Towards 6G sidelink: Distributed scheduling and routing for reliable multi-hop connectivity

—Reliable multi-hop communication in 5G New Radio (NR) Vehicle-to-Everything (V2X) communications remains challenging, especially in dynamic, infrastructure-less scenarios. We present a joint framework for distributed scheduling and multi-hop relaying over the Sidelink interface, tailored to dynamic formations such as virtually coupled trains. Motivated by the railway requirement to operate strictly at Layer 2 (i.e., without the ETSI ITS stack), our design integrates sensing based on inter-UE coordination with a proactive routing protocol inspired by B.A.T.M.A.N. that fits the Sidelink MAC model. Unlike approaches that treat routing and resource selection independently, our cross-layer strategy couples the two via a hybrid next-hop metric– a weighted combination of Signalto-Interference-plus-Noise Ratio (SINR) and available resource blocks– so that paths can avoid weak links and relays with limited resources. Simulations in a virtual train coupling scenario show high delivery ratios, reduced hidden-node collisions, and robust performance across densities, indicating the suitability of the proposed Layer 2 framework for V2X-enabled train automation and future cooperative mobility systems.