adapters support pre-emptive roaming?

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

Reply to
yozhang
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Methinks you're thinking of 802.11r (Fast Roaming):

You gotta have support for that on both the access point and the client. 802.11r was passed by the IEEE in July 2008, so I expect that there will be supported products available. However, I have no experience with any and cannot supply any vendor names.

It takes more than that to switch association from one AP to another. The handoff ritual is listed in the Wikipedia article.

That's about right for Proset. All it does it does is produce a disconnect at the client end (not a normal thing to do), which forces the card to scan. No background scanning involved. With 802.11r, it should be less than 50 msec.

Reply to
Jeff Liebermann

Jeff,

Thanks for your reply. I have heard the 802.11r Fast roaming. What I am looking for now is the pre-emptive roaming like the one in the following link

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It is all up to the station, and AP seems not involved.

Y> > >Anyone know a Wifi adapter that supports pre-emptive roaming?

Reply to
yozhang

~ 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

Reply to
Aaron Leonard

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