OsmoBTS is a software implementation of Layer2/3 of a BTS. It implements the following protocols/interfaces: LAPDm (GSM 04.06) RTP A-bis/IP in IPA multiplex OML (GSM TS 12.21) RSL (GSM TS 08.58)

OsmoBTS is modular and has support for multiple back-ends. A back-end talks to a specific L1/PHY implementation of the respective BTS hardware. Based on this architecture, it should be relatively easy to add a new back-end to support so-far unsupported GSM PHY/L1 and associated hardware.