From Camp 2011 Public Wiki

GSM at the Camp

The usual suspects from the OpenBSC project are going to run a private test GSM network again.

More details for participants of this GSM network will follow as soon as we know them.

Technical information about the setup, frequencies, license, etc. can be found at the CCCammp2011 page in the OpenBSC wiki.

Status

The GSM network is currently running with both cells active and you can place calls from GSM to GSM (no connection to the Eventphone network yet). Because of some problems with the support for the new hardware, the token can not be used yet. Is some cases it worked, but we had to revert to the 'isolated' mode.

You can find out your current number by calling someone who already knows theirs... just ask around...

Solutions:

N900: Settings-->Telefon Pop-Up will show your number
...

FAQ

Where to get a SIM card for this network?

The POC has SIM cards for the camp network available, (EUR 2 / each)

Will the SIM cards from the experimental network at the 27C3 work?

Yes, the SIM cards from 27C3 (in the 262-42 network) will work in the Camp GSM network

Will there be GPRS/EDGE data services?

No, most likely the equipment configuration we will use does not support this. Also, it would reduce the capacity for voice calls and SMS significantly. If you want to use mobile data services at the camp, we suggest using the 802.11 wifi network.

There will be intermittent and very limited coverage of GPRS for the purpose of GPRS sniffing demonstrations in the context of the GPRS intercept talk. We have set aside one ARFCN for that purpose.

How can I register an extension number?

Please register at the GURU tool of the POC. Registering a GSM extension is not that different from registering a DECT extension - you simply select a different extension type.

Will there be a connection to the public network?

Probably. In case we get this fixed, the dial-in number will be +49-461-5056623-xxxx, where xxxx is your extension number.

Network architecture

Regulatory constraints

As we can only get experimental licenses in the 1800 MHz spectrum in Germany, we cannot use the Siemens BS-11 BTS that were used during a similar experimental GSM network at the HAR 2009 event.

The network usage / load is expected to be much higher than in previous events (where a custom GSM network was still something new).

The maximum number of non-interfering GSM 1800 ARFCNs in the DECT guard band is 10. So we will not get more than 10 ARFCN for our network, which limits the number of BTS/TRX we can deploy.

Sectorized or non-sectorized

Running a sectorized network would have the following advantages:

increased range at same output power (directional antennas)
theoretically higher total capacity due to frequency reuse.

However, the second advantage does not really exist, as we cannot reuse frequencies in such a small area.

So instead, it is likely that we will run a few (2-3) high-capacity cells with omni-directional antennas.

The idea is to have two BTS, each with something like 4 TRX capacity. If they run at sufficient transmit power, they should cover the entire camp without any problems. The advantage over e.g. 8 single-TRX cells is that the capacity can be used at any point in the geographical region.

Antenna deployment

There will be two telescope antenna masts (8m length) welded to the steel frames of the door of two of the shelters. The shelters are about 12 meters high, so the total antenna height above ground will likely be 15m. This should give us direct line-of-sight to virtually anywhere on the camp, except the shelter interior, which is not a prime objective for our coverage anyway.

Software side

On the software side, we will run OpenBSC to manage the BTSs, using the MNCC socket interface to Linux Call Router (lcr), which will then in turn connect to the POC for interoperability with the DECT and wired telephony networks.

Thanks / Credits

We'd like to thank the following organizations and individuals for helping us:

FH Deggendorf for borrowing us two Nokia Metrosite BTS
Dieter Spaar for adding Nokia A-bis support to OpenBSC on short notice
NETZING AG for providing 5 GSM 1800 Antennas
sysmocom GmbH for providing antenna and E1 cabling, installation materials, the OpenBSC machine, etc.
Universität Freiburg for two nanoBTS boosters and two GSM 1800 omni antennas
Luftfahrtmuseum Finowfurt for providing the antenna poles and mounting them to the shelters
Bundesnetzagentur for giving us regulatory approval