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Date:      Sat, 02 Apr 2005 21:23:42 -0800
From:      Sam Leffler <sam@errno.com>
To:        Joerg Sonnenberger <joerg@britannica.bec.de>
Cc:        freebsd-hackers@freebsd.org
Subject:   Re: which Wifi cards can be used for a WAP?
Message-ID:  <424F7DDE.80806@errno.com>
In-Reply-To: <424F172E.9070201@errno.com>
References:  <20050402065052.GT44514@numachi.com> <20050402162842.GU44514@numachi.com> <20050402171635.GV44514@numachi.com> <20050402172355.GA1069@britannica.bec.de> <424F172E.9070201@errno.com>
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Sam Leffler wrote:
> Joerg Sonnenberger wrote:
> 
>> On Sat, Apr 02, 2005 at 12:16:35PM -0500, Brian Reichert wrote:
>>
>>> In perusing many of these cards specs, I see many of them offer a
>>> 'turbo mode' of 108 Mbps.
>>
>>
>>
>> That's a vendor-specific mode. I strongly advice you _against_ using it,
>> it's using at least one additional channel and only adds speed for very
>> short distances. If you follow the common recommendation of leaving one
>> channel before and after the active channel, you end up using at least
>> 5 channels for turbo mode compared to three for normal, it's not worth
>> the trouble.
> 
> 
> This is misleading.  First turbo mode can only be used in the 2.4G band 
> on channel 6 and does not impact operation on channels 1 and 11.  Any 
> channels in between already suffer from normal (i.e. non-turbo) use 
> because the channel spread in the 2.4 band means traffic is visible if 
> you use the in-between channels.  Further, turbo mode (as part of 
> SuperG) requires that the AP detect non-turbo capable stations and 
> disable turbo use when such stations are present.

I was wrong; turbo mode requires a 40Mhz wide band so when operating on 
channel 6 it'll splatter 1 and 11.  Regardless, compliant AP's are 
supposed to monitor the air and drop out of turbo if non-turbo traffic 
is detected.  This is part of the Dynamic Turbo component of SuperG and 
happens transparently to SuperG stations.

	Sam
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