Strange signal

Hi all you clever guys,

I have a location with more that one access point. THe users on the location
feel a bad connection - and sometimes they are kicked off the wireles
network. When I look with Netsumbler I get this screen:

http://www.kalsen.dk/signal.jpg

Why do I see all the black lines in the dump.?.

There are not to many access points close to each other (the other have a
very small signal and are on nonoverlapping channels).

Do you have any clue about this?. Have you seen it somewhere before?

Best regards

Lasse

This is an issue with interference with the frequencies you are using.
The red in the graph indicates the noise levels.

When your SNR is low, your users will get kicked offline. Signal too
low, Noise too high.

Chris
--
Chris Hutchison | President and CEO | NetSteady
O: 614-255-5575 | (E-Mail Removed) | 866-678-WIFI
F: 866-856-1914 | http://www.netsteady.cc

"Lasse" <(E-Mail Removed)> wrote:

>Do you have any clue about this?. Have you seen it somewhere before?

Interference from an other user of the 2.4GHz ISM band? I assume that
the hardware itself is OK.

On Tue, 13 Mar 2007 09:57:40 +0100, in alt.internet.wireless , "Lasse"
<(E-Mail Removed)> wrote:

>Hi all you clever guys,
>
>I have a location with more that one access point. THe users on the location
>feel a bad connection - and sometimes they are kicked off the wireles
>network.

Microwave oven? Cordless phone? Video sender for your TV? Any of
these could mess with the wireless.

>There are not to many access points close to each other (the other have a
>very small signal and are on nonoverlapping channels).

Are your own APs all on different channels? They probably need to be.
--
Mark McIntyre

On Tue, 13 Mar 2007 15:34:26 +0000, Mark McIntyre
<(E-Mail Removed)> wrote in
<(E-Mail Removed)>:

>On Tue, 13 Mar 2007 09:57:40 +0100, in alt.internet.wireless , "Lasse"
><(E-Mail Removed)> wrote:
>
>>Hi all you clever guys,
>>
>>I have a location with more that one access point. THe users on the location
>>feel a bad connection - and sometimes they are kicked off the wireles
>>network.
>
>Microwave oven? Cordless phone? Video sender for your TV? Any of
>these could mess with the wireless.
>
>>There are not to many access points close to each other (the other have a
>>very small signal and are on nonoverlapping channels).
>
>Are your own APs all on different channels? They probably need to be.

For maximum speed, yes, but they should still work on the same channel.

--
Best regards, FAQ for Wireless Internet: <http://Wireless.wikia.com>
John Navas FAQ for Wi-Fi: <http://wireless.wikia.com/wiki/Wi-Fi>
Wi-Fi How To: <http://wireless.wikia.com/wiki/Wi-Fi_HowTo>
Fixes to Wi-Fi Problems: <http://wireless.wikia.com/wiki/Wi-Fi_Fixes>

"Lasse" <(E-Mail Removed)> hath wroth:

>I have a location with more that one access point.

Is that 2, 3, 4, 5, or more access points? Can we be a bit less
vague? (Yes, it makes a difference).

>THe users on the location
>feel a bad connection - and sometimes they are kicked off the wireles
>network.

The connection has to be lost for a long time in order for the access
point to initiate a disconnect. Since I have no clue what hardware is
being used, I can't offer any suggestions on how to increase the time
to disconnect.

> When I look with Netsumbler I get this screen:
>http://www.kalsen.dk/signal.jpg

That looks fairly normal.

>Why do I see all the black lines in the dump.?.

Collisions, interference, signals from outer space. Basically, the
black lines are packet loss the ocurrs when a noise or interference
hit coincides with a probe request from Netstumbler or a response from
the unspecified access point.

>There are not to many access points close to each other (the other have a
>very small signal and are on nonoverlapping channels).

If they're on non-overlapping channels, they should be seen or heard
on your access point. It's the ones with the "very small signal" that
are probably causing some problems.

>Do you have any clue about this?. Have you seen it somewhere before?

Sure, but you're doing it wrong. Use ping instead of Netstumbler. It
will give you real numbers. Also, Netstumbler indicates signal
strength, which is not by itelf a good indication of packet loss or
reliability. You can have a very strong signal, but a little
interference will still cause considerable packet loss.

Actually, use fping or some other ping probe that's better than the
marginal ping shipped with Windoze.
<http://www.kwakkelflap.com/fping.html> (Windoze)
<http://fping.sourceforge.net> (Linux)

Ping your access point or nearby router. If you see something like
this mess:
Reply[19] from 192.168.1.50: bytes=32 time=2.3 ms TTL=127
Reply[20] from 192.168.1.50: bytes=32 time=38.4 ms TTL=127
Reply[21] from 192.168.1.50: bytes=32 time=34.7 ms TTL=127
Reply[22] from 192.168.1.50: bytes=32 time=2.4 ms TTL=127
Reply[23] from 192.168.1.50: bytes=32 time=2.5 ms TTL=127
Reply[24] from 192.168.1.50: bytes=32 time=2.6 ms TTL=127
Reply[25] from 192.168.1.50: bytes=32 time=2.5 ms TTL=127
Reply[26] from 192.168.1.50: bytes=32 time=22.9 ms TTL=127
Reply[27] from 192.168.1.50: bytes=32 time=19.0 ms TTL=127
Reply[28] from 192.168.1.50: bytes=32 time=2.4 ms TTL=127
Reply[29] from 192.168.1.50: bytes=32 time=2.3 ms TTL=127
then you have an interference problem. "Normal" ping time is about
2.5 msec. However the larger delays are caused by retransmissions
induced by interfernce, reflections, co-channel users, noise, etc. If
you let it run for a while, you'll probably see a pattern. If you
have traffic at the same time, ICMP ping will probably be at a lower
priority and the packets will be lost or delayed. Try it without any
traffic if possible. It's also fun to graph the results.

Good luck.

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Tue, 13 Mar 2007 09:57:40 +0100, "Lasse" <(E-Mail Removed)> wrote:

>Hi all you clever guys,
>
>I have a location with more that one access point. THe users on the location
>feel a bad connection - and sometimes they are kicked off the wireles
>network. When I look with Netsumbler I get this screen:
>
>http://www.kalsen.dk/signal.jpg
>
>Why do I see all the black lines in the dump.?.
>
>There are not to many access points close to each other (the other have a
>very small signal and are on nonoverlapping channels).
>
>Do you have any clue about this?. Have you seen it somewhere before?
>
>Best regards
>
>Lasse
>



The black lines you are seeing is interference. open up the picture
to show the channel numbers the three signals are on. The only
channels that do not interfere with each other are channels 1, 6, 11.

However, a strong signal on channel 1 could interfere with a weaker
signal on channel 6, a strong signal on channel 6 could interfere with
channel 11 and vis versa.


For a good connection you should see all GREEN across the graph from
your access point, any black lines show interference and the red shows
noise. From your graph you have probably got a 10-15 db difference
between the signal and the noise, this ain't much when it's coupled to
the gaps in the signal caused by the noise.

check netstumbler for all the channels and find one as far away from
the others as you can, then set your access point to that channel,
then you should see the graph all green with some noise , maybe if
your lucky,

Your graphs are pretty common when in a conjested area with more than
two access points.


Bob Smith
Robert Smith Consulting