On Fri, 8 Feb 2008 12:20:31 -0500, rami.qutub
<(E-Mail Removed)> wrote:
>I have a remote office (2 KM) away from my headquarter. They have both
>Senao Long Range Multi Client Bridge/Ap, with 24Grid Antenna. They both
>used to work really well for months at ~80 Quality and 11Mbps
>transmission rate!
Nice.
>One day the internet speed at my office dropped from 3 Mbps to 256kbps,
Interference. Probably someone along the line of sight has discovered
wireless networking. Such are the dangers of unlicensed wireless
links.
>I tried to play with it and change some configuration bu that didn't
>help.
Did you try changing channels? Try 1, 6, and 11 and see if that
helps. If all of those are occupied, try some of the intermediate
channels and you might get partial relief or make it worse depending
on the source of the interference.
>I order my blacksmith to create a 6m tower to have better line of site
>(which is by default good), but that didn't help!
I don't see how you could get a stable antenna position with a 24dBi
dish and what I assume is an un-guyed tower. The -3dB beamwidth of a
24dBi dish is about 5 degrees and must the aimed within about +/- 2
degrees to be usable. Even boresight alignment (remove feed and sight
along the feed mount pipe), is not quite perfect. Are you using some
sort of signal strength indicator to aim the antenna, or are you just
using the "quality" indicator? If you're doing this by crude pointing
or guesswork and/or your antenna tower is mechanically unstable, it's
possible that your loss of signal was simply due to something moving
in the antenna area.
>The transmission rate varies between 11Mbps and 1Mbps and keep
>changing!
Sounds like interference. The Senao bridge will always try to go as
fast as possible and will attempt an 11mbit/sec connection. However,
if it encounters any data errors, caused by a weak signal or
interference, then it will slow down the connection until the error
rate becomes reasonable. Unfortunately it never really becomes
reasonable if interference is the cause. Since the interference
appears to be intermittent, the speed will vary. Change channels.
>I made sure that the antenna are pointing each other!
How? I'm still suspicious. Blacksmith?
>but still no luck.
Luck cannot be engineered.
>Today I change my other end with a flat Antenna, but that didn't help
>as well!
How much gain? Panel antennas have lower gain and wider patterns than
your 24dBi dish. Depending on the location of the intereference along
the line of sight, the lower gain might improve the situation, while
the wider beamwidth might make it worse. Hard to tell from here.
>I am not sure what is going on, and what should I get to return that
>link as good as it used to be!
Well, neigher am I. Have you done any sniffing with Netstumbler,
Kismet, or a spectrum analyzer?
>Now I discovered that if the link is at 11Mbps (no activity on the
>line), but once I do any activity the transmission rate drops!
See my explanation of how the AP sets it's speed. It tries to go at
11Mbits/sec. With no data, there are no errors so it sits at that
speed. As soon as you try to move data, it gets errors from the
interference, and slows down in an attempt to improve the BER.
>What does that mean!!!
The meaning of life is beyond my limited abilities. Please consult a
philosopher.
>what the Antenna/AP is trying to tell me?
>How I can fix this?
First, try a different channel. If that doesn't work, do some
hunting, find the culprit and negotiate. If you discover that your
city has installed a mesh free Wi-Fi network, as is quite common, give
up and get either a licensed wireless link, or telco lease line. If
you would rather fight than switch, 802.11g is far more resistant to
interference than 802.11b.
--
# 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
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