软件定义时间触发网络的调度算法优化

软件定义时间触发以太网（TTE）作为优化航空电子系统中消息调度的一种新模式，其动态在线调度算法必须尽力保证任何情况下所有消息的传输确定性。针对时间触发（TT）消息调度间隔小于消息帧长（小时隙）时，速率约束RC消息延迟增大、传输确定性降低的问题，对TT消息调度算法进行改进。首先，构建了TTE的系统模型，阐明了最小延迟（MID）调度算法和背靠背（B2B）调度算法的机制；然后在其基础上提出了大孔隙（MAV）调度算法，以减少（RC）消息的等待延迟；最后，利用OMNeT++实验分析这3种调度算法的性能。实验结果表明:当无小时隙TT消息时，B2B算法的消息延迟最大、MAV调度算法和MID调度算法的消息延迟接近。当有小时隙TT消息时，MAV调度算法的消息传输确定性更好，相比于MID调度算法，MAV调度算法下RC消息的传输确定性提高了87.3%。 

Scheduling algorithms optimization in software defined time-triggered network

Software defined Time-Triggered Ethernet (TTE) optimizes message scheduling in avionics systems, and its dynamic online scheduling algorithm must ensure the transmission determinacy of all the messages in any case. When time interval of Time-Triggered (TT) message is less than the frame length, the Rate-Constrained (RC) message delay increases, and transmission determinacy goes down. This paper improves the TT message scheduling algorithm. First, a system model of software defined time-triggered Ethernet was established. And the mechanisms of Minimum Delay (MID) scheduling algorithm and Back to Back (B2B) scheduling algorithm were introduced. Then, on this basis, a Macrovoid (MAV) scheduling algorithm was proposed to reduce the waiting delay for RC messages in special cases. Finally, OMNeT++ experiment was conducted to analyze the performance of these three algorithms. Experimental results show when there is no small time interval TT messages, the message delay in the back to back scheduling algorithm is the largest, and the macrovoid scheduling algorithm has similar message delay as the minimum delay scheduling algorithm. However, when there are small time interval TT messages, the macrovoid scheduling algorithm has better transmission determinacy than the minimum delay scheduling algorithm, and the transmission determinacy of RC message by macrovoid scheduling algorithm is improved by 87.3%, compared with minimum delay scheduling algorithm.