Intro

we had GSM networks at CCC events since 2008
- Initially using proprietary, E1-attached Siemens BTS and OpenBSC (later OsmoBSC)
we had GSM networks at European Hacker Camps since 2009 (HAR)
we had UMTS (3G) for a few years now, too
- using Osmocom stack with OsmoHNBGW / OsmoMSC / OsmoSGSN
I’m still involved with developing the related software, but have handed over actual network operation at CCC events to a team around lynxis and bibor
- this means I have time for playing with LTE

LTE

new protocols on all layers of all interfaces
- S1AP between eNodeB and MME
- GTPv2C between MME and SGW and SGW and PGW
- DIAMETER between everyone and HSS

srsLTE for eNodeB and UE
- main focus on UE; eNodeB features somewhat limited
- super simplistic srsEPC suitable for only the scarcest of use cases
OpenAirInterface
- obscure code base; difficult to build
- very research oriented
- RAN part under non-free, non-opensource but source available license
nextepc
- the clear underdog
- very capable; many features (SGs, handover on X2 and S1, SBc)
- readable code!

shared subscriber (and key) database
- LTE: HSS, speaking DIAMETER
- 2G/3G: HLR, speaking MAP (Osmocom:GSUP)
We need a so-called inter-working function (IWF)
- translate from DIAMETER to GSUP and vice-versa

Best FOSS DIAMETER support contained in Erlang/OTP
Fairwaves contributed GSUP protocol codec in Erlang
I wrote a translator for the two minimal procedures
- AuthInfo (Obtain authentication tuples)
- UpdateLocation (registration)
code at https://git.osmocom.org/erlang/osmo_dia2gsup/

6 eNodeBs distributed around the camp inside select Datenklos
- Ericsson RBS6402 with 23dBm in Band 7
- back-haul over regular CCC Ethernet as separate VLAN
Stratum-0 NTP server with GPS receiver for eNB clock sync
- built on Raspi 3B with gpsd + ntpd
Lenovo x240 Laptop running qemu-kvm for core network
- runs nextepc MME, SGW, PGW
- runs osmo_dia2gsup for translating DIAMETER to GSUP
Querying Camp 2G/3G OsmoHLR for subscriber data

Telefonica O2 has provided (borrowed) 10 MHz of spectrum in Band 7 (2600 MHz)
We can use it either as one channel @ 10 MHz or two chnanels @ 5 MHz
- first four days were operated using 5 MHz channels (3 eNB on each channel)
- last day was operated using 10 MHz channels (6 eNB on same channel)

Telekom technician Peter "@33dBm" Schmidt has done some testing
- first test with 5MHz chnanels: https://twitter.com/33dBm/status/1165393409852563457
- problems with neighbor selection due to dual-frequency network
- Average throughput 33.6 Mbps down / 9.1 Mbps up)

Telekom technician Peter "@33dBm" Schmidt has done some testing
- second test with 10 MHz chnanels: https://twitter.com/33dBm/status/1165576180961095680
- better neighbor selection
- improved throughput (Average 62.7 Mbps down / 20.8 Mbps up)

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