
OpenBTS: Cheap, open source cellular network - nir
http://openbts.sourceforge.net/
======
cnvogel
There are currently (to my knowledge) two working open-source/free-software
implementations of the GSM stack.

OpenBTS (<http://openbts.sourceforge.net/>) puts everything, beginning at the
modulation/demodulation of the radio-frequency, into your PC and uses a USRP
(<http://www.ettus.com/products>) as the radio-frequency frontend (~$2000).

OpenBSC (<http://openbsc.gnumonks.org>) uses a different approach and starts
implementing at the Abis-interface, which is what the Base Transceiver Station
(the thing with the antennae...) connects to. Here you don't need the USRP but
a surplus GSM BTS (currently around or a little less than $500/€500 and the
necessary E1-interface (for the Abis-link) is $200/€200, afaik). OpenBSC has
been successfully tested at <https://wiki.har2009.org/page/GSM> and
<http://events.ccc.de/congress/2009/wiki/GSM> using officially allocated
frequencies.

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vaporstun
Looks very cool, excited about the possibilities, but my first thought was
"FCC violation."

Did a quick Google search, looks like they did a test at Burning Man in 2008
and got local FCC approvals: <http://lwn.net/Articles/297038/>

~~~
nimrody
One more problem: Patents.

GSM implementations require licensing IP from several major manufacturers
(Nokia, Ericsson and others). As long as the project is small they probably
won't bother. But just try basing a femtocell product on OpenBTS and they will
be knocking on your door soon.

~~~
nir
I suppose something like this would find much of its use in places where
neither FCC nor patents have a lot of clout.

~~~
vdm
If you dig deeper on OpenBTS, the primary motivation of the project is
altruistic, rolling basic coverage out in the developing world where there is
no current economic incentive, or respect for IP.

That's not to say that it would be disruptive in developed markets as well, or
course.

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ashish01
I have been interested in software radio for some time now but lack the
technical knowledge to understand it fully. Can someone point me to links that
can help me understand this ? I am sure it will be helpful to many people.

From what I have read one needs a Universal Software Radio Peripheral (USRP)
for sending and receiving radio signals but searching for this leads to things
like daughter boards etc. which I did not understand.

Can someone explain it here ?

Thanks

~~~
unwind
The wikipedia page on the USRP seems to explain it pretty well:
<[http://en.wikipedia.org/wiki/Universal_Software_Radio_Periph...](http://en.wikipedia.org/wiki/Universal_Software_Radio_Peripheral>).
It also goes into the issue of daughterboards, although not in-depth.

The reason for daughterboards is given as "[...] designed to be flexible,
allowing developers to make their own daughterboards for specific needs with
regard to connectors, different frequency bands, etc."

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jonnycowboy
I wish they made a (much) cheaper USRP specifically for GSM, I wouldn't use
the rest of the radio functionality (AM, FM, etc).

~~~
cnvogel
The USRP doesn't do any AM, FM,... It's only a very fast ADC/DAC. Some of the
additional modules have up-/downmix capability, though.

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jrockway
My dream of creating a GSM network called "Free Public Wi-Fi" is one step
closer to fruition...

~~~
blasdel
Almost all of those non-AP networks you see (usually with that name, and never
with a route to the internet or dhcp) are due to a pernicious _Thyphoid Mary_
behavior in Windows' wireless networking UI.

In at least Windows XP, if you _ever_ join a "computer-to-computer" network,
your computer will advertise that network (or the last such network) whenever
it is not connected to another SSID, in perpetuity. Airports are the primary
breeding ground for this disease.

~~~
jrockway
Yeah. And I think it would be amusing to see your cell-phone connected to that
network instead of "AT&T" or "T-Mobile" or whatever :)

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toisanji
This would be awesome to try and build my own magicjack femtocell. I wonder
what hardware is needed and how much it would cost to do.

