Subject: RE: [PATCH 24/25] wl1271: Optimize scan duration
From: Juuso Oikarinen <juuso.oikarinen@nokia.com>
To: "ext Gabay, Benzy" <benzyg@ti.com>
Cc: "Coelho Luciano (Nokia-MS/Helsinki)" <Luciano.Coelho@nokia.com>,
	"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
In-Reply-To: <676FD6AA0F002F49B89E70F0C5EFD22C135ADBA311@dlee04.ent.ti.com>
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	 <1286257254.11177.224.camel@wimaxnb.nmp.nokia.com>
	 <676FD6AA0F002F49B89E70F0C5EFD22C135AD3CB17@dlee04.ent.ti.com>
	 <1286341161.11177.254.camel@wimaxnb.nmp.nokia.com>
	 <676FD6AA0F002F49B89E70F0C5EFD22C135ADBA311@dlee04.ent.ti.com>
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Date: Wed, 06 Oct 2010 08:26:54 +0300
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Sender: linux-wireless-owner@vger.kernel.org

On Wed, 2010-10-06 at 07:21 +0200, ext Gabay, Benzy wrote:
> Juuso,
> 
> 
> > Sent: Tuesday, October 05, 2010 11:59 PM
> > 
> > Hi,
> > 
> > On Tue, 2010-10-05 at 17:42 +0200, ext Gabay, Benzy wrote:
> > > Juuso,
> > 
> > > > > >
> > > > > > From: Juuso Oikarinen <juuso.oikarinen@nokia.com>
> > > > > >
> > > > > > Currently then dwell times for each channel in scans is set to
> > an
> > > > > > overly
> > > > > > long value, and excessive number of probe-requests are
> > transmitted
> > > > on
> > > > > > each
> > > > > > channel (for active scans.)
> > > > > >
> > > > > > Based on testing, comparable results can be received with
> > smaller
> > > > > > dwell-time,
> > > > > > and, with fever probe-requests - in fact, reducing the number
> > of
> > > > probe-
> > > > > > requests
> > > > > > to 2 seems to increase the number of found results.
> > > > >
> > > > > I think that this does not making any sense. Less prob requests
> > > > should give you back less results. As less beacons/prob responses
> > are
> > > > getting back to the station.
> > > > > I think also that office with 70 AP is not a normal environment
> > to
> > > > test and optimize numbers.
> > > > > I would suggest to re-test in a 1-6 AP environment which is
> > making
> > > > more sense for both home and enterprise environment.
> > > >
> > > > We have actually performed more testing than just mentioned here,
> > in
> > > > varied environments, and all of the testing seems to indicate that
> > > > reducing the number of probe-reqs per channel is not reducing the
> > > > number
> > > > of acquired results. Instead, in some scenarios, it is increasing
> > the
> > > > number of acquired results.
> > > >
> > >
> > > >>  I don’t know if that is conventional request: can you share the
> > full results and setup details?
> > 
> > No, I don't have any formal documentation to share.
> > 
> > The setup details are simple enough though. The tested this on command
> > line using a simple script that flushes existing scan results, then
> > performs two or three scans counting the number of scan results on the
> > last round using grep and wc.
> > 
> > We performed the testing in office environment and a shielded chamber,
> > which only has selected AP's within it.
> > 
> > Between test rounds we modified the driver parameters related to
> > scanning, i.e. we modified the number of probe-reqs and the dwell time
> > on each channel.
> > 
> > -Juuso
> 
> 
> Sounds great. Just one more: which AP brands (excluding Cisco) ?

In the office environment we have a variety of brands, including D-link,
Buffalo, Telewell, TP-link and linksys, cisco etc.

In the shielded chamber we are using linksys wrt610n AP's.

-Juuso

> 
> 
> > 
> > > > We did not see reduction in the probability of finding a specific
> > AP in
> > > > a few (one or two) AP environment either.
> > > >
> > > > The effect seems to be this way because reducing the number of
> > > > probe-req's dramatically reduces the noise generated by probe-
> > responses
> > > > from AP's on neighbouring channels.
> > > >
> > > > -Juuso
> > > >
> > 
> 
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