"Mesh" Dreams = OLSR

L. Aaron Kaplan aaron at lo-res.org
Tue Aug 24 12:11:11 EDT 2010

>>> The largest of our mesh problems did not have to do with
>>> scalability on sheer number of nodes but rather scalability in
>>> density.  Is there any information available on how these networks
>>> perform when there are 50 - 100 of them next all in the same room
>>> or in adjacent rooms?
>> Yes! And the answer is very very simple: turn down the txpower!
>> ;-)))
> Can you provide me with a pointer to the numbers?  Whats the maximum number of nodes can you have operated in a given area and what sort of network traffic tests did you run?

Well, the community wireless networks are not very much about very dense settings. We try to cover large areas with external (outdoor) antennas but still have very many nodes in one single mesh covering a whole city or so. See the attached current map of the Funkfeuer.at network.

BUT!! Because we don't have a mesh with 100s of laptops in one room, does not mean, we don't know physics ;-)

Since you asked if I know an example where there are many laptops in one room:
One example that I know that worked brilliantly well with many wireless devices in one room was the RIPE meeting in Amsterdam. There they regularly have many small APs below the desks in the meeting room and these are turned down very much in "volume" (txpower).
The effect is that they only cover a small area ( remember, power decreases by the square of the distance).
So this is a way to avoid a lot of noise of many laptops in a small room.
Another feature that you IMHO should look at is 802.11n devices (and of course also turn down the "volume" there!). These offer higher bandwidths in addition to actually using the multipath effects.
When you have many many laptops in one room and everybody "screams"/sends very loud then you have lots of "echos" (multipath fading) bouncing off the walls etc. 802.11n thrives off these multipath effects.

As I said - first solve layer 1 & 2 issues and then think about layer 3 meshing.

I hope I could help.
Best regards,
L. Aaron Kaplan

PS: please forward my answers to the list or allow me to post to the list. I am not subscribed there . Thx.

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