Improved Reliability of C-V2X Communication Based on LTE SC-PTM

Vehicle to Everything (V2X) communication extends the information horizon of individual vehicles beyond the reach of their own sensors, enabling a series of road safety, cooperative driving and automation use cases. V2X over cellular networks is gaining momentum as it enables both short-range and long-distance information sharing with low latency over an existing infrastructure. A suitable cellular technology to relay data between vehicles is Single-Cell Point-To-Multipoint (SC-PTM), which can broadcast V2X messages on a per cell granularity. While SC-PTM is resource efficient, its reliability is still to be improved in the context of V2X especially in dense urban deployments. This paper is first to investigate such scenarios, presenting extensive simulations in a Manhattan area using realistic models of road structures, traffic rules, scale and mobility. Results indicate that with standard SC-PTM having no uplink feedback, a significant percentage of V2X messages are missed by at least one of their intended targets when vehicles are concentrated by traffic lights. Adding hybrid automatic repeat request (HARQ) to SC-PTM brings substantial improvements in reducing such misses without compromising efficiency even at high vehicle densities.