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7/30/2019 CAM Technical Paper LTE.pdf
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Introduction
LTEtechnologypromisestobringspeedsofover100Mbpsdownlinkand50Mbpsuplinktomobileusers
usingmobilebroadbandapplications.With196operatorsin75countriescurrentlyinvestinginthe
technology,LTEisnowgenerallyacknowledgedtorepresentthefutureoftheindustry.
Inturn,demandfordataisrunningatlevelsthatwereunimaginableevenacoupleofyearsago.Thisisdue
totheemergenceofsmartphonesandotherhighenddevicesrunningmultimediaapplicationssuchas
streamingvideoandmobileTV.By2015,itispredictedthattotaldatarateswillexceed6,300,000terabytes
permonth.
Giventhatsome50%oftotalmobiletrafficissaidtooriginateorterminatewithinbuildings,wepredicta
corresponding
massive
increase
in
demand
for
data
from
our
in
building
networks.
Thepurposeofthisdocumentistopresentthefiguresrelatingtothisgrowthindatademandandtoassess
howwemayscaleourexistinginbuildingDASnetworkstohandlethisgrowth.Weconsideroptionssuchas
deployingsmallercellstoimprovecapacityinlocalisedareas;utilisingMIMOtechnologiestoofferhigher
datarates;andupgrading,allorpartofourexistingDASnetworkstoLTEtechnology.Thedocumentis
structuredasfollows:
Firstwehighlightthefiguresbehindthehypesurroundingthiseverincreasingdemandfordata.WelookatthenumberofdevicessuchassmartphonesandtabletPCs,bothnowandintheyearstocome,
andmultimediaservicessuchasvideo,VoIP,gamingetc.Thesefigureswillhelpusbenchmarkthe
requirements
of
future
in
building
network
designers.
Workingwiththesefiguresfordatademand,wemustconsidertheperformanceofbothexistingcellulartechnologies(HSPAandHSPA+)andemergingtechnologies(LTEandLTEAdvanced).Weneed
toestimatehowthesetechnologieswillbeabletocopewithincreasingdemandandforhowlong.
OneofthekeyfactorsinincreasingtheperformanceofwirelessnetworksistheintroductionMIMOtechnologies.MIMOwillplayanimportantroleinourdecisionsonfuturenetworkdesign.Asectionin
thisdocumenthasbeendedicatedtoexplainingmultipleantennatechnologies.
WeconsiderhowaninbuildingDASmaybedesignedtocopewiththevolumesofdatathatwillberequired
in
the
coming
months
and
years.
In
the
case
of
4G
networks,
the
challenge
from
the
outset
willbetoengineerthenetworkstodelivercapacity,asopposedtocoverage,whereitisneeded.
FinallywelookatacoupleofpossiblesolutionsformigratingaDAStoLTEwith2x2MIMO,withoneoptionsimplydoublinguponexistinginfrastructureandamorenovelapproachusingCAT5/6cabling
tocarrytheDASsignals.
LTETechnicalChallengesforInBuildingCoverage
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ThisdocumentisdesignedtohighlightthechallengesinvolvedindesigningaDAStosupportthemassivedatademandsgeneratedbytheproliferationofsmartphonesandthelike,togetherwith
applicationssuchasvideostreamingandmultimediagaming.Itisnottheobjectivetoproposeany
solutionsbuthopefullytostimulatediscussion.
Exponentialgrowth
in
data
consumption
Overtheperiodofthelastthreeyearsto2010,thevolumeofdatabeingconsumedovermobilenetworks
hasalmosttripledyearonyear.In2010,accordingtoCisco,totalglobalmobiledatatrafficwasinexcessof
230petabytespermonth(1petabyte=1,000,000gigabytes).Thisisoverthreetimesgreaterthantotal
globalinternetusageinthewholeoftheyear2000.
