On Thu, 08 Nov 2007 12:25:31 -0800, Darius <dariusjack2006@yahoo.ie>
wrote:
>have you already tested Ekahau ?
Well, if you call 15 minutes of tinkering with an early version to be
testing, yes. I thought it was interesting, but not very useful for
what we were trying to accomplish. What was funny was that we were
"recording" the signal strength in the isles, which was adequate.
However, the signal strengths only a short distance away, on the
actual desktop where the laptops and PDA's were going to be used, was
completely different. In order to do a proper test, we probably
should have walked on everyones desk.
>It doesn't seem to work properly under indoor , office environment
>as topology generated by tracking software is subject to interference
>error,
Interference will not show up on the map. The recorder only measures
signal strength, not signal quality. If interference were measured,
the map would look completely different. Also, there's quite a bit of
frequecy selective fading in an indoor environment. This creates very
small, but also very "deep", nulls and dead areas.
>so a autocad like drawing seems to be a description of conception and
>not a real environment generated map
>http://i.cmpnet.com/nc/design06/0831...1rollout3a.gif.
Well, how real do you want it to be? In this case, it's only a matter
of accuracy, granularity, and number of recordings. If you want more
reality, just take more measurements.
>And for outdoor use there is need to use Matlab tools as a simple
>triangulation algorithm works perfectly.
Such models do not take into consideration topography. I'm not sure I
know what you mean by triangulation. I can locate a wi-fi client
using triangulation using two access points, but this is a essentially
a single access point model, with the access point repeated as
required. What the OP apparently wants is a best effort guess as to
the expected signal strengths for an indoor environment. Ekahau does
that. He apparently also wants it to design and possibly optimize his
network topology. It won't do that.
>I am really surprised Ekahau doesn't go into details of indoor
>tracking showing marketing materials only.
I suppose they don't want anyone to reverse engineer or clone the
product, at least without first buying a copy.
>Of course there is reverse algorithm for discovering x,y,x position of
>each wifi sender/tag for a specific location and a number of wifi
>senders, but what you get is not necessary circular range/ signal
>level pictures as on the
>above picture.
What's an x,y,x ? Do you mean perhaps x, y, z ? I would be rather
interested to know how you're going to get z axis (altitude)
information from any number of access points, all in the same plane.
>What is presented on the above picture is signal level aproximation
>for wifi network switching packets under best reception/signal level
>algorithms and has nothing to do with a real environment
>circumstances.
Yep. Reality varies with the observer.
>Darius
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