RTL-SDR is a cost-effective hardware, with compatible flow
graphs for USRP. This is of extreme importance since GSM
Technology is constantly going forward from year to year.
The publicly available specifications of GSM are verified to
comply with the extremely closed GSM industry. With some
affordable tools like GNU Radio and Wireshark available,
practical research of the GSM industry has become viable.
This gives subscribers the ability to verify the workings of
GSM, e.g. to check whether, and what kind of, encryption is
being used to protect their conversations. The key feature of
GSM is on-the-air-privacy. During this project, it was verified
that observed cell towers used both frequency hopping and
encryption. Airprobe limits itself to the downlink side of the
air interface - cell tower to mobile phone. The bandwidth for
specific network providers was reckoned during the project,
along with the IMSI number, ARFCN channel in use and the
Location Area Identification (LAI) of the mobile device of the
respective network. The captured cell ID too was verified from
the designated test phone device.