Whilstthisrateofgrowthisforecasttoleveloutduring2011,Ciscohasforecastthatby2015wewillseea
26foldincreasein2010rates,withmonthlyusageof6.3exabytespermonth(1exabyte=1,000
petabytes).Pleaseseefigure1below.
Moreover,AlcatelLucenthasforecasta16foldincreaseinmobiledatatrafficto2015butwarnedthatit
couldgrowashighas40timestodayslevels[2].
Figure1:CiscoForecasts6.3Exabytes(6,300,000Terabytes)
perMonthofMobileDataTrafficby2015
Thisdescription
of
the
growth
in
data
rate
consumption
includes
some
newterminologyusedtodescribethevastquantitiesofdataunder
discussion.Thechartoppositeshowsthevaluesofthesenewterms,suchaspetabytesandexabytesrelative
tothemorerecognisablefiguressuchasgigabytes.
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Smartphones,TabletPCsandDataHungryApplications
Thegeneralpatternofacceleratinggrowthinusageofadvanceddataservicesislinkedtoastronguptake
intheusageofsmartphonesandotherhighenddevicessuchasTabletPCsandmobilegamingconsoles.
Smartphones,runningapplicationssuchasstreamingvideoandinteractivegamingareextremelydata
hungry.In
2010,
the
typical
smartphone
generated
24
times
more
mobile
data
traffic
than
abasic
feature
cellphone.CiscoVNI
Tomakemattersworse(forthenetworkdesigner)theiPhoneandtheAndroidbaseddeviceswillconsume
5to10timesasmuchdataasaregularsmartphone.
Typicallyahighendsmartphonewillgeneratearound79MBpermonthcomparedwith3.3MBpermonth
forabasicfeaturesetphone.
Thetablebelowgivesanideaofthelevelsoftrafficgeneratedbydifferentdevicetypes.
Devicetype
Traffic
Generated
cf.
Basic
Mobile
Phone
Basicmobilephone x1
Smartphone x24
Handheldgamingconsole x60
TabletPC x122
Laptop x515
Table1:FiguresCourtesyCiscoVNI2011
ImpactofsmartphonesfromtheMobileOperatorsperspective
FigurescollatedandreleasedbytheGlobalMobileSuppliersAssociation(GSA)showasubstantialgrowthin
revenuethroughout2010whichhasbeendrivenbythesuccessofthesmartphonethroughoutEurope,the
USAandAsiaPacific.
VodafoneUK:2010datarevenuegrowthup30%;drivenbysmartphonesuccess VodafoneItaly:2010datarevenuegrowthup22%;smartphonesales50%oftotalhandsetsales AT&TUSA:2010datarevenuegrowthup27%;7.4milliondevicesales;4.1millioniPhonesalesin2010 PCCWAsia: >80%ofnewsubscribersaresmartphoneusers;3Gdatarevenuegrewby156%inH12010Thisphenomenalgrowthinsmartphoneadoptionandtheexponentialincreaseindatausageisfurther
borneoutbythefollowingfiguresandpredictions:
Googlestatethat300,000Androidphonesareactivatedworldwidedaily. TheITUestimatesthattheglobalnumberofsmartphonesisexpectedtoquadruplefromtoday's(2010)
estimateof200millionhandsetstoalmost1billionby2015.
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Figure2:CourtesyGlobalMobileSuppliersAssociationwww.gsacom.com
AccordingtoInformaTelecoms&Media,whilstsmartphonepenetrationcurrentlyrunsatjust13%,this
accountsfor65%ofallmobilecellulartrafficworldwide.Thisusagefigureissettoincreaseexponentially
overthenextfiveyearswiththeaveragetrafficpersmartphoneuserincreasingby700%by2015.
Inadditiontothesuccessofthesmartphone,therearerangesofother,datahungrydevicesthathave
recentlyemergedonthesceneandarebeingadoptedbytheconsumeratarate:
WorldwidesalesofmediatabletssuchastheiPadwillreach19.5millionbytheendof2010andexceed54millionin2011.Gartner.
