ETSF15CommunicationSystemsandNetworksStefanHöst

4GmobilecommunicationsystemLTE

Planoflecture

• Somehistoryofmobilenetworks—Pastandfuture• EPS:Ideaofnetworkstructure• EPC:Packetnetworks• LTE:Radiochannel• Whatcomesnext?

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1st generation

• Analogtransmissionwithnosecurity• Smallregions(countries)• FirstNTT(‘79),secondNMT(’81)• NMT(Nordic),NTT(Jap),

AMPS(NA+Aus),TACS(UK),Radiocom 2000(Fr),RTMI(It)

• NMTshutdown2007

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2nd generation• Digitalvoicechannel(10kb/s),Circuitswitched• News:

• SIMcard(SubscriberIdentificationModule)• SMS:First3December1992:“MerryChristmas”

• Largerregions(continents)• GSM(Eur),IS-136(N+SAm+Aus),

IS-95(NA+Asia),PDC(Jap)• GSM1991

2.5generation=>Datachannels• HSCSD,GPRS,EDGE(E-GPRS),IS-95B

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3rd generation

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• Packetswitchedforvoiceanddata• 144kb/s– 3Mb/s• Global• CDMA2000(2000)• UMTS(2001)

• News:• UTRAN

UniversalTerrestrialRadioAccessNetwork

4th generation

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• Packetswitcheddatatraffic(VoiceoverIPor3G)

• 100Mb/s-1Gb/s• Global:• LTE(LongTermEvolution)• Feb2007Firstdemo(Ericsson)• Dec2009firstcommercial

(StockholmandOslo)

• News:Smartphonesandapps• iPhone2007

5th generation

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• Packetswitcheddatatraffic• 1-100Gb/s• 1Gb/s/user

• ≈2020• News:Smallcells,homecell,IoT (M2M),Car2Car,MassiveMIMO,etc

https://www.youtube.com/watch?v=Fq2A6bi_sDE

Mobiletraffic(CISCOVNI2016-2021)

• Globalmobiledatatrafficgrew63%in2016• 4.4EBinDec’15to7.2EBinDec’16• 18foldgrowthoverlast5years

• Globalmobiledevicesandconnectionsin2016grewto8.0billion(estimated11.6billionin2021– 1.5/capita)• 45%smartdevicesgenerate81%oftrafficin2016

• 86%in2021

• 26%4Gconnectionsgenerate69%datain2016• 53%4Gin2021willgenerate79%traffic• 0.2%5G(25million)

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TotalIPtraffic

9

194.4

160.6132.1

108.588.772.5

Totalmobiledev.71.9EB/M(≈ totalof2015)

TotalMobiletraffic

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7

49

35

2417

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Growthofdevices

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Growthoftechnology

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Mobiledatatrafficgrowthin2016

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4G– LTELongTermEvolution

Standardizedby3GPP(3rd GenerationPartnershipProject)• RadioAccessNetworks(RAN)• Service&SystemsAspects(SA)• CoreNetwork&Terminals(CT)• GSMEDGERadioAccessNetworks

(GERAN).

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EPS(EvolvedPacketSystem)

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SGW

MME HSS

PGW

eNodeB

Internet

E-UTRAN (LTE) EPC

UE

EPSchallenges• Highspeedradiolink• Bandwidthisextremelyexpensive.Squeezeoutallbitsyoucan

• AccesstoInternet• HowtosendIPpackets

• Authentication,securityandaccounting• Usermobility• HandoverbetweeneNBs• Howtotransferdatainthenetwork

• Costefficientinfrastructure

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EPSinterfacesEPC<->eNB• S1interface• SplitinS1-MMEandS1-U• Nocentralised nodeeNB <->eNB• X2interface• Coordinationandpositioning• SynchronisationeNB <->UE• LTE-Uu orEUTRAN-Uu

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EPC

LTE-Uu

E-UTRANEvolvedUniversalTerrestrialRadioAccessNetwork

RANresponsiblefor• Resourcemanagement• Schedulinganddynamic

resourceallocation

• Compression• IPheadcompression

reducesoverhead

• Security• Encryptionofdata

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• Positioning• UEphysicalposition

• ConnectiontoEPC• Userandcontrolplane

Protocolstack

• S1oftentunneledthroughthefixnetworkarchitecture• Atunnelisawaytosendpacketsoverothertypesof

network,e.g.• IPv6overIPv4andviceversa• IPoverIPsec

• GTP:GPRSTunnelingProtocol

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ExampleoftunnelingIPv4overIPv6usingGRE(GenericRoutingEncapsulation)

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IPpacketsinEPC(Userplane)

SGW• Collectingcharginginfo• LocalanchortowardseNB• Canchangeduetomobility

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SGW

MME HSS

PGWeNB

PGW• IPedgeforuser• IPaddressallocationtoUE• QoS filtering• Mobilityanchor• Doesnotchangeduring

session.PreservestheIPaddr

S5/S8S1LTE-UuUE

IPpacketsinEPC(Usermobility)

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SGW PGW

eNB

eNB

UE

SGW PGWeNB

UE

UE

Protocolstacks(Dataplane)

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GTP:GPRSTunnelingProtocolPDCP:PacketDataConvergenceProtocol

(IP<->Radio,Headercompression,security)RLC:RadioLinkControl

(Segmentation,reordering)

ControlplaneinEPC

HSS(HomeSubscriberServer)• Subscriberdatabase• SIMcardkeyexchange• AAA• Authentication,Authorization

andAccounting24

SGW

MME HSS

PGWeNB

MME(MobilityManagementEntity)• CommunicateswitheNB

andSGW• Managetunnelsand

encryption

S5/S8S1LTE-UuUE

USIMcardUMTSSubscriberIdentityModuleTheUSIMcardisanapplicationonasmartcardandcontains:• IMSI(Internationalmobilesubscriberidentity)15digits• AuthenticationkeyK andsequencenumberSQNAuthenticationprocess:

