In wireless LAN, relatively small-sized beacons that are transmitted by APs(Access Points) can be received successfully in some border area where the larger data packets can not be successfully transmitted because the larger in packet size, the higher in transmission error probability in the wireless communication. New scan procedure in WLAN will not start before a mobile node moves far away from the AP enough to occur a beacon reception error. In this paper, the updated WLAN simulation model is developed to effectively trigger the scan procedure to reduce the packet loss and the threshold of the beacon rx power is optimized by simulation. In the developed WLAN model, The counter increase when a becon rx power is less than both the designated threshold and the previous rx power. New scan procedure starts when the counter exceeds the predefined value.