Shipmentsofmobilebroadbandenabledconsumerproducts,includingebookreaders,mobiledigitalcameras,camcorders,personalmediaplayersandmobilegamingdeviceswillincrease55foldbetween
2008and2014withtotalshipmentsreaching58millionunitsperyearin2014.ABIResearch
GiventhatatabletPCcangenerateaboutfivetimesasmuchdataasahighendsmartphone,thepotential
data
usage
of
a
combination
of
all
these
devices
is
beyond
any
figure
that
the
original
mobile
networks
weredesignedtohandle.
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PredictionsonFutureDemandforDataonInbuildingSystems
UsingthesefiguresasaguidelinewecanmodelthepotentialimpactonaninbuildingDASoftherapidly
increasingdemandfordatadueto:
Thelevelofpenetration(marketshare)ofsmartphonesincreasingfrom13%currentlyto50%andbeyond
by
2015
Asevenfoldincreaseintrafficpersmartphone:CiscoVNI
Inpredictingthedemandonaninbuildingnetworkwemakethefollowingassumptions:
1. Inaninbuildingscenarioweassumethemajorityofthetrafficwillcomefrommobilephones.Wedonotincludelaptopsorotherdevices.(smartphonetraffic+basicphonetraffic=compositetraffic).
2. Therewillbenosignificantincreaseinthenumberofhandsetswithinagiveninbuildingscenarioasweassumethebuildingpopulationwillnotchangesignificantlyovertime.
3. AlthoughtheDASforeachindividualbuildingwillexperiencedifferenttrafficchangesovertime,wecanassumeapredictionforagenericscenariosuchasashoppingcentre.
Tables2and3showthepredictedtrafficlevelsasdescribedaboveperdevice:
Combiningthefiguresforincreaseinpenetrationofsmartphoneswiththesevenfoldincreaseindata
demandfromthesedevices,wecanseefromthetablesabovethatinbuildingtrafficperdeviceis
predictedtoincreasefrom13.2to278.9MBpermonthby2015,morethanadoublingofdatayearon
year.
Table2:Currenttrafficlevels(MBpermonth)
TrafficperMonth Penetration% TrafficxPenetrationBasicPhone 3.3 87% 2.871
SmartPhone 79.2 13% 10.296
CompositeTraffic 13.167
Table3:Predictedtrafficin2015(MBpermonth)
TrafficperMonth Penetration% TrafficxPenetrationBasicPhone 3.3 50% 1.65
SmartPhone 554.4 50% 277.2
CompositeTraffic 278.85
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Indesigninganinbuildingnetworktodeliverthesevolumesofdatathereareanumberofoptions
availabletous:
DeployingHSPA+andLTEtechnologywithinbuildingstoprovidehighthroughput,lowlatencynetworks.
MIMO
antenna
systems
are
an
integral
part
of
LTE
and
HSPA+
technologies
and
may
be
used
to
improveperformance,byimprovingthequalityoftheradiolink,and/orincreasingdatathroughput,
undergivenconditions.
Smallcellarchitecturescanbeusedtoincreasethecapacityofanetworkbydeliveringthedatalocallytoasmallernumberofusers.
Theseoptionswillbediscussedinthefollowingsections.
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ComparativePerformanceofCellularTechnologies:HSPA,HSPA+andLTE
Asthedemandfordataincreaseswemustconsiderthetechnologiesbeingused(withintheinbuilding
system).Althoughtherearemorecriteriathanjustdataratestoconsiderwhendecidingonacellular
technology,itisoneofthemostimportantandwethereforepresentacomparisonofHSPA,HSPA+andLTE
datarates.
HSPAandHSPA+arewellestablishedtechnologies,withhundredsofnetworksdeployedglobally.LTE
rolloutsbeganlate2010andinbuildingLTEisstillintheearlystages.LTEAdvancedisstillindevelopment.
