From: Craig King (craig.king@comcast.net)
Date: Wed Jan 15 2003 - 16:34:05 GMT-3
Not sure about Q#1, but I'll take a shot at Q#2. I am yet to see any
"metrics" that address overlapping channels in overlapping cells, as it is
dependent on the specific config of the wireless network (which channels are
actually used), traffic load, and is a very bad design practice. Based on
what channels are actually used, I suspect that intentional overlap leads to
significant bandwidth problems, potentially making both channels unusable
(e.g. 1 & 2, or 1 & 3). As a reference, the 3 "non-overlapping" channels 1,
6, and 11 *will* overlap if antenna output power is sufficiently high enough
(or they are close enough), dropping effective throughput from 5.5 Mbps to
around 4 Mbps. If so, then channels that overlap by design would likely
have even greater decreases in throughput.
This begs the question why you want to install 2 AP's in an overlapping
configuration? Good design using channels 1, 6 , and 11 allows 3 APs to
offer network access in overlapping wireless cells with minimal
interference, and facilitates roaming. Throw in proper spacing, tweaking
the output power to control the cell size, and the use of proper antennas
for the location, and those 3 channels can co-exist pretty well together.
Or you could look at 802.11a, which can utilize 6 non-overlapping channels,
for significantly higher throughput.
Just my 2 cents though...
HTH,
CK
----- Original Message -----
From: "Some Internet User" <shadowd2@earthlink.net>
To: "Some Internet User" <shadowd2@earthlink.net>
Cc: <ccielab@groupstudy.com>
Sent: Wednesday, January 15, 2003 10:36 AM
Subject: Re: OT: Wireless Question
> Forgot to mention this is 802.11b
>
> -SM
>
> Some Internet User wrote:
>
> > I have a customer that is using MAC based authentication with the
> > Cisco 1200 AP's. One of the problems were having is in several areas
> > of their campus, a client computer will flop back and forth from one
> > AP to another. Now, without any authentication turned on, this is not
> > a big deal, because no traffic is lost. With the MAC based
> > authentication (pointint to a RADIUS server) I'm losing a ping every
> > time it roams (well, actually 7 of 11 times). This is a problem for
> > these clients that are flopping from one AP to another one, causing
> > them to lose traffic. Does anyone know if there's some sort of
> > configuration that I'm missing that allows this information to be
> > cached so I don't have the delay when roaming.
> >
> > Second Question: Does anyone have any good links on what exactly
> > happens when you have overlapping channels? The questions I'm looking
> > to have answered are: how much overlap can you have? what happens to
> > the traffic when you have overlap? What metric do you use to determine
> > whether overlap is going to be a problem.
> >
> > Thanks in advance everyone!
> >
> > -SM
> > .
> .
.
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