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 OpenBSC repository * svn co http://bs11-abis.gnumonks.org/svn/trunk/openbsc * We've got Revision 513 * LCR from git repository * git-clone git://git.misdn.org/git/lcr.git/ * A working kernel for your linux system * Support for your E1 card * mISDN's l1loop module (mISDN_l1loop.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

=== Installation ===

First of all we assume the following: * Layout of your working directory: * 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 OpenBSC first: {{{
$ cd openbsc/
$ sh ../lcr/autogen.sh
$ ./configure --prefix=/opt/openbsc
$ make
$ sudo make install
}}}

After that we're going for LCR. But we had to patch 2 files to make it work: {{{
gsm@bts-ctrl:~/cdc/openbsc$ cd ../lcr
}}}

Edit Makefile.am and change {{{
GSM_LIB = /usr/local/lib/libgsm.a /usr/local/lib/libbsc.a /usr/local/lib/libvty.a -ldbi -lcrypt
}}}
to {{{
GSM_LIB = /usr/lib/libgsm.a /usr/local/lib/libbsc.a /usr/local/lib/libvty.a -ldbi -lcrypt
}}}

And patch gsm_audio.c on line 13 from {{{
#include "/usr/local/include/gsm.h"
}}}
to {{{
#include "/usr/include/gsm.h"
}}}

Now we can go on with compiling LCR: {{{
$ sh autogen.sh
$ ./configure --prefix=/opt/lcr --with-asterisk --with-gsm
$ make
$ sudo make install
}}}

=== LCR configuration ===
'''1. gsm in options.conf'''
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.

'''2. GSM interface in interface.conf'''
/usr/local/lcr/interface.conf holds an example for a GSM interface. Remove the comments
and use the example as is.

'''3. gsm.conf'''
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.

'''4. Routing'''
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.