~ Hi, ~ ~ Anyone know a Wifi adapter that supports pre-emptive roaming? It can ~ find the AP using the AP list got from background scan, instead of do ~ a scan ~ at the time of roaming? ~ ~ I have tried Intel (R) PRO/Wireless 3945 ABG (enabled "aggressive ~ roaming") and ~ Linksys WUSB600N in an IBM notebook. They both will take about 5 or 6 ~ seconds ~ to connect to the other AP after I bring down the current associated ~ AP. ~ ~ Thanks! ~ ~ Yong
Yong,
The 3945 can actively scan (not sure about the WUSB600N.) However, this might not help you much if you abruptly power off the AP to which they are associated.
The point is more like this: you have a client that is moving at 4 mph. If the client isn't actively scanning, it will stay associated to its initial AP, till it completely loses connectivity somewhere around -86dBm, even though it is right next to another AP at -50dBm.
With active scanning, as the client is associated to, and moving away from, the first AP at -74dBm, it will hear the second AP at -64dBm, and will jump over to that one, without having to lose connectivity.
The scenario where the client is associated just fine to an AP at -50dBm but then that AP is vaporized by a capricious admin, is not one for which the client is prepared. In that case, the client will need to miss a bunch of beacons, try to transmit but get no ACKs back, to figure out that this dandy AP that was right here has somehow suddenly gone away, so that it can jump onto another AP at -62dBm.
What exactly are you trying to accomplish?
Aaron