Post on 16-May-2018
TTTTeeeechnicalchnicalchnicalchnical NotesNotesNotesNotes
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Basic of Small Cell and precision timing devices
TN151210TD Over view
SmallμCellμisμaμthinμclientμcommunicationμBaseμStationμthatμsignificantμcontributionsμcanμbeμexpectedμtoμcostμtheμ
suppressionμofμproliferationμandμinfrastructureμofμtrafficμinμtheμInternetμcommunity.μSmallμCellμisμexpectedμinμadditionμ
toμtheμpreviousμMacroμCell,μtoμputμtheμnextμgenerationμcommunicationμsystemμ(4Gμtoμ5G).μ
InμthisμarticleμforμbeginnerμshowsμtheμroleμofμSmallμCell,μfeatures,μand,μrequirementμreasonsμofμhighμprecisionμclock,μ
andμintroduceμaμEPSONμtimingμdeviceμsolutionsμofμoptimalμapplications.μ
Small Cell’s role WeμshowμinμtheμillustrationsμofμtheμmajorμroleμofμtheμSmallμCellμonμFigureμ1μandμFigureμ2.μ
Figureμ 1=μ Smallμ Cellμ servesμ toμ supplementμ theμ communicationμ qualityμ atμ deadμ zoneμ (redμ area,μ beforeμ
implementation)μthatμexistingμBaseμStationμcannotμbeμcoveredμ(orangeμarea).μ
Figureμ2=μSmallμCellμcanμcoverμtrafficμoverflowμwithμexistingμbaseμstationμatμwhereμaμlargeμnumberμofμcommunicationμ
peopleμarea.μ
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Figureμ1:μSmallμCell’sμroleμcase1μ
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Figureμ2:μSmallμCell’sμroleμcase2μ
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Feature of Small Cell SmallμCellμtoμrepresentμitsμname,μsmallμandμeasyμtoμinstall,μasμcomparedμtoμtheμexistingμBaseμStation,μ μ
itμcanμbeμintroducedμatμlowμcostμwhichμisμtheμgreatestμmerit.μ
SmallμCell,μasμshownμinμTableμ1,μisμclassifiedμintoμ4μmajorμcategories.μAnμindividualμdifferenceμbyμ μ userμcapacityμ μ
coverageμareaμ μ transmissionμpowerμoutputμ μ installationμenvironment,μitμdoesμnotμmeanμitμisμstrictlyμdefined.μ
Tableμ1:μtypeμofμSmallμCellμ
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AndμasμshownμinμFigureμ3,μforμfutureμtrafficμgrowth,μinμorderμtoμeffectivelyμutilizeμtheμlimitedμfrequencyμspectrum,μ μ
LTEμ communicationμ schemeμ isμ graduallyμ evolvedμ fromμ FDDμ toμ TDD.μ Inμ thatμ case,μ theμ requiredμ accurateμ timeμ
synchronizationμisμdefinedμasμbelowμ1.5 μsecμaccuracy.μ
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(ULμ=μUpμLink,μDLμ=μDownμlink)μ μ
Figureμ3:μdifferenceμFDDμandμTDDμ
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Requirement high accuracy clock AsμmentionedμinμSectionμ2,μifμtheμTDDμschemeμisμemployed,μinμorderμtoμimproveμtheμreceptionμqualityμofμtheμterminalμ
wouldμrequireμaccurateμ“Frequencyμsynchronization”μandμ“Timeμsynchronization”μbetweenμaμBaseμStationμandμSmallμ
Cell.μItμshowsμtheμimageμinμFigureμ4.μ
- Frequencyμsynchronizationμ=μadjustμcarrierμfrequencyμatμppbμlevel. Airμinterface μ
- Timeμsynchronizationμ=μtimeμdifferenceμisμadjustedμwithinμ1.5μuSμbetweenμBTSμandμSmallμCell. TimeμAccuracy μ
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Figureμ4:μFrequencyμandμTimeμsynchronizationμ
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Critical factor of timing devices Asμelementsμrequiredμforμtheμtimingμdeviceμwhichμgeneratesμaμreferenceμclockμforμstabilizingμbothμofμfrequencyμandμ
timeμsynchronization,μtheμfollowingμthreeμfactorsμareμquiteμimportant.μ
Phase Noise
Frequency Stability = Holdover
Wander Performance
