Bidirectional CSI measurement for V2X Communications

To test the reciprocity of V2X channel, bidirectional channel state information (CSI) measurement is conducted between Alice (RSU) and Bob (OBU) through PSSCH signal. We utilized two USRP X310 SDR platforms equipped with the CBX daughter board as Alice and Bob. Despite the designed fast USRP transceiver switching, there is a signal transmission delay of approximately 0.3 ms, resulting in a gap of about 4 to 5 symbols in the PSSCH subframe actually received by Alice and Bob.

The USRP X310 was configured with a sampling rate of 30.72 MSample/s and the carrier frequency of the V2X signal was set at 5.91 GHz. We incorporated an additional amplifier to amplify the transmitted and received signals for the long-distance outdoor environment.

Our experimental environment was set up on the internal roads of the Purple Mountain Laboratory, Nanjing, China. Alice (RSU) was positioned at the side of the road, while Bob (OBU) was installed in the vehicle. The vehicle traveled at various speeds along the road. Due to the speed limits, we collected CSI obtained at speeds of 40km/h, 30km/h, 20km/h, 10km/h, 5km/h, and stationary, resulting in a dataset with 23, 137, 45, 28, 15, and 96 CSI groups, respectively. The received PSSCH signals and estimated CSIs can be found in this dataset.