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THEUTRASYSTEM:THEUTRASYSTEM:PHYSICALLAYERPHYSICALLAYER
SPECITICATIONSSPECITICATIONS
Elect.AndComput.Engr.Dept.
Calif.StateUniv.,LosAngeles
FredDaneshgaran
DipartimentodiElettronica
PolitecnicodiTorino- Torino(Italy)
MarinaMONDIN
2
COURSETOPICSCOURSETOPICS
DS-CDMAandTD-CDMAtechnologiesbasicprinciples
Currentradiospecificationsof: FDD(W-CDMA)component
TDD(TD-CDMA)component
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DSDS--CDMACDMA
TECHNOLOGYBASICTECHNOLOGYBASIC
PRINCIPLESPRINCIPLES
4
ACCESSACCESS
Bythistermwemeanthewayinwhichtheradioresourceisaccessedandshared,withthegoalofmaximizingthenumberofservicedusersandminimizingtherequired
bandwithandpower.
DEFINITIONDEFINITION
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DUPLEXINGDUPLEXING
Inwirelesssystemstheuserisgenerallyallowedtosendinformationtothebase-stationandsimultaneouslyreceiveinformationfromthebase-stationitself.Inconventionaltelephonesystemsitispossibletotalkandlistenatthesametime:thiseffectisduplexing,andcanbeobtained
witheitherfrequencyortimebasedtechniques.
6
FREQUENCYDIVISIONDUPLEXING(FDD)FREQUENCYDIVISIONDUPLEXING(FDD)
TheFDDschemeisbasedontheuseoftwodifferentfrequencybandsforeachuser,oneforthebase-station-to-mobiletraffic(forwardlink),oneforthemobile-to-base-stationtraffic(reverselink)
Eachduplex channeliscomposedoftwosimplex channelsandaphysicaldevicenamedduplexer isrequiredinsideeachfixedandmobiletranceiverinordertoallowsimultaneoustransmissionandreceptiononthetwoduplexchannels
Inordertobeabletoutilizealow-costRFtechnology,forwardandreverselinkbandwithsshouldbeseparated.
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TIMEDIVISIONDUPLEXING(TDD)TIMEDIVISIONDUPLEXING(TDD)
TheTDDschemeusestimeinsteadoffrequencytoallowbothforwardandreverselinkcommunication
Ifthetimeseparationbetweentemporal slotsallocatedtoforwardandreverselinksissmall,transmissionandreceptionofdataappearsimultaneoustotheusers
TDDallowscommunicationusingasinglechannelandsimplifiestheradiodevicessincenoduplexerisrequired
8
MSBSTRANSMISSION
GUARDTIMES
Samecarrierforbothlinks
TDDTDD
(TIMEDIVISIONDUPLEX)(TIMEDIVISIONDUPLEX)
RFfilteringsimplified
Timeseparationbetweenlinkscannotbeguaranteedincellularsystemsduetopropagationdelaysinmacrocells
Usedincordlesssystems(e.g.,CT2,DECT)whichutilizemicrocellsorpicocell
BSMSTRANSMISSION
FRAMEPERIOD
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THEDSTHEDS--CDMATECHNIQUECDMATECHNIQUE
DS-CDMA(DirectSequence-CodeDivisionMultipleAccess):codedivisionaccesstechnique
Theusersignalsaretransmittedsimultaneouslyandonthesamefrequencyband
Adifferent(andunique)codeassignedtoeachuserallowsonetodistinguishthereceivedsignals
Thesystemcapacityislimitedbytheinterferencegeneratedbytheotherusers
10
DSDS--CDMACDMA
Theinformationbitismultipliedbyasequenceof0sand1scorrespondingtothecodeworduniquelyassociatedtotheuser
Atthereceivertheusefulinformationisrecoverdbymeansofacorrelationoperation
+1
-1
-1
-1
+1
+1
T t
t
t
PNi (f)
Di (f)
Si (f)
f
Ti
PNi (f)
Di (f)
Si (f)
f
f
Bs
Bs
Bss
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DSDS--CDMA(II)CDMA(II)
RECEIVERINPUTSIGNALRECEIVERINPUTSIGNAL
fBs
Bss
INTERFERINGSIGNAL
SSSIGNALNo
SIGNALAFTERDESPREADINGSIGNALAFTERDESPREADING
INTERFERINGSIGNAL
USEFULSIGNAL
f
No
Bs
Bss
Thede-spreadingoperationdistributesthepowerofanarrow-bandinterferingsignalontheentirechannelbandwidthBss,reducingtheinterferingpowerspectraldensityinthebandwidthBsoccupiedbytheusefulsignal
Thewhitenoisepowerspectraldensityisnot
affectedbythede-spreadingoperation,sincewhitenoiseisnotbandlimited
12
CDMACDMA
Signalsaretransmittedoveralltheavailablebandwidthforallthetime.Theresultisthatalltheusersinterferewitheachother,buttheuniquecodeassignedtoeachuserensuresthecorrectrecoveryofinformationatthereceiver
Theuserdata(forinstancetheoutputofthevoicecoder)aregeneratedwithacertainbit-rate,theneachbitismultipliedbythecodeworduniquelyassociatedtoeachnetworkuser
If,forinstance,a64bitcodewordisused,thetransmitterwillsendthiscodewordeachtimethatthevoicecodergeneratesa1,anditscomplementeachtimethatthevoicecodergeneratesa0
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CDMA(II)CDMA(II)
Inthisscheme,foreachusefulbitgeneratedbythevoicecoder,64bitsaresentonthechannel,thereforethebandwidthoccupiedbytheCDMAschemeis64timeslargerthanthebandwidthrequiredbytheFDMAscheme
Theratemeasuredintermsofchannelbits(i.e.thechannelbit-rate)iscalledchiprate
Themultiplicationbytheusercodewordiscalledspreading,whilethecorrelationprocessexecutedatthereciverto
recovertheusefulinformationiscalledde-spreading
14
THETRANSMITTERTHETRANSMITTER
Amplitude
Amplitude
Amplitude
CodeA
Time
Time
Time
Usercode
Informationsequence
Transmittedsequence
xx
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THERECEIVERTHERECEIVER
UserAInformationsequence
Codedsequence
UserBInformationsequence
CodedsequenceCodeA X Y
1
8
=
8
i=1
Xi Yi
Amplitude
TimeTime
ReceiverforuserAIdealchannel
Averageontheusefulbitperiod
Receivedsignal
Recoveredinformationsequence
Time
Time
X
X
16
DSDS--CDMACDMA
b(t):binaryinformationsignal(RateRb)c(t):binaryPNsequence(RateRc)
Rc>>RbThespectrumexpansionisduetothemultiplicationoftheusefulsignalbythePseudo-Noise(PN)signal
BPSKMOD.
