Systems and methods of expanding indication capabilities of existent PPDU preamble fields. The "GI+LTF Size" field is redefined to indicate a new combination of GI duration and HE-LTF size. The redefinition is indicated when the values of the two other existent fields, in combination, indicate an invalid scenario because the two values should have been mutually exclusive. Particularly, the DCM field and the STBC field are both set to the "enabled" mode as an indication for redefine the "GI+LTF Size" field. Upon receiving such a PPDU, a receiver is configured to resolve the PPDU as neither DCM nor STBC is enabled. Rather, the receiver interprets the particular combination of DCM and STBC values as an indication that the "GI+LTF Size" field is redefined to indicate the new combination of GI duration and HE-LTF size.