Return-path: Received: from na3sys009aog109.obsmtp.com ([74.125.149.201]:38730 "EHLO na3sys009aog109.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752525Ab1AQNjx convert rfc822-to-8bit (ORCPT ); Mon, 17 Jan 2011 08:39:53 -0500 Received: by mail-qy0-f181.google.com with SMTP id 12so5743734qyk.19 for ; Mon, 17 Jan 2011 05:39:52 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <1295268140.18570.128.camel@wimaxnb.nmp.nokia.com> References: <1295263943-32110-1-git-send-email-juuso.oikarinen@nokia.com> <1295268140.18570.128.camel@wimaxnb.nmp.nokia.com> Date: Mon, 17 Jan 2011 15:39:52 +0200 Message-ID: Subject: Re: [PATCH] wl12xx: Increase scan channel dwell time for passive scans From: "Kahn, Gery" To: Juuso Oikarinen 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: Ok. Thank you On Mon, Jan 17, 2011 at 14:42, Juuso Oikarinen wrote: > On Mon, 2011-01-17 at 14:33 +0200, ext Kahn, Gery wrote: >> Does it worth to have different value for 5GHz? >> > > I guess the 100ms value benefits 2.4GHz passive scanning as well, does > it not? In 2.4GHz band there are usually very few channels passive > scanned (mostly channels 12 and 13 in the 00 region) so the cost of this > increased wait time is quite little. > > -Juuso > >> 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 >> > --- > >