(Performancefiguresquotedinthissectionare,inthelargepart,peakdatarates,fromwhichwecan
calculatethroughputratesfromonsiteexperience.Throughputfiguresarequotedwhereavailable.)
HSPAhasbeenlaunchedbyover99%ofWCDMAoperatorsglobally:
35%ofHSPAnetworks supportupto3.6MbpspeakDL 30%ofHSPAnetworks supportupto7.2MbpspeakDL 8%ofHSPAnetworks supportupto14.4MbpspeakDLHSPA+hasbeendeployedinstages,asthetechnologyhasevolved.
TheevolutionofHSPA+technologiescanbeseenfromthedatabelow.
HSPA+using64QAM, supportsupto21MbpspeakDL HSPA+using16QAMwith2x2MIMO supportsupto28Mbpspeak DL HSPA+using64QAMand2x5Mhzcarrier supportsupto42MbpspeakDL HSPA+using16QAM supportsupto11.5MbpspeakUL HSPA+usingmulticarrierontheuplink supportsupto23MbpspeakULFurtherdevelopmentofHSPAtechnologieswithinRelease9and10aimsatthefollowingdownlinkrates:
Rel9HSPA+combinesmulticarrierandMIMOin10MHzbandwidthfor84Mbpspeakdownlink HSPA+beyondRelease9shouldleadtopeakdownlinkdataspeedsexceeding100Mbps
LTEtechnologywasfirstrolledoutin2010.Inbuildingthroughputfiguresarescarceatthistime.
Thenumberofcommercialnetworkslaunchedtodateisstillquitelowandactualthroughputfiguresare
hardtocomeby.ThepeakdataratesforLTEareasfollows:
Peakdownlinkspeeds(64QAM) supportsupto100Mbps(SISO)supportsupto172Mbps(2x2MIMO)
supportsupto326Mbps(4x4MIMO)
Peakuplinkspeeds supportsupto50Mbps(QPSK)supportsupto57Mbps(16QAM)
supportsupto86Mbps(64QAM)
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Table2:ComparisonofPeakDataRates:ThroughputFiguresShownWhereAvailable.
DatacourtesyHSPAtoLTEAdvancedRysavyResearchwww.3gamericas.org
MIMOtechnologyisdiscussedindetailinthenextsection.
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MIMOTechnologies
ThispaperisaddressesthechallengesofrollingoutinbuildingLTEnetworks.MIMOtechnologyisa
fundamentalpartofLTE,impactingtheamountofworkandthecostsinvolvedinarolloutmorethanany
othersingleitem.WehavethereforeprovidedadescriptionofMIMOconcepts,terminologyandmodesof
operationas
they
relate
to
LTE.
MIMOisconsideredessentialforLTE,tomaximizesystemcapacityandprovidehighdatarates.Both2x2
and4x4designsarebeingconsideredalthoughonly2x2configurationsarebeingdeployedatthistime.[5]
LTEsystemsspecifythreetypesofantennatechniques;Diversity,BeamformingandMIMO
Fig3:TypicalConfigurationsforMultipleAntennaSystems
AntennadiversitycanincludetransmitdiversityorMultipleInSingleOut(MISO)andreceivediversityor
SingleInMultipleOut(SIMO)configurations:
MISO(transmitdiversity),usestwoormoretransmitantennasandasinglereceiveantenna.Thesamedataissentfrombothtransmittingantennassimultaneously,butcodedinsuchawaythatthereceiver
canidentifythedatafromeachtransmittingantenna.Thistechniquecanmakethesignalmore
resistanttofadingandisusedtoimproveperformanceinpoorcoverageareas.
Transmit Receive
SISO
MISO Transmitdiversity
SIMO Receive
diversity
MIMO
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SIMO(receivediversity)usesonetransmitantennaandtwoormorereceiveantennas.Onlyonedatastreamistransmittedacrossthepathandspatialdiversityatthereceiveendcanbeusedtoimprove
SNRunderpoorchannelconditions.
