车联网中交通安全消息动态优先调度机制

Dynamic Priority Scheduling of Traffic Safety Messages in Internet of Vehicles

车联网中两类交通安全消息共享有限控制信道带宽,在消息突发状态下无法保证事件触发消息的传播性能,导致预警失效。基于差异化的消息传播性能需求提出了一种动态优先级区分的调度机制,按事件优先级分别进行队列管理,赋予事件触发消息优先权,通过设置优先级调度阈值实现对事件触发消息的动态调度。当优先队列长度高于阈值时,其抢占调度时隙。当队列长度低于阈值一半,退出抢占过程,恢复非抢占优先调度方法。仿真显示,所提调度机制能够减小事件触发消息的端到端时延约1.3 ms,提高周期性消息的公平性约0.22。

In Internet of Vehicles, two categories of traffic safety messages share the limited control channel bandwidth, so the performance of disseminating event-driven safety messages can not be guaranteed in e- mergency, which will lead to the failure of traffic accidents warning. The differentiated disseminated per- formance of traffic safety messages based on dynamic priority scheduling mechanism is proposed. The mechanism manages the two queues according to the event priorities, gives high priority to the event-driven safety messages and sets a scheduling threshold for the high priority messages dynamic scheduling. That is to conduct the preemptive priority scheduling when the queue length is over the threshold. When the queue length is less than half of the threshold, the preemptive scheduling terminates and then the non-preemptive priority scheduling is recovered. Simulation shows that the proposed dynamic priority scheduling mecha- nism of event-driven safety messages can reduce the end-to-end delay about 1.3 ms, and the fairness of the periodic safety messages increases about 0.22.