Below,μweμdescribeμtheμdetailsμofμtheseμthreeμfactors.μ
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Phase Noise
PhaseμNoiseμisμnoiseμlevelμthatμnominalμcarrierμfrequencyμpowerμvsμnoiseμpowerμatμeachμoffsetμfrequency.μ
Alsoμreferμto:μhttp://www5.epsondevice.com/en/information/technical_info/pdf/techl_notes_jitter0416.pdfμ
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TheμleftμfigureμinμFigureμ5μisμshowsμtheμPhaseμNoiseμinμtheμgraph.μRightμfigure,μtheμPhaseμNoiseμqualityμhasμ μ
closeμrelationμforμwirelessμsignalμEVMμ(ErrorμVectorμMagnitude).μ
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Figureμ5:μphaseμnoiseμ
Frequency Stability = Holdover
Thereμareμsomeμindicatorsμinμfrequencyμstability,μalthoughμinμtheμSmallμCell,μHoldoverμisμtheμmostμimportant.μ
TheμHoldoverμmeans,μitμisμaμconditionμthatμisμoperatedμbyμstoredμdataμwhichμhasμbeenμretainedμforμtheμphaseμcontrolμ
inμtheμlockμmodeμwhenμclockμsupplyμdeviceμisμlostμtheμreferenceμtimingμinputsμforμtheμcontrolμrefers.μ
TheμleftμfigureμinμFigureμ6μtoμshowμtheμspecificμmeaningμofμtheμHoldover.μAnd,μitμshowsμaμlistμofμHoldoverμstandardμforμ
eachμhierarchyμinμtheμfigureμright.μSmallμCellμisμgenerallyμclassifiedμintoμStratum3.μ
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Figureμ6:μHoldoverμ
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Wander Performance
Wanderμisμaμfluctuationμofμveryμslowμwaveform.μGenerally,μtheμcaseμinμwhichμfluctuatesμtheμfrequencyμinμtheμlongμ
periodμofμmoreμthanμoneμsecondμisμcalledμWander,μitμisμreferredμtoμasμaμJitterμwhenμshakenμtheμfrequencyμinμaμshortμ
periodμofμlessμthanμ0.1μseconds.μ
Alsoμreferμto:μhttp://www5.epsondevice.com/en/information/technical_info/pdf/techl_notes_jitter0416.pdfμ
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Figureμ7:μWanderμ
AsμanμevaluationμindexμofμWanda,μthereμisμaμTIEμandμMTIE,μTDEV.μ
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Features of EPSON timing devices EPSONμprovideμbestμandμoptimumμperformanceμproductsμ forμbelowμ3μ importantμ factorsμbasedμonμownμexclusiveμ
technology.μ
Improving Phase Noise
·μ Theμuniqueμstructuralμdesign,μwasμparticularlyμachieveμgoodμnoiseμcharacteristicsμtoμexternalμinfluencesμ μ μ
μ (temperatureμchangeμdueμtoμtheμflowμofμair).μSeeμFigureμ8.μ
Improving Frequency Stability = Holdover
·μ Anμin-houseμICμdesignμandμmanufacture,μtheμoptimalμcombinationμofμtheμresonatorμelementμaccordingμtoμitsμownμ μ
μ photo-lithographyμtechnique,μtoμachieveμaμgoodμstability.μSeeμFigureμ9.μ
Improving Wander performance
·μ Theμuniqueμstructuralμdesign,μwasμparticularlyμachieveμgoodμwanderμcharacteristicsμtoμexternalμinfluencesμ μ
μ (temperatureμchangeμdueμtoμtheμflowμofμair).μSeeμFigureμ10.μ
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Figureμ8:μEPSON’sμPhaseμNoiseμ
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μFigureμ9:μEPSON’sμstabilityμ
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μFigureμ10:μEPSON’sμWanderμPerformanceμ
EPSON’s products lineup Weμintroduceμaμtimingμdeviceμline-upμofμEPSONμwithμtheμfeaturesμofμmoreμthanμbelow.μ
Fromμtheμfollowingμwebμpagesμlinking,μitμisμpleasedμifμyouμcanμconfirmμdetailedμproductμspecifications.μ
http://www5.epsondevice.com/en/products/tcxo_network/μ
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