TransmitBeamformingisatechniquewherebymultipledatastreamsaretransmittedovermultiple
transmitantennas,andwiththehelpoffeedbackfromthereceiver(ChannelQualityInformationCQI),the
relativephaseofthetransmittedsignalscanbeadjustedsuchthattheywillcombineconstructivelyatthe
receivertofocustheRFbeamonthatdevice.TransmitBeamformingcanbeusedtoimprovesignal
receptionandincreasetherangetoaparticularreceivingdevice.
MIMO(MultipleInMultipleOut)makesuseoftwoormoretransmitantennasandtwoormorereceive
antennas.DependingonthewayMIMOisimplemented,multipleantennaconfigurationscanbeusedto
generatehigherthroughput(spatialmultiplexing)ortoprovideamorereliablelink(diversitytechniques).
Spatialmultiplexingisusedtoincreaselinkcapacity.Theinformationtobetransmittedisdividedintoindependent
data
streams
and
each
stream
is
sent
simultaneously
from
aseparate
antenna
(multiple
spatialstreams).IfwehaveNtransmitantennasthenwemustalsohaveNreceiveantennas.Ifthe
resultantdatastreamsaresufficientlyuncorrelatedtobedistinguishablefromoneanother,thenthe
totalthroughputofthelinkwillbeNtimesthesingledatastream.
Spatialdiversitycanbeusedtoincreasetherangeand/orreliabilityofalink.Thesamedataistransmittedsimultaneouslyovermultipleindependentfadingsignalpathsandbymakinguseofthelow
probabilityofthesesignalpathsexperiencingdeepfadesatthesametime,theincomingsignalscanbe
combinedtoincreaseSNR,henceimprovinglinkreliabilityandrange.Foreffectivediversity,the
antennasattheboththetransmitterandthereceivermustbeplacedwavelengthapart.
SingleUserMIMO(SUMIMO)iscommonlyusedinLTEsystemstoincreasethedataratetooneuserin
goodradioconditions.ThemostcommondownlinkconfigurationforLTEis2x2SUMIMOusingspatial
multiplexing.(seeFig4).
MultiUserMIMO(MUMIMO).Considertwodatastreams,eachstreamoriginatingfromadifferentuser
device(seeFig4).MUMIMOreliesonthefactthatthespatialseparationbetweentheuserdevicesis
sufficientthattheinformationarrivingatthereceiveantennaswillhaveuncorrelatedpaths.Thismaximises
thepotentialcapacitygainatthereceiver(theeNodeviaDASantenna).
Oneof
the
design
motivations
of
the
LTE
standard
is
to
keep
the
terminal
or
mobile
device
cost
low.
Thereforeinordertominimiseactualtransmitantennasonthemobiledevice,multipleuserMIMO(MU
MIMO)isbeingconsideredasanattractiveoption.
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Fig4:SUMIMOandMUMIMOconfiguration
Tosummarisetheabove,MIMOisamethodofusingmorethanoneantennaatthetransmitterand
receiverto
improve
communications
performance.
MIMO
has
the
potential
either
to
increase
the
capacity
ofnetworksortoenlargetheareaofagivencellwithouttheneedforadditionalspectrum.
DASAntennas
SingleUserMIMO
(LTEconfiguration 2x2SUMIMOusingSpatialMultiplexing)
MultiUserMIMO
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CorrelationinMIMOChannels
ForMIMOtobeeffectiveinachievingitsobjectivesofincreasedrangeandcapacity,theenvironmentin
whichitisdeployedmustprovidesufficientmultipath(reflectedwaves).Thisisreferredtoasnonlineof
sight(NLOS)transmissionwhichtypicallyoccursinanindoorenvironment.
In
this
so
called
rich
scattering
environment,
the
transmitted
signals
bounce
off
objects
such
as
walls,
such
thattheyarereceivedwithdistinctlydifferentprofilesatthereceiveantennas;i.e.thesignalsareeasily
distinguishablefromoneanother.Inmathematicalterms,thesignalsaredecorrelatedatthereceiver.
