I'm wondering if anyone can point me to a website
that'll give me some good tools for explaining WiFi
limitations to those without a fair idea of the
underlying technology.

Full story:
My college has begun equipping incoming students
with TabletPCs.  There is some argument now about
the need for wired network connections at each seat
in the classrooms- obviously, some cost is associated
with providing that, but as massive classroom
renovations are scheduled soon anyway, it's not such a
huge deal.

Some people (including those who would claim to be IT
professionals and should know better) are suggeting that
a wireless network is adequate for our needs- namely,
120 students in one room at one time, accessing network
resources.  They argue against our managing the wireless
infrastructure, as well, saying that having the "experts"
from central campus IT install and maintain "enterprise
level" WAPs in each classroom will make the system
somehow better than our doing it ourselves.

The first real stress test occured yesterday.  In a room
set up by the "experts" with "enterprise level" equipment,
120 students turned on their computers and simultaneously
attempted to load a 6 MB slideshow from a shared drive.
It was pandelerium.  I was on hand to provide assistance,
and spent ten minutes running from one person to the next,
advising patience, until some people's file finished loading
and the network's bandwidth slowly thawed out and let some
data through.

The bottom line, what I can't get people to understand, is
that only so many WAPs can be in one place without
interfering with one another, and that interference brings
the bandwidth available to a particular WAP down.  For
some reason, the general understanding is that these
"enterprise level" WAPs can have multiple devices at the
same frequency without causing a problem.  I've tried
explaining it.  I've drawn diagrams, and explained
signal-to-noise ratios and collisions and bandwidth
sharing, and no one listens.  They just nod politely, and
then at the next meeting, they dig in and say "we need
to get the experts out here".

The classroom in question has four WAPs, which means
overlap out of the gate, but I'm not sure how bad it is.
Best case, that gives us 216 Mbps to spread out among
120 students.  Factor in overhead and the worsened S/N
ratio caused by overlap in the frequency bands, and I
doubt we're doing that well.  Now we have a prof who, for
next semester, wants to use a remote desktop program
to control the content on every screen of all 120 students.
I think he's being over optimistic.  In a big way.

Mike H.

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