Enhanced protocols and devices may be used to alleviate loss of spectrum efficiency in wideband transmission. The protocols may implement a wideband transmission opportunity (TXOP) truncation where one or more of the channels involved in communication over the wideband are released. In one scenario, an access point (AP) may receive, from a wireless transmit receive unit (WTRU), a first CF-End frame that includes a duration field and a basic service set identifier (BSSID) field that includes an individual/group bit. On a condition that the individual/group bit of the BSSID field has a value of one (1), the AP may determine that a scrambling sequence of the first CF-End frame indicates a bandwidth associated with a transmit opportunity (TXOP) being truncated by the WTRU. The AP may then transmit a second CF-End frame at the bandwidth indicated by the scrambling sequence of the first CF-End frame.