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1、3GPPTSGRANWG2#58bisTdoc-R2-072721Orlando,U.S.A.,25th–29thJune2007Agendaitem:4.5.1Source:NTTDoCoMo,TelecomItalia,T-MobileTitle:UseofcellspecificoffsetsandreadingneighbourBCHDocumentfor:Discussion1.IntroductionInRAN2#58inKobe,RAN2hasdecidedthat,toallowforsufficientmobili
2、tycontrolwithoutNCL,anoffsetvalueshallbeincludedinBCH,andthattheUEshallreadtheneighbourcellBCHtoobtainthisoffsetvaluebothinACTIVEandIDLEmodes[1].Theoffsetvaluebiasesthemeasuredquantityofthecorrespondingcellformobilitycontrol.Itwasexpressedbyoperatorsthatthisoffsetisnec
3、essaryprimarilytocontrolthecellboudariesconsideringtheDLandULcoverageimbalance,causedbyDL/ULfeedercablelossdifference(duetoTMA)andeNBshavingdifferenttransmissionpowersadjoininginthenetwork[2].However,inRANPlenary#36inBusan,thedecisionwastakenbackaftersomevendorsexpress
4、edconcernsonthehandover/cellreselectiondelaysandUEbatteryconsumption[3].Revisitingthisissue,thisdocumentexplainswhycellspecificoffsetsarethoughtnecessary,summarisesconcernsofreadingneighbourBCH,andpresentsourpositionontheissue.NotethatthesupportforoptionalNCLforintra-f
5、requencycellshasalreadybeenagreedinRAN2,andthishasnotbeenreopened.TheoptionalNCLshouldservepurposessuchastosetserving-neighbourpairwisespecificoffsetsortoblacklistcertaincells.Itcanalsobeusedtospeedupcelldetection,althoughrelevanceofthisispendingRAN4response.Hence,theo
6、nlyopenquestionthatneedstobeaddressedis“whetherUEreadsneighbourBCHandobtainstheoffsetvalueincludedtherewith,”andthisistheexactfocusofthispaper.2.Useofcellspecificoffsets2.1DL/ULimbalanceproblemAsmentionedin[2],theneedforacellspecificoffsetismainlymotivatedbythefactthat
7、eNBsofdifferentpowerclassescanbeadjoininginmanyplacesthroughoutthenetwork,andthateachcellhasdifferentDLandULfeedercablelosses(i.e.,DL/ULfeederlossdifferenceduetoTMA).Bysettingappropriteoffsetvalues,theDL/ULimbalancecanbemitigated.Beforegoingintohowoffsettingworks,theDL
8、/ULimbalanceproblemhastobeunderstood.Figure1showstheprincipleofDL/ULimbalancecausedbycablelossdifference.Assumingtwob
