osmo-bts is a Layer2 + Layer3 implementation of a GSM BTS (Base Transceiver Station).
It implements LAPDm on the network side (TS 04.06), as well as RSL (08.58) and OML (12.21) on the BTS side.
Only A-bis over IP is supported as back-haul to the BSC.
Only OpenBSC is currently supported as BSC.
Hardware / L1 / Transceiver support
It is written in a way to be portable accross different L1 (Layer 1) implementations.
The primary target platform is the sysmoBTS, but some work is being done to make it work with other hadware/l1.
osmo-bts is available from git://git.osmocmo.org/osmo-bts.git, you can check it out via
$ git clone git://git.osmocom.org/osmo-bts.git
or browse the source interactively on the web by accessing http://cgit.osmocom.org/cgit/osmo-bts/
The source code includes a http://cgit.osmocom.org/cgit/osmo-bts/tree/README file with current status information
osmo-bts has recently been extended with a socket interface towards osmo-pcu. This adds GPRS (and later EDGE) support to it.