As some of the readers may already know, a couple of Osmocom developers have been working on a new sub-project: OsmocomGMR.
The primary goal of this project is to provide a reusable and clean implementation of the various layers of GMR-1.
What is GMR-1 ? Well, it stands for "GEO Mobile Radio" and it's a set of specifications describing a satellite based mobile phone network heavily inspired from GSM. One of the major commercial operators of GMR-1 technology is "Thuraya", providing coverage over Europe/Africa/Asia/Australia?.
So far the implementation focused on the lowest layers:
- Physical layer with FCCH sync and demodulation support for pi4-CBPSK and pi4-CQPSK bursts.
- Channel coding layer (scrambling/puncturing/convolutional coding/crc/interleaving/...)
And some ancillary tools to exploit those:
- A good capture tool to listen to particular ARFCN and channelize them properly
- Wireshark support (BCCH only so far)
The first 'demo application' using all of the above provides functionalities similar to what airprobe is for GSM: An air interface protocol analyzer that goes all the way from capturing data off-the-air to sending packets to wireshark for analysis. Limited to BCCH only currently but this will evolve with time.
Development was mainly done by Sylvain Munaut, with help from Dimitri Stolnikov (early signal captures and his great capture tool), Harald Welte (initiating the project) and Steve Markgraf (testing different setup and antenna ideas).