900MHz packet radio?

Scott Weisman sweisman at pobox.com
Thu Sep 1 12:28:59 UTC 2011


After checking out your web site, I see you're trying to use standard
off-the-shelf hardware. In that case, this is the wrong avenue to pursue. I
think a better idea, without knowing anything about the deep technical
details, would be to drop the phone-to-phone mesh network effort and focus
instead on creating some sort of BTS-in-a-box that can be deployed by
airdrop or whatever, using low power components capable of being maintained
on solar alone. The mesh networking could come into play here, where perhaps
a BTS-to-BTS mesh can be developed (again, I don't even know if this is
possible, but this seems to be a better avenue to pursue if stock cell
phones are a goal). There is at least one group working to deploy
OpenBTS-based hardware in extremely remote locations running under very
limited power budgets. This kind of solution could use 100% stock phone
hardware. While carrier-grade BTS hardware is ridiculously expensive, it
doesn't have to be that way for this kind of use case.

Also, in an emergency situation like the Haiti earthquake, which was your
inspiration, are you really going to be concerned with all the strict
legalities involved, or are you going to be more concerned with saving
lives? Let's see. Tens of thousands dead and injured, and more deaths by the
minute. So, we better make sure our hardware is 100% compliant with local
laws and difficult to deploy since it needs custom software and possible
hardware mods to function. Or, maybe, just maybe, in this type of disaster
scenario, since the local cellular service is down anyway, easily deploy a
legally questionable but 100% workable solution many times faster.

As an aside, I read an article in an amateur radio magazine back in the
1980s by someone who designed a portable solar-powered packet radio repeater
with stock hardware of the time. He use an old ammo box to hold everything
and powered it with a solar panel and motorcycle battery. It was
self-contained, had no overheating issues (he checked), and was just cool.

Scott

On Thu, Sep 1, 2011 at 7:11 AM, Paul Gardner-Stephen <paul at servalproject.org
> wrote:

> Greetings all,
>
> At the Serval Project we have created a mobile mesh telephony system
> that currently works over wifi.
>
> From the outset, we have wanted to get it working on the ISM915 and/or
> ISM868 bands that are located adjacent to the GSM 850/900 frequency
> allocations.
>
> My initial investigations and enquiries indicate that this should be
> possible by creative programming of the baseband processor in many
> models of phones.  The trick, as I suspect you well know, is the
> difficulty in getting the information and tools required to reprogram
> these radios.
>
> I am now in a position to potentially fund further work on this.
>
> So, as the open-source group with the most experience reprogramming
> baseband radios, what is the feasibility of creating a
> proof-of-concept using the types of phones you already work with to
> send and receive arbitrary data packets without reliance on a cell
> tower (even for time synchronisation)?
>
> I know there are a lot of constraints and problems, but I am most
> interested in creative solutions that can get us to a working
> prototype, however crude, that can be used to demonstrate the
> feasibility of what I am proposing.
>
> If this discussion is off-topic here, I am happy to hold the
> conversation at the serval-project-developers google group, but I am
> equally comfortable with it continuing here.
>
> Thanks in advance,
> Paul Gardner-Stephen.
> Shuttleworth Telecommunications Fellow at Flinders University.
>
>
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