Cellular Vehicle-to-Everything (C-V2X) communications are the key to connected and autonomous driving, and pave the way for future Intelligent Transport Systems (ITS). To support non-safety and safety critical applications in the demanding out-of-coverage scenario, the 3rd Generation Partnership Project (3GPP) has standardized the distributed C-V2X Mode 4 solution, whose behavior has been thoroughly analyzed for periodic traffic. In the current work, the problem of allocating aperiodic traffic in Mode 4 is tackled, a matter that has not been addressed before and that raises several challenging questions. A solution for serving such traffic type is put forth, and an analytical insight on the attainable performance is offered. Further, it is numerically proved that guaranteeing aperiodic flows good service levels is hard when their packets are not small sized. This holds true even for sophisticated physical layer choices and at relatively modest traffic densities, revealing that novel approaches to radio resource assignment are a necessity in Fifth Generation (5G) vehicular communications.

中文翻译：

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蜂窝车联网中非周期和周期交通的共存

蜂窝车联网 (C-V2X) 通信是互联和自动驾驶的关键，并为未来的智能交通系统 (ITS) 铺平道路。为了在要求严苛的覆盖范围之外的场景中支持非安全和安全关键应用，第三代合作伙伴计划 (3GPP) 对分布式 C-V2X 模式 4 解决方案进行了标准化，其行为已针对周期性流量进行了彻底分析。在当前的工作中，解决了模式 4 中分配非周期性流量的问题，这是以前没有解决的问题，并提出了几个具有挑战性的问题。提出了为此类流量类型提供服务的解决方案，并提供了对可实现性能的分析见解。更多，数值证明，当非周期流的数据包不小时，保证良好的服务水平是很困难的。即使对于复杂的物理层选择和相对适中的流量密度也是如此，这表明无线资源分配的新方法是第五代 (5G) 车载通信的必要条件。