3G Long-Term Evolution (LTE) and System … Long-Term Evolution (LTE) and System Architecture Evolution (SAE) Background System Architecture Radio Interface Radio Resource Management

3G Long-Term Evolution (LTE) andSystem Architecture Evolution (SAE)

BackgroundSystem ArchitectureRadio InterfaceRadio Resource ManagementLTE-Advanced

Cellular Communication Systems 2Andreas Mitschele-Thiel, Jens Mueckenheim Nov. 2017

3GPP Evolution – Background

3G Long-Term Evolution (LTE) is the advancement of UMTS with the followingtargets:

Significant increase of the data rates: mobile broadbandSimplification of the network architectureReduction of the signaling effort esp. for activation/ deactivation

Work in 3GPP started in Dec 2004LTE is not backward compatible to UMTS HSPA.LTE is a packet only network – there is no support of circuit switchedservices (no MSC).LTE started on a clean state – everything was up for discussion includingthe system architecture and the split of functionality between RAN and CN.

Since 2010, LTE has been further enhancedLTE-Advanced with increased performance targetsApplication of new scenarios (MTC) and novel concepts (D2D)


LTE Requirements and Performance Targets

High Peak Data Rates

100 Mbps DL (20 MHz, 2x2 MIMO)

50 Mbps UL (20 MHz, 1x2)

Improved Spectrum Efficiency

3–4x HSPA Rel.6 in DL*

2–3x HSPA Rel.6 in UL

1 bps/Hz broadcast

Improved Cell Edge Rates

2–3x HSPA Rel.6 in DL*

2–3x HSPA Rel.6 in UL

Full broadband coverage

Support Scalable BW

1.4, 3, 5, 10, 15, 20 MHz

Low Latency

< 5 ms user plane (UE to RAN edge)

< 100 ms camped to active

< 50 ms dormant to active

Packet Domain Only

High VoIP capacity

Simplified network architecture

* Assumes2x2 in DLfor LTE,

but 1x2 forHSPA Rel.6


Key Features of LTE to Meet Requirements

Selection of OFDM for the air interfaceLess receiver complexityRobust to frequency selective fading and inter-symbol interference (ISI)Access to both time and frequency domain allows additional flexibility inscheduling (including interference coordination)Scalable OFDM makes it straightforward to extend to differenttransmission bandwidths

Integration of MIMO techniquesPilot structure to support 1, 2, or 4 Tx antennas in the DL and MU-MIMOin the UL

Simplified network architectureReduction in number of logical nodes flatter architectureClean separation between user and control plane


Network Simplification: From 3GPP to 3GPP LTE

3GPP architecture4 functional entities on thecontrol plane and user plane3 standardized user plane &control plane interfaces

3GPP LTE architecture2 functional entities on theuser plane: eNodeB and S-GWSGSN control plane functions

MMELess interfaces, somefunctions disappeared

4 layers into 2 layersEvolved GGSN integratedP-GWMoved SGSN functionalities toS-GWEvolutions to RRM on an IPdistributed network forenhancing mobilitymanagementPart of RNC mobility functionmoved to MME & eNodeB

GGSN

SGSN

RNC

NodeB

ASGW

eNodeB

MMFGGSN

SGSN

RNC

NodeB

Control plane User plane

ASGW

eNodeB

MMF

S/P-GW

eNodeB

MME

Control plane User plane

S/P-GW: Serving/PDN GatewayMME: Mobility Management Entity

eNodeB: Evolved NodeB


Evolved UTRAN Architecture

eNB

eNB

eNB

MME/S-GW MME/S-GW

X2

EPCE-U

TRAN

S1

S1

S1S1

S1S1

X2

X2

EPC = Evolved Packet Core

Key elements of networkarchitectureNo more RNCRNC layers/functionalitiesmostly moved in eNBX2 interface for seamlessmobility (i.e. data/context forwarding) andinterferencemanagement

Note: Standard onlydefines logical structure/Nodes !


EPS Architecture – Functional description of the Nodes

eNodeB contains allradio access functionsRadio ResourceManagementScheduling of UL & DLdataScheduling and trans-mission of paging andsystem broadcastIP header compression& encryption

Serving GatewayLocal mobility anchor for inter-eNB handoversMobility anchor for inter-3GPP handoversIdle mode DL packet bufferingLawful interceptionPacket routing and forwarding

PDN GatewayConnectivity to Packet Data NetworkMobility anchor between 3GPP and non-3GPP accessUE IP address allocation

MME control plane functionsIdle mode UE reachabilityTracking area list managementS-GW/P-GW selectionInter core network node signalingfor mobility bw. 2G/3G and LTENAS signalingAuthenticationBearer management functions


