Apparatus and method for sounding in multiple access point network

A method of operating a first apparatus in a wireless local area network (WLAN) system, the method comprising:

• determining second apparatuses participating in MAP sounding as access points (APs) and third apparatuses participating in the MAP sounding as stations (STAs);
• determining a null data packet (NDP) transmission scheme for the MAP sounding;
• generating a multiple access point (MAP) network frame indicating the second apparatuses, the third apparatuses, and the NDP transmission scheme;
• and
• transmitting the MAP network frame to the second apparatuses and the third apparatuses.

A method of operating a first apparatus in a wireless local area network (WLAN) system, the method comprising:

• receiving a multiple access point (MAP) network frame from a second apparatus;
• identifying a null data packet (NDP) transmission scheme for sounding of MAPs including the first apparatus and the second apparatus from an NDP type subfield of a common information field included in the MAP network frame;
• and
• transmitting an NDP to a third apparatus based on an identified NDP transmission scheme.