A first communication device transmits one or more first communication frames during a transmit opportunity period (TXOP) of the first communication device via a first composite channel. A control frame is generated, wherein the control frame includes information indicating a bandwidth of the first composite channel. After the one or more first communication frames have been transmitted, the first communication device transmits, during the TXOP, the control frame via the first composite channel. Information from a response frame that indicates a bandwidth of a second composite communication channel is extracted, the response frame having been transmitted by a second communication device and received by the first communication device during the TXOP. The first communication device transmits one or more second communication frames during the TXOP, wherein the one or more communication frames span the second composite communication channel and do not span the entire first composite communication channel.