Method and device for performing sounding procedure in wireless lan system

A first station (STA) that performs a sounding procedure in a wireless LAN system, the first STA comprising:

• at least one transceiver;
• and
• at least one processor connected to the at least one transceiver,
• wherein the at least one processor is configured to:
• receive, from a second STA through the at least one transceiver, at least one null data physical layer protocol data unit (NDP) announcement frame on a first frequency unit associated with a first type PPDU format and a second frequency unit associated with a second type PPDU format;
• receive, from the second STA through the at least one transceiver, at least one NDP on the first frequency unit and the second frequency unit;
• receive, from the second STA through the at least one transceiver, at least one trigger frame on the first frequency unit and the second frequency unit;
• and
• transmit, to the second STA through the at least one transceiver, a feedback frame for at least one of the first frequency unit or the second frequency unit,
• wherein the at least one NDP is received from the second STA based on a first type of training sequence and a second type of training sequence.

A second station (STA) that performs a sounding procedure in a wireless LAN system, the second STA comprising:

• at least one transceiver;
• and
• at least one processor connected to the at least one transceiver,
• wherein the at least one processor is configured to:
• transmit, to a first STA through the at least one transceiver, at least one null data physical layer protocol data unit (NDP) announcement frame on a first frequency unit associated with a first type PPDU format and a second frequency unit associated with a second type PPDU format;
• transmit, to the first STA through the at least one transceiver, at least one NDP on the first frequency unit and the second frequency unit;
• transmit, to the first STA through the at least one transceiver, at least one trigger frame on the first frequency unit and the second frequency unit;
• and
• receive, from the first STA through the at least one transceiver, a feedback frame for at least one of the first frequency unit or the second frequency unit,
• wherein the at least one NDP is transmitted to the first STA based on a first type of training sequence and a second type of training sequence.