End To End Delay Improvement In AFDX Networkfor Critical Tasks

Through ahalf century’sdevelopment ofnetwork technology, there are a series of maturebus standardsgradually formed.In the field of aviation network, the ARINC429and1553Bisrepresentative.Due to the development of technology, thedemandfrom the avionics system onnetwork continues to increase; the traditional network standards have failed to meet the needsof thefuture development. A new high speed bus AFDX (Avionics Full Duplex SwitchedEthernet) has been designed and implemented, and successfully applied in the Airbus A380.Compared with previous avionics buses, the AFDX possess a lot of exciting advantagesinmany aspects such as the transmission efficiency, scalability and flexibility and so on. In2005, AFDX was officially included in the ARINC664as the seventh section, whichindicates the aviation field’s identification of AFDX.Avionics network, which has very high demand on end-to-end delay of critical datastreams, is different from the common ones,but the currentstudies on AFDX networkend-to-end delay are relatively pessimistic. This paper focus on the end-to-end delayofcritical data streams in AFDX network;with deepanalysis, designing a set of solutionswhich improves the quality of AFDX network critical data flow delay service.The main work and research results are summarized as follows:(1) AnalyzeEnd System, switch, virtual link and other AFDXelements, and thenmodel them. Take in new task constraint DCTS (Distance-Constrained Task System), choose theCrossBar architecture as the switch core implementation.(2) Analyze and study the AFDX end-to-end delay, through mathematical modeling andcalculation, prove that the selection of conflict free pinwheel scheduling strategy can improvethe performance of critical data flow end-to-end delay; then analyze the applicability of thisstrategy to the existing AFDX network, in which changes are needed.(3) Propose the solution, according to AFDX in global synchronization and eliminate thenon preemptive scheduling and make the appropriate improvements, so that AFDX can useconflict-free scheduling scheme. Give out the new scheduling algorithm, which can guaranteethat the critical data streams arefree from blocking conflicts with each other, at the same time,can guarantee that the critical data streams may be less affected by other non-critical datastreams. Theoretically speaking, critical data flow delay performance has been improved.(4) Choose TrueTime toolbox to construct AFDX network simulation environment, setparameters as close as possible to the actual situation. By setting different scenarios of thecomparative experiments, analyze delay performance.If critical data flow delay performancehas been improved in practice, the effectiveness of our solutionswill also beverified.