This disclosure provides methods, devices and systems for soliciting trigger-based (TB) physical layer protocol convergence protocol (PLCP) protocol data units (PPDUs). Some implementations more specifically relate to trigger frame and PPDU designs that support RU downsizing. For example, an access point (AP) may transmit a trigger frame soliciting a TB PPDU from a wireless station (STA). In some aspects, the trigger frame may carry RU allocation information indicating the allocated RU or MRU (associated with a wireless medium) and downsizing information indicating whether downsizing of the RU or MRU is permitted. If interference is detected in a portion of the wireless medium, and downsizing is permitted, the STA may transmit the TB PPDU on a downsized RU or MRU. The downsized RU or MRU includes a subset of the tones in the RU or MRU allocated by the trigger frame.