Scans

[Sorin PAUN]

Please tell me if I understood the scan mechanism in HostAP:

-in firmware-based roaming mode (prism2_param wlan0 host_roaming 0), the 
firmware do scans whenever the link quality is poor, and the AP with the 
best signal level is chosen.

-in host-based roaming mode (prism2_param wlan0 host_roaming 1), the 
firmware continues to do scans when the link quality is poor, but the AP 
is chosen in the driver (prism2_host_roaming() ), looking also to 
preferred_ap setting. In this mode; the driver can also command a part 
of scans.

How (which type - active or passive) are this scans done ? It seems that 
the scans commanded by SIOCSIWSCAN are done also by the firmware, by 
setting the HFA384X_RID_SCANREQUEST.  What I don't really understand is 
why a JoinRequest is made at every scan results 
(HFA384X_INFO_SCANRESULTS) , even then when the best AP is in fact the 
current AP. Does this slows the card someway, and if it slows, could one 
eliminate the JoinRequest in the case of a same AP?


I've also noticed that for sta f/w>1.3.0, we can command a 
HFA384X_RID_HOSTSCAN, and will we obtain a HFA384X_INFO_HOSTSCANRESULTS 
frame. How is this different (what means "it keeps old association 
status") ? It doesn't made/ We don't have to make a JoinRequest every time?


Abous the passive scans , I see that this can be do by a private ioctl. 
How the passive is done by the f/w and what the results of these passive 
scans are : a HFA384X_INFO_SCANRESULTS or HFA384X_INFO_HOSTSCANRESULTS 
info frame?

Thank you all for this great work,
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Sorin PAUN                           mailto:Laurentiu-Sorin.Paun at imag.fr

Doctorant INPG                             http://drakkar.imag.fr/~lpaun

Laboratoire LSR-IMAG, Equipe Drakkar
681, rue de la Passerelle - BP 72          phone: (+33) (0)4 76 82 72 12
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