Step 5: Running Your First Experiment

Now that you've set up your lab and understood the legal and ethical considerations, it's time to run your first GSM/GPRS experiment. Follow these steps carefully.

1. Set up your LimeSDR to listen to a GSM frequency:
   • Use the ARFCN calculator to determine the frequency for your region
   • Configure your LimeSDR using the command: grgsm_livemon -f <frequency_in_Hz>
2. Use Kalibrate-RTL to identify active GSM channels:
   • Run the command: kal -s GSM900 (adjust for your region if necessary)
   • Note down the frequencies of the strongest signals
3. Capture and analyze GSM broadcast channels using GR-GSM:
   • Start the capture: grgsm_scanner -b GSM900 -v
   • Observe the output for information about nearby base stations
4. Attempt to decode GSM frames:
   • Use GR-GSM's grgsm_decode: grgsm_decode -f <frequency_in_Hz> -c <channel_type>
   • Analyze the decoded information, focusing on unencrypted broadcast data
5. Document your findings and observations:
   • Record the frequencies, signal strengths, and any decoded information
   • Note any challenges or unexpected results encountered during the experiment
   • Reflect on potential security implications of your findings