900MHz packet radio?

Paul Gardner-Stephen paul at servalproject.org
Thu Sep 1 12:47:55 UTC 2011


On Thu, Sep 1, 2011 at 9:58 PM, Scott Weisman <sweisman at pobox.com> wrote:
> 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.

I hear what you are saying, and we are working to support inter-BTS
meshing for OpenBTS and OpenBSC.
However, there is also value in getting the phones to mesh, if only
because there are plenty situations where you might not be able to get
a BTS, or be able to use any BTS that is around.

> 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.

I know what you are saying, and much does happen in emergency
situations that is not tolerated otherwise. However this is not to say
that we should not be aspiring to fully legal solutions.
While we talk much about disaster, we also care about developing world
and rural/remote markets where incumbent cellular carriers will
certainly litigate over any unlicensed BTSes.

> 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.

That is cool, and are aware that we are in many ways just re-spinning
tech that has been around 40 or 50 years, whether it be packet radio,
FIDOnet or other such technologies.


> 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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