Dependability of Directional Millimeter Wave Vehicle-to-Infrastructure Communications

Vehicle-to-infrastructure (V2I) communication is an important enabler for intelligent transportation and rail traffic management systems, which are expected to provide significant road traffic safety and efficiency enhancements. Such systems require a level of dependability of the wireless communication link that can be hard to support by state-of-the-art technologies. Transmissions in the millimeter wave (mmWave) band have the potential to provide sufficient bandwidth to support not only traffic management services, but additionally also web and entertainment applications for car and train passengers. mmWave transmissions require directional antennas at the transmitter and/or receiver to compensate for the significant pathloss and to achieve a practically acceptable maximum coupling loss. Such directional communication is feasible in V2I scenarios, because the mobility of users is confined to streets and roads. In this article, we discuss the dependability of directional mmWave V2I communications under two-ray fading conditions. We review methods for enhancing the dependability of the communication link by exploiting macroscopic spatial diversity and by mitigating interference from other transmitters. We furthermore provide guidelines for a dependable system design under two-ray fading and identify open research questions in this context.