Over a year ago we wrote a tutorial on how to analyze GSM cellular phone signals using a RTL-SDR, a Linux computer with GNU Radio, Wireshark and a GSM decoder called Airprobe. With this combination it is possible to easily decode GSM system messages. Setting up Airprobe is can be difficult as it is unmaintained and incompatible with the new version of GNU Radio without patches.
Now a new software package called gr-gsm has been released on GitHub which seems to be a newer and improved version of Airprobe. The gr-gsm software is also much easier to install, uses the newer GNU Radio 3.7 and seems to decode the system data with much less trouble than Airprobe did. We will soon update our tutorial to use gr-gsm, but the instructions on the GitHub are already quite good. The author of gr-gsm also appears to be actively adding new features to the software as well. The video below shows gr-gsm in action.