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

Vehicle to Everything (V2X) communication over cellular networks is gaining momentum as it enables both short-range and long-distance information sharing with low latency over an existing infrastructure. V2X traffic is dominated by each vehicle's periodic state dissemination targeted to its momentary neighbors within a geographical proximity. As such demand meets high vehicular mobility, the communication infrastructure is challenged to relay data efficiently and reliably within dynamically forming and dissolving groups of users. A suitable cellular technology 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 remains open 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, rules, scale and mobility. Results indicate that with standard SC-PTM having no uplink feedback, up to 35-60% of all 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 reducing such misses below 5-10%. without compromising efficiency even at high vehicle densities.