EPS Architecture – User Plane Layout over S1

UE eNodeB MME

S-Gateway

RLC sub-layer performs:Transfer of upper layer PDUsError correction through ARQReordering of RLC data PDUsDuplicate detectionFlow controlSegmentation/ Concatenation of SDUs

PDCP sub-layer performs:Header compressionCiphering

MAC sub-layer performs:Mapping of logical channels totransport channelsSchedulingError correction through HARQPriority handling across UEs & logicalchannels

Physical sub-layer performs:ModulationCoding (FEC)UL power controlMulti-stream transmission &reception (MIMO)


EPS Architecture – Control Plane Layout over S1

UE eNodeB MME

RRC sub-layer performs:BroadcastingPagingRRC Connection ManagementRadio bearer controlMobility functionsUE measurement reporting & control

PDCP sub-layer performs:Integrity protection & ciphering

NAS sub-layer performs:AuthenticationSecurity controlIdle mode mobility handling/paging origination


EPS Architecture – Interworking for 3GPP and non-3GPP Access

Home Subscriber Server (HSS) is the subscription data repository for permanent userdata (subscriber profile).Policy Charging Rules Function (PCRF) provides the policy and charging control (PCC)rules for controlling the QoS as well as charging the user, accordingly.S3 interface connects MME directly to SGSN for signaling to support mobility across LTEand UTRAN/GERAN; S4 allows direction of user plane between LTE and GERAN/ UTRAN(uses GTP)

GERAN

UTRAN

E-UTRAN

SGSN

MME

non-3GPP Access

Serving GW PDN GWS1-U

S1-MME S11

S3

S4

S5

Internet

EPS Core

S12

SGi

HSSS6a

S10

PCRF

GxGxc


LTE Key Radio Features (Release 8)

Multiple access schemeDL: OFDMA with CPUL: Single Carrier FDMA (SC-FDMA) with CP

Adaptive modulation and codingDL modulations: QPSK, 16QAM, and 64QAMUL modulations: QPSK, 16QAM, and 64QAM (optional for UE)Rel.6 Turbo code: Coding rate of 1/3, two 8-state constituent encoders,and a contention-free internal interleaver.

ARQ within RLC sublayer and Hybrid ARQ within MAC sublayer.Advanced MIMO spatial multiplexing techniques

(2 or 4)x(2 or 4) downlink and 1x(2 or 4) uplink supported.Multi-layer transmission with up to four streams.Multi-user MIMO also supported.

Implicit support for interference coordinationSupport for both FDD and TDD


LTE Frequency Bands

LTE will support all band classes currently specified for UMTS as well asadditional bands


OFDM Basics – Overlapping Orthogonal

OFDM: Orthogonal Frequency Division MultiplexingOFDMA: Orthogonal Frequency Division Multiple-AccessFDM/ FDMA is nothing new: carriers are separated sufficiently in frequencyso that there is minimal overlap to prevent cross-talk.

OFDM: still FDM but carriers can actually be orthogonal (no cross-talk)while actually overlapping, if specially designed saved bandwidth !

conventional FDM

frequency

OFDM

frequency

saved bandwidth


OFDM Basics – Waveforms

Frequency domain: overlapping sincfunctions

Referred to as subcarriersTypically quite narrow, e.g. 15 kHz

Time domain: simple gated sinusoidfunctions

For orthogonality: each symbol hasan integer number of cycles overthe symbol timefundamental frequency f0 = 1/TOther sinusoids with fk = k • f0

f = 1/T

freq.

time

T = symbol time

0 1 2 3 4 5 6-0.2

0

0.2

0.4

0.6

0.8

1

0 0.2 0.4 0.6 0.8 1-1

-0.5

0

0.5

1


OFDM Basics – The Full OFDM Transceiver

Modulating the symbols onto subcarriers can be done very efficiently inbaseband using the FFT algorithm

SerialParallel

..

. IFFT

bitstream .

..

Parallelto Serial

D A

D ASerial toParallel

..

.FFT

..

.

OFDM Transmitter

OFDM Receiver

ParallelSerial

addCP

RFTx

RFRx

removeCP

Encoding +Interleaving+ Modulation

Demod +De-interleave

+ Decode

Estimatedbit stream

Channel estimation& compensation


OFDM Basics – Cyclic Prefix

ISI (between OFDM symbols) eliminated almost completely by inserting aguard time

Within an OFDM symbol, the data symbols modulated onto thesubcarriers are only orthogonal if there are an integer number ofsinusoidal cycles within the receiver window

Filling the guard time with a cyclic prefix (CP) ensures orthogonality ofsubcarriers even in the presence of multipath elimination of same cellinterference

