The present specification proposes a signal processing method for changing an operating mode for configuring a physical-layer protocol data unit (PPDU). Specifically, a first station receives, from a second station, first indication information and second indication information, which indicate a change of an operating mode indicating a number of spatial streams and a channel bandwidth which are supported by the second station. The first station configures a PPDU for the second station using last received indication information of the first indication information and the second indication information. Here, the first indication information is received through an operating mode indication (OMI) field, the second indication information is received through an operating mode notification (OMN) field, and the OMI field and the OMN field are not received through the same PPDU.