BPSKDEMOD.
b(t)
c(t)
x(t)
j(t)
z(t)
c(t)
~~
fo
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DSDS--CDMA(II)CDMA(II)
c(t)1
-1
t
b(t)1t
-1
c(t)b(t)
1
-1
t
Gc(f)
f
1/Tc
f1/Tb
Gb
(f)
Gc*Gb
f
1/Tc
productspectrum
18
DSDS--CDMA(III)CDMA(III)
Thesignalb(t)c(t)ismodulated,transmitted,alteredbynarrow-bandinterferingsignalj(t)andthendemodulated,obtaining:
Therecoveredsignalisobtainedbymultiplyingz(t)byc(t):
z(t)=b(t)c(t)+j(t)~
Spreadedinterferingsignal
z(t)c(t)=b(t)c2(t)+j(t)c(t)=b(t)+j(t)c(t)~ ~
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DSDS--CDMA(IV)CDMA(IV)
Spectrumofz(t)c(t)
f
f
Gz(f)
f
Spreadedinterferingsignal
Usefulsignal
Usefulsignal
Interferingsignal
Afterfilteringonlyafractionoftheinterferingsignalisleft,withpowerreducedbyafactorG=Rc/Rb (spreadinggain)
20
CDMATRANSMISSIONCDMATRANSMISSION
DATA
0 f0 0
BACKGROUNDNOISE
f0
EXTERNALINTERFERENCE
f0
OTHERCELLINTERFERENCE
f0
OTHERUSERINTERFERENCE
f0
ENCODING&INTERLEAVINGDATA
CARRIER
PNSOURCE
CARRIER
DIGITALFILTER
PNSOURCE
CORRELATOR
DEINTERLEAVING&DECODING
DATA
WIDEBANDSPECTRUM
f0
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SPREADINGCODESFORCDMASPREADINGCODESFORCDMA
InanisolatedCDMAcell(withoutinterferingcells)eachuserusesadifferentspreadingcode(codewordorsequence)
Thespreadingsequencesshouldbeorthogonalinordernottogenerateinterference
Twocodewordsareorthogonaliftheirscalarproductonthesequencelength(multiplicationandadditionoftheresultingterms)isequaltozero
Example:thesequences1,-1,1,-1,1,-1,1,-1and1,1,-1,-1,1,1,-1,1areorthogonal
22
SPREADINGCODESFORCDMA(II)SPREADINGCODESFORCDMA(II)
TheprevioussequencesbelongtothefamilyoftheWalshcodes,whichareallorthogonaltoeachother
InanisolatedcellitispossibletoassignaWalshsequenceto eachuserinordertomaximizecapacity(whichislimitedbythenumberofavailablesequences,dependentonthesequencelength)
Inasystemwithmanycells,alltheusersinthedifferentcellsshouldhavedifferentsequences,sincealsoadjacentcellsare
usingthesamefrequencyband,butthiswouldstronglylimitthesystemcapacity
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Ifshortsequencesareused:itiseasiertocontrolinterference,butthecodemanagementismorecomplex
Ifonlyonebutverylongsequenceisused:codemanagementiseasybutitismoredifficulttocontrolinterference
LONGCODEANDSHORTCODELONGCODEANDSHORTCODE
24
THEFAMILYOFWALSHCODESOFLENGTH8THEFAMILYOFWALSHCODESOFLENGTH8
Code0 1
1
1
1
1
1
1
1
1
-1
-1
-1
1
1
-1
-1
-1
1
1
1
-1
1
1
-1
1
-1
-1
1
-1
1
1
-1
-1
-1
1
-1
1
-1
1
-1
1
1
1
-1
1
1
-1
-1
Code1
Code2
Code3
Code4
Code5
Code6
Code7
-1 -1 1 1 -1 -1 1 1
-1 1 -1 1 1 -1 1 -1
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SPREADINGCODESFORCDMA(III)SPREADINGCODESFORCDMA(III)
Inmulti-cellCDMAsystems,quasi-orthogonalcodesareused,thatallowmaintainingtheinterferenceamongdifferentusersatadmissiblelevels,evenifthislevelislargerthanintheorthogonalsequencescase
Thefamilyofquasi-orthogonalcodesiscomposedoftheso-calledpseudo-noiseorPNsequences
PNsequencesrepeatthemselvesperiodically:iftheyaremultipliedbythemselvesandadded,theresultisequaltothesequencelength(likefortheWalshcodes),whileiftheyare
multipliedbyashiftofthemselvesandaddedtheresultis-1(insteadof0,thereforesomeinterferenceisgenerated).TheadvantageisthatPNsequencesarepracticallyunlimited
26
PSEUDOPSEUDO--NOISESEQUENCESNOISESEQUENCES
Theyaretypicallyobtainedbyshiftsoffeed-backregistersproperlyinitialized,orbytheircombinations(GOLDsequencesareobtainedbycombiningtheoutputsoftwodifferentregisters)
IftheregisterhasNstages,thePNsequenceperiodis2N-1
IfPNsequenceshaveauto-correlationfunctionR(t)alwayszeroexceptfort=0andnullcross-correlationfunctions,thenitispossibletodistinguishthedifferentusersignals
Output
0 0 1
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t t
n
x1
f
t
f
t
+
1ej1
nejn
x
PROPAGATIONCHANNELEFFECTSPROPAGATIONCHANNELEFFECTS
28
RECEIVER:RAKERECEIVERRECEIVER:RAKERECEIVER
