Modeling V2X Communications across Multiple Road Levels

Multi-level traffic scenarios such as highway stack interchanges or parking garages require special consideration when it comes to the analysis of Vehicular Ad-Hoc Networks (VANETs). Near-vertical signal paths and obstructions by floor slabs can have a negative influence on the reception conditions. Nevertheless, state-of-the-art simulators are not able to represent these effects assuming a planar environment only. In this paper, we discuss how the consideration of multi-level communications can be accomplished in packet-based VANET simulation. We create a 3D road network using Digital Surface Models (DSMs) and detect floor obstructions by performing polygon-segment intersection checks. The resulting losses are estimated based on floor attenuation factors. Using the described extensions we simulate a sample scenario featuring a complex stack interchange. The results indicate that a significant proportion of packets is influenced by floors and antenna gains vary widely due to changing elevation angles. As a consequence, the number of reachable neighbors is significantly reduced as compared to the results of a conventional 2D simulation run, demonstrating the need for the consideration of multi-level communications.