1. A station (STA) configured for wireless communication, the STA comprising: a transceiver configured to: receive a downlink (DL) transmission comprising a packet destined to a plurality of STAs; and one or more processors configured to: use a field included in the packet to determine a total number of space-time streams (STSs) included in the packet and further use the field to select a subset of values from a set of values indicating a number of STSs destined to each of at least some of the plurality of STAs; and determine a value of a user position (UP) assigned to the STA and select which of the plurality of STSs in the packet are destined to the STA by considering a number of STSs allocated to one or more other STAs each assigned a UP value that is different from the UP value assigned to the STA, wherein the transceiver is further configured to: receive, from an access point (AP), an uplink (UL) transmission request (ULTR) configured to trigger simultaneous UL transmissions by the plurality of STAs within a period of time after receiving the ULTR, wherein the one or more processors are further configured to: in response to receiving the ULTR, consider a network/navigation allocation vector (NAV) unless the NAV was set by a frame originating from an apparatus from which the ULTR was transmitted; determine a number of the resource units (RUs) assigned by the ULTR for random access and reduce a back-off counter based on the determined number of RUs assigned by the ULTR for random access; and depending on a value of the reduced back-off counter, randomly select one or more of the RUs assigned by the ULTR for random access, wherein the transceiver is further configured to transmit an UL transmission using the randomly selected one or more RUs assigned by the ULTR for random access simultaneously with a transmission of one or more other STAs of the plurality of STAs.