Methods and apparatus are described. A station includes a transceiver and a processor, which detect a trigger frame for an uplink (UL) multi-user (MU) transmission. The trigger frame includes a user information field with an allocation of one or more random access resource units (RUs) and a common information field with information to set high efficiency (HE) SIGNAL-A (HE-SIG-A) fields in the UL MU transmission. The transceiver and the processor generate an HE trigger-based (TB) physical layer protocol data unit (PPDU) and set an HE-SIG-A field in the HE TB PPDU using the information in the trigger frame. The transceiver and the processor select one of the one or more random access RUs and transmit the HE TB PPDU, using the selected one of the one or more random access RUs, a short inter-frame space after the trigger frame.