Cellular Network Infrastructure » cni-legacy » OpenBSC » OsmoNITB

== Howto OpenBSC with Asterisk and LCR ==

This is a short walk-through to setup OpenBSC and LCR with Asterisk.

In the end we'll have a working setup to route calls from our BTS to

the PTSN via VoIP.

=== Prerequisites ===

 * OpenBSC equipment (BTS, E1 Card)

  * We're using a Siemens BS11 microBTS and a Cologne Chips E1 PCI card

 * The latest snapshot from the !LibOmsocore repository

   * git clone git://git.osmocom.org/libosmocore.git

 * The latest snapshot from the OpenBSC repository

   * git clone git://bs11-abis.gnumonks.org/openbsc.git

 * LCR from git repository

   * git-clone git://git.misdn.org/lcr.git/

 * A working kernel for your linux system

   * Support for your E1 card

   * mISDN's l1loop module (mISDN_l1loop.ko)

   * mISDN's DSP module (mISDN_dsp.ko)

   * You can obtain a working package for Debian at https://brezn.muc.ccc.de/~codec/openbsc/

     * Supports cards from Cologne Chips and Junghanns

 * libgsm + header files (libgsm / libgsm-dev on Debian)

 * A working Asterisk setup

 * Original howto from https://brezn.muc.ccc.de/~codec/openbsc/howto.txt

Alternatively you can download a snapshot of the source codes, which have been tested: http://www.linux-call-router.de/download/ (go to the latest lcr-* subdirectory)

=== Installation ===

First of all we assume the following:

 * Layout of your working directory:

   * libosmocore/ - checkout from !LibOmsocore rep

   * openbsc/  - checkout from OpenBSC repo

   * lcr/      - checkout from LCR repo

 * Installation directories:

   * /opt/openbsc for OpenBSC

   * /opt/lcr for LCR

We need to compile and install !LibOsmocore and OpenBSC first:

{{{

$ cd libosmocore/

$ autoreconf -i

$ ./configure

$ make

$ sudo make install

$ cd ../openbsc/openbsc/

$ autoreconf --install --force

$ ./configure --prefix=/opt/openbsc

$ make

$ sudo make install

}}}

After that we're going for LCR:

{{{

$ cd ../../lcr

}}}

First of all, we have to link the source directory of OpenBSC and !LibOsmocore in the lcr-Directory:

{{{

$ ln -s ../libosmocore/ .

$ ln -s ../openbsc/openbsc/ .

}}}

Now we can go on with compiling LCR. Unfortunately, due to changes in OpenBSC, we have to install a patch

for LCR, until the programmer of LCR will include this patch in the current version.

The patch is attached to this document.

{{{

$ sh autogen.sh

$ git-apply --verbose lcrOpenBSC.patch

$ ./configure --prefix=/opt/lcr --with-asterisk --with-gsm-bs

$ make

$ sudo make install

}}}

and now we can copy the module into the modules' directory of Asterisk:

{{{

$ sudo cp chan_lcr.so /usr/lib/asterisk/modules/

}}}

=== LCR configuration ===

'''1. gsm in options.conf'''[[BR]]

The gsm option in /usr/local/lcr/options.conf needs to be activated. This can be

simply done by adding 'gsm' as a single line to the file.[[BR]]

Because it is a good idea to start Asterisk without root's privileges, we want to add these lines, too:

{{{

socketuser asterisk

socketgroup asterisk

}}}

'''2. GSM interface in interface.conf'''[[BR]]

/usr/local/lcr/interface.conf holds an example for a GSM interface. Remove the comments

and use the example as is.

'''3. gsm.conf'''[[BR]]

Enable the debugging option in /usr/local/lcr/gsm.conf. We also need 2 mISDN loopback interfaces.

Create them with

{{{

  $ sudo modprobe mISDN_l1loop pri=1 nchannel=30

}}}

You can check for the interfaces names with the misdn_info tool. All the default settings

should work in a BS11 setup.

You have just to give a value for 'config' and 'hlr', with the full path of your OpenBSC configuration

file and HLR-!DataBase.

'''4. Routing'''[[BR]]

We route all our calls to to asterisk at the moment, as we only have outgoing connectivity via IAX/SIP in our setup.

{{{

[main]

interface=GSM                           : remote application=asterisk context=btsctrl

}}}

Calls will go to the context btsctrl in Asterisk.

=== Asterisk configuration ===

Our setup connects to an external Asterisk via SIP - as we don't have a second ISDN interface.

chan_lcr for Asterisk comes with LCR (compiled with --with-asterisk). You only need to load the

channel driver and maybe check the permissions of the LCR socket (/var/tmp/lcr.socket) - Asterisk

on Debian uses a Set UID wrapper.

To load chan_lcr automagically on startup add the following to your modules.conf:

{{{

load => chan_lcr.so

}}}

We've created an exclusive context in extensions.conf for OpenBSC/LCR:

{{{

[btsctrl]

exten => _02X.,1,GotoIf($[${CALLERID(name)} != ""]?4)

exten => _02X.,2,Set(CALLIDORIG=${CALLERID(num)})

exten => _02X.,3,Set(CALLERID(num)=02${CALLIDORIG})

exten => _02X.,4,Dial(LCR/GSM/${EXTEN:2},120)

}}}

=== Running OpenBSC/LCR and Asterisk ===

Now we're ready to start with our GSM network.

Boot up the BS11 and start LCR with

{{{

$ sudo /opt/lcr/sbin/lcr start

}}}

You can also use 'fork' instead of 'start' to run LCR in daemon mode,

but I'd rather go with fork AFTER you made you first successful call. (;

Now start Asterisk. It should connect to LCR right after startup. You

can check this by running

{{{

$ sudo /opt/lcr/bin/lcradmin state

}}}

The UI should show

{{{

Remote: asterisk

}}}

in the upper left part.

Connect your phone and make your call(s).

=== Troubleshooting ===

==== Phones unable to connect ====

On the first run I had some problems with connecting my phones as

the registration just timed out. I fixed this by starting over with a fresh HLR.

==== The call routing fails (somewhere) ====

Most problems occured within Asterisk for me as neither IAX2 or SIP was working.

This was just some kind of problem within the configuration.

I can provide a working dialplan and SIP configuration if you need it.

==== Can't see the network ====

This was either related to the phone (a restart fixed it) or the BS11. After the

first start I sometimes had to hardreset (as in reboot) the BS11.