[c-nsp] Question about Cisco AIR-AP 1200 series access point?

[Ryan O'Connell]

On 11/02/2005 11:42, jordi wrote:

>I am not sure How many users can be supported concurrently? I am working on a project with more than 100 people in one floor. How many APs should be needed?
>

For 100 people on 802.11b/g, you will need quite a few APs if you want
to come even close to reasonable office performance. With that many
users, personally I'd be looking somewhere in the region of at least 5
APs - ideally 802.11g - but so much depends on local conditions (E.g.
lift shafts can cause reception blackspots, IT staff tend to use more
bandwidth than a receptionist...) that it's hard to give a definitive
answer.

Assuming you're in China as your signature suggests, you'll have 11 or
13 channels available to you but they overlap so you can only use 3 at
once - 1, 6 and 11 - so installing three APs is quite easy. Beyond that,
you need to start thinking very carefully about the local layout - if
people are spread out over a large area, you can put radios on the same
frequency at opposite ends of the area. 100-200m between radios on the
same frequency in an office area is a good rule of thumb if you're using
50mW TX power and an omni aerial. You *could* squeeze in more APs by
reducing the TX power on them, but unless you can guarantee that the
clients will also run at a reduced power you'll run into lots of
interference problems.

802.11a has more channels available so it's much eaiser to do things
such as you describe - however, the range of 802.11a is shorter so more
APs may be needed.

When working out bandwidth, don't forget it's a shared medium like
unswitched Ethernet, so you'll never see annywhere close to 11Mb/s from
802.11b. You can get anything from 2Mb/s up to about 5Mb/s depending on
the quality of the equipment - Cisco-to-Cisco generally gives the best
performance.

-- 
         Ryan O'Connell - CCIE #8174
<ryan at complicity.co.uk> - http://www.complicity.co.uk

I'm not losing my mind, no I'm not changing my lines,
I'm just learning new things with the passage of time