5-GHz Vehicle-to-Vehicle Channel Characterization for Example Overpass Channels

The overpass is a special over-road structure for vehicular travel, constituting one type of roadway intersection. Real-time communications between on-and under-overpass vehicles can contribute to effective vehicle-to-vehicle (V2V) communications, including, for example, optimal route selection and overpass accident warning messaging. Ensuring effective communication requires a quantitative characterization of the overpass propagation channel. In this paper, we provide measurement and analytical results for V2V propagation path loss and root-mean-square delay spread, and from these results, we develop tapped-delay line channel models that are applicable to the 5-GHz band for two example overpasses. These two example overpasses are termed i) one-lane metal-bottom overpass and ii) two-lane metal-bottom overpass. Due to the unique structure of the overpasses, we divide the radio propagation space around the overpass into four different areas: a two-ray area, a short-term partial-shadowing area, a (full) shadowing area, and a long-term partial-shadowing area. In the two-ray area, a line-of-sight (LOS) path and a ground-reflected path are the dominant propagation mechanisms, whereas in the other areas, the overpass body (floor, walls, and columns) attenuates the LOS signal. The accuracy of our measurement results and the developed channel model are verified by a geometry-based stochastic channel modeling approach, in which the height dimension is first introduced to characterize the diffraction phenomenon in V2V communication. The actual measurement and simulation results show good consistency.