IEEE 802.11e in Industrial Environments a Quality

IEEE802.11einIndustrialEnvironments:aQualityofServiceSurveyMARKUSJ¨AGERMaster’sDegreeProjectStockholm,Sweden2005-12-05IR–SB–EX–0525AbstractThecommunicationbetweencontrolunitsandfielddevicesinindustrialenvi-ronmentsisbasedonso-calledfieldbustechnologies-networksoptimizedfortherealtimetransmissionofhighlysensitivedataforcontrolandmonitoringpurposes.Asastrongneedforwirelessfieldbussystemsarose,theapplicabilityofavailablewirelessstandardshasbeenexamined.Somespecializedwirelesssystemsarearisingonthemarketbutsofar,noappropriategeneralsolutionbasedonacommonstandardcouldbefound.Inthisproject,theupcomingstandardIEEE802.11eisanalyzedanditsappli-cabilitytestedbymeansofsimulationsinthenetworksimulatorns-2.Severaltrafficscenarios,typicalforcommunicationsintheautomationindustryareconsidered.Inordertoenhancetheachievableperformanceinanerror-proneenvironment,differentalgorithmsandretransmissionproceduresareproposed.Theobtainedresultsshowthat,eventhoughIEEE802.11eisnotoptimizedforindustrialapplications,ithasapotentialforrealtimeapplicationswithsomejitteranderrormargins.iAcknowledgementsFirstofallIwouldliketothanktheAdvancedIndustrialCommunicationgroupatABBCorporateResearchinV¨aster˚as/Swedenforgivingmetheopportunitytoworkonthisinterestingprojectaswellasforthehelpfulnessofallgroupmembers.IamparticularlythankfulfortheexcellentsupportanddedicationofmysupervisorJimmyKjellsson.IwouldalsoliketothankErikLarssonforbeingmyadviserandexamineratKTH.Furthermore,IwouldliketothankmyprojectpartnerMaximeMauryforthegreatteamwork,hisenthusiasmandcountlessinterestingdiscussionswehadduringthelastsixmonths.IamreallygratefulthatIhadhimasmyprojectpartner.ThanksalsotoallotherthesisstudentsatABBCorporateResearchforthepleasantworkingatmosphereandthegreattimewehadtogether.Myfamilyandfriendsdeserveaparticularacknowledgment-youaremostimportantinmylifeandgivemesomuch!Withallmyheart,Iwanttothankmyparentsfortheirnever-endingsupport,loveandforlettingmeknowwhereIamathome.Furthermore,IwanttoexplicitlymentionafriendshipIhighlyappreciateanddonotwanttomiss:thankyou,Pancho,forbeingsuchagoodbuddy.LastbutnotleastIamdeeplygratefulfortheencouragementandloveofawonderfulperson.Annemarie,youreallymakemehappy!iiiContents1Introduction11.1ProjectDefinition...........................21.2Motivation..............................31.3ScopeoftheThesis..........................42IEEE802.11e52.1GeneralDescription.........................52.1.1ReferenceModel.......................52.1.2NetworkComponentsandArchitecture..........62.1.3Services............................72.2PhysicalLayer............................72.2.1GeneralDescription.....................72.2.2OFDMPhysicalLayerConvergenceProcedure......82.2.3OFDMPhysicalMediumDependent............82.3MediumAccessControlLayer....................92.3.1MACLayerArchitecture..................92.3.2FundamentalConceptsoftheIEEE802.11eMAC....92.3.3EnhancedDistributedChannelAccess...........112.3.4HCFControlledChannelAccess..............122.3.5FurtherQualityofServiceEnhancements.........143IndustrialCommunicationSystems173.1CommunicationHierarchyintheAutomationIndustry......173.2FieldbusSystems...........................183.2.1GeneralDescription.....................193.2.2CommunicationModel....................193.2.3MediumAccessMethods..................203.2.4TrafficClassification.....................203.2.5QualityofServiceRequirements..............213.3WirelessFieldbusSystems......................223.3.1RequirementsandChallenges................223.3.2IEEE802.11einIndustrialEnvironments.........233.3.3RelatedWork.........................244SystemandScenarios274.1SystemDescription..........................274.1.1TopologyandProtocols...................274.1.2PacketErrorMeasurements.................28vviContents4.1.3ErrorModel..........................294.1.4PerformanceMeasuring...................314.2ScenarioDefinition..........................324.2.1Scenario1...........................324.2.2Scenario2...........................334.2.3Scenario3...........................335SimulationEnvironment355.1RealizationApproach........................355.2NetworkSimulatorns-2.......................365.3ProtocolImplementation.......................375.3.1RetransmissionProcedures.................375.3.2EnhancedScheduler.....................405.4SimulatorConfiguration.......................415.4.1GeneralSettings.......................415.4.2RetryLimitDefinition....................426Results456.1Scenario1...............................456.1.1PerformanceAnalysisofCyclicData............456.1.2PerformanceAnalysisofAcyclicData...........526.2Scenario2...............................556.3Scenario3...............................576.3.1PerformanceAnalysisofCyclicData............576.3.2PerformanceAnalysisofAcyclicData...........587ConclusionsandFutureWork61References63AParameterSettings67ListofTables2.1ModulationandcodingfordifferentdataratesinIEEE802.11a.82.2InterFrameSpacesinIEEE802.11e................112.3UserPrioritytoAccessCategorymapping.............113.1Typicalcontrolla