X
i
i
je i
X
n
n
je n
propagationchannelspreadingsequence
de-spreading
channelestimation
de-spreading
channelestimation
receiver
i
n
phaserecovery
phaserecovery
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POWERCONTROLANDINTERLEAVINGPOWERCONTROLANDINTERLEAVING
INCASEOFFASTFADINGINCASEOFFASTFADING
GOODGOOD
GOODGOODBADBAD
BADBAD
FadingSLOW
(Lowspeed)
FadingFAST
(Highspeed)
PowerControl
Coding&
interleaving
t
t
30
POWERCONTROL(PC)POWERCONTROL(PC)Closedlooppowercontrol- uplink(UL)anddownlink(DL)
Adjuststhetransmittedpowerfromthemobileterminal(fromthenetwork)inordertomaintaintheSIR(SignaltoInterferenceRatio)inUL(DL)equaltoagiventargetSIR
Outerlooppowercontrol- ULandDL
AdjuststhetargetSIRvalueusedbytheclosedlooppowercontrolonthebasisofaconnectionqualityestimate
Openlooppowercontrol- onlyULinUMTS
AdjuststhepowertransmittedontherandomaccessburstonthebasisofthepathlossvalueandtheinterferencelevelevaluatedinUL
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CLOSEDCLOSED--LOOPPOWERCONTROLLOOPPOWERCONTROL
Returnchannel
W-CDMAtransmitter
Poweramplifier
Receivedcommand(up/down)
BSCchannel FIFOregister
Roundtripdelay(kslot)Errorsonthecommand(Pe)
Receivingfilter
Rakereceiver
Max./Min.Transmittedpower W-CDMAreceiver
W-CDMAtransmitter
C
Cref
Transmittedcommand(up/down)
Comparator
+
-
32
GAINDUETOTHECLOSEDLOOPGAINDUETOTHECLOSEDLOOPPOWERCONTROLPOWERCONTROL
-2
-1
0
1
2
3
4
5
6
7
8
9
0 50 100 150 200 250 300
mobilespeed[km/h]
Eb/Noga
in[dB]
Mobilechannelvoiceserviceat8kbps
CONSTRAINTS:thetransmittermusthaveasufficientdynamictobeabletofollowthechannel;itneedsamarginattheedgesofthecoverage
area.Ifthedynamicisinsufficient,thegaintendstozero.
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EXAMPLEOFPROBABILITYDENSITYFUNCTIONSEXAMPLEOFPROBABILITYDENSITYFUNCTIONSOFTRANSMITTEDANDRECEIVEDPOWERSOFTRANSMITTEDANDRECEIVEDPOWERS
OutdoortoindoorpedestrianA
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
-20 -15 -10 -5 0 5 10 15 20
Power[dB]
Prob
.densityfunction
P.d.f.transmittedpower
P.d.f.receivedpower
34
CoreNetwork
RNC RNC
SiteContr
BTS BTS BTS
SiteContr
BTS BTS BTS
SiteContr
BTS BTS BTS
SiteContr
BTS BTS BTS
RNS
UTRAN
RNS
Iub
Iub
Iub
Iub
Iur
Iu
Iu
UTRANARCHITECTUREUTRANARCHITECTURE
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HANDHAND--OVER:SOFTHOOVER:SOFTHODEDICATEDDATACHANNELDEDICATEDDATACHANNEL
RNCRNC
MSreceivesfrombothBTSthesameinformationatthesametime
BTS1BTS1
BTS2BTS2
LC=X
LC=Y
LC=LongCode
36
HANDHAND--OVER:SOFTERHOOVER:SOFTERHODEDICATEDDATACHANNEL,DEDICATEDPACKETCHANNELDEDICATEDDATACHANNEL,DEDICATEDPACKETCHANNEL
RNCRNC
MSreceivesfrombothsectors
thesameinformationatthesametime
LC=X
Sector1Sector1
Sector2Sector2
BTSBTS
LC=Y
LC=LongCode
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SOFTHANDSOFTHAND--OVERANDMACRODIVERSITYOVERANDMACRODIVERSITY
CELLA CELLB
CELLC
Signalmargin
SoftHand-overregion
ADDthreshold
DROPthreshold
Timemargin
Ec/No
time
38
TYPESOFHANDTYPESOFHAND--OVEROVER
GSM
SIST TYPE
HardHardHandHand--overover
BEFORE DURING AFTER
DECT
SeamlessSeamlessHandHand--overover
UMTS
SoftSoftHandHand--overover
MSC
RNC
F1
BS#1
RFP#1
CCFP
BSS#1
F2
F2
BS#2
RFP#2
BSS#2BSS#2
MSC
F1
BS#2
RNC
F1BS#1
BSS#1BSS#2
MSC
F1
BS#2
RNC
F1
BS#1
RFP#1 RFP#2
CCFP
F1
BSS#1
RFP#2
CCFP
F2
RFP#1
F1
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SITESELECTIONDIVERSITYSITESELECTIONDIVERSITY
Itisanoptionalvariantoftheusualsofthand-over/macrodiversityscheme
Themobileidentifiesaprimarycellandsomenonprimarycellswithinitsactiveset
Withthegoalofreducingtheinterferenceduetothesofthand-over,thedownlinkinformationistransmittedonlybytheprimarycell
40
CAPACITY:ISOLATEDCELL,IDEALPCCAPACITY:ISOLATEDCELL,IDEALPC
Eb
Io
CT
I/W
C/R
I/W==
C=usefulsignalpower
R=bitrate
W=spreadingbandwidth
Incaseofidealpowercontrol
I=C(N-1)
1
(N-1)=
Eb
Io
C/R
C(N-1)/W= .
W
R
1
Eb/Io= .
