Enhancing Reliability in 5G NR V2V Communications Through Priority-Based Groupcasting and IR-HARQ

Vehicle-to-vehicle (V2V) communication is a technology that can wirelessly exchange information on the speed and position of nearby vehicles, helping to avoid collisions, to alleviate traffic congestion, and to improve the environment. The 3rd Generation Partnership Project (3GPP) has specified methods to improve the reliability of V2V sidelink (SL) technology by implementing hybrid automatic repeat request (HARQ) in a casting strategy composed of broadcast, unicast, and groupcast. However, the retransmission process in HARQ results in increased delay and reduced throughput. In this paper, we propose the priority-based groupcasting method to achieve high reliability and throughput when applying HARQ in various casting strategies. Additionally, the amount of retransmitted data is adjusted through constraints on delay and outage probability to maximize throughput. Simulation results evaluate HARQ performance in various casting strategies and confirm that the proposed method significantly improves reliability and resource efficiency compared to the conventional broadcasting. The system performance is enhanced with throughput increasing from 1.05 [Mbps] to 2.08 [Mbps], indicating an improvement of over 98%. These results emphasize that the proposed method significantly enhances communication reliability and efficiency in the 5G new radio (NR) V2V environment.