A method includes measuring a first congestion level of the first access point, determining to change a coupling destination of a terminal device from a first access point to a second access point, transmitting a request from the first access point to the plurality of access points, the request from the first access point requesting the plurality of access points other than the second access point not to send a response to a request from the terminal device, the request from the terminal device requesting the plurality of access points to send the response to the terminal device, cutting off a coupling between the first access point and the terminal device, transmitting the request from the terminal device to the plurality of access points, sending the response to the request from the terminal device, and establishing a coupling between the second access point and the terminal device.