Fluctuating SNR - Lancom L54ag Wireless

Hi!

I would like to connect to buildings with a a Wireless Bridge. This
Wireless Bridge consists of two "Lancom L54ag Wireless" Access-Points
using 11b-Point-to-Point-Mode. Unfortunatelly the Signal-to-Noise-Rate
(SNR) is fluctuating. For one hour the SNR is high and for another hour
it is low and I don't know why. I believe that this is because of a
physical effect, that I do not know.

Has anybody an Idea what this could cause?

Attached file: signalquality_mrtg.png
That is the SNR when I connect the two buildings.

Attached file: signalquality2.png
This is the SNR when the devices are in two adjacent rooms. SNR is also
fluctuating, but in shorter intervals and the difference between min and
max is less.

Attached file: skizze.gif
This is a draft of the buildings and the wireless bridge. Distance is
400m, Lancom-A is on third floor (Building A), Lancom-B is on first
floor (Building B). Both Lancoms are connected with omni directional
wireless Antennas. There is an obstacle (building) in between, but there
is intervisibility between Lancom-A and Lancom-B.

Any ideas? Thanks!

Hans

Thank you for your answer. There are the pictures:

http://hgzojer.i6networks.com/images...ality_mrtg.png
(That is the SNR when I connect the two buildings.)

http://hgzojer.i6networks.com/images/signalquality2.png
(This is the SNR when the devices are in two adjacent rooms. SNR is also
fluctuating, but in shorter intervals and the difference between min and
max is less.)

http://hgzojer.i6networks.com/images/skizze.gif
(This is a draft of the buildings and the wireless bridge. Distance is
400m, Lancom-A is on third floor (Building A), Lancom-B is on first
floor (Building B). Both Lancoms are connected with omni directional
wireless Antennas. There is an obstacle (building) in between, but there
is intervisibility between Lancom-A and Lancom-B.)

Valentín Guillén wrote:
>
>
> Hans Zojer wrote:
> Hi!
>
> I would like to connect to buildings with a a Wireless Bridge. This
> Wireless Bridge consists of two "Lancom L54ag Wireless" Access-Points
> using 11b-Point-to-Point-Mode. Unfortunatelly the Signal-to-Noise-Rate
> (SNR) is fluctuating. For one hour the SNR is high and for another hour
> it is low and I don't know why. I believe that this is because of a
> physical effect, that I do not know.
>
> Has anybody an Idea what this could cause?
>
> Here in the US, we have all types of devices operating in the WiFi Radio
> Frequency band, and they cause much interference to our WiFi signals.
> This shows up or manifests itself as noise or interference to our
> networking signals. I believe it is the same situation in Austria.
>
>
> Attached file: signalquality_mrtg.png
> That is the SNR when I connect the two buildings.
>
> Attached file: signalquality2.png
> This is the SNR when the devices are in two adjacent rooms. SNR is also
> fluctuating, but in shorter intervals and the difference between min and
> max is less.
>
> Most Usenet servers will refuse to propagate Usenet posts which have
> file attachments. Certainly your post has no attachments when viewed at
> two different Usenet servers available to me. FTP your images to some
> server available to you on the web, and then reference those publicly
> available images with URL links in your Usenet post, like these examples:
>
> http://pwp.netcabo.pt/lfmartins/www....t_wireless.png
> http://pwp.netcabo.pt/lfmartins/www.tvcabo.pt_wired.png
>
>
>
> Attached file: skizze.gif
> This is a draft of the buildings and the wireless bridge. Distance is
> 400m, Lancom-A is on third floor (Building A), Lancom-B is on first
> floor (Building B). Both Lancoms are connected with omni directional
> wireless Antennas. There is an obstacle (building) in between, but there
> is intervisibility between Lancom-A and Lancom-B.
>
> There are basically two solutions to your problem. You can eliminate
> the interference, or you can increase the signal level.
>
> OK! It may not be so easy to eliminate the interference.........
>
> So you are left with increasing the signal level. One way is to put
> amplifiers on your devices. The other way to do this is to change from
> omnidirectional antennnae to more directional types. This will "focus"
> more of the RF energy into the directions you require.
>
> Good Luck!
>
>
> vg
>

Hans Zojer wrote:
Hi!

I would like to connect to buildings with a a Wireless Bridge. This
Wireless Bridge consists of two "Lancom L54ag Wireless" Access-Points
using 11b-Point-to-Point-Mode. Unfortunatelly the Signal-to-Noise-Rate
(SNR) is fluctuating. For one hour the SNR is high and for another hour
it is low and I don't know why. I believe that this is because of a
physical effect, that I do not know.

Has anybody an Idea what this could cause?

Here in the US, we have all types of devices operating in the WiFi Radio
Frequency band, and they cause much interference to our WiFi signals.
This shows up or manifests itself as noise or interference to our
networking signals. I believe it is the same situation in Austria.


Attached file: signalquality_mrtg.png
That is the SNR when I connect the two buildings.

Attached file: signalquality2.png
This is the SNR when the devices are in two adjacent rooms. SNR is also
fluctuating, but in shorter intervals and the difference between min and
max is less.

Most Usenet servers will refuse to propagate Usenet posts which have
file attachments. Certainly your post has no attachments when viewed at
two different Usenet servers available to me. FTP your images to some
server available to you on the web, and then reference those publicly
available images with URL links in your Usenet post, like these examples:

http://pwp.netcabo.pt/lfmartins/www....t_wireless.png
http://pwp.netcabo.pt/lfmartins/www.tvcabo.pt_wired.png



Attached file: skizze.gif
This is a draft of the buildings and the wireless bridge. Distance is
400m, Lancom-A is on third floor (Building A), Lancom-B is on first
floor (Building B). Both Lancoms are connected with omni directional
wireless Antennas. There is an obstacle (building) in between, but there
is intervisibility between Lancom-A and Lancom-B.

There are basically two solutions to your problem. You can eliminate
the interference, or you can increase the signal level.

OK! It may not be so easy to eliminate the interference.........

So you are left with increasing the signal level. One way is to put
amplifiers on your devices. The other way to do this is to change from
omnidirectional antennnae to more directional types. This will "focus"
more of the RF energy into the directions you require.

Good Luck!


vg

Hans Zojer wrote:

Any ideas? Thanks!

Hans


Hans Zojer wrote:
 
> Any ideas? Thanks!
>
> Hans
>

In my previous post, I hastily dismissed the idea of lowering the level of interference or "noise".  However, depending upon your situation and level of financial resources, this might be the most expeditious avenue for you to pursue.

Refering to   this diagram leads me to believe that the antennae are located on the outside of the buildings, or at least perhaps in windows.  You mentioned that these were omnidirectional antennae.  

Depending upon what size the antennae are, it might be very easy and economical to simply build shielding around the two antennae, perhaps in the form a a  "U", which would surround the antennae except in the direction in which you wish to receive/transmit in.  Alternately, if the antenna are merely connected to the two devices, you could still build shielding devices which would surround the device except in the desired direction of reception.  

You'll want to build these out of either solid metal, or even more easily out of wire mesh.  The wire mesh can be of the type we call "chicken wire" or other similar construction materials.  I've constructed shielding out of material for home construction meant to hold stucco, as it is very flexible and has "openings" in the mesh which are small enough that the waves of this wavelength cannot pass through.  Look for material with openings of no larger than 2~3cm for best shielding.  

This asumes of course that the interference is being received at the antennae, and not through the device.   If this were a device sold in the US, I could guarantee you of it's internal shielding.  I am not certain of what regulations pertain to devices legally sold in Austria.  

Good Luck,

vg