简介:未预见到的活动数据爆炸象一样光谱资源姿势少见对今天的性能的主要挑战在新奇解决方案的迫切需要处理如此的多卷的活动数据的细胞的网络。长期进化放纵(LTE-U),它扩大给没有执照的乐队动手术的LTE标准,被建议了改进系统产量。在LTE-U系统,到达用户们将与无线忠实(WiFi)竞争放纵的光谱资源播送数据信息的用户。不过,至于用为LTE用户的没有执照的乐队的传播的好处没有清楚的一致。到这个目的,在这份报纸,一个分析模型基于一个队列系统被介绍理解考虑服务(QoS)和LTE-U用户行为的质量的放纵的基于的LTE系统完成的性能。获得队列系统的替代状态答案,一个矩阵几何方法被用来解决它。然后,为LTE-U用户的没有执照的乐队的平均延期和利用被使用排队模型导出。LTE-U共存的表演用建议模型与WiFi被评估并且在实践至于LTE-U的优点提供一些起始的卓见。
简介:Globalpositioningsystem(GPS)forvehicleapplicationsintheurbanareaischallengedbylowsignalintensity.ThecarrierloopbasedonfastFouriertransform(FFT)canobtainahighsignaltonoiseratio(SNR)gainbyincreasingtheobservationtime.However,thisleadstoamajorproblemthattheaccelerationcannotbeignored.TheperformanceoftheFFT-basedloopwilldeclinewiththeaccelerationincreasing.ThispaperdiscussestheeffectofthedynamiconFFTfirst.ThenahighperformancecarriertrackingloopforweakGPSL5signalsisproposed.Itcombinesdiscretechirp-Fouriertransform(DCFT)andthephasefittingmethodtoestimateDopplerfrequencyandDopplerratesimultaneously.First,asequenceofintegrationresultsisusedtoperformDCFTtoestimatecoarseDopplerfrequencyandDopplerrate.Second,thephaseofthesequenceiscalculatedandusedtoperformlinearfitting.Bythephasefittingmethod,thefineDopplerfrequencyandDopplerratecanbeestimated.ThecomputationcostissmallbecausetheintegrationresultsareusedandthephasefittingmethodneedsonlycoarseestimatesofDopplerfrequencyandDopplerrate.ComparedwithFFTandDCFT,theprecisionofthephasefittingmethodisnotlimitedbytheresolution.Thustheproposedloopcangethighprecisionandlowcarriertonoiseratio(C/N0)trackingthreshold.Simulationresultsshowthisloophasagreatimprovementthanconventionalloopsforurbanweak-signalapplications.
简介:A2D-directionofarrivalestimation(DOAE)formultiinputandmulti-output(MIMO)radarusingimprovedmultipletemporal-spatialsubspacesinestimatingsignalparametersviarotationalinvariancetechniquesmethod(TS-ESPRIT)isintroduced.InordertorealizetheimprovedTS-ESPRIT,theproposedalgorithmdividestheplanararrayintomultipleuniformsub-planararrayswithcommonreferencepointtogetaunifiedphaseshiftsmeasurementpointforallsub-arrays.TheTS-ESPRITisappliedtoeachsub-arrayseparately,andinthesametimewiththeotherstorealizetheparallellytemporalandspatialprocessing,sothatitreducesthenon-linearityeffectofmodelanddecreasesthecomputationaltime.Then,thetimedifferenceofarrival(TDOA)techniqueisappliedtocombinethemultiplesub-arraysinordertoformtheimprovedTS-ESPRIT.Itisfoundthattheproposedmethodachieveshighaccuracyatalowsignaltonoiseratio(SNR)withlowcomputationalcomplexity,leadingtoenhancementoftheestimatorsperformance.
简介:UnipolarresistiveswitchingbehaviorsoftheZnOandAl2O3/ZnOfilmsfabricatedonflexiblesubstratesbypulselaserdepositionwerestudiedinthispaper.Thefilmsweredepositedatroomtemperaturewithoutpost-annealingtreatmentduringtheprocess.XraydiffractionresultsindicatedthatZnOfilmhasadominantpeakat(002).ScanningelectronmicroscopyobservationshowedacolumnargrainstructureoftheZnOfilmtothesubstrate.ThebilayerdeviceofAl2O3/ZnOfilmshadstableresistiveswitchingbehaviorswithagoodenduranceperformanceofmorethan200cycles,highresistiveswitchingratioofover103atareadvoltageof0.1V,whichisbetterthanthatofthesingleoxidelayerdeviceofZnOfilm.Apossibleresistiveswitchingfilamentarymodewasdemonstratedinthispaper.TheconductionmechanismsofhighandlowresistancestatescanbeexplainedbyspacechargelimitedconductionandOhmic’sbehaviors.Theenduranceofthebilayer(BL)devicewasnotdegradeduponbendingcycles,whichindicatesthepotentialoftheflexibleresistiveswitchingrandomaccessmemoryapplications.