Return-path: Received: from na3sys009aog105.obsmtp.com ([74.125.149.75]:55322 "EHLO na3sys009aog105.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752007Ab1AQMd2 convert rfc822-to-8bit (ORCPT ); Mon, 17 Jan 2011 07:33:28 -0500 Received: by qyk27 with SMTP id 27so5270035qyk.1 for ; Mon, 17 Jan 2011 04:33:26 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <1295263943-32110-1-git-send-email-juuso.oikarinen@nokia.com> References: <1295263943-32110-1-git-send-email-juuso.oikarinen@nokia.com> Date: Mon, 17 Jan 2011 14:33:26 +0200 Message-ID: Subject: Re: [PATCH] wl12xx: Increase scan channel dwell time for passive scans From: "Kahn, Gery" To: juuso.oikarinen@nokia.com Cc: coelho@ti.com, linux-wireless@vger.kernel.org Content-Type: text/plain; charset=UTF-8 Sender: linux-wireless-owner@vger.kernel.org List-ID: Does it worth to have different value for 5GHz? On Mon, Jan 17, 2011 at 13:32, wrote: > From: Juuso Oikarinen > > The passive scan channel dwell time currently used is 30ms-60ms. A typical > beacon interval for AP's is 100ms. This leads to a ~30% worst-case probability > of finding an AP via passive scanning. > > For 5GHz bands for DFS frequencies passive scanning is the only scanning > option. Hence for these, the probability of finding an AP is very low. > > To fix this, increase the passive channel scan dwell times (also the early > leave value, as 5GHz channels are still typically very silent.) Use a value > of 100ms, because that covers most typical AP configurations. > > Based on testing the probability of finding an AP (102.4ms beacon interval) on > a single scan round are as follows (based on 100 iterations): > > dwell min/max (ms)   | probability > ---------------------+------------ > 30/60                | 35% > 60/60                | 56% > 80/80                | 77% > 100/100              | 100% > > Total scan times now and after the change: > > Region | Before (s) | After (s) > -------+------------+---------- > 00     | 0.77       | 1.48 > FI     | 0.95       | 2.01 > US     | 0.91       | 1.76 > > Signed-off-by: Juuso Oikarinen > --- >  drivers/net/wireless/wl12xx/conf.h |   16 ++++++++-------- >  drivers/net/wireless/wl12xx/main.c |    4 ++-- >  2 files changed, 10 insertions(+), 10 deletions(-) > > diff --git a/drivers/net/wireless/wl12xx/conf.h b/drivers/net/wireless/wl12xx/conf.h > index f5c048c..21b72a5 100644 > --- a/drivers/net/wireless/wl12xx/conf.h > +++ b/drivers/net/wireless/wl12xx/conf.h > @@ -1084,30 +1084,30 @@ struct conf_scan_settings { >        /* >         * The minimum time to wait on each channel for active scans >         * > -        * Range: 0 - 65536 tu > +        * Range: u32 tu/1000 >         */ > -       u16 min_dwell_time_active; > +       u32 min_dwell_time_active; > >        /* >         * The maximum time to wait on each channel for active scans >         * > -        * Range: 0 - 65536 tu > +        * Range: u32 tu/1000 >         */ > -       u16 max_dwell_time_active; > +       u32 max_dwell_time_active; > >        /* >         * The maximum time to wait on each channel for passive scans >         * > -        * Range: 0 - 65536 tu > +        * Range: u32 tu/1000 >         */ > -       u16 min_dwell_time_passive; > +       u32 min_dwell_time_passive; > >        /* >         * The maximum time to wait on each channel for passive scans >         * > -        * Range: 0 - 65536 tu > +        * Range: u32 tu/1000 >         */ > -       u16 max_dwell_time_passive; > +       u32 max_dwell_time_passive; > >        /* >         * Number of probe requests to transmit on each active scan channel > diff --git a/drivers/net/wireless/wl12xx/main.c b/drivers/net/wireless/wl12xx/main.c > index 863e660..c1814f2 100644 > --- a/drivers/net/wireless/wl12xx/main.c > +++ b/drivers/net/wireless/wl12xx/main.c > @@ -279,8 +279,8 @@ static struct conf_drv_settings default_conf = { >        .scan = { >                .min_dwell_time_active        = 7500, >                .max_dwell_time_active        = 30000, > -               .min_dwell_time_passive       = 30000, > -               .max_dwell_time_passive       = 60000, > +               .min_dwell_time_passive       = 100000, > +               .max_dwell_time_passive       = 100000, >                .num_probe_reqs               = 2, >        }, >        .rf = { > -- > 1.7.1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-wireless" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at  http://vger.kernel.org/majordomo-info.html >