[Server-devel] Technical questions

Martin Langhoff martin.langhoff at gmail.com
Thu Jan 21 06:28:53 EST 2010

On Thu, Jan 21, 2010 at 3:45 AM, James Cameron <quozl at laptop.org> wrote:
> There are rules of thumb, and there is engineering.

I have two thumbs and no engine in me, so I prefer the former.

Is there any simple "5-step guide" to make an _initial_ antenna
placement  & frequency selection for APs? It will of course not be
perfect. I have several books on wifi but I always wish for a "simple
approach". Something that starts with

1 - Get a floorplan of the building

2 - Test (or guess if you haven't been there) if the construction
material for all/most walls blocks/reflects wifi radio signals. Same
with floor/ceiling for multi-storey buildings. (It is always possible
that some walls are different than ohers and block the signal - that's
something to explore once on-site)

3 - Define how many users you can connect to an AP -- some APs have
"configured" hard limits in the software they ship. If you have to
guess, assume ~40 as the upper limit.

A - If the walls block wifi

A1 - Are your classrooms more than N users (N being the limit defined
in step 3)? You can place 2 APs per classroom - in channels 1 and 11.
Plus some APs in the common (presumably open) areas (use strategy B1
for open areas).

B - If the walls do not block wifi

B1 - Draw circles on the floorplan with the expected radius of reach
of the AP, so that you got the areas you care about well covered.
Write down in pencil a 1, 6 or 11 in each circle. The circles can
overlap, but only if their frequencies are different.

Of course AP placement will also depend on where you can place an AP
so that it is safe for the kids around, protected from the
environment, secure, and with power and ethernet wiring.


 martin.langhoff at gmail.com
 martin at laptop.org -- School Server Architect
 - ask interesting questions
 - don't get distracted with shiny stuff  - working code first
 - http://wiki.laptop.org/go/User:Martinlanghoff

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