Automotive radar radiations as signals of opportunity for millimeter wave V2I links

Millimeter wave (mmWave) vehicular channels are highly dynamic, and the communication link needs to be reconfigured frequently. In this work, we propose to use a passive radar receiver at the roadside unit to reduce the training overhead of establishing an mmWave communication link. Specifically, the passive radar will tap the transmissions from the automotive radars of the vehicles on the road. The spatial covariance of the received radar signals will be estimated and used to establish the communication link. We propose a simplified radar receiver that does not require the transmitted waveform as a reference. We also present simulation results based on ray-tracing data. The results show that the radar-assisted strategy significantly reduces the training overhead, being particularly useful in non-line-of-sight scenarios.