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

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  • 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)

  • Cellular Communication Systems 3Andreas Mitschele-Thiel, Jens Mueckenheim Nov. 2017

    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

    34x HSPA Rel.6 in DL*

    23x HSPA Rel.6 in UL

    1 bps/Hz broadcast

    Improved Cell Edge Rates

    23x HSPA Rel.6 in DL*

    23x 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

  • Cellular Communication Systems 4Andreas Mitschele-Thiel, Jens Mueckenheim Nov. 2017

    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

  • Cellular Communication Systems 5Andreas Mitschele-Thiel, Jens Mueckenheim Nov. 2017

    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

  • Cellular Communication Systems 6Andreas Mitschele-Thiel, Jens Mueckenheim Nov. 2017

    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 !

  • Cellular Communication Systems 7Andreas Mitschele-Thiel, Jens Mueckenheim Nov. 2017

    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

  • Cellular Communication Systems 8Andreas Mitschele-Thiel, Jens Mueckenheim Nov. 2017

    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)

  • Cellular Communication Systems 9Andreas Mitschele-Thiel, Jens Mueckenheim Nov. 2017

    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

  • Cellular Communication Systems 10Andreas Mitschele-Thiel, Jens Mueckenheim Nov. 2017

    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

  • Cellular Communication Systems 11Andreas Mitschele-Thiel, Jens Mueckenheim Nov. 2017

    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

  • Cellular Communication Systems 12Andreas Mitschele-Thiel, Jens Mueckenheim Nov. 2017

    LTE Frequency Bands

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

  • Cellular Communication Systems 13Andreas Mitschele-Thiel, Jens Mueckenheim Nov. 2017

    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

  • Cellular Communication Systems 14Andreas Mitschele-Thiel, Jens Mueckenheim Nov. 2017

    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

  • Cellular Communication Systems 15Andreas Mitschele-Thiel, Jens Mueckenheim Nov. 2017

    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-

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