Conversely,inanenvironmentwithpurelylineofsightLOScharacteristics.thereisonepredominantsignal
arrivingatthereceiver.TheadvantagesofMIMOcannotbeaseasilyrealisedasthesignalsarenolonger
decorrelated.Furtherdescriptionisbeyondthescopeofthisdocument;howevermoredetailisavailable
onrequestfromCAM.
MIMOisacrucialtechnologyforimprovinginbuildingcellularcoverage.Inarichscatteringenvironment
withahighsignaltonoiseratio,aMIMOsystemcandeliverbetween70%to100%throughputandcapacity
gainsover
asingle
input
single
output
(SISO)
deployment.
The
rich
scattering
environment
describes
most
inbuildingenvironmentsandinbuildingdistributedantennasystems(DASs)canprovidehighsignal
quality.(ADCJune2010)
AchallengeforradioplannersisleveragingthemaximumperformancefromMIMOsystems,thiswill
requireinbuildingsystemsdesignedtoprovideasufficientlymultipathrichenvironmentwhilestill
achievingahighsignaltonoiseratio.
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ChallengesforInbuildingSolutions
Thusfarinthisdocumentwehavehighlightedthesoaringincreasesindataconsumptionmainlydueto
smartphonesusingdatahungrymultimediaapplications.Predictionsfordataconsumptiongoingforward
show
more
than
a
doubling
of
traffic
year
on
year
from
2011
to
2015.
Thisraisesthequestion:howlongcantheexisting2G/3GinbuildingDASscopewiththedatademands
uponthemandwhatwouldbeanappropriateupgradepathtothenextgenerationofnetworks?
HowlongcananexistingDASsupporttheincreasingtraffic?
InordertoestimatehowlonganexistingDAScansupporttheincreasingtrafficlevelswemustmakea
coupleofassumptions:
Forsitesthatcansplitintosmallercellsthecapacityofthesitemaybedoubledforadoublingofcells. NetworksupportforhigherHSPA+withoutMIMOwillalsoliftcapacitybyafactoroftwoAseachofthesechangesdoublescapacityofthesitewecanseethattheexistingDASwillbeableto
supporttrafficgrowthforanothercoupleofyearswithinanyparticularbuildingbeforeMIMObecomes
necessary.
AddedtothisisthefactthatneitherMIMOnorSmallCelltopologieswillbeaddedasanetworkwide
upgrade,butwillbedeployedinlocalisedareasonly.Thenetworkupgradescanbeperformedgradually
overtime,spreadingboththecostsandtherisksaswelearnfromeachstageofanupgrade.
WhatOptionsareAvailableforUpgradinganExistingInbuildingDAS?
Reducingcellsizebysectorisationorusingsmallcells. Largebuildingscanbedividedintosmallercells(orsectors),reducingthenumberofuserspercell(orsector),therebyincreasingcapacity.The
disadvantagesarethattherearephysicallimitationstohowsmallcellscanbemade;smallercellsmay
meanmorecellswhichinturnrequiremoreNodeBs,whichrequiremorespaceandmorepower.Re
cablingofthesystemeachtimeasmallcellisaddedcanbeexpensive.
IncreasingdatarateswithMIMO.Thishastheadvantagethatcapacitycanbeincreasedwithoutusingmorespectrum.Thisoptioncouldproveexpensiveifcablinghadtobedoubledup;however,thereare
optionsavailableforrunningmultipleantennasoveronecable,oroveranEthernetlink.
DeployingLTEtospecificareaswithinthebuilding.ThisisundoubtedlythewayLTEwillbedeployedforthereasonsgivenearlieri.e.capacityisonlydeliveredwhereitisneeded.AnyupgradetoLTE
technologywillfollowthisupgradepathforreasonsofcostandefficiency.TheadvantagesofMIMO
arethatcapacitycanbeincreasedwithoutusingadditionalspectrum.Themaindisadvantageas
mentionedaboveisdoublinguponcablingtothemultipleantennas.
