[CS-FSLUG] wireless network in a disaster?

[Ron Thompson]

On Tuesday 05 May 2009 23:33, Marco Tedaldi wrote:
> Ron Thompson wrote
>
> > > Although I've not done it; a router should be able to present it's own
> > > page whenever a client computer tries to connect to *any* webpage. 
> > > Just think about what happens in many hotels.  You open your browser
> > > and you see the hotel's page asking for credentials to use the system. 
> > > You could put your page in that place.  Your page could have multiple
> > > links because you might have redundant "command centres".
> >
> >     This is the information I wanted to know.  Its do-able and may be
> > easier
> > and better than I'd thought.
>
> There is almost nothing that has not been done before. It's about messing
> around with iptables and some java-script in the case of freifunk firmware
> and it works quite well.
>
> > > When Marco and I mentioned "limited range"; we are talking about not
> > > being able to reach the other end of your own block.  You need a
> > > *large* number of routers in a mesh network (like one on every block)
> > > for many computers to communicate in this manner.  If the mesh is dense
> > > enough, there should be alternate routes available for access to the
> > > "command centre".
> >
> >     What if a high gain external antenna and a higher powered router were
> > used?  I found this product, and while I don't understand all the lingo,
> > it
> > looked interesting.
> > http://www.ubnt.com/products/ps2.php
>
> This is a quite cool product. One thing to remember is, that the figures
> about range are only true if here are about similar devices on each end of
> the link. So a notebook might be able to receive the signal from the router
> over a vast distance. But will it be able to answer? I'd say: no.
>
> Another point is that there are quite strict regulations about tx-power in
> most industrial countries. In case of a desaster I think this is not an
> issue, but if you want to run the network the whole time (which should be
> done to make sure it works) it could be.
>
> You can extend the range of many routers (also the linksys ones) by using
> better antennaes. But when mounting a better antenna don't forget to reduce
> the output power of the sender. More output power on only one side of the
> link only increases noise levels for all the others without improving the
> performance.

   Power output and antenna gain won't be an issue on 2. or 5 GHz, if its 
operated on the channels assigned to amateur radio use as secondary licenced 
users, as long as the requirements for station identification are complied 
with and the transmitters are under the direct control of a licenced amateur 
radio operator.  This wouold be the situation in most countries, with small 
variations on the sprectrum assigned to amateur radio use, and whether a 
particular country has approved broadband digital modes for amateur use.
>
> My own observation is that two routers can connect over distances of up to
> 600m in free air. In urban areas with houses this goes down to 30m
> sometimes. It's best to put the routers in water proof cases (I'm using
> tupperware boxes, the are still useable even after over a year in direct
> sunlight while other plastic boxes break apart after some months outside)
> outside. At walls of buildings or on roofs (unused chimneys are really
> good, since you can get the power cable trough there).

    This may be worth trying, with a few volunteers, to see what the coverage 
area might be, and to test the concept.  Thanks for sharing your experiences.

   Ron


-- 
Ron Thompson, |^|
Yellowknife, NT, Canada
"Who are are these that fly as a cloud, and as doves to their window?" Is 60:8