Null data packet announcement (NDPA) frame indication

The present disclosure provides methods and apparatus related to NDPA frame indication. An aspect of the disclosure provides a method. The method includes sending, to one or more stations (STAs), a request for channel state information (CSI). The request includes a null data packet announcement (NDPA) frame including a first field and a second field. The first field indicates presence of the second field, and the second field indicates a variant of the NDPA frame. The method further includes receiving, from the one or more STAs, a CSI feedback response based on the request. In some embodiments, the first field is one of a sounding dialog token field and indicates the presence of the second field via at least two bits. In some embodiments, the first field is a frame control field and indicates the second field via a 4-bit subtype subfield.