A communication device generates a first packet and a second packet. The first packet includes a first physical layer (PHY) preamble having: a first legacy signal field (L-SIG) having first duration information that indicates a first duration of the first packet; and first non-legacy signal field information having first modulation information that indicates a first modulation used in the first packet. The second packet includes a second PHY preamble having: a second L-SIG having second duration information that indicates a second duration of the second packet, wherein the second duration is different than the first duration; and second non-legacy signal field information having second modulation information that indicates a second modulation used in the second packet, wherein the second modulation is different than the first modulation. The communication device simultaneously transmits the first packet in a first frequency segment and the second packet in a second frequency segment.