LTE-Tracker is open source software that continuously searchers for LTE cells on a particular frequency and then tracks, in realtime, all found cells. With the addition of a GPS receiver, this program can be used to obtain basic cellular coverage maps.
Download source code and build instructions.
LTE-Tracker -f frequency [optional_parameters] Basic options -h --help print this help screen -v --verbose increase status messages from program -b --brief reduce status messages from program -i --device-index N specify which attached RTLSDR dongle to use Frequency options: -f --freq fc frequency where cells are located Dongle LO correction options: -p --ppm ppm crystal remaining PPM error -c --correction c crystal correction factor
Launch the tracker to track all LTE cells on 739 MHz:
LTE-Tracker -f 739e6
After a short initial frequency calibration, the program enters its main display screen which provides a list, updated in realtime, of all the LTE cells it is tracking. The program tracks each cell's SNR, frequency offset, time offset, and MIB decoding status.
Furthermore, while all the cells are being tracked, a separate parallel searcher thread is searching for new cells to be added to the tracked cell list. As the receiver is moved around among different basestation coverage areas, it is normal to see new cells pop up and weak cells removed from the display.
Above is an example display where 5 cells are being tracked. All cells display their time offset (relative to the dongle's frame timing), the SNR of all the antenna ports, and the SNR of the synchronization channel. The residual frequency offset of the dongle is displayed at the bottom of the screen.
The up/down arrow keys can be used to highlight different ports and pressing 'enter' will display the transfer function of the wireless channel from that port on the basestation to the dongle's antenna.
The screen capture above shows the instantaneous transfer function of port 0 of cell 271. This is a magnitude plot and a phase plot is also available by pressing 'enter' one more time.
While the transfer function is displayed, pressing up/down arrow will switch to displaying the transfer function of different ports.
At any time, press Esc to return to the main menu or 'q' to exit the program.
To view further options (refresh rate, buffer status, etc.), press 'h'.
A dual core i7-2640 cpu can track approximately 4 cells with two antenna ports per cell. If the cell trackers fall too far behind, they will automatically drop some data and a message will be printed on the main screen.
LTE-Tracker accepts the same --correction and --ppm options that LTE Cell Scanner
did. Please see the documentation for LTE Cell Scanner for details on how to use these options. Proper use of these options will significantly speed up the initial frequency calibration, but will have no effect on the realtime functioning of this program.
The time offset of all the tracked cells drifts very slowly (about 0.1 time offset samples every second). For perfect tracking it is necessary to know the exact ratio between the sampling rate of the dongle's A/D and the dongle's LO frequency. Crystal frequency offsets will not affect this ratio since both of these frequencies are derived from the same crystal reference. However, because of finite word lengths in the divisors built into the chips, the actual ratio is not simply fs/fc.
See also: LTE Cell Scanner
Video of LTE-Tracker on a drivetest going in and out of the coverage area of several basestations.