Reliable multi-RAT connectivity in urban V2X architectures: An experimental campaign

The future of smart cities relies on the quick and reliable exchange of contextual information between devices. Deploying access points at the edge of the network significantly reduces the propagation distance of sidelink messages, resulting in very low latencies. However, urban environments pose significant challenges, as numerous obstacles can block direct links between devices and their intended destinations. While the typical fallback solution is cellular connectivity, the difference in performance is substantial. To address this, the present work puts forward solutions for improved reliability in multiple Radio Access Technology urban vehicular architectures. On the one hand, we address situations where multiple links are available, by establishing a make-before-break vertical handover scheme for optimized radio interface selection, monitoring the performance of received packets. On the other hand, we also reflect on the situations where communication ranges are shortened, and thus propose a method where packets sent via Cellular-Vehicle-to-Everything (C-V2X) sidelink are relayed. Here, the initial message is received by an intermediary with better connectivity to the target access point and then retransmitted from this improved position. These solutions have yet to be studied in real-life urban testbeds. We thus present experimental campaigns aimed at exploring the performance and reliability of such communications in urban V2X architectures, exploiting C-V2X, 5G, autonomous vehicles and state-of-the-art hardware. We study multiple scenarios, extending or shortening line-of-sight situations to analyze coverage and performance. Performance analysis of our vertical handover solution shows a reduced usage of cellular connectivity, leading to a 27% reduction of packet latency. Then, relayed C-V2X packets show high reliability at up to 200-meter ranges from one peer to another, with observed latencies being, at worst, 42% more favorable than the cellular fallback.