CP Useful OFDM symbol time

OFDM symbol


OFDM symbol


OFDM symbol

OFDM Symbol OFDM Symbol OFDM Symbol

TG TG


Comparison with CDMA – Principle

OFDM: particular modulation symbol is carried over a relatively long symboltime and narrow bandwidth

LTE: 66.67 µs symbol time and 15 kHz bandwidthFor higher data rates send more symbols by using more sub-carriersincreases bandwidth occupancy

CDMA: particular modulation symbol is carried over a relatively shortsymbol time and a wide bandwidth

UMTS HSPA: 4.17 µs symbol time and 3.84 Mhz bandwidthTo get higher data rates use more spreading codes

time

freq

uenc

y

symbol 0symbol 1symbol 2symbol 3

time

freq

uenc

y

sym

bol0

sym

bol1

sym

bol2

sym

bol3OFDM CDMA


Comparison with CDMA – Time Domain Perspective

Short symbol times in CDMA lead to ISI in the presence of multipath

Long symbol times in OFDM together with CP prevent ISI from multipath

1 2 3 4

1 2 3 4

1 2 3 4

CDMA symbols

Multipath reflections from one symbolsignificantly overlap subsequentsymbols ISI

1 2CPCP

1 2CPCP

1 2CPCP

Little to no overlap insymbols from multipath


Comparison with CDMA – Frequency Domain Perspective

In CDMA each symbol is spread over a large bandwidth, hence it willexperience both good and bad parts of the channel response in frequencydomainIn OFDM each symbol is carried by a subcarrier over a narrow part ofthe band can avoid send symbols where channel frequency response ispoor based on frequency selective channel knowledge frequencyselective scheduling gain in OFDM systems

Frequency

ChannelResponse

f = 15 kHz

5 MHz


OFDM Basics – Choosing the Symbol Time for LTE

Two competing factors in determining the right OFDM symbol time:CP length should be longer than worst case multipath delay spread, and the OFDMsymbol time should be much larger than CP length to avoid significantoverhead from the CPOn the other hand, the OFDM symbol time should be much smaller than theshortest expected coherence time of the channel to avoid channel variabilitywithin the symbol time

LTE is designed to operate in delay spreads up to ~5 s and for speeds up to 350 km/h(~600 µs coherence time @ 2.6 GHz). As such, the following was decided:

CP length = 4.7 sOFDM symbol time = 66.67 s (~1/10 the worst case coherence time)

f = 15 kHz

CP

~4.7 µs ~66.7 µs


Scalable OFDM for Different Operating Bandwidths

With Scalable OFDM, the subcarrier spacingstays fixed at 15 kHz (hence symbol time isfixed to 66.67 µs) regardless of the operatingbandwidth (1.4 MHz, 3 MHz, 5 MHz, 10 MHz,15 MHz, 20 MHz)

The total number of subcarriers is varied inorder to operate in different bandwidths

This is done by specifying different FFTsizes (i.e. 512 point FFT for 5 MHz, 2048point FFT for 20 MHz)

Influence of delay spread, Doppler due to usermobility, timing accuracy, etc. remain the sameas the system bandwidth is changed robustdesign

common channels

10 MHz bandwidth

20 MHz bandwidth

5 MHz bandwidth

1.4 MHz bandwidth

3 MHz bandwidth

centre frequency


LTE Downlink Frame Format

Subframe length is 1 msconsists of two 0.5 ms slots

7 OFDM symbols per 0.5 ms slot 14 OFDM symbols per 1ms subframeIn UL center SC-FDMA symbol used for the data demodulation referencesignal (DM-RS)

slot = 0.5 ms slot = 0.5 ms

subframe = 1.0 ms

OFDM symbol

Radio frame = 10 ms


Spatial Multiplexing

Rank of the MIMO channel determines the number of independent TX/RXchannels offered by MIMO for spatial multiplexing

Rank min(#Tx, #Rx)To properly adjust the transmission parameters the UE provides feedbackabout the mobile radio channel situation

Channel quality (CQI), pre-coding matrix (PMI) and rank (RI)

HVUH

UHV


Multiple Antenna Techniques Supported in LTE

SU-MIMOMultiple data streams sent to the same user(max. 2 codewords)Significant throughput gains for UEs in highSINR conditions

MU-MIMO or BeamformingDifferent data streams sent to different usersusing the same time-frequency resourcesImproves throughput even in low SINRconditions (cell-edge)Works even for single antenna mobiles

Transmit diversity (TxDiv)Improves reliability on a single data streamFall back scheme if channel conditions donot allow MIMOUseful to improve reliability on commoncontrol channels


MIMO Support is Different in Downlink and Uplink

DownlinkSupports SU-MIMO, MU-MIMO, TxDiv

UplinkInitial release of LTE does only support MU-MIMO with a single transmitantenna at the UE Desire to avoid multiple power amplifiers at UE


LTE Duplexing Modes

LTE supports both Frequency Division Duplex (FDD) and Time DivisionDuplex (TDD) to provide flexible operation in a variety of spectrumallocations around the world.

