机载时间触发光网络的设计与实时性分析

摘要

Wavelength division multiplexing (WDM) network is featured by almost unlimited bandwidth potential,great flexibility,strong expandability and transparent to protocol and bit rate,which makes it a good choice for avionics systems.However,the end-to-end delay of message transmitted on WDM avionics is uncertain on the real-time performance.WDM network cannot ensure determinacy for the time-critical message transmitted on future avionics network.This paper introduces time-triggered mechanism to WDM network and proposes the architecture of time-triggered avionics WDM (TTAWDM) network,including protocol layer,data format,scheduling procedure,etc.The time-triggered mechanism can process a statically configured communication schedule for time-critical message,which can ensure determinacy for the transmission process and end-to-end delay of message,and can meet real-time requirements.Then the real-time property of messages is analyzed based on the architecture design of TTAWDM,and based on network calculus,the calculation method of upper bound delay of rate-constrained messages is given.Finally,a simulation experiment of TTAWDM is conducted,and the results show that TTAWDM can be a totally deterministic network for time-critical messages and the calculation method of upper bound delay is effective.%波分复用光(WDM)网络是目前较好的航空电子网络解决方案之一,具有高带宽、强灵活性、对协议和比特率透明、强扩展性等优点.但在实时性方面,WDM网络的消息传输存在不确定性,无法满足未来航空电子网络对于时间关键消息强实时性保障的要求.本文将时间触发机制引入WDM网络,设计了时间触发航空电子WDM(TTAWDM)网络的体系结构,包含协议栈、消息类型、调度流程等.TTAWDM用时刻调度表规划时间关键性消息的传输,保障消息传输过程和传输延时的确定性,以满足强实时性要求.在TTAWDM体系结构设计的基础上分析了网络消息的实时性,基于网络演算推导出速率限制消息的延时上界计算方法,并构造仿真实验展示了TTAWDM对于强实时性保障,同时验证了延时上界计算方法的有效性.