Method and apparatus for changing operating mode in wireless local area network system

A method of processing control information for transmitting a physical layer protocol data unit (PPDU) in a wireless local area network (LAN) system, the method comprising:

• transmitting, by a first station, request information requesting a change in an operating mode to a second station;
• transmitting, by the first station, a first PPDU supporting a first wireless LAN system to the second station based on the request information;
• and
• receiving, by the first station, a Block ACK (BA) as a response to the first PPDU,
• wherein the request information includes first information on the change in the operating mode based on a number of spatial streams and a number of first channel bandwidths supported by the first station, and second information related with a time in which the first information is applied,
• wherein if the second information includes a predetermined value,
• the first information is applied to the first station and the second station after receiving the BA, and the first PPDU is transmitted by not applying the first information,
• wherein if the second information does not include the predetermined value,
• the first information is applied to the first station, the first information is not applied to the second station, the first PPDU is transmitted by the first station by applying the first information, the BA is received by the first station by not applying the first information, and the BA is received through a second PPDU supporting a second wireless LAN system supporting a second channel bandwidth,
• wherein the first PPDU is transmitted and the BA is received in a same transmission opportunity (TXOP), and
• wherein the second channel bandwidth is lowest receiving channel bandwidth among the first channel bandwidths.