to the UL MU transmission,
• second information for a plurality of uplink frequency resources allocated for the plurality of STAs,
• third information for a time interval during which the UL MU MIMO transmission is performed,
• fourth information for modulation and coding scheme (MCS) applied to the plurality of STAs, and
• fifth information for a channel coding scheme for the plurality of STAs;
• and
• when the trigger frame is received during the second duration, transmit a trigger-based packet to the AP,
• wherein the trigger-based packet includes a buffer status report (BSR) of the STA,
• wherein an interval between the trigger frame and the trigger-based packet is set to a short inter-frame space (SIFS),
• when the trigger frame is not received during the second duration, transmit a data packet to the AP after the second duration, the data packet including the OM field having the second value.