Wireless NIC recommendation

[Sam Leffler]

John Nielsen wrote:
> On Monday 15 January 2007 15:54, Lars Stokholm wrote:
>> John Nielsen wrote:
>>> On Monday 15 January 2007 12:54, Lars Stokholm wrote:
>>>> Hi, I hope someone can help me with this, before I go mad (no pun
>>>> intended.) :)
>>>>
>>>> I was initially looking for a relatively cheap 54Mbps, 802.11g- and
>>>> WPA-capable network card, based on an Atheros chipset, but after
>>>> spending the whole of last night looking for one - to no avail - I gave
>>>> up.
>>>>
>>>> I'm almost about to conclude that Atheros is not the way to go. So now I
>>>> want to know, if anyone can recommend ANY card, being cheap and
>>>> supporting the features mentioned above. I don't mind using NDIS, as
>>>> long as it works flawlessly. Also it would be good, if the card was a
>>>> popular one, so community support is more available.
>>> For driver support in FreeBSD, Atheros is definitely the way to go. Have
>>> you looked through the listings here?
>>>
>>> http://customerproducts.atheros.com/customerproducts/default.asp
>> Wow, I actually think I found a card there, that is guaranteed to work.
>> Is this really the end of all my struggles? :) For only 50 USD. There
>> seem to be only one version of the card.
>>
>> http://www.dlink.com/products/?pid=12
>> http://edbpriser.dk/Products/Listprices.asp?ID=38373 (in Danish)
>>
>> The two cards /are/ the same, right?
> 
> This is actually the card I have and use in my FreeBSD box as an access point 
> (I didn't know it was still available or I would have said so sooner.) Yes, 
> they should be the same.
> 
> There is an early revision ("A1") card of the same name that actually used a 
> non-Atheros chip, but anything you buy today should be "B" or "C" and work 
> fine. I have the "B" revision.
> 
> Check out the D-Link website (pretend like you're looking for a Windows 
> driver) for slightly more information on the different revisions and how to 
> identify them.
> 
>> Also, it says 108Mps? Does it matter that my AP is only 54Mbps?
> 
> Shouldn't matter at all. 108Mbps is often advertised and rarely 
> used/practical. The idea is to use two 54Mbps streams at once. You need to 
> have a card (and driver) that suport it ("Super-G" or "Extreme-G"), an AP 
> that supports it and that acknowledges that your card supports it, and little 
> to no other traffic or interference, since most AP's will automatically fall 
> back to 54Mbps at the drop of a hat. I'm not sure if ath(4) supports it or 
> not, but I've never really cared too much.

Thanks, your description is good.  Let me try to elaborate.  108Mb/s is
the marketing speak for cards that are capable of Turbo mode.  Turbo
mode is a chip feature whereby a 2x wide channel is used to get
effectively 2x the bandwidth.  Radios capable of doing turbo mode can do
this in either 2.4G or 5G.  When configured to use turbo mode only it's
said you are operating in "static turbo mode".  When the driver switches
the radio between turbo and non-turbo operation on the same frequency
then it is said you are using "dynamic turbo mode".  You are not
supposed to use static turbo in 2.4G, only dynamic turbo.  In 11a you
can use either.

The freebsd driver only supports static turbo mode.  It's done so since
the first commit.  The current linux driver supports both static and
dynamic turbo modes.  I have support in p4 for dynamic turbo but to be
honest it's not really useful and you cannot use it when operating as an
ap unless you also do radar detection so you can drop out of turbo mode
when you hear non-turbo stations operating on the channel.

In testing I routinely see 40+ Mb/s using static turbo mode with tcp
netperf; probably more (been a while).  If you add in some other stuff
that is part of the Atheros SuperG protocol (vendor-specific extensions
to 802.11) then you can get 60+ Mb/s.  Under certain circumstances you
can hit 90+Mb/s.  The code in p4 supports most of the important bits to
get 60+ with turbo mode under good conditions.

Finally, understand also that 11n is coming along very soon and will
have interoperability and higher throughput than SuperG.

	Sam