[PROPOSAL] Add hostapd.conf parameter to skipcheckforneighboring BSS (prevent fallback in 150Mb mode)

Valeriy Kucherenko darkside_ua
Tue Apr 10 15:35:10 PDT 2012

> On Sun, Apr 08, 2012 at 01:49:38PM +0300, Valeriy Kucherenko wrote:
> > I guess that this is my case. Hostapd won't start in 40 mhz mode if any overlapping BSS is found on 13+9 channel,
> That would need to be another 40 MHz BSS with different
> primary/secondary channels..
> > but the main problem, as I write before, is that even if it starts in 40 mhz mode (clients shows 270-300 mbps connection), 
> > then from time to time it fallback in 20 mhz mode (clients shows 150 mbps connection). I can't understand why this happens,
> > but it happens. And after overriding scan results with oper40 = 1; this problem seems to go away.
> Have you verified that the AP Beacon frames are indeed changing at that
> point or is this based just on what a client may show based on whatever
> mechanism implemented at that device? hostapd does currently update the
> HT Protection field dynamically based on what kind of stations are
> around it in the operating channel, but I don't think it even has
> capability of disabling 40 MHz mode without a restart..

I don't know how to verify AP Beacon frames. I'm relying on what my notebook (Win7, Intel Centrino Adv-N 6200 AGN) is showing in wireless connection status (mbps) and real data transfer rate (mb/sec).

> > Anyway, you wrote that hostapd check for overlapping BSSes only at startup. Let's assume that at the moment of start there was one
> > conflicting BSSes on our channels, so as result hostapd started in 20 mhz mode. Then, after some time this conflicting AP has 
> > gone away (this is an example from real life). In this case, I guess, hostapd will still work in 20 mhz mode and will not switch 
> > into 40 mhz mode because check for neighboring BSSes performed only at startup. Am I correct?
> Yes, that's the current implementation. This will hopefully get more
> dynamic in the future to allow 20/40 MHz mode to be enabled (and also
> disabled) automatically based on periodic scans by the AP and/or
> associated stations indicating that conflicting device leave/enter the
> radio range.

Thanks for info.

> -- 
> Jouni Malinen                                            PGP id EFC895FA
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