Impact of the Communication Direction on the Reliability of Vehicle-to-Everything (V2X) Communications

Communications between vehicles and their surroundings can improve the safety of road users. Other vehicles can be identified via radio broadcast messages and the safety in non-line-of-sight situations can be improved. One emerging technology is Cellular Vehicle-to-Everything (C-V2X) communications, which enables various direct communications applications, mainly safety use cases. Broadcast messages are received by all road users in the vicinity, while signal propagation determines the maximum distance over which messages can be decoded. Field tests often use test antennas, set up on the vehicles' roof to test the communications link. While this is suitable for testing general use cases, in a real-life deployment of the technology, the antenna placement will have to comply with design aspects. In this paper we have conducted different field tests with an antenna prototype integrated into the existing shark fin housing. We measured the achievable packet error rates (PER) for different distances and communication directions. The influence of the car on the transmission of radio waves asymmetrically affects the propagation. The maximum distance for reliable communication in C- V2X is influenced by characteristics and placement of the antenna and the shape of the vehicle. Additionally, we could observe a significant impact by panorama glass roofs. Antenna placement will, therefore, be an important factor for the capability of V2X communications.