Network Performance Analysis Based On Compositional Schedule In AFDX Avionics System

Hierarchical scheduling analysis methods have been widely adopted to simplifythe design of real-time systems and to ensure tasks schedulability. Compositionalscheduling analysis and design methods can also ensure the independence of theinternal system. At the same time, the virtual links is hierarchical in AFDX (AvionicsFull Duplex Switched Ethernet) network. Compositional scheduling analysis whichcan simplify the set of virtual links in a hierarchical way in an AFDX network,meanwhile, it can prevent virtual link traffic from interfering during transmission.But compositional scheduling analysis methods cannot be directly applied inAFDX network. Re-modeling of AFDX virtual link and adjust the compositionalscheduling analysis method based on real-time task can be a way to make it possible.This paper studies on how to use compositional scheduling method to analyze thenetwork data flow. A virtual link period resource model is established to meet the demand of compositional scheduling analysis. Then, scheduling algorithms aremodified to be the non-preemptive one due to the virtual link constraints.The main work and research results are summarized as follows:(1).AFDX network modeling. For end system modeling and virtual linkmodeling. Mainly used AFDX data flow, AFDX data packet queue, AFDX regulatorand scheduler; redefined and assuming virtual link and virtual link compositionalnode additionally so that it can meet the requirements of compositional schedulinganalysis.(2).Combined with the AFDX network characteristics, and modifiedcompositional scheduling analysis model based on real-time tasks which is used in theanalysis virtual link data flow. Preemptive task scheduling way is modified to be thenon-preemptive one. Period resource model based on virtual has been established.(3).RM (Rate-Monotonic) scheduling algorithms and EDF (Earliest DeadlineFirst) scheduling algorithm have been applied to compositional scheduling analysis,so that for the different characteristics of the data flow, more analysis schedulingmethods can be used. At the same time, reasonable allocation method of BAG(Bandwidth Allocation Gap) and Lmax in virtual link has been proposed.(4).By modifying compositional scheduling analysis tools CARTS(Compositional Analysis of Real-Time Systems), it can be applied to thecompositional scheduling analysis of data flow and used in experiments.