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

3GPP Evolution – Background Discussion started in Dec 2004 State of the art then: The combination of HSDPA and E-DCH provides very efficient packet data transmission capabilities, but UMTS should continue to be evolved to meet the ever increasing demand of new applications and user expectations. 10 years have passed since the initiation of the 3G programme and it is time to initiate a new programme to evolve 3G which will lead to a 4G technology. From the application/user perspectives, the UMTS evolution should target at significantly higher data rates and throughput, lower network latency, and support of always-on connectivity. From the operator perspectives, an evolved UMTS will make business sense if it: Provide significantly improved power and bandwidth efficiencies Facilitate the convergence with other networks/technologies Reduce transport network cost Limit additional complexity

Evolved-UTRA is a packet only network - there is no support of circuit switched services (no MSC) Evolved-UTRA starts on a clean state - everything is up for discussion including the system architecture and the split of functionality between RAN and CN Led to 3GPP Study Item (Study Phase: 2005-4Q2006) „3G Long-term Evolution (LTE)” for new Radio Access and “System Architecture Evolution” (SAE) for Evolved Network UMTS Networks

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Nov. 2011

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LTE Requirements and Performance Targets

Improved Spectrum Efficiency

High Peak Data Rates 100 Mbps DL (20 MHz, 2x2 MIMO) 50 Mbps UL (20 MHz, 1x2)

3-4x HSPA Rel’6 in DL* 2-3x HSPA Rel’6 in UL

* Assumes 2x2 in DL for LTE, but 1x2 for HSPA Rel’6

1 bps/Hz broadcast

Improved Cell Edge Rates Support Scalable BW

2-3x HSPA Rel’6 in DL*

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

2-3x HSPA Rel’6 in UL Full broadband coverage

Low Latency

UMTS Networks

< 5ms user plane (UE to RAN edge)

Packet Domain Only

1 Reduced inter-cell interference leads to improved SINR, especially at cell-edge Reduction in available transmission bandwidth leads to poor overall spectral efficiency

UMTS Networks

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 through intelligent scheduling and power allocation

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Random-Access Procedure RACH only used for Random Access Preamble Response/ Data are sent over SCH Non-contention based RA to improve access time, e.g. for HO

UE

1

eNB

Random Access Preamble

Random Access Response

3

2

Scheduled Transmission

Contention Resolution

4

Non-Contention based RA

Contention based RA

UMTS Networks

Andreas Mitschele-Thiel, Jens Mückenheim

Nov. 2011

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LTE Handover LTE uses UE-assisted network controlled handover UE reports measurements; network decides when handover and to which cell Relies on UE to detect neighbor cells no need to maintain and broadcast neighbor lists Allows "plug-and-play" capability; saves BCH resources

For search and measurement of inter-frequency neighboring cells only carrier frequency need to be indicated X2 interface used for handover preparation and forwarding of user data Target eNB prepares handover by sending required information to UE transparently through source eNB as part of the Handover Request Acknowledge message New configuration information needed from system broadcast Accelerates handover as UE does not need to read BCH on target cell

Buffered and new data is transferred from source to target eNB until path switch prevents data loss UE uses contention-free random access to accelerate handover

UMTS Networks

Andreas Mitschele-Thiel, Jens Mückenheim

Nov. 2011

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LTE Handover: Preparation Phase

Target eNB

Source eNB

UE

MME

sGW

Measurement Control Packet Data

Packet Data L1/L2 signaling

UL allocation Measurement Reports

L3 signaling User data

HO decision HO Request Admission Control HO Request Ack DL allocation RRC Connection Reconfig.

