毕业论文外文文献翻译计算机专业：ieee802

毕业论文外文文献翻译计算机专业IEEE802英文资料与中文翻译IEEE80211MEDIUMACCESSCONTROLTHEIEEE80211MACLAYERCOVERSTHREEFUNCTIONALAREASRELIABLEDATADELIVERY,MEDIUMACCESSCONTROL,ANDSECURITYTHISSECTIONCOVERSTHEFIRSTTWOTOPICSRELIABLEDATADELIVERYASWITHANYWIRELESSNETWORK,AWIRELESSLANUSINGTHEIEEE80211PHYSICALANDMACLAYERSISSUBJECTTOCONSIDERABLEUNRELIABILITYNOISE,INTERFERENCE,ANDOTHERPROPAGATIONEFFECTSRESULTINTHELOSSOFASIGNIFICANTNUMBEROFFRAMESEVENWITHERRORCORRECTIONCODES,ANUMBEROFMACFRAMESMAYNOTSUCCESSFULLYBERECEIVEDTHISSITUATIONCANBEDEALTWITHBYRELIABILITYMECHANISMSATAHIGHERLAYERSUCHASTCPHOWEVER,TIMERSUSEDFORRETRANSMISSIONATHIGHERLAYERSARETYPICALLYONTHEORDEROFSECONDSITISTHEREFOREMOREEFFICIENTTODEALWITHERRORSATTHEMACLEVELFORTHISPURPOSE,IEEE80211INCLUDESAFRAMEEXCHANGEPROTOCOLWHENASTATIONRECEIVESADATAFRAMEFROMANOTHERSTATIONITRETURNSANACKNOWLEDGMENTACKFRAMETOTHESOURCESTATIONTHISEXCHANGEISTREATEDASANATOMICUNIT,NOTTOBEINTERRUPTEDBYATRANSMISSIONFROMANYOTHERSTATIONIFTHESOURCEDOESNOTRECEIVEANACKWITHINASHORTPERIODOFTIME,EITHERBECAUSEITSDATAFRAMEWASDAMAGEDORBECAUSETHERETURNINGACKWASDAMAGED,THESOURCERETRANSMITSTHEFRAMETHUS,THEBASICDATATRANSFERMECHANISMINIEEE80211INVOLVESANEXCHANGEOFTWOFRAMESTOFURTHERENHANCERELIABILITY,AFOURFRAMEEXCHANGEMAYBEUSEDINTHISSCHEME,ASOURCEFIRSTISSUESAREQUESTTOSENDRTSFRAMETOTHEDESTINATIONTHEDESTINATIONTHENRESPONDSWITHACLEARTOSENDCTSAFTERRECEIVINGTHECTS,THESOURCETRANSMITSTHEDATAFRAME,ANDTHEDESTINATIONRESPONDSWITHANACKTHERTSALERTSALLSTATIONSTHATAREWITHINRECEPTIONRANGEOFTHESOURCETHATANEXCHANGEISUNDERWAYTHESESTATIONSREFRAINFROMTRANSMISSIONINORDERTOAVOIDACOLLISIONBETWEENTWOFRAMESTRANSMITTEDATTHESAMETIMESIMILARLY,THECTSALERTSALLSTATIONSTHATAREWITHINRECEPTIONRANGEOFTHEDESTINATIONTHATANEXCHANGEISUNDERWAYTHERTS/CTSPORTIONOFTHEEXCHANGEISAREQUIREDFUNCTIONOFTHEMACBUTMAYBEDISABLEDMEDIUMACCESSCONTROLTHE80211WORKINGGROUPCONSIDEREDTWOTYPESOFPROPOSALSFORAMACALGORITHMDISTRIBUTEDACCESSPROTOCOLS,WHICH,LIKEETHERNET,DISTRIBUTETHEDECISIONTOTRANSMITOVERALLTHENODESUSINGACARRIERSENSEMECHANISMANDCENTRALIZEDACCESSPROTOCOLS,WHICHINVOLVEREGULATIONOFTRANSMISSIONBYACENTRALIZEDDECISIONMAKERADISTRIBUTEDACCESSPROTOCOLMAKESSENSEFORANADHOCNETWORKOFPEERWORKSTATIONSTYPICALLYANIBSSANDMAYALSOBEATTRACTIVEINOTHERWIRELESSLANCONFIGURATIONSTHATCONSISTPRIMARILYOFBURSTTRAFFICACENTRALIZEDACCESSPROTOCOLISNATURALFORCONFIGURATIONSINWHICHAUMBEROFWIRELESSSTATIONSAREINTERCONNECTEDWITHEACHOTHERANDSOMESORTOFBASESTATIONTHATATTACHESTOABACKBONEWIREDLANITISESPECIALLYUSEFULIFSOMEOFTHEDATAISTIMESENSITIVEORHIGHPRIORITYTHEENDRESULTFOR80211ISAMACALGORITHMCALLEDDFWMACDISTRIBUTEDFOUNDATIONWIRELESSMACTHATPROVIDESADISTRIBUTEDACCESSCONTROLMECHANISMWITHANOPTIONALCENTRALIZEDCONTROLBUILTONTOPOFTHATFIGURE145ILLUSTRATESTHEARCHITECTURETHELOWERSUBLAYEROFTHEMACLAYERISTHEDISTRIBUTEDCOORDINATIONFUNCTIONDCFDCFUSESACONTENTIONALGORITHMTOPROVIDEACCESSTOALLTRAFFICORDINARYASYNCHRONOUSTRAFFICDIRECTLYUSESDCETHEPOINTCOORDINATIONFUNCTIONPCFISACENTRALIZEDMACALGORITHMUSEDTOPROVIDECONTENTIONFREESERVICEPCFISBUILTONTOPOFDCFANDEXPLOITSFEATURESOFDCFTOASSUREACCESSFORITSUSERSLETUSCONSIDERTHESETWOSUBLAYERSINTURNFIGURE145IEEE80211PROTOCOLARCHITECTUREDISTRIBUTEDCOORDINATIONFUNCTIONTHEDCFSUBLAYERMAKESUSEOFASIMPLECSMACARRIERSENSEMULTIPLEACCESSALGORITHM,WHICHFUNCTIONSASFOLLOWSIFASTATIONHASAMACFRAMETOTRANSMIT,ITLISTENSTOTHEMEDIUMIFTHEMEDIUMISIDLE,THESTATIONMAYTRANSMITOTHERWISETHESTATIONMUSTWAITUNTILTHECURRENTTRANSMISSIONISCOMPLETEBEFORETRANSMITTINGTHEDCFDOESNOTINCLUDEACOLLISIONDETECTIONFUNCTIONIECSMA/CDBECAUSECOLLISIONDETECTIONISNOTPRACTICALONAWIRELESSNETWORKTHEDYNAMICRANGEOFTHESIGNALSONTHEMEDIUMISVERYLARGE,SOTHATATRANSMITTINGSTATIONCANNOTEFFECTIVELYDISTINGUISHINCOMINGWEAKSIGNALSFROMNOISEANDTHEEFFECTSOFITSOWNTRANSMISSIONTOENSURETHESMOOTHANDFAIRFUNCTIONINGOFTHISALGORITHM,DCFINCLUDESASETOFDELAYSTHATAMOUNTSTOAPRIORITYSCHEMELETUSSTARTBYCONSIDERINGASINGLEDELAYKNOWNASANINTERFRAMESPACEIFSINFACT,THEREARETHREEDIFFERENTIFSVALUES,BUTTHEALGORITHMISBESTEXPLAINEDBYINITIALLYIGNORINGTHISDETAILUSINGANIFS,THERULESFORCSMAACCESSAREASFOLLOWSFIGURE146FIGURE146IEEE80211MEDIUMACCESSCONTROLLOGIC1ASTATIONWITHAFRAMETOTRANSMITSENSESTHEMEDIUMIFTHEMEDIUMISIDLEITWAITSTOSEEIFTHEMEDIUMREMAINSIDLEFORATIMEEQUALTOIFSIFSO,THESTATIONMAYTRANSMITIMMEDIATELY2IFTHEMEDIUMISBUSYEITHERBECAUSETHESTATIONINITIALLYFINDSTHEMEDIUMBUSYORBECAUSETHEMEDIUMBECOMESBUSYDURINGTHEIFSIDLETIME,THESTATIONDEFERSTRANSMISSIONANDCONTINUESTOMONITORTHEMEDIUMUNTILTHECURRENTTRANSMISSIONISOVER3ONCETHECURRENTTRANSMISSIONISOVER,THESTATIONDELAYSANOTHERIFSIFTHEMEDIUMREMAINSIDLEFORTHISPERIOD,THENTHESTATIONBACKSOFFARANDOMAMOUNTOFTIMEANDAGAINSENSESTHEMEDIUMIFTHEMEDIUMISSTILLIDLE,THESTATIONMAYTRANSMITDURINGTHEBACKOFFTIME,IFTHEMEDIUMBECOMESBUSY,THEBACKOFFTIMERISHALTEDANDRESUMESWHENTHEMEDIUMBECOMESIDLE4IFTHETRANSMISSIONISUNSUCCESSFUL,WHICHISDETERMINEDBYTHEABSENCEOFANACKNOWLEDGEMENT,THENITISASSUMEDTHATACOLLISIONHASOCCURREDTOENSURETHATBACKOFFMAINTAINSSTABILITY,ATECHNIQUEKNOWNASBINARYEXPONENTIALBACKOFFISUSEDASTATIONWILLATTEMPTTOTRANSMITREPEATEDLYINTHEFACEOFREPEATEDCOLLISIONS,BUTAFTEREACHCOLLISION,THEMEANVALUEOFTHERANDOMDELAYISDOUBLEDUPTOSOMEIMUMVALUETHEBINARYEXPONENTIALBACKOFFPROVIDESAMEANSOFHANDLINGAHEAVYLOADREPEATEDFAILEDATTEMPTSTOTRANSMITRESULTINLONGERANDLONGERBACKOFFTIMES,WHICHHELPSTOSMOOTHOUTTHELOADWITHOUTSUCHABACKOFF,THEFOLLOWINGSITUATIONCOULDOCCURTWOORMORESTATIONSATTEMPTTOTRANSMITATTHESAMETIME,CAUSINGACOLLISIONTHESESTATIONSTHENIMMEDIATELYATTEMPTTORETRANSMIT,CAUSINGANEWCOLLISIONTHEPRECEDINGSCHEMEISREFINEDFORDCFTOPROVIDEPRIORITYBASEDACCESSBYTHESIMPLEEXPEDIENTOFUSINGTHREEVALUESFORIFSSIFSSHORTIFSTHESHORTESTIFS,USEDFORALLIMMEDIATERESPONSEACTIONS,ASEXPLAINEDINTHEFOLLOWINGDISCUSSIONPIFSPOINTCOORDINATIONFUNCTIONIFSAMIDLENGTHIFS,USEDBYTHECENTRALIZEDCONTROLLERINTHEPCFSCHEMEWHENISSUINGPOLLSDIFSDISTRIBUTEDCOORDINATIONFUNCTIONIFSTHELONGESTIFS,USEDASAMINIMUMDELAYFORASYNCHRONOUSFRAMESCONTENDINGFORACCESSFIGURE147AILLUSTRATESTHEUSEOFTHESETIMEVALUESCONSIDERFIRSTTHESIFSANYSTATIONUSINGSIFSTODETERMINETRANSMISSIONOPPORTUNITYHAS,INEFFECT,THEHIGHESTPRIORITY,BECAUSEITWILLALWAYSGAINACCESSINPREFERENCETOASTATIONWAITINGANAMOUNTOFTIMEEQUALTOPIFSORDIFSTHESIFSISUSEDINTHEFOLLOWINGCIRCUMSTANCESACKNOWLEDGMENTACKWHENASTATIONRECEIVESAFRAMEADDRESSEDONLYTOITSELFNOTMULTICASTORBROADCASTITRESPONDSWITHANACKFRAMEAFTER,WAITINGON1YFORANSIFSGAPTHISHASTWODESIRABLEEFFECTSFIRST,BECAUSECOLLISIONDETECTIONISNOTUSED,THELIKELIHOODOFCOLLISIONSISGREATERTHANWITHCSMA/CD,ANDTHEMACLEVELACKPROVIDESFOREFFICIENTCOLLISIONRECOVERYSECOND,THESIFSCANBEUSEDTOPROVIDEEFFICIENTDELIVERYOFANLLCPROTOCOLDATAUNITPDUTHATREQUIRESMULTIPLEMACFRAMESINTHISCASE,THEFOLLOWINGSCENARIOOCCURSASTATIONWITHAMULTIFRAMELLCPDUTOTRANSMITSENDSOUTTHEMACFRAMESONEATATIMEEACHFRAMEISACKNOWLEDGEDAFTERSIFSBYTHERECIPIENTWHENTHESOURCERECEIVESANACK,ITIMMEDIATELYAFTERSIFSSENDSTHENEXTFRAMEINTHESEQUENCETHERESULTISTHATONCEASTATIONHASCONTENDEDFORTHECHANNEL,ITWILLMAINTAINCONTROLOFTHECHANNELUNTILITHASSENTALLOFTHEFRAGMENTSOFANLLCPDUCLEARTOSENDCTSASTATIONCANENSURETHATITSDATAFRAMEWILLGETTHROUGHBYFIRSTISSUINGASMALLREQUESTTOSENDRTSFRAMETHESTATIONTOWHICHTHISFRAMEISADDRESSEDSHOULDIMMEDIATELYRESPONDWITHACTSFRAMEIFITISREADYTORECEIVEALLOTHERSTATIONSRECEIVETHERTSANDDEFERUSINGTHEMEDIUMPOLLRESPONSETHISISEXPLAINEDINTHEFOLLOWINGDISCUSSIONOFPCFABASICACCESSMETHODBPCFSUPERFRAMECONSTRUCTIONFIGURE147IEEE80211MACTIMINGTHENEXTLONGESTIFSINTERVALISTHEPIFSTHISISUSEDBYTHECENTRALIZEDCONTROLLERINISSUINGPOLLSANDTAKESPRECEDENCEOVERNORMALCONTENTIONTRAFFICHOWEVER,THOSEFRAMESTRANSMITTEDUSINGSIFSHAVEPRECEDENCEOVERAPCFPOLLFINALLY,THEDIFSINTERVALISUSEDFORALLORDINARYASYNCHRONOUSTRAFFICPOINTC00RDINATIONFUNCTIONPCFISANALTERNATIVEACCESSMETHODIMPLEMENTEDONTOPOFTHEDCETHEOPERATIONCONSISTSOFPOLLINGBYTHECENTRALIZEDPOLLINGMASTERPOINTCOORDINATORTHEPOINTCOORDINATORMAKESUSEOFPIFSWHENISSUINGPOLLSBECAUSEPIFSISSMALLERTHANDIFS,THEPOINTCOORDINATORCALLSEIZETHEMEDIUMANDLOCKOUTALLASYNCHRONOUSTRAFFICWHILEITISSUESPOLLSANDRECEIVESRESPONSESASANEXTREME,CONSIDERTHEFOLLOWINGPOSSIBLESCENARIOAWIRELESSNETWORKISCONFIGUREDSOTHATANUMBEROFSTATIONSWITHTIME,SENSITIVETRAFFICARECONTROLLEDBYTHEPOINTCOORDINATORWHILEREMAININGTRAFFICCONTENDSFORACCESSUSINGCSMATHEPOINTCOORDINATORCOULDISSUEPOLLSINAROUNDROBINFASHIONTOALLSTATIONSCONFIGUREDFORPOLLINGWHENAPOLLISISSUED,THEPOLLEDSTATIONMAYRESPONDUSINGSIFSIFTHEPOINTCOORDINATORRECEIVESARESPONSE,ITISSUESANOTHERPOLLUSINGPIFSIFNORESPONSEISRECEIVEDDURINGTHEEXPECTEDTURNAROUNDTIME,THECOORDINATORISSUESAPOLLIFTHEDISCIPLINEOFTHEPRECEDINGPARAGRAPHWEREIMPLEMENTED,THEPOINTCOORDINATORWOULDLOCKOUTALLASYNCHRONOUSTRAFFICBYREPEATEDLYISSUINGPOLLSTOPREVENTTHIS,ANINTERVALKNOWNASTHESUPERFRAMEISDEFINEDDURINGTHEFIRSTPARTOFTHISINTERVAL,THEPOINTCOORDINATORISSUESPOLLSINAROUND,ROBINFASHIONTOALLSTATIONSCONFIGUREDFORPOLLINGTHEPOINTCOORDINATORTHENIDLESFORTHEREMAINDEROFTHESUPERFRAME,ALLOWINGACONTENTIONPERIODFORASYNCHRONOUSACCESSFIGUREL47BILLUSTRATESTHEUSEOFTHESUPERFRAMEATTHEBEGINNINGOFASUPERFRAME,THEPOINTCOORDINATORMAYOPTIONALLYSEIZECONTROLANDISSUESPOLLSFORAGIVEPERIODOFTIMETHISINTERVALVARIESBECAUSEOFTHEVARIABLEFRAMESIZEISSUEDBYRESPONDINGSTATIONSTHEREMAINDEROFTHESUPERFRAMEISAVAILABLEFORCONTENTIONBASEDACCESSATTHEENDOFTHESUPERFRAMEINTERVAL,THEPOINTCOORDINATORCONTENDSFORACCESSTOTHEMEDIUMUSINGPIFSIFTHEMEDIUMISIDLETHEPOINTCOORDINATORGAINSIMMEDIATEACCESSANDAFULLSUPERFRAMEPERIODFOLLOWSHOWEVER,THEMEDIUMMAYBEBUSYATTHEENDOFASUPERFRAMEINTHISCASE,THEPOINTCOORDINATORMUSTWAITUNTILTHEMEDIUMISIDLETOGAINACCESSTHISRESULTINAFORESHORTENEDSUPERFRAMEPERIODFORTHENEXTCYCLEFCFRAMECONTROLSCSEQUENCECONTROLD/IDURATION/CONNECTIONIDFCSFRAMECHECKSEQUENCEMACFRAMEDSDISTRIBUTIONSYSTEMMDMOREDATAMFMOREFRAGMENTSWWIREDEQUIVALENTPRIVACYRTRETRYOORDERPMPOWERMANAGEMENTBFRAMECONTROLFILEDFIGURE148IEEE80211MACFRAMEFORMATMACFRAMEFIGURE148ASHOWSTHE80211FRAMEFORMATWHENNOSECURITYFEATURESAREUSEDTHISGENERALFORMATISUSEDFORALLDATAANDCONTROLFRAMES,BUTNOTALLFIELDSAREUSEDINALLCONTEXTSTHEFIELDSAREASFOLLOWSFRAMECONTROLINDICATESTHETYPEOFFRAMEANDPROVIDESCONTR01INFORMATION,ASEXPLAINEDPRESENTLYDURATION/CONNECTIONIDIFUSEDASADURATIONFIELD,INDICATESTHETIMEINMICROSECONDSTHECHANNELWILLBEALLOCATEDFORSUCCESSFULTRANSMISSIONOFAMACFRAMEINSOMECONTROLFRAMES,THISFIELDCONTAINSANASSOCIATION,ORCONNECTION,IDENTIFIERADDRESSESTHENUMBERANDMEANINGOFTHE48BITADDRESSFIELDSDEPENDONCONTEXTTHETRANSMITTERADDRESSANDRECEIVERADDRESSARETHEMACADDRESSESOFSTATIONSJOINEDTOTHEBSSTHATARETRANSMITTINGANDRECEIVINGFRAMESOVERTHEWIRELESSLANTHESERVICESETIDSSIDIDENTIFIESTHEWIRELESSLANOVERWHICHAFRAMEISTRANSMITTEDFORANIBSS,THESSIDISARANDOMNUMBERGENERATEDATTHETIMETHENETWORKISFORMEDFORAWIRELESSLANTHATISPARTOFALARGERCONFIGURATIONTHESSIDIDENTIFIESTHEBSSOVERWHICHTHEFRAMEISTRANSMITTEDSPECIFICALLY,THESSIDISTHEMACLEVELADDRESSOFTHEAPFORTHISBSSFIGURE144FINALLYTHESOURCEADDRESSANDDESTINATIONADDRESSARETHEMACADDRESSESOFSTATIONS,WIRELESSOROTHERWISE,THATARETHEULTIMATESOURCEANDDESTINATIONOFTHISFRAMETHESOURCEADDRESSMAYBEIDENTICALTOTHETRANSMITTERADDRESSANDTHEDESTINATIONADDRESSMAYBEIDENTICALTOTHERECEIVERADDRESSSEQUENCECONTROLCONTAINSA4BITFRAGMENTNUMBERSUBFIELDUSEDFORFRAGMENTATIONANDREASSEMBLY,ANDAL2BITSEQUENCENUMBERUSEDTONUMBERFRAMESSENTBETWEENAGIVENTRANSMITTERANDRECEIVERFRAMEBODYCONTAINSANMSDUORAFRAGMENTOFANMSDUTHEMSDUISALLCPROTOCOLDATAUNITORMACCONTROLINFORMATIONFRAMECHECKSEQUENCEA32BITCYCLICREDUNDANCYCHECKTHEFRAMECONTROLFILED,SHOWNINFIGURE148B,CONSISTSOFTHEFOLLOWINGFIELDSPROTOCOLVERSION80211VERSION,CURRENTVERSION0TYPEIDENTIFIESTHEFRAMEASCONTROL,MANAGEMENT,ORDATASUBTYPEFURTHERIDENTIFIESTHEFUNCTIONOFFRAMETABLE144DEFINESTHEVALIDCOMBINATIONSOFTYPEANDSUBTYPETODSTHEMACCOORDINATIONSETSTHISBITTO1INAFRAMEDESTINEDTOTHEDISTRIBUTIONSYSTEMFROMDSTHEMACCOORDINATIONSETSTHISBITTO1INAFRAMELEAVINGTHEDISTRIBUTIONSYSTEMMOREFRAGMENTSSETTO1IFMOREFRAGMENTSFOLLOWTHISONERETRYSETTO1IFTHISISARETRANSMISSIONOFAPREVIOUSFRAMETABLE144VALIDTYPEANDSUBTYPECOMBINATIONSTYPETYPEDESCRIPTIONSUBTYPEVALUESUBTYPEDESCRIPTION00MANAGEMENT0000ASSOCIATIONREQUEST00MANAGEMENT0001ASSOCIATIONRESPONSE00MANAGEMENT0010REASSOCIATIONREQUEST00MANAGEMENT0011REASSOCIATIONRESPONSE00MANAGEMENT0100PROBEREQUEST00MANAGEMENT0101PROBERESPONSE00MANAGEMENT1000BEACON00MANAGEMENT1001ANNOUNCEMENTTRAFFICINDICATIONMESSAGE00MANAGEMENT1010DISSOCIATION00MANAGEMENT1011AUTHENTICATION00MANAGEMENT1100DEAUTHENTICATION01CONTROL1010POWERSAVEPOLL01CONTROL1011REQUESTTOSEND01CONTROL1100CLEARTOSEND01CONTROL1101ACKNOWLEDGMENT01CONTROL1110CONTENTIONFREECFEND01CONTROL1111CFENDCFACK10DATA0000DATA10DATA0001DATACFACK10DATA0010DATACFPOLL10DATA0011DATACFACKCFPOLL10DATA0100NULLFUNCTIONNODATA10DATA0101CFACKNODATA10DATA0110CFPOLLNODATA10DATA0111CFACKCFPOLLNODATAPOWERMANAGEMENTSETTOIFTHETRANSMITTINGSTATIONISINASLEEPMODEMOREDATAINDICATESTHATASTATIONHASADDITIONALDATATOSENDEACHBLOCKOFDATAMAYBESENTASONEFRAMEORAGROUPOFFRAGMENTSINMULTIPLEFRAMESWEPSETTO1IFTHEOPTIONALWIREDEQUIVALENTPROTOCOLISIMPLEMENTEDWEPISUSEDINTHEEXCHANGEOFENCRYPTIONKEYSFORSECUREDATAEXCHANGETHISBITALSOISSETIFTHENEWERWPASECURITYMECHANISMISEMPLOYED,ASDESCRIBEDINSECTION146ORDERSETTO1INANYDATAFRAMESENTUSINGTHESTRICTLYORDEREDSERVICE,WHICHTELLSTHERECEIVINGSTATIONTHATFRAMESMUSTBEPROCESSEDINORDERWENOWLOOKATTHEVARIOUSMACFRAMETYPESCONTROLFRAMESCONTROLFRAMESASSISTINTHERELIABLEDELIVERYOFDATAFRAMESTHEREARESIXCONTROLFRAMESUBTYPESPOWERSAVEPOLLPSPOLLTHISFRAMEISSENTBYANYSTATIONTOTHESTATIONTHATINCLUDESTHEAPACCESSPOINTITSPURPOSEISTOREQUESTTHATTHEAPTRANSMITAFRAMETHATHASBEENBUFFEREDFORTHISSTATIONWHILETHESTATIONWASINPOWERSAVINGMODEREQUES