Unlike UMTS TDD there is a high commonality between LTE TDD & LTE FDDSlot length (0.5 ms) and subframe length (1 ms) is the same using thesame numerology (OFDM symbol times, CP length, FFT sizes, samplerates, etc.)

Half-Duplex FDD (HD-FDD) as additional methodLike FDD, but UE cannot transmit and receive at the same timeUseful e.g. in frequency bands with small duplexing space


LTE Downlink

The LTE downlink uses scalable OFDMAFixed subcarrier spacing of 15 kHz for unicast

Symbol time fixed at T = 1/15 kHz = 66.67 µs

Different UEs are assigned different sets of subcarriers so that theyremain orthogonal to each other (except MU-MIMO)

Serial toParallel

..

.

IFFTbit

stream ..

.

Parallelto Serial

addCP


20 MHz: 2048 pt IFFT10 MHz: 1024 pt IFFT5 MHz: 512 pt IFFT


Physical Channels to Support LTE Downlink

eNodeB

Carries DL traffic

DL resource allocation

HARQ feedback for DLCQI reporting

MIMO reporting

Time span of PDCCH

Carries basic systembroadcast information

Allows mobile to get timing andfrequency sync with the cell


Mapping between DL Logical, Transport and Physical Channels

LTE makes heavy use of sharedchannels common control,paging, and part of broadcastinformation carried on PDSCHPCCH: paging control channel

BCCH: broadcast control channel

CCCH: common control channel

DCCH: dedicated control channel

DTCH: dedicated traffic channel

PCH: paging channel

BCH: broadcast channel

DL-SCH: DL shared channel


LTE Uplink Transmission Scheme (1/2)

To facilitate efficient power amplifier design in the UE, 3GPP chose singlecarrier frequency division multiple access (SC-FDMA) in favor of OFDMAfor uplink multiple access.

SC-FDMA results in better PAPRReduced PA back-off improved coverage

SC-FDMA is still an orthogonalmultiple access scheme

UEs are orthogonal in frequencySynchronous in the time domainthrough the use of timing advance(TA) signaling

Only needed to be synchronouswithin a fraction of the CP length0.52 s timing advance resolution

Node BUE C

UE B

UE A

UE A Transmit Timing

UE B Transmit Timing

UE C Transmit Timing


LTE Uplink Transmission Scheme (2/2)

SC-FDMA implemented using an OFDMA front-end and a DFT pre-coder, thisis referred to as either DFT-pre-coded OFDMA or DFT-spread OFDMA (DFT-SOFDMA)

Advantage is that numerology (subcarrier spacing, symbol times, FFTsizes, etc.) can be shared between uplink and downlinkCan still allocate variable bandwidth in units of 12 sub-carriersEach modulation symbol sees a wider bandwidth

+1-1

-1+1

-1-1

-1+1

+1+1

-1

DFT pre-coding

Serial toParallel IFFT

bitstream .

..

Parallelto Serial

addCP


.. DFT

..

.

.. Subcarrier

mapping


Physical Channels to Support LTE Uplink

eNodeB

Random access for initialaccess and UL timing

alignment

UL scheduling grant

Carries UL Traffic

UL scheduling request fortime synchronized UEs

HARQ feedback for UL

Allows channel stateinformation to beobtained by eNB


Mapping between UL Logical, Transport and Physical Channels

CCCH: common control channel

DCCH: dedicated control channel

DTCH: dedicated traffic channel

RACH: random access channel

UL-SCH: UL shared channel

PUSCH: physical UL shared channel

PUCCH: physical UL control channel

PRACH: physical random access channel


LTE Supported Data Rates

The data rates supported by LTE depend on a number of parameters:bandwidth, modulation scheme, MIMO scheme

Downlink peak rates Uplink peak rates


LTE Release 8 System Parameters

Access Scheme UL DFTS-OFDMDL OFDMA

Bandwidth 1.4, 3, 5, 10, 15, 20 MHzMinimum TTI 1 msSub-carrier spacing 15 kHzCyclic prefix length Short 4.7 µs

Long 16.7 µsModulation QPSK, 16QAM, 64QAMSpatial multiplexing Single layer for UL per UE

