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