W
R(N-1)
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EXPLOITATIONOFTHESOURCEEXPLOITATIONOFTHESOURCE
ACTIVITYANDSECTORINGACTIVITYANDSECTORING
d:sourceactivityfactor(forvoice,inidealconditions,itisequalto0.38,inpractice0.5istypicallyassumed)
Gsect:sectoringgain(2.2-2.4inthethreesectorscase)
1
Eb/Io .
W
RN
1
d. . Gsect Sitecapacity
42
CAPACITYINTHEMULTICAPACITYINTHEMULTI
--CELLCASECELLCASE
Theinter-cellinterferenceisaccountedforbymeansofaproperfactorgenerallydenotedasforianddefinedas:
f=(interferencefromothercells)/(intracellinterference)
1
Eb/Io .
W
RN
1
d. . Gsect. 1/(1+f)
f,variesaccordingtothescenario(typicalvaluesare0.4-0.6);thefactorf(alsodenotedasi),issometimescalledthereusefactoroftheCDMAsystem
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NOTESONTERMINOLOGYANDHYPOTHESISNOTESONTERMINOLOGYANDHYPOTHESIS
N0 isoftenusetoindicatetheoverallinterferencepowerspectraldensity(realinterferenceplusthermalnoise)insteadofthemoreappropriateexpression(I0+N0)
Itisimportanttopayattentiontothepointwithinthetransmissionchainwherewearemakingourcalculations:theprocessinggainshouldalwaysbeevaluatedatthepointinwhichtheratioEb/(I0+N0)isknown
Inthecapacitycomparison,attentionshouldbegiventowhetherwearetalkingaboutfulltimeusersornot,andifthecapacity
valuesarereferredtoasectorortoasite
44
CELLDYNAMICSCELLDYNAMICS
C/I 1/N
CellofradiusRwithNusers
Theuserdensityincreases:CellwithradiusRwith(N+X)>>>> Nusers
(C/I) 1/(N+X)
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CELLBREATHINGCELLBREATHING
UMTS:voiceserviceat8kbit/sinurbanenvironment(fc=2GHz)
Constraintsonthecoverageradius:mobilemaximumpower(21dBm),BaseTransceiverStation(BTS)maximumpower,maximumsourcebitrate,systemmargins
andload(maximum78activeusers,Equivalentof1)
0.6
0.8
1.0
1.2
1.4
1.6
1.8
0 0.2 0.4 0.6 0.8 1
load
radius[km]
46
COVERAGERADIUSCOVERAGERADIUS
2Mbit/s
144kbit/s
13kbit/s
Thecellcoverageradiusdependsonthetypeofofferedservice
Asaconsequence,adifferentcellularplanningmustbedesignedand
foreseendependingonthetypeofofferedservices
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COVERAGERADIUSCOVERAGERADIUS
Thecoverageradiusislimitedbythemaximumpowerthatcanbetransmittedbythemobileuser
Itispossibletoofferserviceswithasymmetrictransmissionratesonthetwolinks(b-mandm-b)withlargecoverageradius
Thebasestationhaslessconstraintsonthemaximumtransmittedpower:
asaconsequence,itispossibletoguaranteealargecoverageradiusofferingforinstanceonly8kbit/sinuplinkand144kbit/sindownlink
inthisway,itispossibletoguaranteeapplicationssuchaswebbrowsing,inwhichthemobileterminalmakessomerequestsorsendsacknowledgementwhilereceivingalargeamountofdata
48
POWERTRANSMITTEDBYTHEBASEPOWERTRANSMITTEDBYTHEBASE--STATIONSTATION
30
32
34
36
38
40
42
0 0.2 0.4 0.6 0.8 1
load
PowerBTS[dBm]
MaximumpowertransmittedbytheBTSintheworstcase(usersonthecellborder)- loadof1=78activeusers
Duetothecellbreathingphenomenon,themaximumpowertransmittedbythebasestationdoesnotincreaselinearlywiththenumberofusers
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LINKPERFORMANCELINKPERFORMANCE
50
Channeldecoding
Channelcoding
sourcepuncturing
unequalinterleaver
modulation
spreading
filter
BER
channel
AWGN
CRC&tail
insertionor
repetition
&TX
Fading
filterRX
demodulation
de-spreading&de-interleaverCRC&tail
removal
counter de-puncturing
repetitionorremoval
Powercontrolcommand
DPCCH
generator
MUX
DEMUX
DPCCH
DPDCH
DPCCH
DPDCH
WW--CDMADOWNLINKRADIOCHAINCDMADOWNLINKRADIOCHAIN
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6
7
8
9
10
11
12
13
14
15
16
17
1 10 100 1000
velocitdelmobile(km/h)
Eb/No[dB]@
BER=0
.1%
OutdoortoindoorA
OutdoortoindoorB
VehicularA
VehicularB
W-CDMA:VOICESERVICE(8KBIT/S)
DOWNLINKWORKINGPOINT
52
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
1.E+00
4 4.5 5 5.5 6 6.5 7 7.5
Eb/No[dB]
BER
it.#1
it.#2
it.#3
it.#4
it.#5
it.#6
it.#7
it.#8
TPCHard
TPCSoftBLER
PerformanceofthedataserviceLCDat144kbit/swithTurboCodeasafunctionofthenumberofdecodingiterations
downlink(VehicularA- 120km/h)
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Channeldecoding
Channelcoding
sourcepuncturing
unequalinterleaver modulation
spreading
filter
BER
channel
AWGN
CRC&tail
insertionor
repetition&
TX
Fading
filterRX
Demodulation
De-spreading&
Combining
&
de-interleaverCRC&tail
removal
counter de-puncturing
repetitionor
removal
Powercontrolcommand
DPCCH
generator
DPCCH
DPDCH
DPCCH
DPDCH
channel
AWGN
Fading
filterRX
WW--CDMAUPLINKRADIOCHAINCDMAUPLINKRADIOCHAIN
54
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
1.E+00
0 1 2 3 4
E b/N o[ dB ]
BER
it.#1
it.#2
it.#3
it.#4
it.#5
it.#6
it.#7
it.#8
TPCHard
TPCSoft
BLER
PerformanceofthedataserviceLCDat144kbit/swithTurboCodeasafunctionofthenumberofdecodingiterations
uplink(VehicularA- 120km/h)
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CONSIDERATIONSCONSIDERATIONS
