From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from main.gmane.org ([80.91.229.2]:56779 "EHLO ciao.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752677AbYIOLZG (ORCPT ); Mon, 15 Sep 2008 07:25:06 -0400 Received: from root by ciao.gmane.org with local (Exim 4.43) id 1KfCCV-00044v-9y for linux-wireless@vger.kernel.org; Mon, 15 Sep 2008 11:25:03 +0000 Received: from 220.227.207.12 ([220.227.207.12]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 15 Sep 2008 11:25:03 +0000 Received: from pavan.k.pujari by 220.227.207.12 with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Mon, 15 Sep 2008 11:25:03 +0000 To: linux-wireless@vger.kernel.org From: Pavan Subject: Channel scan during the AP re-association increases delay Date: Mon, 15 Sep 2008 11:18:53 +0000 (UTC) Message-ID: (sfid-20080915_132524_401693_4106696E) Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-wireless-owner@vger.kernel.org List-ID: Hi All, I am working on fast handovers to APs during roaming of wireless devices. I have been looking through the mac80211 code to understand how the re-associations are initiated in wireless STAs. To my surprise, I see that everytime I issue a associate command using the `iwconfig' utility, it starts with scanning on all channels collecting information from each AP in the ESSID set. Subsequently, begins the authentication and association process. This results in large re-association delays which is unacceptable to real time traffic like voice. As I went through the code, I could trace that `hw->scan' is initiated before authentication and association process. I could not figure the exact reason for having a channel scan every time an association command is issued, instead it could be done passively when the STAs are immobile or experiencing good channel conditions (as one of the conditions). This way a lot of time could be saved during roaming to bring down the total re-association delays. I would appreciate any help in this regard. Thanks, Pavan