On 11 May 2007 10:36:23 -0700, ShoutyMcNasty <(E-Mail Removed)> wrote:
>we are looking to roll out wireless for voip and handhelds around our
>environment however senior management are leery about the cost of a
>site survey and so they want to do it in pieces, paying as they go.
What cost? Site surveys are done based on the probable location of
access points. Go down to the store, buy an access point (or wireless
router), find a wireless laptop, and do some plotting. Move the
access to all the probable locations and record the signal strength at
each location using Nestumbler or Kismet.
I've done a few of these in office buildings and got a surprise. The
timer burner is not in doing the survey. It's in arguing over the
probable number location of the wireless access points. You can't
just plaster the place with a zillion wireless access points because
they interfere with each other. You also can't just run the whole
building on one wireless access point. Obviously, there's an optimum
number and that number is usually not obvious. If in doubt, pick 3
access points per floor (on channels 1, 6, 11) and you've hit maximum.
Light reading:
<http://www.cisco.com/en/US/products/hw/wireless/ps430/products_technical_reference_chapter09186a008043a3 c8.html>
<http://www.cisco.com/en/US/products/sw/cscowork/ps3915/products_user_guide_chapter09186a008052dbff.html#w p1656856>
<http://www.ekahau.com>
<http://www.airmagnet.com/products/survey.htm>
<http://www.wi-fiplanet.com/tutorials/article.php/1116311>
<http://www.cisco.com/en/US/docs/wireless/wlan_adapter/350_cb20a/user/windows/1.1/configuration/guide/win5_apF.html>
<http://www.cisco.com/en/US/tech/tk722/tk809/technologies_q_and_a_item09186a00805e9a96.shtml>
>Does anyone out there have any documented evidence that this is a bad
>idea.
Unless I'm missing something here, you're looking for documentation
for the wrong way to do something or documentation of a failed
installation. It's possible to find those, but I don't know of any.
Actually, I do know of some failures, but they weren't because the
site survey was performed in an odd manner. It was because no site
survey was performed in the first place.
>Common sense says you should do the whole building at once (it
>is a 9 storey hospital) but I need evidence to support my proposal of
>not breaking the survey up.
Can I render my opinion in the matter? My experience with hospital
construction is that each floor can be considered a separate RF
environment. There is so much concrete, steel, foil backed
insulation, and shielding in the walls, that nothing penetrates the
walls. Same with the floors and ceilings. The biggest headache I had
in planning a hospital wireless system was getting sufficient coverage
through all these barriers to RF. For example, we had a waiting room
and lobby with a series of office radiating from the center. I
installed an access point near the middle of the lobby on the theory
that it would also cover the offices. It did, but only if the doors
were open. I could be 5 meters away, but if the door was closed,
wireless was a lost cause. The floor layout also included a
substantial number of zig-zag corridors. The idea was to keep the
noise level down by not creating a tunnel. That worked fine but
blocked RF going down the corridors. I setup one wing of the hospital
to be "illuminated" from an access point located OUTSIDE of the
hospital on a nearby roof. That worked better than trying to light up
the rooms from inside. Like I said, location of access points is far
more difficult than actually performing the site survey. Of course,
it's useless to perform a site survey without first knowing where the
access points and users are going to be located.
>My thought is that there will be some problem stitching the surveys
>together if you don't have it all done at once and that there may be
>dead areas around the perimiter of the survey areas.
True. However, there are going to be dead areas no matter what you
do. The construction of the hospital largely creates this condition.
It's not like corporate offices, which tend to be more like a
partition infested warehouse, that can be illuminated from above the
partitions. It's more like a labyrinth, dungeon, or bomb shelter.
If dead zones are as bad as I predict, you might want to look into
"leaky coax" cable.
<http://www.andrew.com/products/trans_line/radiax/>
These can be snaked through the overhead utility areas. They really
only offer coverage for short distances (about 3 meters) but are
perfect for snaking corridors and labyrinths.
I'm not sure what you're thinking of in the way of VoIP Wi-Fi
handsets, but methinks you should try using one for a short test
before committing the hospital to what I consider to be an R&D
project. Wi-Fi VoIP is very new technology, with lots of potential
for surprises. Try it before you buy it.
>Please help out if you can... if you wish, email me directly at skay
>AT nygh.on.ca
Wanna pay for my time and advice? I answer questions in public
newsgroups and mailing lists for free. I charge for personal
consulting via email or phone. Unless proprietary info is required,
answers should be posted where everyone can learn from both the
questions and answers. Otherwise, it's consulting.
--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
(E-Mail Removed)
#
http://802.11junk.com (E-Mail Removed)
#
http://www.LearnByDestroying.com AE6KS
Similar Threads
Linear Mode
