An AP and UE, which perform access control using CSMA/CA, perform a step judging an exposed level in transmission of the AP based on a congesting level in transmission, which is caused by a wireless station in defer transmission that is in a neighborhood of the AP; a step judging an exposed level in reception of the UE based on a congesting level in reception, which is caused by a wireless station in defer transmission that is in a neighborhood of the UE; and a step performing control which changes a channel of the AP, when the exposed level in transmission cannot satisfy expected quality of the AP, and performing control which changes a connected AP of the UE, or control which changes to other network, when the exposed level in transmission or in reception cannot satisfy required quality of the UE or the expected quality of the AP.