Up to 4 layers for DL per UEMU-MIMO supported for UL and DL


LTE Release 8 User Equipment Categories

Category 1 2 3 4 5

Peak rateMbps

DL 10 50 100 150 300

UL 5 25 50 50 75

Capability for physical functionalities

RF bandwidth 20 MHz

Modulation DL QPSK, 16QAM, 64QAM

UL QPSK, 16QAM QPSK,16QAM,64QAM

Multi-antenna

2 Rx diversity Assumed in performance requirements.

2x2 MIMO Notsupported

Mandatory

4x4 MIMO Not supported Mandatory


Scheduling and Resource Allocation

Basic unit of allocation is called a Resource Block (RB)12 subcarriers in frequency (= 180 kHz)1 timeslot in time (= 0.5 ms, = 7 OFDM symbols)Multiple resource blocks can be allocated to a user in a given subframe

The total number of RBs available depends on the operating bandwidth

12 sub-carriers(180 kHz)

Bandwidth (MHz) 1.4 3.0 5.0 10.0 15.0 20.0

Number of availableresource blocks

6 15 25 50 75 100


LTE Downlink Scheduling & Resource Allocation

Channel dependent scheduling is supported in both time and frequencydomain enables two dimensional flexibility

CQI feedback can provide both wideband and frequency selectivefeedbackPMI and RI feedback allow for MIMO mode selectionScheduler chooses bandwidth allocation, modulation and coding set(MCS), MIMO mode, and power allocation

HARQ operation is asynchronous and adaptiveAssigned RBs need not be contiguous for a given user in the downlink

14 OFDM symbols12

subcarriers

Slot =0.5 ms

Slot =0.5 ms

UE A

UE B

UE C

Time

Freq

uenc

y

<=3 OFDM symbols for L1/L2 control


LTE Uplink Scheduling & Resource Allocation

Channel dependent scheduling in both time and frequency enabled throughthe use of the sounding reference signal (SRS)

Scheduler selects bandwidth, modulation and coding set (MCS), use ofMU-MIMO, and PC parameters

HARQ operation is synchronous, and can be adaptivePRBs assigned for a particular UE must be contiguous in the uplink(SC-FDMA)

To reduce UE complexity, restriction placed on # of PRBs that can beassigned

14 SC-FDMA symbols(12 for data)

12subcarriers

Slot =0.5 ms

Slot =0.5 ms

UE A

UE B

UE C

Time

Freq

uenc

y


Uplink Power Control

Open-loop power control is the baselineuplink power control method in LTE(compensation for path loss and fading)

Constrain the dynamic range betweensignals received from different UEsFading is exploited by rate control

Target SINR is now a function of the UE’spathloss:

SINR(dBm) = SINRnom(dB) – (1 – ) · PL(dB)

PLdB: pathloss, estimated from DLreference signalFractional compensation factor 1

only a fraction of the path loss iscompensated

TargetSINR


Interference Coordination with Flexible Frequency Reuse

Cell edge users with frequency reuse > 1,

eNB transmits with higher power

Improved SINR conditions

Cell centre users can use whole frequency band

eNB transmits with reduced power

Less interference to other cells

Flexible frequency reuse realized throughintelligent scheduling and power allocation

Cell edge

Reuse > 1

Cell centre

Reuse = 1

Scheduler can place restriction on whichPRBs can be used in which sectors

Achieves frequency reuse > 1

Reduced inter-cell interference leads toimproved SINR, especially at cell-edge

Reduction in available transmissionbandwidth leads to poor overall spectralefficiency


Random-Access Procedure

RACH only used for Random Access PreambleResponse/ Data are sent over SCH

Non-contention based RA to improve access time, e.g. for HO

UE eNB

Random Access Preamble1

Random Access Response 2

Scheduled Transmission3

Contention Resolution 4

Contention based RA Non-Contention based RA


LTE Handover

LTE uses mobile-assisted & network-controlled handoverUE reports measurements using reporting criteriaNetwork decides when handover and to which cellRelies on UE to detect neighbor cells no need to maintain andbroadcast neighbor lists

Allows "plug-and-play" capability; saves BCH resources

For search and measurement of inter-frequency neighboring cells onlycarrier frequency need to be indicated

X2 interface used for handover preparation and forwarding of user dataTarget eNB prepares handover by sending required information to UEtransparently through source eNB as part of the Handover RequestAcknowledge message

New configuration information as taken from system broadcastAccelerates handover as UE does not need to read BCH on target cell

Buffered and new data is transferred from source to target eNB until pathswitch prevents data lossUE uses contention-free random access to accelerate handover


LTE Handover: Preparation Phase

UEUE SourceeNB

SourceSourceeNB

Measurement Control

TargeteNB

TargeteNB MMEMME sGWsGW

Packet Data Packet Data

UL allocation

Measurement Reports

HO decision

Admission Control

HO Request

HO Request AckDL allocation

RRC Connection Reconfig.

