Systems and techniques relating to wireless communications are described. A described technique includes monitoring wireless communication channels, including a first channel and a second channel, to produce a monitoring output, determining a first transmission period for the first channel, determining a second transmission period for the second channel, transmitting, based on the first transmission period, a first packet on the first channel to cause one or more wireless communication devices to set a transmission protection period for the first channel and the second channel based on a reception of the first packet, transmitting, based on the second transmission period, a second packet on the second channel, and monitoring, after the end of the first transmission period, for one or more acknowledgements. An end of the second transmission period can be aligned with an end of the first transmission period.