针对基于商用现成组件技术(Commercial Off-The-Shelf,COTS)的交换式以太网不能满足工业数据通信的实时性要求问题,给出了改进的FTT(Flexible Time-Triggered communication paradigm)网络调度模型,提出了新的周期性实时消息链路可调度性优化判定方法,在此基础上设计了一种基于EDF(Earliest Deadline First)的实时调度算法。算法通过对网络消息流量进行有效控制防止交换机缓冲区溢出,同时充分发挥网络在同一时间存在多个并行传输链路的优势,提高了网络实时性。仿真实验表明该算法在提高网络的聚合带宽、减小消息的平均等待延时和丢失率方面均有明显的优势。
To overcome the drawback that COTS-based switched Ethernet can not meet the real-time requirements in industrial communications,an improved FTT(Flexible Time-Triggered communication) paradigm which is based on event- and time-triggered approach is proposed.In addition,a novel link scheduling method for periodic messages is given.Particularly,it proposes an EDF-based scheduling algorithm which can provide adequate queues management and prevent memory overflows on a switched Ethernet by limiting the load submitted to the network.Moreover,it becomes possible for the scheduler to take full advantage of multiple transmission paths,thus enhancing real-time communication over a COTS-based switched Ethernet.Simulation results show the advantages of the proposed real-time scheduling algorithm in terms of increasing the aggregated bandwidth,reducing the average message waiting delay and the missing rate of message.