RetroV2X: A new vehicle-to-everything (V2X) paradigm with visible light backscatter networking

The Vehicle-to-Everything (V2X) technology has become essential with the increasing interest in intelligent transportation systems. It connects multiple vehicles and infrastructure by digitizing road traffic signs, signals, and other facilities and arranging sensing devices. However, conventional V2X solutions, such as Celluar Vehicle-to-Everything (C-V2X), have been slow to deploy due to their high cost, external power requirement, and dependence on Internet backhaul connectivity. Recently, Visible Light Backscatter Communication (VLBC) technology has emerged as a promising solution to overcome the practical issues of conventional V2X technologies. This paper presents RetroV2X, a protocol designed to support a networked VLBC-based V2X system that facilitates the transmission of road sensory data between vehicles and road infrastructure. We have designed several mechanisms, including backoff, virtual ID assignment, and excitatory carrier sensing, to handle different types of collisions, namely downlink, synchronous uplink, and asynchronous uplink collisions. Overhear and relay mechanisms are also designed to improve the performance at high vehicle densities. Our evaluation demonstrates that RetroV2X is capable of meeting the needs of V2X applications in typical rural road, town road, and highway scenarios with varying road sign densities, vehicle densities, and velocities.