L1/L2signaling

L3 signaling

User data

HO decision is made by source eNB based on UE measurement report

Target eNB prepares HO by sending relevant info to UE through source eNB as partof HO request ACK command, so that UE does not need to read target cell BCCH

SN Status Transfer


LTE Handover: Execution Phase

UEUE SourceeNB

SourceeNB

TargeteNB


Detach from old cell,sync with new cell

Deliver buffered packets and forwardnew packets to target eNB

DL data forwarding via X2

Synchronisation

UL allocation and Timing Advance

RRC Connection Reconfig. Complete

L1/L2signaling

L3 signaling

User dataBuffer packets fromsource eNB

Packet Data

Packet Data

RACH is used here only, so target eNB can estimate UE timing and provide timingadvance for synchronization

RACH timing agreements ensure UE does not need to read target cell PBCH toobtain SFN (radio frame timing from SS is sufficient to know PRACH locations)

UL Packet Data


LTE Handover: Completion Phase

UEUE SourceeNB

TargeteNB


DL Packet Data

Path switch req

User plane update req

Switch DL path

User plane update responsePath switch req ACK

Release resources

Packet Data Packet Data

L1/L2signaling

L3 signaling

User data

DL data forwarding

Flush DL buffer,continue deliveringin-transit packets

End Marker

Release resources

Packet Data

End Marker


LTE Handover: Illustration of Interruption Period

UL

U- plane active

U-plane active

UEUE SourceeNB

SourceeNB

TargeteNB

TargeteNB

UL

U- plane active

U-plane active

UEs stops

Rx/Tx on the old cell

DL sync

+ RACH (no contention)

+ Timing Adv

+ UL Resource Req andGrant

ACK

HO Request

HO Confirm

HandoverLatency

(approx 55 ms)approx20 ms

MeasurementReport

HO Command

HO Complete

HandoverInterruption

(approx 35 ms)

Handover Preparation


Tracking Area

BCCHTAI 1

BCCHTAI 1

BCCHTAI 1

BCCHTAI 1

BCCHTAI 1

BCCHTAI 2

BCCHTAI 2

BCCHTAI 2

BCCHTAI 2

BCCHTAI 2

BCCHTAI 2

BCCHTAI 3

BCCHTAI 3

BCCHTAI 3

BCCHTAI 3

Tracking Area 1

Tracking Area 2 Tracking Area 3

Tracking Area Identifier (TAI) sent over Broadcast Channel BCCH

Tracking Areas can be shared by multiple MMEs

One UE can be allocated to multiple tracking areas


EPS Bearer Service Architecture


LTE RRC States

No RRC connection, no context ineNodeB (but EPS bearers are retained)UE controls mobility through cellselectionUE specific paging DRX cycle controlledby upper layersUE acquires system information frombroadcast channelUE monitors paging channel to detectincoming calls

RRC connection and context in eNodeBNetwork controlled mobilityTransfer of unicast and broadcast datato and from UEUE monitors control channelsassociated with the shared datachannelsUE provides channel quality andfeedback informationConnected mode DRX can beconfigured by eNodeB according to UEactivity level

RRC_IDLE RRC_Connected

Release RRC connection

Establish RRC connection


EPS Connection Management States

No signaling connection between UEand core network (no S1-U/ S1-MME)No RRC connection (i.e. RRC_IDLE)UE performs cell selection and trackingarea updates (TAU)

Signaling connection establishedbetween UE and MME, consists of twocomponents

RRC connectionS1-MME connection

UE location is known to accuracy ofCell-IDMobility via handover procedure

ECM_IDLE ECM_Connected

Signaling connection released

Signaling connection established


EPS Mobility Management States

EMM context holds no valid location orrouting information for UEUE is not reachable by MME as UElocation is not known

UE successfully registers with MME withAttach procedure or Tracking AreaUpdate (TAU)UE location known within tracking areaMME can page to UEUE always has at least one PDNconnection

EMM_Deregistered

Detach

AttachEMM_Registered


LTE – Status

3GPP quickly delivered stable LTE standardsRel.8 frozen in 2Q2009

Since 2010, LTE has been deployed worldwideTotally new infrastructureFirst target was often to provide broadband coverage for fixed users

Worldwide, 560 LTE networks are in service (Oct. 2017)*

Mostly implemented according to Release 8/9, increased deployment ofLTE-AdvancedMostly FDD, but also some TDD networksMobile packet data support with fallback to 3G/2G for CS voice service,starting with VoIPSpectrum allocation in new frequency bands as well as existing 2G/3Gbands (refarming)

3GPP continues LTE developmentRel.9: technical enhancements/ E-MBMSRel.10 – 12: LTE-Advanced (cf. next slides)

*[Source: 5G Americas/TeleGeography]


