In a wireless communication system where communication devices utilize physical layer (PHY) data units that conform to a first format to communicate information associated with a layer of a protocol stack above a media access channel (MAC) layer, where the first format is associated with a first number of symbols in a preamble, a method for generating a PHY data unit that conforms to a second format includes generating a preamble of the PHY data unit, where the preamble includes a second number of symbols, wherein the second number is smaller than the first number; and generating another portion of the PHY data unit.