Systems and techniques relating to wireless communications are described. A described technique includes sensing a group of channels for a channel contention operation that acquires two or more channels of the group of channels and detects a busy channel of the group of channels; determining a channel bonding indicator based on the channel contention operation; generating a preamble portion of a frame that includes the channel bonding indicator; generating a data portion of the frame, and transmitting the frame to one or more devices. Generating the preamble portion can include duplicating a legacy preamble on each of the acquired channels within the preamble portion. Generating the data portion can include setting first subcarriers that correspond to the acquired channels to data values, and setting second subcarriers that correspond to the busy channel to null values for at least a portion of the data portion of the frame.