A method of generating packets for transmission in a wireless communication system, wherein each packet includes a SIG field that includes a first SIG subfield, includes generating a data packet and a null data packet. Generating the data packet includes generating information bits of the first SIG subfield of the data packet and generating the data portion of the data packet. The information bits of the first SIG subfield of the data packet indicate, to a receiving device, a length corresponding to a data portion of the data packet. Generating the null data packet includes generating information bits of the first SIG subfield of the null data packet. The information bits of the first SIG subfield of the null data packet indicate, to a receiving device, a first physical layer (PHY) parameter value associated with the null data packet. The first PHY parameter value is not a length value.