A method of generating packets for transmission in a wireless communication system. The method comprises generating a data packet and generating a null data packet. Generating the data packet includes generating a data packet signal (SIG) field including a first data packet SIG subfield indicating a first physical layer (PHY) parameter to a receiving device. Generating the data packet also includes generating a data field. Furthermore, generating the null data packet includes generating a null data packet SIG field. The null data packet SIG field includes a first null data packet SIG subfield indicating a second PHY parameter to a receiving device. The data packet SIG field excludes any SIG subfield indicating the second PHY parameter to a receiving device, and (ii) the null data packet SIG field excludes any SIG subfield indicating the first PHY parameter to a receiving device.