From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-iw0-f174.google.com ([209.85.214.174]:63749 "EHLO mail-iw0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753775Ab1BFUXZ convert rfc822-to-8bit (ORCPT ); Sun, 6 Feb 2011 15:23:25 -0500 Received: by iwn9 with SMTP id 9so3954111iwn.19 for ; Sun, 06 Feb 2011 12:23:25 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <4D4EFF68.9060101@candelatech.com> References: <4D4EF004.3040109@candelatech.com> <4D4EF99D.5020601@openwrt.org> <4D4EFC76.6090000@candelatech.com> <4D4EFD87.4010005@openwrt.org> <4D4EFF68.9060101@candelatech.com> From: Daniel Halperin Date: Sun, 6 Feb 2011 12:23:04 -0800 Message-ID: Subject: Re: Scanning and channel types. To: Ben Greear Cc: Felix Fietkau , "linux-wireless@vger.kernel.org" Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-wireless-owner@vger.kernel.org List-ID: Could be rate selection. Ben, a sanity check: is it possible for the device to be associated to an "HT-Only" AP and thus not be able to sent NO_HT packets? Could that be why there might need to be a channel change sometimes? Dan On Sun, Feb 6, 2011 at 12:07 PM, Ben Greear wrote: > On 02/06/2011 11:59 AM, Felix Fietkau wrote: >> >> On 2011-02-06 8:54 PM, Ben Greear wrote: >>> >>> On 02/06/2011 11:42 AM, Felix Fietkau wrote: >>>> >>>> On 2011-02-06 8:01 PM, Ben Greear wrote: >>>>> >>>>> Current code always sets the channel type to NO_HT when scanning. >>>>> >>>>>   From what I can tell, we should be able to send NO_HT packets on >>>>> any channel type, and for passive scanning, it should not matter >>>>> at all what channel-type we are using. >>>>> >>>>> I tested relaxing scanning to use the current channel type >>>>> when scanning on the operating channel, and it seems to >>>>> work. >>>>> >>>>> Does anyone see any problems with this approach? >>>> >>>> One thing you should make sure is that once you're done associating to >>>> an NO_HT or HT20 AP (and you have no other interfaces to consider), the >>>> channel mode must not be HT40 - otherwise it could reduce throughput. >>> >>> That is currently handled correctly by the ieee80211_set_channel_type >>> method, as far as I can tell... >>> >>> Regardless of that, in my multi-vif testing, I see lower throughput when >>> using HT40- than using HT20 (between 128 ath9k vif machine and 1 VAP >>> ath9k machine). >>> The VIFS all claim 300Mbps rate. >>> I haven't looked into this any further at this point... >> >> Well, with HT40 you take a hit from not just the busy time of the >> primary channel, but also from the busy time of the extension channel. >> If you have other wifi activity on the extension channel, then it's >> normal that this would reduce throughput. > > There were a few other APs on that channel, but they were not doing any > active work > (just beacons and such).  The two ath9k systems were very busy > talking to each other.  My typical work-load is STA sending to STA > through the AP. > > So, would that scenario be likely to cause the slowdown that you > mention? > > Thanks, > Ben > >> >> - Felix >> -- >> 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 > > > -- > Ben Greear > Candela Technologies Inc  http://www.candelatech.com > -- > 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 >