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KASME isusedforencryptionofmessages

K,SQN->AUTNK,RAND->XRESK,SQN,RAND->KASME

Theradiochannel

• Licensedfrequencybands(slotsof20MHz)• In0.5-4GHz

• CostinorderofBillions$• Alternative:FDDandTDD• MostcommonFDD

• Efficienttransmission• UElowpower=>long(er)batterylife

=>signalverylowpoweratreceiver26

Frequencyallocation(3kHz-300GHz)

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2.4/5.8GHzFree(WiFi)LTE

eNodeBstructure(physicallayer)

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OFDMError

controlFraming

interleaveDACAFE RF

shift

OFDMOrthogonalFrequencyDivisionMultiplexing

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P2S

S2P

(a1,...,aN )

ai ∈Z16

16-QAM mapping:

(x1,..., xN ) (y1,..., yN ) = IFFT (

!x)

(yN−L+1,..., yN ,y1,..., yN )

QAM

QAM

QAM

IFFT

cos2π f0t

sin2π f0ts(t)

Re DAC

CP

Im DAC

Can be used with M=4, 16, 64 or 256

AFE

Time-frequecymultipleaccess

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TDMA:

Time

Freq

uenc

y

…

User 1User 2User 3User 4

FDMA:

Time

Freq

uenc

y

…

Time-frequecymultipleaccess

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OFDMA:

Time

Freq

uenc

y

…

User 1User 2User 3User 4

InLTE• AResourceElement(RE)isonecarrieroveroneOFDM

symbolThisistheleasttime-frequencyresolution• 15kHzX71.4us

Resourceblock(RB)

ApairofRB(sub-frame)istheleastassignedresource

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Framestructureintime

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Resourceallocationinfrequency

BW [MHz] 1.4 3 5 10 15 20

N 128 256 512 1024 1536 2048

#alloc RB (in Freq) 6 12 25 50 75 100

#used carrier 72 144 300 600 900 1200

Oversampling 1.78 1.78 1.71 1.71 1.71 1.71

Max Rate [Mb/s] 6 12 25 50 75 100

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Max Rate is for 64-QAM, i.e. 6 bit/carrierThen [b/s]Impact of control signals and error control is not included

R = # carrier ⋅6 ⋅7 ⋅2 ⋅10 ⋅100

ExampleOneOFDMsymbolforBW=10MHzand64-QAM

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ExampleOneOFDMsymbolforBW=10MHzand64-QAM

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Plotof(all) frequencydomainsamplesasI-Q

4Gmobilenetworks

• PacketNetwork:EPC• Dataplane:PGW&SGW• Controlplane:MME&HSS• Incorenetwork

• AccessNetwork:LTE(E-UTRAN)• Upto20MHzbandwidth(=>100Mbps)• OFDMsignaling

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Whatcomesnext1C-RAN

Basebandunit(BBU)• BinarydatatoBBsamples

• QAMmapping• IFFT• Coding

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BBU EPCRU

eNodeB (SoA)

Radiounit(RU)• BBsamplestoRFsignal

• Digital/analogconversion• MixingtoRF• AFE

CPRI

BBU hotel@ Data center

BBU

Whatcomesnext1C-RANToutilizerecoursesbettersplitBBUandRRUinnetwork• UseCPRItotransmitBBsamplesbetweenBBUandRRU

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BBU EPCRRU

RRU

RRU=RemoteRadioUnit

Problem:Datarateexpansionintransmissionofradiosamplesofapproximatelyafactor10Needcompression

backhaulfronthaul

Whatcomesnext2Smallcells

• Smallcellsworkin• Shortdistance(lowpower)• Highdatarate(fewusers)

• Inpublicplaces,offices,shoppingmalls,etc

• Evenplansforsmallcellsinhomes• Insteadof,orcombinedwith,WiFi?

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EPC

Internet

Problems• Howtobackhaul/fronthaul• Cantheybepartof

coordination?• Picocell:withcoordination• Femto cell:nocoordination

Whatcomesnext3Convergednetwork• Usersbecomesmoremobile

• Whenpriceandratedifferencesdiminishmostusersdon’tcareaboutchoiceofconnection

• Convergence:• Onenetwork,manyaccesses• Flexiblenetwork• OneAuthentication(andpricing)• Seamlesshandoverbetweennetworks,e.g.LTE-WiFi• Dualconnectionsandtrafficoff-loading• Allunitseverywhere

• Problem:• Partlynewnetworkstructure(e.g.whereisIPedge)

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Whatcomesnext3Convergednetwork

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Fixedormobilenetwork(separated,SoA)

Fixedandmobilenetwork(convergednetwork)

MassiveMIMO

• Highcapacity• Pinpointusersor

equipment• Efficientsignalling

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Tx

Rx

X

Y1

Rx Y2

Rx Yn

MIMO:Multiple-inMultiple-outantennas

Problems:• Synchronisation• Backhaul/fronthaul

Whatcomesnext45G• Roughlyafactorof10inperformance

• 10timesfaster,bandwidth,Datarate,etc• 10batterylife(forlowpowerdevices)• 1000timestrafficvolume• 10timesharder(atleast)

• Smallcellseverywhere• Everythingisconnected

• Car2Car,M2M/IoT,Cloudcomputing,Skynet,…

• Expectedtolaunchtestslatest2020• Problems:

• Backhaul/fronthaul,RANsync,Energyefficiency,etc

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