An electronic device communicates frames with an access point (AP) by receiving, from the AP, a frame header that includes information specifying a first set of tones of an OFDMA communication, the first set of tones associated with first resource block subchannels having a first bandwidth used by the AP to transmit a frame payload. The electronic device obtains a second set of tones associated with second resource block subchannels having a second bandwidth that differs from the first bandwidth, and receives the frame payload using the OFDMA communication, the second resource block subchannels, and the second set of tones. Alternatively, an electronic device dynamically switches a channel-access mode when communicating a frame with the AP depending on whether the communication includes a primary 20 MHz channel. In a technique, an MU-PPDU is communicated using a frame via a non-primary 20 MHz channel without using the primary 20 MHz channel.