Schedulability Analysis In Multi-mode AFDX Network

With the development of communication business in avionics system fromtraditional voice communication to diversified business such as multimedia, images,the demand of scalability, reliability, bandwidth, etc. in avionics data network hasbecome increasing. ARINC429and Mil-STD-1553bus technology are currentlywidely used in avionics data network, which can’t meet the need for higher bandwidthand rate. Avionics Full Duplex Switched Ethernet (AFDX), which is a newcommunication standard, will become the basis of building a new generation avionicssystems because of its low cost, good scalability. Based on the IEEE802.3standard,AFDX is a deterministic network with the use of integrated communicationstechnology.But an aircraft system based on an AFDX network need to change from one flightmode to another flight mode, which is called a mode change. During the transitionbetween two modes, data flows in two modes are transmitted in the AFDX network, and data burst will lead to overload and data loss. Therefore, it is very important toguarantee the timing requirements in every steady mode, and also during the transition.This paper studies how to guarantee data flows’ schedulability when a mode changehappens in an AFDX network.The main work and research results are summarized as follows:(1) Researching into AFDX network, the mechanism and characteristic of EndSystem, Virtual Link and Switch have been discussed. Then the AFDX network modelis analyzed.(2) Research into mode change theory of real-time systems, and then comparereal-time systems and AFDX network. Finally, the mode change model is proposed,regarding to some requirements for mode change, some assumptions and somedefinitions.(3) In a single-hop network, all data flows are analyzed to compute theirworst-case response time during a mode change transition based on the mode changemodel. Then in a multi-hop network, similarly, all data flows are analyzed to computetheir worst-case response time during a mode change transition based on the modechange model.(4) Using simulation tool TrueTime, the small AFDX network topology is set up.Comparing the simulation results with theoretical worst-case response time of dataflows, it is found that offset can guarantee data in network schedulability.