Patent ID: 7289472
Filing Date: 2007-10-30
Classification: H04W

Abstract:
1. A handoff method of a wireless local area network (LAN), wherein each of access points in the wireless LAN periodically broadcasts a message of a time beacon, signal separation, an access point ID, and a traffic indication map, the handoff method comprising: 1) immediately starting to count time from a time point of association of the mobile terminal with an access point of the wireless LAN; 2) always tracking a signal-to-noise ratio (SNR) of old access point ( 3) judging by the mobile terminal whether or not to associate the new access point according to a signal strength and an association time of each of the access points, and if a judging result is yes, issuing a reassociation request signal to the new access point; wherein when the handoff function is IST, it is expressed as follows: where SNR(t) is a signal-to-noise ratio, T is an association time between the mobile terminal ( 3 ) and the access point, and k 6 and k 7 are function parameters: and wherein a handoff strategy comprising the steps of: first, with respect to the old access point, setting two threshold values of H and h, wherein H is a high threshold value and h is a low threshold value; judging the SNR of the received signal at the old access point, and: when SNR>H, indicating that the signal strength of the old access point is still strong, handoff is not performed in this region; and, when SNR<h, indicating that the signal strength of the old access point is rather weak, handoff is performed; and under the condition of h<SNR<H, using an IST value to decide whether or not the handoff is performed, that is, if a difference between the IST value of the new access point and the IST value of the old access point is greater than or equal to a threshold value Ts, performing the handoff, and if a difference between the IST value of the new access point and the IST value of the old access point is less than the threshold value Ts, not performing the handoff.