Research on the scheduling method of AFDX terminal system based on time triggered and event triggered

摘要

A new scheduling strategy of terminal system virtual link (VL) is put forward. The alternate trigger is constructed by time triggered and event triggered, based on the requirement of delay time of periodic and nonperiodic data. This strategy takes the time triggered protocol (TTP) as the dominant, the periodic data with determinate transmission time is scheduled as the schedule, and the nonperiodic data are transmitted by event triggered in the free time of the schedule according to priority. Based on the theory of network calculus, the paper derived the delay upper bound of different virtual links through the new alternate scheduling strategy and researched the relation among the maximum delay upper bound, the parameters of VL and the schedule and the frame length of VL with time scheduling. By studying comparatively the difference between the new alternate scheduling strategy and the single time or event trigger scheduling strategy, the AFDX network model based on OPNET is established, the terminal system data transmission efficiency under the three scheduling strategy is simulated and compared. The results show that the new scheduling strategy can insure the confirmation of the time triggered link, reduce the maximum delay time of the event triggered link, improve the ability of data processing and transmission efficiency effectively, and insure the stability and certainty of the periodic signal transmission. Above all, it is feasible and applicable to airborne network with different kinds of data with different delay requirements.