[Freedombox-discuss] [HacDC:Byzantium] Re: Serval Mesh Extenders

Jack Wilborn jkwilborn at gmail.com
Sat Jul 13 12:02:38 UTC 2013

Amateur radio has been using Packet UHF communications for decades, I used
it to communicate with the space shuttle many times during it's thousands
of orbits around the earth.  That should give you some idea about i's
range.  Although pretty much line of site, as it only bends slighty as the
earth curves.  It's dependable and part of that is the frequency not so
much the mode.  It also helps that we can use much more power and most of
us use beam antennas to reach out there as far as possible.

Most of this was 144 Mhz (2 meter band)...

That's something that the mesh people need to look at is the distribution
of the signal.  You can get antennas that will let you direct it to
different widths such as a 20 deg or 180 area, making the signal twice as
strong in 1/2 the direction available.  If you are on the outskirts you
direct most of your signal to where you have the majority of users.



On Fri, Jul 12, 2013 at 11:59 PM, haxwithaxe <me at haxwithaxe.net> wrote:

> On 07/12/2013 10:02 AM, Eugen Leitl wrote:
> > ----- Forwarded message from John Gilmore <gnu at toad.com> -----
> >
> > Date: Thu, 11 Jul 2013 17:13:15 -0700
> > From: John Gilmore <gnu at toad.com>
> > To: Paul Gardner-Stephen <paul at servalproject.org>
> > Cc: freedombox-discuss <freedombox-discuss at lists.alioth.debian.org>
> > Subject: Re: [Freedombox-discuss] Serval Mesh Extenders
> >
> >> The idea is that it uses the UHF packet radio to mesh over greater
> >> distances than is possible with Wi-Fi, the trade-off being lower
> bandwidth.
> > PPS:  "Mesh doesn't scale over radio." is the 5-word summary of my
> > experience. Merely making mesh work over wired connections is still
> > a hard research problem that nobody has great solutions for.
> mesh over wired networks is kinda silly. mesh over wireless is far more
> useful and has been around for more than 20 years, and has gotten heavy
> improvements since wifi has become popular.
> if you expect every single device to be a mesh node in the same
> collision domain within range of each other of course it won't work :P
> in a weird way mesh doesn't scale _down_. if you have a one room mesh
> with a chatty protocol it's going to talk itself into the ground like
> the OLPC implemetation of the pre802.11s protocol. if you use the mesh
> like a normal network is used (outside of classrooms and conferences) it
> will generally work fine. if you have it spread across a large city and
> to outlying islands of that city then it still works fine.
> (see the Athens mesh, and Freifunk)
> if you have a mesh infrastructure and non-mesh distribution at endpoints
> you can use different collision domains for the mesh and user networks.
> wifi sucks when there is no 100% clear line of sight (as in not your
> rooftop antenna), end of story. UHF works better than wifi given a
> partially obstructed line of sight (keeping in mind that is unobstructed
> for that particular chunk of spectrum not physical objects ... which for
> 2.4GHz those are the same :P).
> with slightly clear line of sight UHF can go miles. if you set the
> device in a window that is enough for it to get signal through from the
> inside to anything in a ~90deg cone of the window. it obviously isn't
> ideal, but it's cheap and UHF-based extenders could be as good as a
> similar system using only wifi, for much fewer units, and require less
> people to collude or less unattended units strewn across a rural area.
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