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摘要:
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。
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关键词:
- 时间触发 /
- 波分复用(WDM)网络 /
- 体系结构 /
- 实时性 /
- 网络演算
Abstract: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.
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表 1 TT消息延时结果对比
Table 1. Comparison of delay of TT messages
消息ID 周期/ms 长度/Byte 延时/μs 规划延时 仿真延时 最大允许延时 1 32 365 310 310 400 2 32 970 772 772 1 000 3 32 64 81 81 200 4 64 310 269 269 300 5 64 260 230 230 300 6 64 800 642 642 1 000 7 128 1 150 909 909 1 000 8 128 640 520 520 600 -
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