Over the last years, the evolution of Vehicle-to-Everything (V2X) services from basic safety-related to enhanced V2X (eV2X) applications prompted the development of the 5G New Radio (NR)-V2X technology. Standardized by the Third Generation Partnership Project (3GPP) in Release 16, NR-V2X features a distributed resource allocation mode, known as Mode 2, that allows vehicles to autonomously select their transmission resources employing a Semi-Persistent Scheduling (SPS) or a Dynamic Scheduling (DS) scheme. The SPS approach relies on the periodic reservation of resources, whereas the DS scheme is a reservation-less solution that forces the selection of new transmission resources for every generated message. 3GPP standards do not indicate under which conditions each scheduling scheme should be used. In this context, this study analyzes and compares the performance of SPS and DS under different traffic types and Packet Delay Budget (PDB) requirements. Simulation results demonstrate that the SPS scheme represents the best solution for serving fixed size periodic traffic, whereas DS is more adequate for aperiodic traffic (of fixed or variable size). The study shows that the superiority of DS over SPS becomes more evident when tighter PDB requirements are considered, and that the performance of the DS scheme is independent of the PDB. It is also demonstrated that an adaptive scheduling strategy, which allows vehicles to select the scheduling scheme that best suits the type of generated traffic, is the best solution in mixed traffic scenarios where fixed size periodic traffic and variable size aperiodic traffic sources coexist.

在过去几年中，车联网 (V2X) 服务从基本安全相关到增强型 V2X (eV2X) 应用的演变推动了 5G 新无线电 (NR)-V2X 技术的发展。在第 16 版中由第三代合作伙伴计划 (3GPP) 标准化，NR-V2X 具有分布式资源分配模式，称为模式 2，允许车辆使用半持久调度 (SPS) 或动态调度自主选择其传输资源调度 (DS) 方案。SPS 方法依赖于资源的周期性预留，而 DS 方案是一种无预留解决方案，它强制为每个生成的消息选择新的传输资源。3GPP 标准并未指明应在何种条件下使用每种调度方案。在这种情况下，本研究分析和比较了 SPS 和 DS 在不同流量类型和数据包延迟预算 (PDB) 要求下的性能。仿真结果表明，SPS 方案代表了为固定大小的周期性流量提供服务的最佳解决方案，而 DS 更适合非周期性流量（固定或可变大小）。研究表明，当考虑更严格的 PDB 要求时，DS 优于 SPS 的优势变得更加明显，并且 DS 方案的性能独立于 PDB。还证明了自适应调度策略允许车辆选择最适合生成的流量类型的调度方案，是固定大小的周期性流量和可变大小的非周期性流量源共存的混合流量场景中的最佳解决方案。