Decoupling scanning from handoff for reduced delay over wireless LAN

摘要

Methods and systems for handing off a wireless client between access points wherein the scanning for access points is decoupled from the handing off, thus reducing the delay in handing off. Channel scan delay may be eliminated or reduced in some embodiments by scanning early (prior to actual handoff) and interleaving the channel scan with ongoing traffic in a non-intrusive way. A smart handoff trigger may be used in some embodiments that covers both uplink and downlink quality, and addresses link asymmetry problems. The methods or systems may be implemented in some embodiments in a software-only client-only solution without the need to modify the networks themselves or their access points.

主权项

1. A method for use in a wireless communication system comprising a wireless client and a plurality of wireless access points, wherein the wireless client associates with one of the plurality of wireless access points to enable communication therethrough, the method comprising acts of:
a) in response to a first set of at least one triggering condition depending on a property of a first wireless connection between the wireless client and a first wireless access point of the plurality of wireless access points, actively scanning using an adaptive scanning interval to detect which of the plurality of access points is within range to enable association with the client, wherein the first wireless access point has a service set identifier (SSID), and the actively scanning using an adaptive scanning interval comprises: maintaining a priority scan channel list, wherein each channel in the priority scan channel list contains an access point that has the SSID of the first wireless access point, actively scanning each channel in the priority scan channel list by broadcasting a probing request frame before waiting for at least one response to the probing request frame from wireless access points in the channel, and after a channel scanning time interval, actively scanning each channel in the priority scan channel list a second time, wherein the channel scanning time interval is determined based on a measure of connectivity; and b) in response to a second set of at least one triggering condition that differs from the first set of at least one triggering condition, handing off the wireless client from the first wireless access point to a second wireless access point of the plurality of wireless access points to create a second wireless connection between the wireless client and the second wireless access point.