US Patent 10153857 Orthogonal frequency division multiple access protection

A method for simultaneous communication in a wireless local area network is described. A first control frame is transmitted by a first communication device to a plurality of communication devices, is duplicated across each of a plurality of sub-channels of an orthogonal frequency division multiplexing channel, and indicates that the communication devices are requested to simultaneously transmit respective control frames to the first communication device. Respective control frames are received, including second and third control frames from second and third communication devices, respectively, that are transmitted via a same sub-channel having a smallest bandwidth of the wireless local area network and indicate that at least some of the plurality of sub-channels are available. One of an orthogonal frequency division multiple access data unit and a duplicated legacy data unit is transmitted by the first communication device in response to the control frames via the available sub-channels.