LTE-Advanced

The evolution of LTECorresponding to LTE Release 10 and beyond

Motivation of LTE-AdvancedIMT-Advanced standardisation process in ITU-RAdditional IMT spectrum band identified in WRC07Further evolution of LTE Release 8 and 9 to meet:

Performance requirements for IMT-Advanced of ITU-R

Future operator and end-user requirements

Other important requirementsLTE-Advanced to be backwards compatible with Release 8Support for flexible deployment scenarios including downlink/uplinkasymmetric bandwidth allocation for FDD and non-contiguous spectrumallocationIncreased deployment of indoor eNB and HNB in LTE-Advanced

Cf. T. Nakamura (RAN chairman): “Proposal for Candidate Radio Interface Technologies for IMT-Advanced Basedon LTE Release 10 and Beyond LTE-Advanced),” ITU-R WP 5D 3rd Workshop on IMT-Advanced, October 2009.


Evolution from IMT-2000 to IMT-Advanced

Interconnection

IMT-2000

Mobility

Low

High

1 10 100 1000Peak useful data rate (Mbit/s)

EnhancedIMT-2000

Enhancement

IMT-2000

Mobility

Low

High

1 10 100 1000

Area Wireless Access

EnhancedIMT-2000

Enhancement

Digital Broadcast SystemsNomadic / Local Area Access Systems

New Nomadic / Local

IMT-Advanced encompassthe capabilities of previous

systems

New capabilities ofIMT-Advanced

New MobileAccess


Peak data rate1 Gbps data rate will be achieved by 4-by-4 MIMO and transmissionbandwidth wider than approximately 70 MHz

Peak spectrum efficiencyDL: Rel.8 LTE satisfies IMT-Advanced requirementUL: Need to double from Release 8 to satisfy IMT-Advanced requirement

Rel.8 LTE LTE-Advanced IMT-Advanced

Peak data rateDL 300 Mbps 1 Gbps

1 Gbps(*)

UL 75 Mbps 500 Mbps

Peak spectrum efficiency[bps/Hz]

DL 15 30 15

UL 3.75 15 6.75

*“100 Mbps for high mobility and 1 Gbps for low mobility” is one of the key features as written inCircular Letter (CL)

System Performance Requirements


Technical Outline to Achieve LTE-Advanced Requirements

Support wider bandwidthCarrier aggregation to achieve wider bandwidthSupport of spectrum aggregationPeak data rate, spectrum flexibility

Advanced MIMO techniquesExtension to up to 8-layer transmission in downlinkIntroduction of single-user MIMO up to 4-layer transmission in uplinkPeak data rate, capacity, cell-edge user throughput

Coordinated multipoint transmission and reception (CoMP)CoMP transmission in downlinkCoMP reception in uplinkCell-edge user throughput, coverage, deployment flexibility

RelayingType 1 relays create a separate cell and appear as Rel.8 LTE eNB toRel.8 LTE UEsCoverage, cost effective deployment


Carrier Aggregation

Further increase of theavailable bandwidth by flexibleaggregation of the transmissionchannels (Carrier)

Increase of the available peakdata rateMore flexible channel allocation

For each channel (ComponentCarrier) there is a separatetransmitter/ receiver chain

Combination of the datastreams (aggregation) in theMAC-Layer

MAC

HARQ1 HARQ1 HARQ1 HARQ1

PHY1 PHY2 PHY3 PHY4

CC1 CC2 CC3 CC4

Band 1 Band 2


Advanced MIMO Techniques

Extension up to 8-stream transmission forsingle-user (SU) MIMO in downlink

improve downlink peak spectrumefficiency

Enhanced multi-user (MU) MIMO indownlink

Specify additional reference signals (RS)

Introduction of single-user (SU)-MIMO upto 4-stream transmission in uplink

Satisfy IMT requirement for uplink peakspectrum efficiency

Max. 8 streams

Higher-order MIMO upto 8 streams

EnhancedMU-MIMO

CSI feedback

Max. 4 streams

SU-MIMO up to 4 streams


Coordinated Multipoint Transmission/ Reception (CoMP)

Enhanced service provisioning, especiallyfor cell-edge usersCoMP transmission schemes in downlink

Joint processing (JP) from multiplegeographically separated points

Coordinated scheduling/beamforming(CS/CB) between cell sites

Similar for the uplinkDynamic coordination in uplinkschedulingJoint reception at multiple sites

Coherent combining ordynamic cell selection

Joint transmission/dynamic cell selection

Coordinated scheduling/beamforming

Receiver signal processing atcentral eNB (e.g., MRC, MMSEC)

Multipoint reception


eNB RNUE

Cell ID #x Cell ID #y

Higher node

Relaying

Type 1 relayRelay node (RN) creates a separate cell distinct from the donor cellUE receives/transmits control signals for scheduling and HARQ from/to RNRN appears as a Rel.8 LTE eNB to Rel.8 LTE UEs

