[Server-devel] [laptop.org #8321] Questions about XO mesh networking

Michail Bletsas mbletsas at laptop.org
Fri Mar 28 08:04:02 EDT 2008

Bryan Berry <bryan.berry at gmail.com> wrote on 03/28/2008 12:55:28 AM:

> I am cc'ing Martin Langhoff, John Watlington who are in charge of the
> School Server at OLPC
> > 1.  ideally the school server (running XS) will have 3 active antenna
> > each running on a diff channel (1,3,6) and XOs will connect to one of
> > these.
It will have three 3 active antennas running on the three non-overlapping 
WiFi channels which are 1,6 and 11
These active antennas will be configured as Access Points in dense 
deployment scenarios.

> >2. Or should we replace the WRT54G with
> > another AP/Router in the short term?
> I would replace the WRT54G. I hate them. I have had 3 fail on me in the
> last year. I would get 3 other wireless routers. I like DLink
WRT54G's are prefrectly fine devices when used in the context that they 
were designed for (home gateways).
I wouldn't use them in schools that will require more than 1 (because of 
the way they spport lazyWDS with the stock firmware) and if they have to 
be used, I would load them with some openWRT firmware variant (so that 
lazyWDS can be partially controlled)

For a school with 200 laptops, one low-cost solution that doesn't involve 
too much tinkering with device firmware is the DWL2100AP from Dlink. In 
general one has to always keep in mind that the less a device has to do, 
there is more probability that it would do it without many bugs.

> My understanding is that in a dense deployment such as yours you should
> use a regular wireless router and not the active antennas, for the short
> and the long term. Wad and Michailis, pls correct me if I am wrong.
The correct wording is to use access points. The cheapest way to get an 
access point is to use a WiFi router with the routing functionality 
disabled. (Relatively easy to do on most of them, connect everything on 
the LAN ports after making sure that the internal DHCP server is 

> >3. Running ejabberd on a central server means that collaboration
> > features will work while the XOs are connected to an AP (or school
> > server with active antenna)? The only change we need to make on the 
> > is to support this, is to change the jabber server using
> > sugar-control-panel?
> Correct
> >4. Can we expect to get around 50 XOs per channel?
> Don't know, sounds good to me. We are planning 60 XO's per channel 
> w/ a Deliberant Radio + Omni 12 dbi antenna
> (Dev can provide more details)
> Wad, Michailis can you advise?
Yes (with an Access point currently)


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