A third device stores a receive signal strength of a received response data unit transmitted by a second device in response to reception by the second device of a first data unit transmitted by a first device, obtains a clear channel access parameter included in a header of a second data unit transmitted by the first device to the second device. The clear channel access parameter is based on a sum of a transmit power used by the first device to transmit the second data unit to the second device and a receive signal strength of the response data unit at the first device. The third device determines a transmit power to be used by the third device to send a transmission to the fourth device based on transmission exchanges between devices in a particular service set.