This patent document describes technologies, among other things, slotted orthogonal frequency-division multiple access (SOFDMA) channel access mechanism to improve the medium usage efficiency and reduce access latency in wireless communications.

In one aspect, a method is provided to commence the SOFDMA channel access process via transmitting a trigger frame with indication of channel access transmission opportunity (CA-TXOP) and setting the duration of TXOP to protect SOFDMA procedure from being interfered by other stations.

In another aspect, a method is provided for the AP to configure the periodical trigger frame transmission time in the broadcast beacon frame so that the SOFDMA capable stations are able to use the SOFDMA channel access transmission opportunity.

In another aspect, a method is provided for stations to contend the medium in slotted OFDMA mechanism. In some embodiments, the SOFDMA channel access mechanism can manage the contention time period into a couple of channel access time slots in which a station could perform channel access over an orthogonal frequency-division multiple access (OFDMA) sub-channel.

In another aspect, a method of expanding channel access slots is provided via information field in trigger frame, so that the SOFDMA capable AP could be able to configure and change the channel access duration dynamically based on the traffic load of BSS.