[srslte-users] C-V2X sidelink without GPSDO

[sebi at faho.rwth-aachen.de]

Hi all,

has anyone tried using the C-V2X sidelink without a GPSDO on a USRP B200/B210 by directly applying a PPS signal from an external GPS receiver?

I followed the application note at [1] but am unable to receive packets from a commercial C-V2X modem. The I/Q-Plots look very noisy and no constellation pattern can be identified. Do I need both a PPS signal and a 10 MHz reference signal? Unfortunately, my GPS receiver does not have a 10 MHz reference clock output. I even tried adjusting the code in [2] in order to set the USRP time to the GPS synchronized system time in the absence of a GPSDO but to no avail. Can I somehow check the srsLTE synchronization status?

Thanks in advance for your help!

Best regards,
Sebastian

[1] https://docs.srslte.com/en/latest/app_notes/source/cv2x/source/index.html
[2] https://github.com/srsLTE/srsLTE/blob/master/lib/src/phy/rf/rf_uhd_imp.cc