SN Status Transfer

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 part of HO request ACK command, so that UE does not need to read target cell BCH UMTS Networks

Andreas Mitschele-Thiel, Jens Mückenheim

Nov. 2011

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LTE Handover: Execution Phase Target eNB

Source eNB

UE

MME

sGW

Packet Data Detach from old cell, sync with new cell

Deliver buffered packets and forward new packets to target eNB

L1/L2 signaling

DL data forwarding via X2

L3 signaling User data

Buffer packets from source eNB Synchronisation UL allocation and Timing Advance RRC Connection Reconfig. Complete Packet Data

UL Packet Data

RACH is used here only so target eNB can estimate UE timing and provide timing advance for synchronization; RACH timing agreements ensure UE does not need to read target cell P-BCH to obtain SFN (radio frame timing from SCH is sufficient to know PRACH locations) UMTS Networks

Andreas Mitschele-Thiel, Jens Mückenheim

Nov. 2011

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LTE Handover: Completion Phase

UE

Target eNB

Source eNB

MME

sGW

DL Packet Data DL data forwarding Packet Data Path switch req User plane update req End Marker

Switch DL path Path switch req ACK

Release resources

User plane update response

Flush DL buffer, continue delivering in-transit packets

L1/L2 signaling End Marker

L3 signaling User data

Release resources

Packet Data

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Packet Data

Andreas Mitschele-Thiel, Jens Mückenheim

Nov. 2011

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LTE Handover: Illustration of Interruption Period

Source eNB

UE

UEs stops

Target eNB

Rx/Tx on the old cell UL

Measurement Report

U- plane active

HO Request HO Confirm

Handover Preparation

HO Command

DL sync

Handover Interruption (approx 35 ms)

approx 20 ms

Handover Latency (approx 55 ms)

+ RACH (no contention) + Timing Adv + UL Resource Req and Grant HO Complete ACK

U-plane active

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Nov. 2011

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Tracking Area

BCCH TAI 2

BCCH TAI 2

BCCH TAI 1

BCCH TAI 3

BCCH TAI 2

BCCH TAI 1

BCCH TAI 1

BCCH TAI 3

BCCH TAI 2

BCCH TAI 2

BCCH TAI 1

BCCH TAI 3

BCCH TAI 3

BCCH TAI 2

BCCH TAI 1

Tracking Area 2

Tracking Area 3

Tracking Area 1 • • •

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

UMTS Networks

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Nov. 2011

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EPS Bearer Service Architecture

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LTE RRC States

Establish RRC connection

RRC_IDLE

RRC_Connected Release RRC connection

No RRC connection, no context in eNodeB (but EPS bearers are retained) UE controls mobility through cell selection UE specific paging DRX cycle controlled by upper layers UE acquires system information from BCH UE monitors paging channel to detect incoming calls

UMTS Networks

RRC connection and context in eNodeB Network controlled mobility Transfer of unicast and broadcast data to and from UE UE monitors control channels associated with the shared data channels UE provides channel quality and feedback information Connected mode DRX can be configured by eNodeB according to UE activity level

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Nov. 2011

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EPS Connection Management States

Signaling connection established

ECM_IDLE

ECM_Connected Signaling connection released

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

UMTS Networks

Signaling connection established between UE and MME, consists of two components RRC connection S1-MME connection UE location is known to accuracy of Cell-ID Mobility via handover procedure

Andreas Mitschele-Thiel, Jens Mückenheim

Nov. 2011

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EPS Mobility Management States

Attach

EMM_Deregistered

EMM_Registered Detach

EMM context holds no valid location or routing information for UE UE is not reachable by MME as UE location is not known

UMTS Networks

UE successfully registers with MME with Attach procedure or Tracking Area Update (TAU) UE location known within tracking area MME can page to UE UE always has at least one PDN connection

Andreas Mitschele-Thiel, Jens Mückenheim

Nov. 2011

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LTE – Summary LTE is a new air interface with no backward compatibility to WCDMA Combination of OFDM, MIMO and HOM SAE/ EPS realizes a flatter IP-based network architecture with less complexity eNodeB, S-GW, P-GW Some procedures/protocols are being re-used from UMTS Protocol stack Concept of Logical/ Transport/ Physical Channels Complexity is significantly reduced Reduced UE state space Most transmission uses SCH LTE standard (Rel. 8) is stable Rel. 9: technical enhancements/ E-MBMS Rel. 10: LTE-Advanced (cf. next slides)

UMTS Networks

Andreas Mitschele-Thiel, Jens Mückenheim

Nov. 2011

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LTE-Advanced The evolution of LTE Corresponding to LTE Release 10 and beyond Motivation of LTE-Advanced IMT-Advanced standardisation process in ITU-R Additional IMT spectrum band identified in WRC07 Further evolution of LTE Release 8 and 9 to meet: Requirements for IMT-Advanced of ITU-R Future operator and end-user requirements

2008

ITU

2009

2010

Proposals

Circular Letter

Evaluation Specification

IMT-Advanced recommendation

3GPP

Study Item phase

3GPP WS IMT-Advanced

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Work Item phase

First submission

LTE release 10 (”LTE-Advanced”)

Final submission

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Evolution from IMT-2000 to IMT-Advanced IMT-Advanced will encompass the capabilities of previous systems

Mobility

New capabilities of IMT-Advanced High

IMT-2000

Enhanced IMT-2000

New Mobile Access

Enhancement t Enhancemen

New Nomadic / Local Area Wireless Access

Low

1

Interconnection

10 100 Peak useful data rate (Mbit/s)

Nomadic / Local Area Access Systems

1000

Digital Broadcast Systems •

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Nov. 2011

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System Performance Requirements Peak data rate 1 Gbps data rate will be achieved by 4-by-4 MIMO and transmission bandwidth wider than approximately 70 MHz Peak spectrum efficiency DL: Rel. 8 LTE satisfies IMT-Advanced requirement UL: Need to double from Release 8 to satisfy IMT-Advanced requirement

DL

Rel. 8 LTE

LTE-Advanced

300 Mbps

1 Gbps 1 Gbps(*)

Peak data rate

Peak spectrum efficiency [bps/Hz]

IMT-Advanced

UL

75 Mbps

500 Mbps

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 in Circular Letter (CL)

UMTS Networks

Andreas Mitschele-Thiel, Jens Mückenheim

Nov. 2011

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Technical Outline to Achieve LTE-Advanced Requirements Support wider bandwidth Carrier aggregation to achieve wider bandwidth Support of spectrum aggregation Peak data rate, spectrum flexibility Advanced MIMO techniques Extension to up to 8-layer transmission in downlink Introduction of single-user MIMO up to 4-layer transmission in uplink Peak data rate, capacity, cell-edge user throughput Coordinated multipoint transmission and reception (CoMP) CoMP transmission in downlink CoMP reception in uplink Cell-edge user throughput, coverage, deployment flexibility Relaying Type 1 relays create a separate cell and appear as Rel. 8 LTE eNB to Rel. 8 LTE UEs Coverage, cost effective deployment Further reduction of delay AS/NAS parallel processing for reduction of C-Plane delay

UMTS Networks

Andreas Mitschele-Thiel, Jens Mückenheim

Nov. 2011

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Carrier Aggregation Wider bandwidth transmission using carrier aggregation Entire system bandwidth up to, e.g., 100 MHz, comprises multiple basic frequency blocks called component carriers (CCs) Each CC is backward compatible with Rel. 8 LTE Carrier aggregation supports both contiguous and non-contiguous spectrums, and asymmetric bandwidth for FDD

System bandwidth, e.g., 100 MHz

CC, e.g., 20 MHz

Frequency

UE capabilities • 100-MHz case • 40-MHz case • 20-MHz case (Rel. 8 LTE)

UMTS Networks

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Nov. 2011

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Advanced MIMO Techniques Extension up to 8-stream transmission for single-user (SU) MIMO in downlink improve downlink peak spectrum efficiency

Max. 8 streams

Higher-order MIMO up to 8 streams CSI feedback

Enhanced multi-user (MU) MIMO in downlink Specify additional reference signals (RS) Enhanced MU-MIMO

Introduction of single-user (SU)-MIMO up to 4-stream transmission in uplink Satisfy IMT requirement for uplink peak spectrum efficiency

