A communication device generates a first packet for transmission in a first frequency segment, and generates a first physical layer (PHY) preamble of the first packet to include a first field that indicates a first overall bandwidth that the first packet spans. The communication device generates a second packet for transmission in a second frequency segment, and generates a second PHY preamble of the second packet to include a second field that indicates a second overall bandwidth that the second packet spans. The communication device transmits the first packet in the first frequency segment beginning at a first time, and simultaneously transmits the second packet in the second frequency segment beginning at a second time that is different than the first time.