简介:【摘要】 NR-MIMO作为 5G无线接入技术,满足增强的移动带宽、大规模机器式通信、超可靠和低时延通信等需求,支持高达 100GHz的宽频率范围,但对于 6GHz以上的高频通信存在着明显的路径损耗和穿透损耗。通过部署大型天线阵列以获得高波束赋形增益,研究包括模拟 /数字 /混合波束形成在内的各种波束赋形的增强型大规模 MIMO在内的新型无线电接口的多天线方案,是解决 5G NR-MIMO路径损耗和穿透损耗的一种有效途径。
简介:Theimpactofmutualcouplingontheperformanceofmultiple-inputmultiple-output(MIMO)systemswithcompactantennaarraysisanalyzed.ThisarticleaimstousetheS-parametermodelingapproachtoexaminetheimpactofmutualcouplingonthreesystem-relatedperformancemeasures:antennacorrelation,efficiencyandbandwidth.Itisshownthatimplementingagoodmatchingnetworkcandrasticallyimprovethesystemperformanceinthepresenceofstrongmutualcoupling.Experimentresultsindicatethesuperiorityofcross-shapedantennatodipoleantenna.
简介:RandomMatrixTheory(RMT)isavaluabletoolfordescribingtheasymptoticbehaviorofmultiplesystems,especiallyforlargematrices.Inthispaper,usingasymptoticrandommatrixtheory,anewcooperativeMultiple-InputMultiple-Output(MIMO)schemeforspectrumsensingisproposed,whichshowshowasymptoticfreepropertyofrandommatricesandthepropertyofWishartdistributioncanbeusedtoassistspectrumsensingforCognitiveRadios(CRs).SimulationsoverRayleighfadingandAWGNchannelsdemonstratetheproposedschemehasbetterdetectionperformancecomparedwiththeenergydetectiontechniqueseveninthecaseofasmallsampleofobservations.
简介:Theresearchandapplicationofwirelesslocalareanetworks(WLAN)technologyareinastageofrapiddevelopment.Ithasbeenoneofresearchfocusesofthewirelesscommunicationsfield.Throughtheuseofenhancedsingle-user(SU)/multi-user(MU)multipleinputmultipleoutput(MIMO)-orthogonalfrequencydivisionmultiplexing(OFDM)technology,thenextgenerationWLANIEEE802.11acdramaticallyincreasesthethroughput.AnimprovedMIMO-OFDMschemebasedonmodulationdiversityisproposedforthenextgenerationWLAN.Itusestwo-dimensionalmodulationdiversitytothecurrentIEEE802.11actransmissionscheme.Throughthespace-time-frequencycomponentinterleaverandtherotationalmodulation,theproposedschemeexhibitshighspectralefficiencyandlowerrorrateinfadingchannels.ThesimulationresultsshowthattheproposedschemesignificantlyoutperformstheSU/MUMIMO-OFDMschemeinthecurrentIEEE802.11acstandard,whichisupto5dB.
简介:Vertically-layeredBellLaboratoriesLayeredSpace-Time(VBLAST)isoneofthemostpromisingtechniquesforrealizinghighspectralefficienciesoverwirelesslink.Inpreviouslypublishedwork,theperformanceofVBLASThasbeenprimarilyinvestigatedinuncorrelatedRayleighfadingchannels.Howeverinrealenvironmentssomecorrelationbetweenantennaelementscanbepresented.Inthispaper,westudytheimpactoftransmitcorrelationontheperformanceofVBLASTsystems.FinallyweprovidesimulationresultsdemonstratingtheimpactofspatialfadingcorrelationonthesymbolerrorrateofVBLAST.
简介:Bydeducingthedistributionofthenormalizedchannelcovariancematrix,anovellimitedfeedbackschemeisproposedundermultipleusers(MU)multiple-inputmultiple-output(MIMO)broadcastchannel(BC)system.Theproposedschemehasadvantagesinthreeaspects.First,ithasnoconstraintsonthenumberofusersorantennas.Second,eachuser'sfeedbackbitsareindependentofthenumberofreceivingantennas.Third,theproposedschemeavoidsthestorageoflarge-sizecodebookonthetransceivers.Simulationresultsshowthattheperformanceoftheproposedschemeisclosetotheperfectchannelstateinformation(CSI)caseanditjustneedsasmallnumberoffeedbackbits.
简介:Theproblemofdetectingsignalwithmultipleinputmul-tipleoutput(MIMO)radarincorrelatedGaussianclutterdominatedscenariowithunknowncovariancematrixisdealtwith.Thegen-eralMIMOmodel,withwidelyseparatedsub-arraysandco-locatedantennasateachsub-array,isadopted.Firstly,thegeneralizedlikelihoodratiotest(GLRT)withknowncovariancematrixisob-tained,andthentheRaoandWalddetectorsaredevised,whichhaveprovedthattheRaoandWaldtestcoincidewithGLRTdetec-tor.Tomakethedetectorsfullyadaptive,thesecondarydatawithsignal-freewillbecollectedtoestimatethecovariance.Theper-formanceoftheproposeddetectorisanalyzed,however,itisjustancillary.Athoroughperformanceassessmentbyseveralnumer-icalexamplesisalsogiven,whichhasconsideredthesensewithco-locatedantennasconfigureoftransmittersandreceiversarray.Theresultsshowthattheperformancetheproposedadaptivede-tectorisbetterthanLJ-GLRT,andthelosscanbeacceptableincomparisontotheirnon-adaptivecounterparts.
简介:沙特拉比格项目部关于无损检测方法的选用,检测中心与业主探讨多次,业主坚决不同意手动超声,要求全部采用射线探伤,故探伤工作量很大。由于工期紧的原因,采用自动超声的新技术TOFD和相控阵,这样可以交叉作业,降低工作强度,提高探伤效率,保证工程进度。通过沙特拉比格项目部一年多的TOFD和相控阵超声检测的实践经验,TOFD和相控阵超声波检测技术已经被证实是非常实用于现场焊缝检测的无损检测方法。在检测的过程中,展现出相当的优越性,如高效率,安全,低成本,储存数据,提高生产率等。