Inthecaseofvoiceservicestheperformancesarepracticallyindependentofthespeed (withintherange25250km/h)becauseoftheclosedlooppowercontrol.Thisbehaviourisnotexactlytrueanymoreforhighbitrateservices
Forveryhighspeeds (500km/h)theperformancesareaffectedbya56dBdegradationbecausethechannelestimationalgorithmandthepowercontrolarelessreliable
56
BASICPRINCIPLESOFTHEBASICPRINCIPLESOFTHE
TDTD--CDMATECHNIQUECDMATECHNIQUE
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TDDCOMPONENT(TDTDDCOMPONENT(TD--CDMA)CDMA)
Freq
uenc
y
8TCHpertime
slot
OneTimeSlot
3.84
MHz
1 2 3 . . . 14 15
Codes1-16
Energy
Time
framewith15timeslots
WB-TDMA/CDMA
58
USERCODESUSERCODES
Withineach0.667msslot,afurtherseparationisgivenviatheuseofcodewords withlength16
Severalburstscanbetransmittedinasingletimeslot:
theburstscanbeallocatedtodifferentusers,
and/ortheburstscanbeallocatedtoasingleuser
Themostcriticallinkistheuplink,whereuptoeightburstscanbetransmittedinasingletimeslot(with
moreburststheperformanceswouldbeexcessivelydegraded)
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RESOURCESALLOCATIONRESOURCESALLOCATION
IntheTDDcomponent,aphysicalchannelischaracterisedbyacombinationofcarrierfrequency,slotandcodeword
ResourcesareallocatedbymeansofslowDCA:
inordertoobtainaunitaryreuseparameter,differenttimeslotsareallocatedtoadjacentcells(slotclustering)
eachcellslotcanbeusedinuporindownlink(forasymmetrictraffic)
ResourcesareallocatedtothebearersbymeansoffastDCA:
thehigherbitrateservicescanbeobtainedbytransmittingusingmultiplecodewordsandmultipletimeslots
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THETDDFRAMETHETDDFRAME
Problem:mobile-mobileinterference
canbesolvedbyforcingthebasestationssynchronism
inanasynchronousnetwork,itisnecessarytohaveadynamicresourceallocationpolicyinordertoavoidinterference(likeintheDECTcase);thiswillcauseanefficiencylossinthebandlimitedcase(5
MHz) Timingadvancetechniquesareemployedinorderto
reducetheguardtimesbetweentwosuccessiveslots
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SYNCHRONIZATIONAMONGTDDCELLSSYNCHRONIZATIONAMONGTDDCELLSCellA
Cell B
Withsynchronouscells,timingadvanceandguardtimesitispossibletoavoidthemobiletomobileinterference
Mobiletomobileinterference
Withnonsynchronizedcells,inordertoavoidmobiletomobileinterference,resourcesneedtobeallocatedforthecasesofpotentialconflict
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BASICFUNCTIONINGPRINCIPLEBASICFUNCTIONINGPRINCIPLE
CDMAcode1
Midamblechannel1
Trafficchannel1inputdata
Mobile1
1
ChannelestimationofK
radiochannels
JointDetection(JD)ofK
trafficchannels
1 K2
TrafficchannelK
outputdata
Trafficchannel1outputdata
Radiochannels Estimatedradio
channels1- K
Basestation
Midambleschannels1- K
CDMAcodes1- KK
CDMAcodeK
MidamblechannelK
TrafficchannelKinputdata
MobileK
X
X
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THEJOINTDETECTIONTECHNIQUETHEJOINTDETECTIONTECHNIQUE
Itisusedtoreduce(ideallytocancel)interferenceamongdifferentsignals
Thereceiver,exploitingtheknowledgeofthesequencesusedtodistinguishthedifferentusersignals,jointlydemodulatesthedifferentsignals
Theoutputisaseriesofinformationsequences,oneforeachusersignal
64
THEUMTSSYSTEMRADIOTHEUMTSSYSTEMRADIO
INTERFACEINTERFACE
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ETSIDECISIONSETSIDECISIONS
AdoptionoftheW-CDMAsolutionwithFDDduplexinginthepairedportionoftheavailablespectrum
AdoptionoftheTD-CDMAsolutionwithTDDduplexinginthenon-pairedportionoftheavailablespectrum
Parametersoptimization inordertoguarantee: low-costterminals
smoothevolutionwithrespecttoGSM
dualmodeTDD/FDDterminals
Thesolutionmustbeabletooperatewithaminimumspectrum
assignmentequalto2x5MHz(FDD)
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HARMONIZATIONWITHHARMONIZATIONWITHCDMA2000CDMA2000
Agreementamongthemajoroperators
Threeoperatingmodes:
FDDDS(basedonUTRANWCDMA)
FDDMC(basedoncdma2000,withpossibilityofoverlaywithcdmaOnenetworks)
TDD(basedonUTRANTD-CDMA)
PossibilityofconnectiontoGSMMAPandANSI41core
networks
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HARMONIZATIONWITHHARMONIZATIONWITHCDMA2000CDMA2000(II)(II)
Chiprate:3.84McpsforDSandTDD,3.6864(3x1.2288)McpsforMC
AdoptionofacommonpilotchanneltransmittedinCDMAfortheDSsolution
Possibilityofbothsynchronousorasynchronousnetworks.
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POSSIBILITYOFOPERATIONINAPOSSIBILITYOFOPERATIONINA
2X5MHZBANDWIDTH2X5MHZBANDWIDTH
Thisrequirementimposesconstraintsontheout-of-bandemissions
SinceboththeTDDandtheFDDcomponentsoccupythesamebandwidth,theyhavesimilarrequirementsasfarasguardbandsandadjacentchannelprotectionisconcerned
Employedmethods: Evaluationoftheminimumcouplingloss(minimumdistance
amongtransmitterandreceiver)abletoguaranteethereceiver
operation(worstcasecondition). Statisticalapproach(Montecarlosimulation)toevaluatethe
capacitylossduetothedifferentmulti-operatorscenarios
Problem:isitpossibletooperateTDDintheFDDband?
