Jack,
Of course the throughput on 4 cards is not 4 times the throughput on a
single card. The processors cannot handle that at this time. It
needs more than a 533 to drive 4 Atheros cards to full throughput and
then you have the limitation that most units today are only using 100
mbps Ethernet. The current systems are not perfect but they represent
an improvement. We are pretty confident that there will soon be more
powerful embedded units that can drive 4 cards to full throughput. As
usual we work with the tools we are given.
When I said no great issues, I thought the very next sentence
qualified that with the requirement that they not use the same
channels.
I'd have to disagree and say that if they don't link up then they have
no appreciable leakage and thus will not interfere to any great
extent. Don't forget that Spread Spectrum by its very nature is able
to handle some interference and not degrade.
The way we look at it is that a single unit with 4 cards is much
easier to deploy and the configuration is much easier to setup.
Routing is easier and the kernel can pass data between radios rather
than going in/out Ethernet ports for a repeater use.
Our standard AP deployment is to use X2 cloaking with 10 MHz wide RF
to give us 6 channels with no overlap. We use 2 WLM-54G cards for 2.4
GHz and 2 SR9 for 900 MHz on a 4 port unit. It might not be "optimum"
but in our experience it beats the last generation of systems with
singles using a switch at the tower base. We get all of that with
less than 8 Watts of normal power draw and about 12 to 15 Watts under
high load. This means my batteries can last for a very long time and
we have 40% of our repeater sites on Solar Power only, with no real
requirement to consider commercial power, which is good, because some
of the sites cannot get it anyway.
There might be better units out there, but any we have looked at are a
lot more money and they draw a lot more power. For the intended use
these are good enough and in fact exceed our requirements, which means
they exceed what the average ISP will need as well. If someone needs
absolute maximum on 4 radios at the same time then all they have to do
is use multiple units, but for an average set of AP's with residential
and light commercial customers there is no need to get that
complicated.
Lonnie
On 2/15/07, Jack Unger <[EMAIL PROTECTED]> wrote:
Lonnie,
Just so I understand your information more completely...
What is the definition of "no great issues". Does this mean that when
all four radios in one box were tested running at full throughput the
aggregate throughput was equal to four times the maximum throughput of
one radio running in a box all by itself?
Also, there is a difference between side-by-side cards that don't link
up and side-by-side cards that are interference-free. The leakage level
needed for cards to link up is higher than the leakage level where cards
will mutually interfere with each other. It's possible for the leakage
level to be high enough to interfere and cause throughput reduction but
still be below the leakage level that will enable linking up.
If simultaneous all-card throughput testing has been done and you're
getting full throughput from each card simultaneously then either you've
done excellent engineering, grounding, and shielding work OR the cards
ARE exceptionally well shielded and there are no motherboard or
backplane leakage issues.
Thanks,
jack
Lonnie Nunweiler wrote:
> Standard Wifi has 3 channels that do not overlap. X4 cloaking has 6
> channels that do not overlap and X4 cloaking has 11 channels that do
> not overlap.
>
> We use 4 WLM-54G radios in a WAR4 and have seen no great issues unless
> two active radios are on the same channel. I am not sure about 6 but
> I know for sure that 4 works fine. Incidentally the SR9 has almost NO
> leakage. Even with the cards side by side they will not link up. In
> order to get anything from them you need a pigtail and an antenna.
>
> Lonnie
>
> On 2/15/07, Marlon K. Schafer <[EMAIL PROTECTED]> wrote:
>
>> I'd recommend against that idea Matt. ALL devices leak some energy. And
>> the amount of interference you'll create for yourself at inches vs.
>> feet is
>> amazing. If you can keep things 3 feet apart there is much less energy,
>> small small fractions in fact.
>>
>> Alvarion with their FHSS gear can get away with such things because
>> they can
>> always stay enough hopping channels away from near by radios. FHSS
>> has 72
>> (or is it only 70?) channels to choose from. WiFi has basically 2 these
>> days.
>>
>> Where this one gets hard to explain is that people build such
>> critters, test
>> them in the lap and then say that they work. Life will change
>> dramatically
>> however, once installed into a working system AND with the addition of
>> real
>> customers with real traffic.
>>
>> laters,
>> marlon
>>
>> ----- Original Message -----
>> From: "John Scrivner" <[EMAIL PROTECTED]>
>> To: "WISPA General List" <[email protected]>
>> Sent: Wednesday, February 14, 2007 11:24 AM
>> Subject: Re: [WISPA] multi-radio Wi-Fi base stations
>>
>>
>> >I thought you were already working with Deliberant on just such an
>> animal.
>> >Where are you guys with that? I know they have a dual radio unit
>> capable of
>> >5 GHz and 2.4 GHz in the same box.
>> > Scriv
>> >
>> >
>> > Matt Liotta wrote:
>> >
>> >> We don't do much Wi-Fi, so I figured I would ask the list. If I
>> wanted to
>> >> deploy a number of Wi-Fi radios at the same location what kind of
>> setups
>> >> are available? I am looking for something where I can deploy one
>> physical
>> >> box that has multiple radios as opposed to a single box per radio.
>> >> Ideally, it would be something modular where I can have a variable
>> number
>> >> of radio interfaces by simply adding cards.
>> >>
>> >> Does anything like that exist?
>> >>
>> >> -Matt
>> >
>> > --
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>
>
--
Jack Unger ([EMAIL PROTECTED]) - President, Ask-Wi.Com, Inc.
Serving the License-Free Wireless Industry Since 1993
Author of the WISP Handbook - "Deploying License-Free Wireless WANs"
True Vendor-Neutral WISP Consulting-Training-Troubleshooting
Newsletters Downloadable from http://ask-wi.com/newsletters.html
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Lonnie Nunweiler
Valemount Networks Corporation
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