Embodiments of a high-efficiency Wi-Fi (HEW) station, access point (AP), and method for communication in a wireless network are generally described herein. In some embodiments, the HEW station may perform random access contention with other HEW stations for uplink resources for data transmission to the HEW AP. The HEW station may determine transmission activity during a first portion of a channel sensing period, and may select a sub-channel on which transmission activity is not determined. The HEW station may transmit an announcement signal on the selected sub-channel during a second portion of the channel sensing period. The announcement signal transmission may indicate, to other contending HEW stations, an intention by the HEW station to transmit on the same selected sub-channel during a subsequent access period.