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UTRA/FDD UTRA/TDD
Multipleaccess WCDMA HybridWCDMA+TDMA
Chiprate
Carrierspacing 4.4-5MHz(200kHzcarrierraster)
3.84Mcps(SFFDD:4-256,TDD1-16)
Frameduration 10ms
N.ofslotsperframe 15
BTSsynchronisationNotnecessary Notnecessary
butpreferable
Modulation DL:QPSK
UL:Dual-codeBPSK UL:QPSKCoherentreception uplinkanddownlink
Multi-rate VariableSF+Multi-code+Multi-slot(onlyTDD)
THEMAINPARAMETERSTHEMAINPARAMETERS
DL:QPSK
70
FDDCOMPONENT(WFDDCOMPONENT(W--CDMA)CDMA)
TheFDDcomponentisbasedonthesystemdevelopedbytheAlphagroupandestablishestheadoptionofawide-bandCDMAaccesstechnique:
chiprateof3840kchip/s(theywere4096beforetheharmonisationwithcdma2000)
3dBbandwidthequalto3840kHz(raisedcosinefilter,roll-off0.22)
optionwithchiprateof2x3840and4x3840kchip/s
Coverageofpico-,micro- andmacro-cellsobtainedbyadoptingdifferentCDMAcarriersinthedifferentenvironments:
hierarchicalcoveragebasedontheFDMAaccess
Inacertainhierarchicallevelitispossibletohaveafrequencyreusefactorequalto1
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DPxCHCHANNELSFRAMESTRUCTUREDPxCHCHANNELSFRAMESTRUCTURE
Frame:has10msofdurationAframeisformedby15slots(0.666ms),correspondingtoapowercontrolperiod
Spreadingfactor:belongingtothe
range4-256,canbedifferentforDPDCHandDPCCH
DataNdatabits
0.666ms,10x2k
bits(k=0..6)
Tf =10ms
DPDCH
DPCCH
Slot#iSlot#1 Slot#2 Slot#15
PilotN
pilot bitsTPC
NTPC bitsFBI
NFBIbitsTFCI
N TFCI bits
74
MAPPINGBETWEENTHEMAINTRANSPORTMAPPINGBETWEENTHEMAINTRANSPORTANDPHYSICALCHANNELSANDPHYSICALCHANNELS-- DOWNLINKDOWNLINK
Physicalchannels: DPDCHandDPCCHaretransmittedlikeintheuplinkbuttime-multiplexed
DSCH(downlinkSharedChannel)isusedtotransmitpackettrafficscheduledbythebasestationaccordingtothetrafficgenerated bythevarioususers.Italwayshasanassociateddedicatedchannelusedtotransportphysicallevelsignalling(forinstancepowercontrolandinformationratebits)
BCHisthecommonchannelusedtotransmitsysteminformationto allmobiles;itistransmittedonthePrimaryCommonControlPhysicalChannel(PCCPCH).TheSynchronisationChannel(SCH)istime-multiplexedwithit,anditallowsthemobiletoacquirethesynchronisationsignalnecessarytodemodulatethebasestationsignal
SCCPCH(SecondaryCommonControlPhysicalChannel)isusedtotransmitthepagingandtheFACHchannelwhich,togetherwiththeAICH,areusedtoindicatethatthecallgeneratedbythemobilecanstart.Thesechannelscanalsobeusedtotransmitshortpackets(likeSMSin GSM)
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PHYSICALCHANNELS:DOWNLINKPHYSICALCHANNELS:DOWNLINK
DPCCHandDPDCHaredefinedasintheuplink,buttheyaretimemultiplexed
Thededicatedpilotsymbolsaretransmittedalsointhedownlinkinordertosupportthe
useofsmartantennas
Slot#1 Slot#2 Slot#i
Tf =10ms
0.666ms,20x2k
bits(k=0..6)
Slot#15
TPCN TPC bits
Data2N data2 bits
DPDCH
PilotN
pilotbits
DPCCHDPDCH DPCCH DPCCH
TFCITFCIN bits
Data1Ndata1 bits
76
COMMONCONTROLCHANNELS(CCPCH)COMMONCONTROLCHANNELS(CCPCH)TheCCPCHchannelsare:primary - usedtotransporttheBCCH(systemandcellspecificinformation);theyaretransmittedonallthecell;secondary - usedtotransporttheFACH(mobilespecificcontrolinformationandshortpackets)andthepagingchannelPCH.