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WhatOptionsareAvailableforDeployingaNewInbuildingDAS?
ItisafactthatGSM/UMTSwillcomprisetheoverwhelmingmajorityofsubscribersoverthenextfivetoten
years,evenasnewwirelesstechnologiesareadopted.Therefore,eveninthelightoflargeincreasesindata
demand,anewDASdeploymentwouldmostlikelystillbebasedonabuildingwide2G/3Gnetworkwith
smallerareasofhighcapacityLTEnetworks,onlywherethedatademandisrequired.TheLTEsectionsof
thenetwork
would
be
similar
to
the
upgrade
options
given
in
the
previous
section.
EstimatedcostsfromCAM,foranewDASinstallationcomprisingmaterialsdescribedbelow,areasfollows:
20antennas 700mcoaxialcable 10splitters 10couplersCosts:
1.
2G
/
3G
/
4G
SISO
System:
22,000
to
design
and
install
2. 2G/3G/4G2x2MIMOSystem: 32,000todesignandinstall
3. 2G/3G/4G4x4MIMOSystem: 46,000todesignandinstall
Figuresarebasedonthefactthatthematerialsaredoubledineachcasebutthelabourrequiredforeach
installationdoesnotdouble.Asapercentage,a2x2systemwouldbe45%moreexpensivetoinstallanda
4x4system109%moreexpensive.
ThesecostshoweverwouldonlybeapplicableifweweretodeployMIMOoveranequivalentareatothe
SISOinstallation.Aswehaveseeninthisdocument,thisrolloutscenariomaynotbethemostsuitable,or
themost
cost
effective.
Todeliverpoolsofhighcapacity,usingMIMO,onlywhereitisneededwouldprobablycostmorefromthe
pointofviewofplanningandsitesurveysbutwillultimatelybecheaperthandeployingMIMOthroughout
thebuilding.Thisissueisopentodiscussion.
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ANovelApproachtoDeployingInbuildingLTECoverage:(CellularoverLAN)
InprevioussectionswehavediscussedtheadvantagesanddisadvantagesofdeployingMIMOtechnologies
forinbuildingnetworks.Oneofthemaindisadvantagesisthecostofrunningmultiplecablestothe
multipleantennasinaMIMOsystem.Thereareafewoptionswherebymultipleantennascanbefedfrom
asinglefeeder.OneoptioninvolvesfeedingtheantennasviatheexistingCAT5/6cablingwithinthe
building.
Thissolution,calledMobileAccessVEisdesignedtodeliverinbuildingLTEcellularservicesoveranexisting
CAT5/6LANinfrastructure,whilemaintainingfullEthernetandwirelessLANcapabilities.Thevendor
claimsthefollowingperformancefiguresandfacilities:
Extendscarriergrade,5barcoveragefor2G,3G,4GserviceswithMIMO Reducesinstallationtimebyhalf,ascomparedwithconventionalsolutions transparentlycoexistsalongsidetheLANwithoutimpactingLANperformance SupportsconnectivitytoanytypeofoperatorRFcapacitysource Offersproactiveendtoendnetworkmonitoring
Plug
and
play
design
scales
cost
effectively,
allowing
customers
to
choose
where
new
services
are
activated
ResultsfromanactualMobileAccessVEinstallationgivethroughputfiguresforanindoorLTEdeployment:
70dBmcoveragewastestedin90%ofthebuilding,followingMobileAccessVEdeployment EachVEPodcovered10,000squarefeet. Spatialmultiplexed2x2MIMOand64QAMwasverifiedusingtheLTELGUSBdongle ThemeasureddatathroughputatMIMOconfigurationwas:
15MbpsforUL(uplink)dataspeed
40
Mbps
for
DL
(downlink)
data
speed
SISOperformanceequivalentsofferlessthan35%ofMIMOthroughput(15MbpsUL,25MbpsDL)(http://www.mobileaccess.com)
Thissolutionprovidesanadvantageinitsquickandeasyinstallation timesandMIMOsupportat4G,
withoutimpactingontheexistingLANperformance.MobileAccessVEisalsothefirstcellularsolution
validatedwiththeCiscoUnifiedWirelessNetwork.MoredetailisavailableonrequestfromCAM.
