OsmocomGMR

h1. Getting Started

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h2. Prerequisites

You must first prepare your system by installing the required development packages.

For debian/ubuntu:

<pre>

apt-get install build-essential libtool autoconf git-core pkg-config libfftw3-dev talloc-dev libpcsclite-dev

</pre>

If you want to capture samples off the air, you'll also need gnuradio and uhd. Installing those is outside the scope of this page, refer to the GNURadio / Ettus documentation.

h2. Compiling the software

h3. libosmocore

You obviously need to install our main utility library:

<pre>

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

cd libosmocore

autoreconf -i -f

./configure

make

sudo make install

cd ..

</pre>

h3. libosmo-dsp

Then you need to install our new Software Defined Radio helper library:

<pre>

git clone git://git.osmocom.org/libosmo-dsp

cd libosmo-dsp

autoreconf -i -f

./configure

make

sudo make install

cd ..

</pre>

h3. osmo-gmr

And finally compile the main Osmocom GMR software stack:

<pre>

git clone git://git.osmocom.org/osmo-gmr

cd osmo-gmr

autoreconf -i -f

./configure

make

cd ..

</pre>

h3. Capture tool

The current version of the capture tool is not integrated with the main autotool process yet and has to be built separately:

<pre>

cd osmo-gmr/utils/gmr_multi_rx

make TARGET=uhd

cd ../../..

</pre>

There are several possible targets depending on your hardware:

* usrp: To use the libusrp drivers for the USRP1 hardware (gnuradio has to be compiled with gr-usrp enabled)

* uhd: For using any ettus hardware (see "UHD Wiki":http://code.ettus.com/redmine/ettus/projects/uhd/wiki for build instructions)

* fcd: To use the specific Fun Cube Dongle Pro drivers ("gr-fcd":https://github.com/csete/gr-fcd has to be installed)

h3. Wireshark

<pre>

git clone git://git.osmocom.org/wireshark

cd wireshark

git checkout sylvain/gmr

./autogen.sh

./configure

make

sudo make install

cd ..

</pre>

h2. Running the software

h3. Capturing samples

You need to capture samples off the air and of course "there's an app for that".

For a first try the easier is to lookup a beam that match your geographic area by looking at "Thuraya_Beams":http://gmr.osmocom.org/trac/wiki/Thuraya_Beams and the associated map.

This example will capture ARFCN 941 and 942 for 10 second using the 'B' side daughterboard and the RX2 input :

<pre>

./gmr_multi_rx --gmr1-dl 941 942 -a RX2 -S B:0 -T 10

</pre>

The given channels will be frequency shifted, filtered, resampled and finally written to files with the given --prefix (/tmp/ by default). The file names will be autogenerated based on ARFCN and final sample rate.

A few notes concerning multi ARFCN capture:

* All the ARFCN need to fit within the bandwidth of your device (so you can't get ARFCN1 and 1007 at once for example)

* It can be pretty CPU intensive depending on the # of ARFCNs and how much they're spaced.

h4. "FunCube Dongle":http://tetra.osmocom.org/trac/wiki/Funcube_Dongle Build

<pre>

./gmr_multi_rx --gain 30 --gmr1-dl 941 942 943

</pre>

* when receiving 3 consecutive channels, the middle channel will be distorted by the center peak caused by dc offset / iq imbalance

* when receiving 2 channels, each channel will have a small contribution of the center peak on the right or left side.

* best results may be achieved when receiving only one channel.

h4. Default USRP clock

<pre>

./gmr_multi_rx --gain 45 --gmr1-dl 941 942 943

</pre>

Only 75% of the master output rate will be used on the usrp/uhd builds, because of insufficient attenuation of the FPGA channelizer at filter edges.

h4. Modified USRP clocks

* use --mcr to tell custom fpga frequency in Hz

<pre>

./gmr_multi_rx --gain 45 --gmr1-dl 941 942 943 --mcr 52e6

</pre>

* mcr of 59.904e6 Hz is gmr1-friendly, thus allowing to save on interpolation stage

<pre>

./gmr_multi_rx --gain 45 --gmr1-dl 941 942 943 --mcr 59.904e6

</pre>

h4. RTL SDR dongles

The attached gnuradio flowgraph has been tested and works well for ARFCN 1007. A decent LNA might be required to be able to receive Thuraya signals. It is essential to adjust "corr_ppm" according to your dongle's frequency error. For recording, set the "arfcn" value and enable the file sink before launching the flowgraph.

h3. Analyzing them

* Launch wireshark and listen to the lo interface

** Make sure to use the proper version (see above)

** Also make sure you have the rights to capture on lo

* View packets in wireshark using gmr1_bcch.* filters