GSM @ Camp 2011 preparations
laforge at gnumonks.org
Fri Jul 22 23:44:15 CEST 2011
The camp is getting closer and closer. In the past weeks, folks like
Sylvain, Dieter and I were trying desparately to find a good technical
solution for running the GSM network at the CCC Camp.
The original intention of using the Motorola Horizon macro BTSs has
unfortunately not worked out, despite spending man-weeks of time in
exploring and reverse engineering the highly proprietary Motorola
variant of GSM. While it has been a fascinating journey in distributed
systems, it has not come anywhere close to using the equipment for
actual network operation.
The nanoBTSs that we use during the 26C3, 27C3 and other events are too
low-power / low-range for the area we want to cover. There are some
boosters and LNAs, but we don't have them in the quantity that we
anticipate to require (ideally 6TRX).
The BS-11 units we have are higher power but all GSM 900 only, for which
we cannot get a license from the regulatory authority.
The Ericsson RBS2308 are higher power and 4TRX, but they are 1900 MHz :/
Luckily, Dieter has recentl done some work for a university of applied
sciences in Bavaria. They have obtained some Nokia Metrosite equipment
(from O2 Germany, I believe), and Dieter is helping them with OpenBSC
support for it.
So just in time, Dieter has managed to get them working _plus_ the
university thankfully has agreed to borrow them the two units for the
camp. One of them is 2TRX, the other is 3TRX. They have integrated
duplexers but no combiners, i.e. we need one Antenna for each TRX.
Each of the TRX has 5W output power.
I have ordered some nice 140cm long omnidirectional 8dBi gain antennas
as well as cable that will only produce 2dB loss over the estimated 10m
that we have to cover.
The back-haul to the BSC will be classic E1 based.
All equipment should be at my place around August 1st. I'm planning to
slowly build the network starting from August 3rd onwards. This depends
a bit on when we will have electrical power in the shelters where the
units are to be located, and when the museum will have the telescope
antenna poles ready for us.
The license permits us operating from August 3rd onwards, so we can do
coverage testing and the like as soon as the BTSs (or even only one of
them) is operational.
It would be great to know who will be able to give me a hand with the
build-up starting from which day/time on.
- Harald Welte <laforge at gnumonks.org> http://laforge.gnumonks.org/
"Privacy in residential applications is a desirable marketing option."
(ETSI EN 300 175-7 Ch. A6)
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