GEO Mobile Radio

This is the homepage of the Osmocom sub-project GEO Mobile Radio.

It is collecting information and software related to the ETSI GEO Mobile Radio specification and its practical implementations like the Thuraya satellite phone network

GEO Mobile Radio is a set of specifications describing a satellite based mobile phone network.

Osmo-GMR now implements voice codec decoder

GMR-1 uses an undocumented codec in the AMBE family and as such Osmo-GMR didn't have any implementation of it and converting TCH3 frames to actual audio wasn't possible.

Now, after quite a bit of effort to figure things out, I'm pleased to announce that an open-source decoder is available. It's not perfect and doesn't match the quality of the of ...

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GMR-1 dissection merged in Wireshark mainline

All the current patches that were pending in the sylvain/gmr branch of our osmocom Wireshark tree have now been merged into the official trunk. Thanks to the Wireshark folks for reviewing them and merging them quickly.

What's supported :

  • BCCH partial support (segment 1/2A/3A fully dissected)
  • CCCH partial support (all messages ever seen o ...

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Osmo-GMR now supports A5-GMR-1 cipher

Osmo-GMR now has support for cipher stream generation. This allows to see past the CIPHER MODE COMMAND in the examples (I will put the key along with the demo files soon).

You can see the actual code in the git :

The algorithm was re-implemented by the O ...

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Lecture on cryptoanalysis of GMR-1 and GMR-2 ciphers

On February 2nd, researchers Be­ne­dikt Dries­sen und Ralf Hund of the University of Bochum will report on their analysis of the GMR-1 and GMR-2 ciphers.

According to the abstract, the cipher used in GMR-1 and thus Thuraya is more or less the same than GSM's A5/2, an ...

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Video and Slides of Sylvain's 28C3 GMR talk

OsmocomGMR main author Sylvain Munaut has given a presentation about the GMR-1 standard and the OsmocomGMR software at the 2011 annual CCC conference (28C3).

It is a great introduction into the topic, and a recommended read/view for everyone wanting to experiment with our OsmocomGMR software.

The slides are available from ...

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Radio aspects

It uses the L-band frequencies 1634 to 1656 MHz (earth to space) and 1532.5 to 1554.5 MHz (space to earth) for communication between mobile phones and the respective satellites. The polarization is circular (left) and the modulation is pi/4 QPSK, using a channel spacing of 31.25 kHz




Last modified 10 months ago Last modified on Dec 3, 2013, 11:03:56 AM