Trigger frame format for orthogonal frequency division multiple access (OFDMA) communication

An access point for communicating in a wireless communication network, the access point comprising:

• a wireless network interface device having one or more integrated circuit (IC) devices configured to:
• generate one or more trigger frames to trigger an uplink multi-user (MU) transmission by one or more client stations, wherein each of the one or more trigger frames is generated to include a medium access control (MAC) header portion and a MAC frame body portion, wherein each MAC frame body portion is generated to include one or more per-station information fields that include respective information to indicate respective transmission parameters to be used by one or more respective client stations for the uplink MU transmission, wherein each per-station information field is generated to include a resource unit (RU) allocation subfield that provides information indicating frequency resources for the uplink MU transmission, wherein each per-station information field is generated to include a station identifier (STA-ID) subfield that provides information indicating one or more client stations that are permitted to use the frequency resources indicated in the RU allocation subfield to participate in the uplink MU transmission, and wherein generating a first trigger frame of the one or more trigger frames includes:
• generating a first RU allocation subfield in a first per-station information field of the first trigger frame to include an indication of first frequency resources, and
• generating a first STA-ID subfield in the first per-station information field of the first trigger frame to include a reserved station identifier value that indicates that multiple client stations are permitted to contend for the first frequency resources as part of a contention-based transmission;
• wherein the one or more IC devices are further configured to:
• control the wireless network interface device to transmit the one or more trigger frames, and
• receive the triggered uplink MU transmission, wherein the triggered uplink MU transmission includes a contention-based transmission in the first frequency resources from a first client station;
• wherein the one or more IC devices are configured to:
• generate each MAC frame body portion of each trigger frame to include a common information field that includes information to indicate transmission parameters to be used for the uplink MU transmission;
• and
• generate a first common information field of the first trigger frame to include (i) a subfield that indicates a bandwidth of the uplink MU transmission, and (ii) information that indicates a guard interval and a long training field (LTF) mode to be used for the contention-based transmission.