In an example of wireless communications, an access point (AP) may send a first trigger frame to multiple stations. In response, some or all of the stations may transmit their respective uplink frames to the AP. The uplink frames may include status information of the stations such as buffered data size. The AP may send a second trigger frame, including resource allocation assignments to inform stations which sub-bands may be used to send their payloads to the AP. The AP may allocate sub-bands to stations based on the status information of the station. The AP may allocate a relatively narrow sub-band to one or more stations when the status information is not known to the AP. Status information may be provided in certain control fields of a data frame. Random access may be provided by assigning a sub-band to multiple stations. Other methods, apparatus, and computer-readable media are also disclosed.