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LTEFemtocells
AFemtocellisasmallbasestation,designedtobedeployedwithinhomeorsmallbusinesspremisesto
provideenhancedcoverage.Thecoverageandcapacitymadeavailablebyusingthesmallcellapproach
withinbuildingsiswellsuitedtoLTEdeployment.
LTEFemtocells
are
supported
within
3GPP
as
early
as
Release
8(2008)
and
are
identified
as
Home
eNode
Bs(HeNB).However,unlikethe3GFemtocell,thereiscurrentlynodefinedarchitecturalstandardinplace.
ThelevelofinterestfromoperatorsisdrivingtheFemtocellecosystemforwardatapace.Enterprise
Femtocellsthatcouldprovidecoverageinlargebuildingsarenowinthepipeline,supportingfemtofemto
handovers.
CellularAssetManagementwillbehappytodiscussthepotentialofFemtocellsuponrequest.
Conclusions
Thepurposeofthisdocumenthasbeentopromotediscussiononthebestwaytoservethesoaringlevels
ofdatademandexpectedoverthenextfewyears,usinganinbuildingDASsystemandnewtechnologies
suchasLTE.Themainpointsare:
Smartphonedevicesareexpectedtomorethandoublethetrafficdemandedofinbuildingsystemsyearonyearfrom2010to2015.
ToupgradeanexistinginbuildingDASfortheincreaseindatatherearetwomainoptions:reducethesizeofeachcellandincreasethedataratessupportedbytheDAS.
TosupportthedataratesofHSPA+andLTEtheinbuildingsystemswillneedtobeupgradedforMIMOantennatechnology.
FemtocelltechnologyforLTEcouldprovidesmallcellcapacitysolutions,althoughitisstillindevelopment.
AlternativedistributionsystemssuchasMobileAccessVEcouldprovideaquickandsimplerupgradepathwithextracapacitybeingaddedtoareasasthetrafficincreases.
Doweupgradenow?Inthenexttwoyears?Morelikelywewillseenetworksupgradegradually,providing
extracapacityonlyinlocalisedareaswhereitisrequiredandleavingthe2G/3GDASinstallationstohandle
thewiderareacoverage.
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LTETechnicalChallengesforInbuildingCoverage
Copyright:CellularAssetManagementLtd2010 www.cellularasset.com Page17
References
1. CiscoVisualNetworkingIndex:GlobalMobileData:TrafficForecastUpdate,20102015.www.cisco.com2. MobileBroadbandGrowthReport:PublishedbytheGlobalmobileSuppliersAssociation(GSA)www.gsacom.comFeb20113. TheIET EngineeringandTechnologyMagazine:Article:Willmobilenetworksbereadyforthe4Gdatadeluge?
http://eandt.theiet.org/magazine/pastissues/index.cfm
4. Ofcom TheCommunicationsMarket2010(August)http://stakeholders.ofcom.org.uk/binaries/research/cmr/753567/CMR_2010_FINAL.pdf
5. AgilentTechnologies.http://www.home.agilent.com/agilent/application.jspx?nid=34563.0.00&lc=eng&cc=GBLTEimplementationofMIMO
6. HSPAtoLTEAdvanced,RysavyResearchSept2009http://www.4gamericas.org/
7. NECShowsHowSmallCellLTEDeploymentisSmarterWaytoSustainableFuture:MobileBroadbandMobileWorldCongress
Feb
2011
http://www.nec.com/