The present application provides an apparatus for a non-AP STA, including: RF interface circuitry; and processor circuitry coupled with the RF interface circuitry and configured to: monitor a trigger frame from an AP or ongoing uplink transmission from one or more non-AP STAs in a BSS associated with the AP and the non-AP STA to detect a location of a resource unit pre-allocated for transmission of urgent data; encode the urgent data for transmission to the AP via the RF interface circuitry on the resource unit, when the non-AP STA needs to transmit the urgent data; and pause the ongoing uplink transmission on the resource unit while continuing transmission of a pilot signal on the resource unit, when the non-AP STA does not need to transmit the urgent data.