I also found out that iwconfig wlan0 ap auto should invoke reassociation to the
strongest AP according to man page. It seems it does nothing.

I believe the driver doesn't support roaming, and instead it relays on user
space tool such as the network manager. Yi?

Roaming can be done by NetworkManager or directly running command
"wpa_supplicant". But once we connect with one AP by "wpa_supplicant", even
there's another station/AP nearby which has stronger signal quality, it won't
roam to a new station.

Driver will not support roaming. Instead user can use some user space tools 
(such as wpa_supplicant) for it.

(In reply to comment #4)
> Driver will not support roaming. Instead user can use some user space tools 
> (such as wpa_supplicant) for it.
> 

is this kind of a bad joke?

Well, maybe you can use user space tools such as wpa_supplicant, NetworkManager
to do th roaming?

(In reply to comment #6)
> Well, maybe you can use user space tools such as wpa_supplicant, NetworkManager
> to do th roaming?
> 

well, do not know whether wpa_supplicant can handle non-authenticated networks,
and craps like the NetworkManager I do not use. Why did this work just fine
with the older cards? (IWL2915)

Yes. You can use wpa_supplicant to assocate to these networks. For example, for
open authentication without WEP, you can use configure file similar to:

network={
        ssid="plaintext-test"
        key_mgmt=NONE
}