Deploy cells in the areas where wired backhaul is not available or veryexpensive


Heterogenous Networks (HetNet)

Network expansion due to varying traffic demand & RF environmentCell-splitting of traditional macro deployments is complex and iterativeIndoor coverage and need for site acquisition add to the challenge

Future network deployments based on Heterogeneous NetworksDeployment of Macro eNBs for initial coverage onlyAddition of Pico, HeNBs and Relays for capacity growth & better userexperience

Improved in-building coverage and flexible site acquisition with low powerbase stationsRelays provide coverage extension with no incremental backhaul expense


Machine-to-Machine (M2M) Communication

Large variety of M2M applications already in useStationary applications: metering of consumption data, environmentmonitoring, telemedicine, telemonitoringMobile M2M applications: tracking of goods (logistics), autonomouscommunication between vehicles (Car2X)

Communication over cellular systemsIn parts of the world (nearly) completecoverageLow cost connection to even hardlyaccessible locationsOften in 2G systems, 3G/ 4G upcoming

Challenges for cellular M2M communicationOccurrence of variable radio conditionsTimes with bad or no radio linkSmall data reports but for a high numberof M2M devices

3GPP provides various LTE improvementsunder Machine Type Communication (MTC)enhancements


Device-to-Device (D2D) Communication

D2D enables a directcommunication betweenadjacent devices.

Avoid delays frominfrastructureProvide high data rate at lowtx powerAllow reuse of resourcesPossible operation w/oinfrastructure

3GPP implementationProximity servicesCommunication over sidelinkchannelseNB reserves D2D resources(eNB grant)

D2D-UETx

D2D-UERx

C-UE

Uplink data

eNBgrant

Sidelinkdata

Principle of Sidelink Communication


LTE References

Literature:H. Holma/ A. Toskala (Ed.): “LTE for UMTS - Evolution to LTE-Advanced,”2nd edition, Wiley 2011E. Dahlman et al: “4G: LTE/LTE-Advanced for Mobile Broadband,” 2nd edition,Academic Press 2013S. Sesia et al: “LTE, The UMTS Long Term Evolution: From Theory to Practice,”2nd edition, Wiley 2011H. Holma/ A. Toskala (Ed.): “LTE Advanced: 3GPP Solution for IMT-Advanced,”Wiley 2012

StandardsTS 36.xxx series: RAN AspectsTS 36.300 “E-UTRAN; Overall description; Stage 2”TR 25.912 “Feasibility study for evolved Universal Terrestrial Radio Access (UTRA)and Universal Terrestrial Radio Access Network (UTRAN)”TR 25.814 “Physical layer aspect for evolved UTRA”TR 23.882 “3GPP System Architecture Evolution: Report on Technical Options andConclusions”TR 36.912 “Feasibility study for Further Advancements for E-UTRA (LTE-Advanced)”TR 36.814 “Further Advancements for E-UTRA – Physical Layer Aspects”


Abbreviations

CP Cyclic PrefixDFT Discrete Fourier TransformationDRX Discontinuous ReceptionECM EPS Connection ManagementEMM EPS Mobility ManagementeNodeB/eNB Evolved NodeBEPC Evolved Packet CoreEPS Evolved Packet SystemE-UTRAN Evolved UMTS Terrestrial Radio Access

NetworkFDD Frequency-Division DuplexFDM Frequency-Division MultiplexingFFT Fast Fourier TransformationHD-FDD Half-Duplex FDDHO HandoverHOM Higher Order ModulationHSS Home Subscriber ServerIFFT Inverse FFTISI Inter-Symbol InterferenceLTE Long Term EvolutionMIMO Multiple-Input Multiple-OutputMME Mobility Management EntityMU Multi-User

OFDM Orthogonal Frequency-DivisionMultiplexing

OFDMA Orthogonal Frequency-DivisionMultiple-Access

PCRF Policy & Charging FunctionPDN Packet Data NetworkP-GW PDN GatewayRA Random AccessRB Resource BlockRRC Radio Resource ControlSAE System Architecture EvolutionSCH Shared ChannelS-GW Serving GatewaySC-FDMA Single Carrier FDMASON Self-Organizing NetworkSS Synchronization SignalSU Single UserTDD Time-Division DuplexTA Timing Advance/ Tracking AreaTAI Tracking Area IndicatorTAU Tracking Area UpdateUE User EquipmentVoIP Voice over Internet Protocol

Documents

3G Long-Term Evolution (LTE) and System … Long-Term Evolution (LTE) and System Architecture Evolution (SAE) Background System Architecture Radio Interface Radio Resource Management