As an enormous increase of wireless network usage, WLAN devices interfere with each other in a crowded place, such as downtown. Hence, it is important that choose the least interfered channel around it for better network condition. In this paper, we propose a method which estimates the interfering nodes accurately in a shadow fading environment without localization systems like GPS. This estimation algorithm considers the varying interference area that is caused by the data rate and radio propagation property, especially shadow fading. To evaluate our scheme, we simulate and compare it to other schemes in various scenarios.