Max. 4 streams

SU-MIMO up to 4 streams UMTS Networks

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Coordinated Multipoint Transmission/ Reception (CoMP) Enhanced service provisioning, especially for cell-edge users CoMP transmission schemes in downlink Joint processing (JP) from multiple geographically separated points

Coherent combining or dynamic cell selection

Joint transmission/dynamic cell selection

Coordinated scheduling/beamforming (CS/CB) between cell sites Similar for the uplink Dynamic coordination in uplink scheduling Joint reception at multiple sites

Coordinated scheduling/beamforming

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

Multipoint reception UMTS Networks

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Nov. 2011

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Relaying Type 1 relay Relay node (RN) creates a separate cell distinct from the donor cell UE receives/transmits control signals for scheduling and HARQ from/to RN RN appears as a Rel. 8 LTE eNB to Rel. 8 LTE UEs Deploy cells in the areas where wired backhaul is not available or very expensive

Higher node Cell ID #x

UE

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eNB

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Cell ID #y

RN

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EASY-C Overview EASY C Project topics / objectives BMBF project 3 year project: 2007 – 2010 Preparation of a new Standard: “LTE Advanced” Focus on improved spectral efficiency, cell border throughput, fairness, and latency Working groups WG1: Algorithms and Concepts WG2: Technology Test Beds WG3: Hardware Architecture Web page: http://www.easy-c.de Project partners:

UMTS Networks

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Nov. 2011

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EASY-C Testbeds in Dresden and Berlin Dresden: testbed focussed on physical layer aspects

UMTS Networks

Berlin: focus on new algorithms, services and applications

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LTE References Literature: H. Holma/ A. Toskala (Ed.): “LTE for UMTS - OFDMA and SC-FDMA Based Radio Access,” 2nd edition, Wiley 2011 E. Dahlman et al: “3G Evolution, HSPA and LTE for Mobile Broadband,” 3rd edition, Academic Press 2011 S. Sesia et al: “LTE, The UMTS Long Term Evolution: From Theory to Practice,” Wiley 2011 T. Nakamura (RAN chairman): “Proposal for Candidate Radio Interface Technologies for IMT-Advanced Based on LTE Release 10 and Beyond LTEAdvanced),” ITU-R WP 5D 3rd Workshop on IMT-Advanced, October 2009 Standards TS 36.xxx series: RAN Aspects TS 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 and Conclusions” TR 36.912 “Feasibility study for Further Advancements for E-UTRA (LTEAdvanced)” TR 36.814 “Further Advancements for E-UTRA - Physical Layer Aspects” UMTS Networks

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Abbreviations CP DFT DRX ECM EMM eNodeB/eNB EPC EPS E-UTRAN FDD FDM FFT HD-FDD HO HOM HSS IFFT ISI LTE MIMO MME MU

UMTS Networks

Cyclic Prefix Discrete Fourier Transformation Discontinuous Reception EPS Connection Management EPS Mobility Management Evolved NodeB Evolved Packet Core Evolved Packet System Evolved UMTS Terrestrial Radio Access Network Frequency-Division Duplex Frequency-Division Multiplexing Fast Fourier Transformation Half-Duplex FDD Handover Higher Order Modulation Home Subscriber Server Inverse FFT Inter-Symbol Interference Long Term Evolution Multiple-Input Multiple-Output Mobility Management Entity Multi-User

OFDM OFDMA PCRF PDN P-GW RA RB RRC SAE SCH S-GW SC-FDMA SU TDD TA TAI TAU UE

Andreas Mitschele-Thiel, Jens Mückenheim

Orthogonal Frequency-Division Multiplexing Orthogonal Frequency-Division Multiple-Access Policy & Charging Function Packet Data Network PDN Gateway Random Access Resource Block Radio Resource Control System Architecture Evolution Shared Channel Serving Gateway Single Carrier FDMA Single User Time-Division Duplex Timing Advance/ Tracking Area Tracking Area Indicator Tracking Area Update User Equipment

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