| CPC H04B 7/0626 (2013.01) [H04L 5/0048 (2013.01)] | 12 Claims |

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1. A method of acquiring channel-state information from one or more stations, the method comprising:
sending, by an access point (AP) to one or more stations (STAs), a request for channel state information (CSI), the request comprising a null data packet announcement (NDPA) frame including a NDPA variant field for indicating information that is common to the one or more STAs, the NDPA variant field including an indicator for indicating whether trigger based (TB) sounding or non-trigger based (non-TB) sounding is being used;
when the indicator indicates non-TB sounding is being used, after a shortest interframe spacing (SIFS) time unit, sending, by the AP to the one or more STAs, an initiator to responder (I2R) null data packet (NDP) frame,
after a second SIFS time unit, sending, by the AP to the one or more STAs, a sensing trigger report frame; and
receiving, by the AP from the one or more STAs, a CSI feedback response based on the request.
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