Experimenting Towards Reliable Packet Relaying in V2X Architectures

The future of smart cities depends on the ability of devices to share contextual data in a quick and reliable manner. Deploying access points in close proximity to the side of the road greatly reduces the propagation distances of messages sent over the sidelink, achieving extremely low latencies. However, in challenging situations encountered in urban contexts, multiple obstacles hinder the availability of direct links between a device and its destination. While the usual fallback solution resides in cellular connectivity, the gap in performance is immense. We propose relaying packets sent using Cellular-V2X (C-V2X) sidelink, where the initial message is received by an intermediary with better connectivity to the targeted access point, then retransmitted from this new position. To explore the performance and reliability of such communications in urban V2X architectures, we present experimental campaigns exploiting C-V2X PC5, 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. Results analysis highlights high reliability of relayed C-V2X packets at up to 200-meter ranges from one peer to another, with observed latencies being, at worst, 42% more favorable than the cellular fallback.