RadioNetworks,DEI,AlmaMaterStudiorum-UniversitàdiBologna

TelecomItaliaMobileS.p.a.-TIM

LucaFeltrin

LTEandNB-IoT

Ø  3GPPandLTESpecificationsØ  LTE

o  Architectureo  PHYLayero  Procedures

Ø  NB-IoT

Index

Ø  ExtendedCoverageo  LargeAreaso  Environmentswithpoorcoverage

LowPowerWideAreaNetworks

Basement

20km

Ø  LongRange:ZigBee/802.15.4o  Multi-hop

Ø  LongRange:LPWANo  Single-hop

WhyLPWAN?

CoordinatorRouter

Source

SourceSink

Ø  MoreEnergyConsumed(Routers)

Ø  Routing/Synchoverhead

Ø  SimpleØ  TXPowerhassmall

overallimpact

Ø  BiggerArea->moredevicestoserveo  MassiveMTC(mMTC)

Ø Whattosacrifice?o  Throughputo  OKforsomeapplications

•  Alarms•  SporadicSensorData

WhyLPWAN?

Ø  Generalrequirementssetby3GPP:o  Coverage:MorethanGPRS+20dB(164dB)o  Throughput:Morethan160bpso  Latency:Lessthan10secondso  BatteryLife:Morethan10years(5Whbattery@MCL=164dB)o  Deployment:OnlySWupdateo  Capacity:Morethan52500devicespercell

LongRangeLowPowerTechnologies

DetailsonevaluationframeworkinTS45.820

Ø  NarrowBandtransmissiono  LessNoise

Ø  TimeDiversity

HowtoachieveLongRange?

NoiseFloorWideBand

NarrowBandSamePower

BetterSNR

0 1 2 3

Ø  NB-IOT:anewclassofLTEdeviceso  EnhancedCoverage->Narrowbando  Reducedenergyconsumptiono  Reducedcost/complexity

Ø  Deploymentoptions

NB-IOTOverview

𝑓LTEGSM

InBand Guard-BandStand-Alone

LTE

1PRB=180kHz

Ø  3CoverageClasses(Normal,Robust,Extreme)Ø  RSSIMeasurementØ  DecisionBasedonThresholds

CoverageClasses

ExtremeRobust

Normal

Ø  ContentionbasedØ  PseudorandomfrequencyhoppingØ  AcollisionhappensiftwoUEstarttransmittingthe

preamblefromthesamesubcarriero  InsuchcaseattheendoftheRandomAccessProcedure(Msg4)onedevice

willreceivetheULGrant,theotherswillfail

Ø  Preambleisrepeated 𝑷↓𝑵𝑷𝑹𝑨𝑪𝑯 times

PhysicalLayer-NPRACH

𝑆↓𝑁𝑃𝑅𝐴𝐶𝐻 Sub

carriers

Rep.1 Rep.2 Rep.3 Rep. 𝑃↓𝑁𝑃𝑅𝐴𝐶

𝐻 

…

User1User3

User2

Ø  1 NPRACH definition per Coverage Class Ø  Remaining resources are used by NPUSCH Ø  ≃𝟏 𝑹𝑼/𝒎𝒔 Ø  BPSK or QPSK (from 96 to 288 bit per RU)

PhysicalLayer-Uplink

Ø  NPBCH(BroadcastChannel):Carriesbroadcastmessages(MIB)

Ø  NPDCCH(ControlChannel):CarriesUL/DLGrants(NCCE)Ø  NPDSCH(SharedChannel):CarriesDataandotherbroadcast

information(SIB1,SIB2,…)

PhysicalLayer-Downlink

Ø  ImplicitACK/NACK

Ø  Iffailed,eNBsendsaUL-Granttotriggeraretransmission

Ø  Eachretransmissionisencodeddifferently

Ø  Ifsucceeded,nopacketsent,theUEconsiderssucceededafteratimeout

UplinkHARQUE eNB

Packet(NPUSCH)

UL-Grant(NPDCCH)

UL-Grant(NPDCCH)Packet(NPUSCH)

OK!

Ø  ACK/NACKonNPUSCH

Ø  Eachretransmissionisencodeddifferently

Ø  DL-GrantcarriestheGrant(andtimeoffset)forACK/NACKpacket

DownlinkHARQUE eNB

DL-Grant(NPDCCH)

DL-Grant(NPDCCH)

NACK(NPUSCH)

OK!

Packet(NPDSCH)

ACK(NPUSCH)

Packet(NPDSCH)

*36.213Table16.4.2-2

Ø  Preambleo  Canbeoverlappedwith

anotherUE’spreamble

Ø  Msg2o  ULGrantforMsg3

Ø  Msg3o  ContainsarandomIDo  Incaseofmultipleusers,the

strongestoneisdecodedbyeNB

Ø  Msg4o  MaycontainUL-Grantfor

Data

RandomAccessProcedureUE eNB

preamble(NPRACH)

Msg3withHARQ

Msg4withHARQ

Msg2withHARQ

Ø  MIBo  WheretofindSIB1o  CurrentFrame

Ø  SIB1o  WheretofindSIB2,…o  CurrentHyperFrame

Ø  SIB2o  PHYchannelsconfig

Ø  SIBxo  GPSCoordinates,Time,

NeighboringCells,…

InitializationUE eNB

MIB(NPBCH)

SIB1(NPDSCH)

SIB2(NPDSCH)

CellSearch