Theprimarychannelspeedisconstant,thatofthesecondarychannelscanvaryfromcelltocell
Thecommonpilotchannel(CPICH)isusedforchannelestimationontheprimaryCCPCHandtoimprovethechannelestimationonthededicatedchannels
Slot#1 Slot#2 Slot#i
Tf =10ms
0.666ms,20x2k
bits(k=0..6)
Slot#15
Data19 bits
(TxOFF)
256chips
CPICH20bits
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MULTIPLEXINGOFMULTIPLEXINGOFTHETRANSPORTTHETRANSPORT
CHANNELSCHANNELSRate-Matching
Multiplexing
2nd Interleaving
MappingtoPhysicalchannels
AddCRCtoTr.block
AddCRCto
Tr.block
Channelcoding
Channelcoding
TrCH TrCH
1st Interleaving 1st Interleaving
78
CODINGTECHNIQUESCODINGTECHNIQUES
Channelinterleaving
BER=10-3
Service-specificcoding
BER=10-6 Channelinterleaving
Convolutionalcoding
Turbocoding
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MAPPINGOFTHEMAPPINGOFTHE
UPLINKVOICEUPLINKVOICE
SERVICESSERVICES
80bits
i nformati on CRC tai l
8 8
96x3=288bits
convolutionalencoding
288x24/25=300bits
unequalrepetition
spreading
Slot#1 Slot#15
in-phasecomponentDPDCH(SF=128)
quadraturecomponentDPCCH(SF=256)
frame(10ms)
1536chips6bits
5122
5122
1536chips6bits
5122
5122
Pilot TPC TFCI
2560chips20bits
2560chips20bits
300x128=38400chips
80
i nformati on CRC tai l
80bits 8 8
96x3=288bits
convolutionalencoding
288x25/16=450bits
unequalrepetition
450x128=57600chips
spreading
512chip4bits
1281
1920chip15bits
Slot#1 Slot#15
Pil ot T PC DataDPCCH+DPDCH(SF=128)
in-phasecomponent
quadraturecomponent
frame(10ms)
MAPPINGOFMAPPINGOF
THEDOWNTHEDOWN
LINKVOICELINKVOICE
SERVICESSERVICES
512chips4bits
1281
1920chip15bits
512chip4bits
1281
1920chips15bits
512chips4bits
1281
1920chips15bits
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SPREADINGANDMODULATIONSPREADINGANDMODULATION-- UPLINKUPLINK
Channelisationcodes(OVSF)
cD,cC :channelisationcodesc scramb:scramblingcode(shortorlong)p(t):pulse-shapingfilter(rootraisedcosine,roll-off0.22)
EachmobiletransmitsatleasttheDPCCH,towhichauniquechannelisationcodeisassigned;toeachDPDCHachannelisationcode
isassigned Thesamecodecanbereusedonin-phase&quadraturecomponents Thescramblingcodeisacomplexsequence QPSKmodulationisused
DPDCH
cD
I
DPCCH
cC
Qj
I+jQ
cscramb
cos(t)
p(t)
p(t)
Real
Imag
sin(t)
84
SPREADINGANDMODULATIONSPREADINGANDMODULATION-- DOWNLINKDOWNLINK
Thesamechannelisationcodemultipliesatthesametimethein-phaseandquadraturecomponents Thescramblingcodeisarealsequencethatmultipliesboth
components QPSKmodulationisused
cch:channelisationcodesc scramb:scramblingcodep(t):pulse-shapingfilter(rootraisedcosine,roll-off0.22)
cos(t)
DPDCH/DPCCH
I
Q
p(t)
p(t)
cscrambS P cch sin(t)
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OPENLOOPPOWERCONTROLOPENLOOPPOWERCONTROL
IsusedtoestimatetherequiredpowerfortheaccessburstonthePRACH
ThemobilemeasuresthereceivedpoweronthecommonpilotchannelandevaluatestheattenuationonthedownlinkonthebasisofthepowerusedtotransmittheprimaryCCPCH(valuetransmittedontheBCH)
IftheinterferenceontheuplinkandtheSIRtargetareknown(valuestransmittedontheBCH),themobileestimatesthepowertobetransmittedonthePRACHunderthehypothesisofidenticalattenuationontheuplinkandanddownlink
86
ULCLOSEDLOOPPOWERCONTROLULCLOSEDLOOPPOWERCONTROL
ThebasesoftheactivesetestimatetheusefulpowerreceivedontheDPCCHinuplink,thetotalinterferenceandthecurrentvalueofSIRinuplink
ThebasegeneratesTPCcommandsandsendthemtothemobiletocommandanincrease(TPC=0)ordecrease(TPC=1)ofthetransmittedpower
ThemobilecombinesmultiplereceivedTPCcommandsintoauniqueTPCcommand
Themobileincreasesordecreasesbyapredefinedstepitstransmitpower
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DLCLOSEDLOOPPOWERCONTROLDLCLOSEDLOOPPOWERCONTROL
ThemobileterminalestimatestheusefulreceivedpowerindownlinkontheDPCH,thetotalreceivedinterferenceandthecurrentvalueofSIRindownlinkrelativetotheconnection
ThemobileterminalgeneratesaTPCcommandandsendsittothenetwork(nodeB)
Thenetworkadjuststhetransmittedpowervaryingitby
apredefinedstep
88
UPLINKVARIABLERATE(NODTX)UPLINKVARIABLERATE(NODTX)
1-rate
10ms
Variablerate
1/2-rate
1/4-rate
0-rate
:DPCCH(Pilot+TPC+RI)
:DPDCH(Data)
R=1 R=1/2 R=0 R=0 R=1/2
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DOWNLINKVARIABLERATE(DTXBASED)DOWNLINKVARIABLERATE(DTXBASED)
1-rate
1/2-rate
1/4-rate
0-rate
0.625ms
:DPCCH-part(Pilot+TPC+RI)
:DPDCH-part(Data)
90
INTERINTER--FREQUENCYMEASUREMENTSFREQUENCYMEASUREMENTS
TDMA:Discontinuoustransmission
RXRXdownlink
TX TXuplink
IdletimeforIFmeasurements
RXdownlink
TXUplink
UTRA/FDD:Normallycontinuoustransmission
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DOWNLINKSLOTTEDTRANSMISSIONDOWNLINKSLOTTEDTRANSMISSION
Tf =10ms IdletimeforIFmeasurements
SF=SF0
SF=SF0/2
SF=SF0
92
HANDHAND--OVERWITHINATDDSCHEMEOVERWITHINATDDSCHEME
BothTDDandFDDcomponentshave10msframeduration
ThebasestationmustindicatetheTDDandFDDcarriersusedinthearea
TheFDDmodecanuseslottedtransmission(ortworeceivers)inordertoexecutetherequiredmeasurements:
theFDDterminalsmustsynchroniseitselfwiththeTDDdownlink
sincetheTDDcellsinacertainareaaresynchronous,itissufficienttoobtaintheup/downlinktiminginonecelltobesynchronisedontheentirearea
sincethefrequencyseparationbetweenTDDandFDDcannotbesufficienttoprotecttheTDDreceiverfromtheinterference
