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laforge, 02/21/2016 07:55 AM

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{{>toc}}
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*OpenBSC* is the current name for a software project that started with the name bs11-abis.
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h2. What is [[OpenBSC]]
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It started as a [[BSC]] (Base Station Controller) side implementation of the A-bis protocol, as implemented in the GSM Technical Specification 08.5x and 12.21.  It can run either
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* as [[osmobsc:|OsmoBSC]], exposing an A interface towards an external MSC, or 
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* as [[osmonitb:|OsmoNITB]] (Network In The Box), whert implements a minimal subset of the [[BSC]], [[MSC]]. [[SMSC]] and [[HLR]]. 
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The goal of the project is to
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* provide a basis for experimentation and security research with GSM from the network side
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* provide a zero-cost alternative for hands-on experience with GSM systems in education and training
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* learn more about GSM networks on a lower level, particularly the practical aspects with real-world equipment
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* provide a stable/reliable network-side GSM implementation for small networks that don't need millions of subscribers or 99.99999% availability
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h2. Requirements
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While [[OpenBSC]] is mainly written in portable C99 code, there are is one non-portable part: The E1 input driver requires a Linux kernel with mISDN support and an [[E1]] interface card compatible with [[mISDN]].  You only need this if you have an E1 based BTS!
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To operate a GSM network, you not only need [[OpenBSC]] but of course also some kind of GSM [[BTS]].  The only currently tested configurations are with a
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* sysmocom "sysmoBTS":http://www.sysmocom.de/products/sysmobts (using [[OsmoBTS]])
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* "fairwaves":https://fairwaves.co [[UmSITE]] and [[UmDESK]] (using [[OsmoBTS]])
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* Siemens [[BS11|BS-11]] microBTS
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* [[nanoBTS|ipaccess nanoBTS]]
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IF you feel geeky, you could also build a BTS yourself, using full-duplex capable SDR (Software Defined Radio) hardware and a usual PC with [[OsmoTRX]] and [[OsmoBTS]] software. The software installation is described at the [[network_from_scratch]] page.
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h2. Configurations / Modes
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h3. [[OpenBSC]] network-in-the-box (NITB) mode
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This is _very different_ from a classic GSM network in which the BSC is only one minor element in the distributed network consisting
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of many different elements like BSC, MSC, HLR, etc.  Nonetheless, it is the _classic_ mode to operate [[OpenBSC]].  In this configuration, you only need (at least) one BTS and [[OpenBSC]].  There is no need for a MSC, HLR, VLR, AuC or any other traditional GSM network components.
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{{graphviz_link()
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digraph G {
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rankdir=LR 
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bs11->OpenBSC    [ label="Abis/E1" ]
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nanobts->OpenBSC [ label="Abis/IP" ]
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sysmobts->OpenBSC [ label="Abis/IP" ]
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umsite->OpenBSC [ label="Abis/IP" ]
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osmobts->OpenBSC [ label="Abis/IP" ]
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bs11    [ label = "Siemens\nBS-11" ]
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nanobts [ label = "ip.access\nnanoBTS" ]
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sysmobts [ label = "sysmocom\nsysmoBTS" ]
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umsite [ label = "fairwaves\nUmSITE" ]
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osmobts [ label = "osmoBTS +\nSDR hardware" ]
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OpenBSC [ label = "OpenBSC\nNITB" ]
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}
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}}
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In order to use the NITB mode, you will use the [[osmo-nitb]] program.
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h4. Interconnecting [[OpenBSC]] with an ISDN or SIP PBX
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If you want to connect calls outside of your [[OpenBSC]] based GSM network, you can have "Linux Call Router":http://isdn.eversberg.eu/ and [[OpenBSC]]
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work together to create a setup like this:
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{{graphviz_link()
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digraph G {
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    rankdir=LR 
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    bs11->OpenBSC    [ label="Abis/E1" ]
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    nanobts->OpenBSC [ label="Abis/IP" ]
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    sysmobts->OpenBSC [ label="Abis/IP" ]
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    umsite->OpenBSC [ label="Abis/IP" ]
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    osmobts->OpenBSC [ label="Abis/IP" ]
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    OpenBSC->LCR     [ label="MNCC Socket" ]
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    LCR->ISDN        [ label="E1/PRI/BRI" ]
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    LCR->SIP         [ label="SIP/RTP" ]
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    bs11     [ label = "Siemens\nBS-11" ]
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    nanobts  [ label = "ip.access\nnanoBTS" ]
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    sysmobts [ label = "sysmocom\nsysmoBTS" ]
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    umsite   [ label = "fairwaves\nUmSITE" ]
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    osmobts  [ label = "OsmoBTS +\nSDR hardware" ]
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    OpenBSC  [ label = "OpenBSC\nNITB" ]
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}
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}}
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h3. [[OpenBSC]] in BSC-only mode
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If you want to use [[OpenBSC]] as a classic GSM BSC, you can do that as well.  However, you will need all other parts of the GSM
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network and a MSC that can provide an A-over-IP interface using SCCP-lite
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{{graphviz_link()
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digraph G {
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    rankdir=LR;
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    bs11->OpenBSC    [ label="Abis/E1" ];
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    nanobts->OpenBSC [ label="Abis/IP" ];
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    sysmobts->OpenBSC [ label="Abis/IP" ]
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    umsite->OpenBSC [ label="Abis/IP" ];
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    osmobts->OpenBSC [ label="Abis/IP" ];
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    OpenBSC->MSC     [ label="A/SCCP-Lite/IP" ];
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    subgraph core {
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        MSC->VLR;
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        MSC->HLR;
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        HLR->AUC;
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        label = "not included";
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        color = blue;
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    }
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    bs11    [ label = "Siemens\nBS-11" ];
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    nanobts [ label = "ip.access\nnanoBTS" ];
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    sysmobts [ label = "sysmocom\nsysmoBTS" ]
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    umsite [ label = "fairwaves\nUmSITE" ];
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    OpenBSC [ label = "OpenBSC\nosmo-bsc" ];
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    osmobts [ label = "OsmoBTS +\nSDR hardware" ]
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}
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}}
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In order to use the BSC-only mode, you will use the [[osmo-bsc]] program.
