Millimeter-wave V2X channel measurements in urban environments

Vehicle-to-everything (V2X) communications is an important part of future driver assistance and traffic control systems that will reduce accidents and congestion. The millimeter-wave (mmWave) band shows great promise to enable the high-data-rate links that are required or at least beneficial for such systems. To design such systems, we first need a detailed understanding of the vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2X) propatation channels. This paper provides a systematic account of a series of measurement campaigns for such channels, conducted by the four research institutions of the authors over the past year. After a description of the similarities and differences of the channel sounders used in the campaigns, a description of the measurements in two European and one American city is given, and the scenarios of convoy, opposite-lane passing, and overtaking, are described. This is then followed by key results, presenting both sample results of power delay profiles and delay Doppler (or angular) spectra, as well as the statistical description such as delay spread and size of stationarity region. We also discuss the availability of spatial diversity in V2I connections and the correlation of the channels between different frequency bands.