generatedbytheFDDcomponent,itcanbenecessarytointerrupttheFDDtransmissionduringmeasurements:thisisthesocalledslottedmodeinuplink
TheTDDterminalscanexploittheidleperiodstoexecutemeasurementsontheFDDcomponent
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PACKETACCESSPACKETACCESS
Therearethreepossibleschemes:
shortpackets(ornotfrequent)transmittedovercommonchannels(PRACHandSCCPCH),similartoSMSintheGSMcase
largedimensionpacketsorpacketsscheduledathighrate,thatcanbetransmittedusingadedicatedchannel
indownlinkitispossibletouseacommonchannel(PDSCH)onwhichthebasestationschedulesthe
accessofpacketsbelongingtodifferentclients.InuplinkthePCPCH(contestchannel)canbeused
94
COMMONCHANNELPACKETACCESSCOMMONCHANNELPACKETACCESS
Nolinkmaintenancewhennopackettotransmit
Limitedtosmallpacketsandmediumdatarates
Accessrequest
Userpacket
Accessrequest
Userpacket
Arbitrarytime
CommonChannel(RACH/FACH)
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DEDICATEDCHANNELMULTIDEDICATEDCHANNELMULTI--PACKETPACKET
TRANSMISSIONTRANSMISSION
Scheduledandnon-scheduledpacketaccess
Closed-looppowercontrolduringpackettransmission Linkreleasedaftertime-outperiodhasexpired
Userpacket
Userpacket
DedicatedChannel(DTCH)
Accessrequest
Userpacket
Accessrequest
Linkmaintenance(pilot,TPC)
Scheduledpackets
Non-scheduledpacket
96
DSCHANDCPCHCHANNELSDSCHANDCPCHCHANNELS
DSCHisachannel(downlink)commontoalltheuserswhichtransportscontrolanddedicatedtrafficbits
CPCHisachannel(uplink)thatcanbeaccessedbymanyusersthroughacontestmechanism,used
forresourceoptimization inpackettransmission
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ETSIDECISIONETSIDECISION
Parametersoptimization inordertoguarantee:
low-costterminals
dualmodeTDD/FDDterminals
98
FDDANDTDDPARAMETERSHARMONIZATIONFDDANDTDDPARAMETERSHARMONIZATION InordertosatisfytheETSISMGrequirements,ithasbeen
decidedtoharmonisetheTDDandFDDcomponentsparameters:
chiprate:3840kchip/s
frameduration:10ms
numberofslotsperframe:15
modulation:QPSK
filtering:raisedcosine(roll-off0.22)
unitaryfrequencyreuse
Thespecificationsareharmonised,i.e.theyhavethesame
structure:manypartsarepracticallyidenticalforthetwomodes(codingtechnique,multiplexingofthetransportchannels,andsoforth)
Somedifferencesstillexistbecauseofthedifferentaccesstechnique
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THETDDFRAMETHETDDFRAME
3.84Mchip/s
time
frequency
666s
10ms
10ms
10ms
Examplesofswitchingmodesbetweenupanddownlink:theswitchinginstantsmustbethesameforallthecellsinacertainarea
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RADIORESOURCESRADIORESOURCES
Aphysicalchannelisdefinedbythefollowingparameters:
frequency
timeslot
channelisationcode
burstformat
frameallocation(i.e.,transmissiononalltheframesoronlyduringcertainframes,forinstanceonlyontheevenframes)
Ineachframeitismandatorytoallocateatleastonetimeslotfordownlinkandonetimeslotforuplink
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SPREADINGSPREADING
Theinformationsequencesaremultipliedwithachannelisationcode(thatcausesthebandwidthincrease)andtheresultingsignalismultipliedbyascramblingsequence
Indownlink,thespreadingfactorassumesthefixedvalueSF=16;inordertoprovidehighsymbolrateservices,morethanonechannelisationcodepertimeslotisassigned
TheoptionSF=1isalsopossible
Inuplinkthespreadingfactorcanassumevaluesinthe
range1-16 Amobilecansimoultaneouslytransmitnotmorethan
twophysicalchannelsinthesametimeslot
102
SIGNALLINGCHANNELSSIGNALLINGCHANNELS
TheprimarycommoncontrolchanneltransportstheinformationassociatedwiththeBCHanditistransmitted:
withknownpower
overallthecell(nobeamforming)
inknownposition(i.e.,timeslotnumber,burstformatandcodeareknown)ontheSCH,usingSF=16andtype1bursts
ifotherchannelsaretransmittedonthesameslotwiththesamecode(indifferentframesinamultiframepattern),thesehavethesamecharacteristicsasPCCPCH:knownreferencepowerandandnobeamforming
Thesynchronisationchannel(SCH)istransmittedovereachframe(oneortwoslotsperframe)
itallowsthemobiletoacquiresynchronisation
itisusedforpowermeasuresfortheuplinkpowercontrol
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BURSTFORMAT:THETRAFFICBURSTBURSTFORMAT:THETRAFFICBURST
Therearetwotypesoftrafficbursts:thefirsttypehasalongermidambleandisparticularlysuitedto
uplinkinthecaseofchannelswithlargedelayspreads;thesecondtypecanbeusedinchannelswithlowdelayspreadsBothcanalsobeusedtotransmittheS-CCPCH
Datasymbols61(976chips)
Midamble512chips
Datasymbols61(976chips)
GP96CP
666s
Datasymbols69(1104chips)
Midamble256chips
666s
Datasymbols69(1104chips)
GP96CP
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PHYSICALLEVELSIGNALLINGPHYSICALLEVELSIGNALLING
Thephysicallevelsignallingistime- multiplexedwiththetrafficchannel
Theonlymandatoryfieldisthemidamble(usedforchannelestimationandjointdetection)
Datasymbols Midamble DatasymbolsGP
512/256chips
2560*Tc
TPC
TFCI
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PHYSICALLEVELSIGNALLING(II)PHYSICALLEVELSIGNALLING(II)
Whenmorethanonecodeisused,themidamblepowerisequaltothesumofthetrafficchannelpowers
TheTFCIbitsaretransmittedonlyonthefirstcode/timeslot
t
Code
2560*Tc
Data
Midamble
TFCI
t
2560*Tc
Data
Midamble
TFCI