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h2. Source code
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h3. Releases
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The [[OpenBSC]] project does not publish official releases.  Users are recommended to use the latest git master.
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h3. Repository
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You can check out the source code via
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<pre>
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git clone git://git.osmocom.org/openbsc.git
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</code></pre>
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or browse it at http://cgit.osmocom.org/cgit/openbsc/
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h2. Mailing list
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There's a *developer* mailing list called openbsc@lists.osmocom.org
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Subscription is available at "h2. IRC (Internet Relay Chat)
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We have an IRC channel where some developers and users hang out.  You can find it at:
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irc.freenode.net/#osmocom
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h2. Project status
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h3. Things that work
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* Housekeeping
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** [[OML"httplistsosmocomorgmailmanlistinfoopenbsc]] Initialization of the BTS
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** Support for frequency hopping channels on BTS equipment that supports it (like BS-11)
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** [[RSL]] bringup, channel allocation, Channel required / Immediate Assign
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* Mobility Management
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** Very simplistic [[HLR]] implemented as sqlite database
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** Non-secure Authorization using [[IMEI]]/[[IMSI]] and regular SIM cards.
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** Authentication using COMP128v1 if you have SIM cards with known Ki
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** [[IMEI]]/[[IMSI]] skimming of all phones that try to register with [[OpenBSC]]
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** Transmission of MM INFO packets with operator name and local time / timezone
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** paging of mobiles that are registered to the BTS
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** keeping track of which location area a phone has last performed location updating
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** in-call handover between multiple cells inside one BSC
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* SMS Support
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** [[SMS]] reception and [[SMS]] sending, including routing between subscribers
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** Sending of SMS from [[OpenBSC]] command line
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** Sending and receiving of SMS through SMPP
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* Voice Call Support
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** MO (Mobile Originated) and MT (Mobile Terminated) calls
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** TCH/F support with FR and EFR codec
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** TCH/H support with HR and AMR codec
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* Cell Broadcast Support
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* USSD (only for built-in USSD commands, no external interface)
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* E1 support
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** demultiplex of the four 16k sub-channels with voice data contained in one [[E1]] timeslot
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** support for multiple [[TRX]] in one [[BTS]]
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** support for multiple [[BTS]] connected to the same E1 link (multi-loop configuration)
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* Abis/IP support
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** Abis/IP protocol with IPA multiplex for [[osmo-bts]] and [[nanoBTS]]
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** RTP gateway to interoperate E1 based BTS and IP based BTS on one BSC and switch calls between them
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* GPRS/EDGE support
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** configuring the OML objects/attributes for GPRS and EDGE
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** setting SYSTEM INFORMATION 13 via RSL
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** configurable RAID/CGI/NSVCI/NSEI/BVCI
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** have the PCU in the BTS interoperate a SGSN with Gb (NS-over-IP) interface
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** beta state [[OsmoSGSN]] included along [[OpenBSC]]
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h3. Things that are implemented but don't work yet or aren't tested yet
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* dynamic PDCH / TCH switching
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h3. Things that are not implemented
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* Any type of transcoding of voice data (we leave this to the external MNCC handler / media gateway)
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* [[CSD]] calls
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* emergency call handling (works in [[osmo-bsc]], but not in [[osmo-nitb]])
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h2. Authors
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[[OpenBSC]] was mainly developed by "Harald Welte":http://laforge.gnumonks.org/ and Holger Freyther. 
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Contributions (in no specific order) by Dieter Spaar, Stefan Schmidt, Daniel Willmann, Jan Luebbe, Thomas Seiler, Andreas Eversberg, Sylvain Munaut, Ciaby, Alexander Chemeris, Neels Hofmeyr, Nico Golde, Pablo Neira.
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Special thanks to Dieter Spaar for [[BS11-Init]] and tons of feedback and comments, without which we would not have been able to make progress as quickly as we did.
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