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From: "Luis R. Rodriguez" <mcgrof@gmail.com>
Date: Wed, 18 Nov 2009 16:21:03 -0800
Message-ID: <43e72e890911181621g4c2c28e1m693e8bc4796e73e1@mail.gmail.com>
Subject: Re: [Madwifi-devel] Survey: What are you using MadWifi for, and why?
To: "Luis R. Rodriguez" <mcgrof@gmail.com>,
	Pavel Roskin <proski@gnu.org>, David Acker <dacker@roinet.com>,
	Andrey Yurovsky <andrey@cozybit.com>,
	Michael Renzmann <mrenzmann@madwifi-project.org>,
	madwifi-devel@lists.sourceforge.net,
	madwifi-users@lists.sourceforge.net,
	linux-wireless <linux-wireless@vger.kernel.org>
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Sender: linux-wireless-owner@vger.kernel.org

On Wed, Nov 18, 2009 at 3:05 PM, Jouni Malinen <j@w1.fi> wrote:
> On Wed, Nov 18, 2009 at 02:08:16PM -0800, Luis R. Rodriguez wrote:
>> Are you aware of any regulatory rules which prohibit narrower
>> channels? It just seems odd.
>
> I don't remember any rules that would explicitly do that, but there may
> be some implicit limitations due to the slower TX rate. I don't know
> whether this would hit anywhere, but at least quarter width channel with
> 1 Mbps TX rate and maximum frame length might get pretty close to some
> maximum TX-without-sensing limits. Though, that is less likely to be an
> issue on 5 GHz band due to 6 Mbps minimum TX rate even at quarter
> channels could be fast enough. There could also be some rules that state
> the minimum TX rate, so there could potentially be need to change
> supported rate sets and/or fragmentation threshold in some corner cases.
>
> Actually, even with 6/4 Mbps TX rate, the channel sensing rule in Japan
> (carrier sense every 4 ms) (if that rule is still valid.. haven't
> really checked), we could hit the limit with maximum frame length.

Thanks for the details, we'll poke our regulatory guys just to confirm.

  Luis