Osmocom Base Transceiver Station (BTS) https://osmocom.org/projects/osmobts
Go to file
Pau Espin c88ed31d9e cosmetic: gsm_pchan2chan_nr(): Update spec documentation
Change-Id: If1de230f022c69f3dfce8a7c66d494a984e7f3f9
2023-03-17 15:29:17 +01:00
contrib Bump version: → 1.6.0 2023-02-07 17:15:53 +01:00
debian Bump version: → 1.6.0 2023-02-07 17:15:53 +01:00
doc doc: rsl: add RSL_IE_IPAC_RTP_CSD_FORMAT 2023-03-14 09:59:15 +00:00
include GSMTAP: allow configuring local address 2023-03-04 11:24:37 +00:00
src cosmetic: gsm_pchan2chan_nr(): Update spec documentation 2023-03-17 15:29:17 +01:00
tests tests: use -no-install libtool flag to avoid ./lt-* scripts 2023-03-14 20:09:44 +00:00
.gitignore gitignore: add vty pdf 2023-03-10 10:18:41 +00:00
.gitreview Add .gitreview 2016-06-17 15:33:01 +00:00
.mailmap Add .mailmap for mapping mail addresses in shortlog 2016-08-08 11:31:00 +00:00
COPYING re-work original osmo-bts with support for sysmocom femtobts 2011-06-27 11:25:35 +02:00
Makefile.am Makefile.am: EXTRA_DIST: debian, contrib/*.spec.in 2020-05-22 13:37:41 +02:00
README.md update git URLs (git -> https; gitea) 2022-06-18 11:39:25 +02:00
TODO-RELEASE Bump version: → 1.6.0 2023-02-07 17:15:53 +01:00
configure.ac Bump version: → 1.6.0 2023-02-07 17:15:53 +01:00
git-version-gen auto-generate a version 2011-09-07 21:28:27 +02:00


osmo-bts - Osmocom BTS Implementation

This repository contains a C-language implementation of a GSM Base Transceiver Station (BTS). It is part of the Osmocom Open Source Mobile Communications project.

This code implements Layer 2 and higher of a more or less conventional GSM BTS (Base Transceiver Station) - however, using an Abis/IP interface, rather than the old-fashioned E1/T1.

Specifically, this includes

  • BTS-side implementation of TS 08.58 (RSL) and TS 12.21 (OML)
  • BTS-side implementation of LAPDm (using libosmocore/libosmogsm)
  • A somewhat separated interface between those higher layer parts and the Layer1 interface.

Several kinds of BTS hardware are supported:

  • sysmocom sysmoBTS
  • Octasic octphy
  • Nutaq litecell 1.5
  • OpenCellular 2G (OC-2G)
  • software-defined radio based osmo-bts-trx (e.g. USRP B210, UmTRX, LimeSDR)


The official homepage of the project is https://osmocom.org/projects/osmobts/wiki

GIT Repository

You can clone from the official osmo-bts.git repository using

git clone https://gitea.osmocom.org/cellular-infrastructure/osmo-bts

There is a web interface at https://gitea.osmocom.org/cellular-infrastructure/osmo-bts


User Manuals and VTY reference manuals are [optionally] built in PDF form as part of the build process.

Pre-rendered PDF version of the current "master" can be found at User Manual as well as the VTY reference manuals

There also is an Abis reference Manual describing the OsmoBTS specific A-bis dialect.

Mailing List

Discussions related to osmo-bts are happening on the openbsc@lists.osmocom.org mailing list, please see https://lists.osmocom.org/mailman/listinfo/openbsc for subscription options and the list archive.

Please observe the Osmocom Mailing List Rules when posting.


Our coding standards are described at https://osmocom.org/projects/cellular-infrastructure/wiki/Coding_standards

We us a gerrit based patch submission/review process for managing contributions. Please see https://osmocom.org/projects/cellular-infrastructure/wiki/Gerrit for more details

The current patch queue for osmo-bts can be seen at https://gerrit.osmocom.org/#/q/project:osmo-bts+status:open

Known Limitations

As of January 2021, the following known limitations exist in this implementation:

Common Core

  • No Extended BCCH support
  • System Information limited to 1,2,2bis,2ter,2quater,3,4,5,6,9,13
  • No support of TS 08.58 MultiRate Control
  • No support of TS 08.58 Supported Codec Types
  • No support of Bter frame / ENHANCED MEASUREMENT REPORT


  • No CSD / ECSD support (not planned)
  • GSM-R frequency band supported, but no NCH/ASCI/SoLSA
  • All timeslots on one TRX have to use same training sequence (TSC)
  • No multi-TRX support yet, though hardware+L1 support stacking
  • Makes no use of 12.21 Intave Parameters and Interference Level Boundaries
  • MphConfig.CNF can be returned to the wrong callback. E.g. with Tx Power and ciphering. The dispatch should take a look at the hLayer3.


  • No support of EFR, HR voice codec (lack of PHY support?)
  • No re-transmission of PHY primitives in case of time-out
  • Link Quality / Measurement processing incomplete
  • impossible to modify encryption parameters using RSL MODE MODIFY
  • no clear indication of nominal transmit power, various power related computations are likely off
  • no OML attribute validation during bts_model_check_oml()