Due to lack of inexpensive hardware and complex signaling
present, remarkable attempts were not carried out for acquisition
and decoding of downlink GSM traffic. Nonetheless, the
recent existence of open-source tools viz SDR, GNU Radio,
Airprobe and Wireshark has changed the outlook remarkably.
Several versatile and inexpensive SDRs have become prominent
in investigating the Radio Frequency (RF) spectrum.
Some of these are RTL-SDR, USRP, FUNcube Dongle etc.
Instead of USRP, RTL-SDR is used to further investigate the
GSM downlink traffic.