01 Introduction v04

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1 Nokia Siemens Networks

IntroductionLTE Air Interface Course


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At the end of this module, you will be able to:

Recall the LTE key aspects, benefits and applications

Introduce LTE FDD and TDD commonalities and differences

List the LTE/SAE main requirements

Underline the LTE/SAE key features

Review the LTE network architecture

Review the LTE air interface key features

Introduce the main 3GPP specifications

Module Objectives


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Introduction

Overview

Requirements

Delay & QoS

Throughput & data rates

Spectrum

LTE/ SAE key features

Network architecture

LTE Air Interface

Specification


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Schedule for 3GPP Releases

year

UMTS Rel 99/4UMTS Rel 99/4 UMTS Rel 5UMTS Rel 5 UMTS Rel 6UMTS Rel 6 UMTS Rel 7UMTS Rel 7 UMTS Rel 8UMTS Rel 8

2007200520032000 2008

IMS

HSDPA

MBMS

WLAN IW

HSUPA

IMS Evolution

LTE Studies

iHSPA

LTE

UMTS WCDMA

HSDPA

IMS

HSUPA

LTE

Commercial

Specification

2009

Focus of this course is onRelease 8 UMTS!

The evolution of UMTS is termed Evolved Packet System (EPS).

In more detail, the evolution of the 3GPP radio technology is being specified under thename Long Term Evolution (LTE). The Evolved Packet Core (EPC) describes the non-

RAN aspects of the system.

EPS = LTE + EPC

EPS: Evolved Packet System (describes evolution of UMTS)LTE: Long Term Evolution (describes the new radio access technology)EPC: Evolved Packet Core

LTE/EPC is the 3GPP system for the years 2010 to 2020 and beyond.

LTE/EPC shall be ready for commercial launch around 2010.

The motivation of LTE/EPC is mainly driven by the need to stay competitive. In order tobe future-proof, UMTS shall be evolving towards a true mobile broadband packet accesssystem. In many aspects it will be superior compared with existing 3G alternatives.


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Summary of Capabilities & Benefits of LTE/EPC

Fully packet-oriented mobile

broadband network providing:

Peak data rates of 150 Mbps (DL)

Peak data rates of 50 Mbps (UL)

Very low latency

Seamless and lossless handover

Sophisticated QoS to support

important real time applications

such as voice, video and

interactive gaming

Support for terminal speeds of

150-500 Km/h

Cell ranges of up to 100 Km.

Reduced cost per bit

Simplified Architecture

All IP

Maximised exploitation of frequency

Resources

Supports flexible frequency

bandwidths

by means of OFDM, MIMO, HARQ etc.

an outstanding spectrum efficiency

can be achieved

Extended Interworking Functionality

seamless mobility with other 3GPP

access systems (UMTS, GPRS),

with 3GPP2/cdma2000

Reduced Terminal Complexity

Specific transmission schemes

Minimize power consumption

Fully packet-oriented mobile broadband network providing:

- Peak data rates of 100 Mbps (DL) and 50 Mbps (UL)

- Very low latency- Seamless and lossless handover

- Sophisticated QoS to support important real time applications such as voice, video andinteractive gaming

- Support for terminal speeds of 150-500 Km/h and cell ranges of up to 100 Km.

- Reduced cost per bit:

LTE/EPC deploys a simplified architecture and open interfaces. It is full IP-based anduses IP transport. In this way it utilizes low-cost equipment and infrastructure. Additionallythis contributes to reduction of operational costs. Further sophisticated features like self-configuration / self-optimization capabilities are beneficial in this context.

- Maximized exploitation of frequency resources:

LTE provides high throughput per cell and supports flexible frequency bandwidths and inparticular allows for re-farming of existing and deployment of new frequency bands.Furthermore by means of OFDM, MIMO, HARQ etc. an outstanding spectrum efficiencycan be achieved.

- Extended interworking functionality: LTE/EPC provides seamless mobility with other3GPP access systems (UMTS, GPRS), with 3GPP2/cdma2000 and where possible withnon-3GPP (e.g. WLAN).

- Reduced terminal complexity. Due to the specific transmission schemes thecomplexity of the terminals is kept reasonable. Also the power consumption shall beminimized. Both contributes to cost reduction and makes it attractive for mass marketdeployment.


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LTE FDD and TDD Modes

1,4

3

5

10

20

Channel Bandwidth scalability

1,4, 3, 5, 10, 15 or 20 MHz

= 1 component carrier

15


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FDD and TDD modes (2/2)

FDD and TDD modes Harmonisation(commonalities) FDD and TDD modesdifferences

FDD and TDD mode includedtogether in the samespecification

Same radio interface schemesfor both uplink and downlink

Same subframe formats

Same network architecture

Same air interface protocols

Same physical channelsprocedures

FDD developed in the paired 3GPPspectrum

TDD developed in the unpaired3GPP spectrum

Small differences in the physicalchannels design

Different frame formats

FDD mode has commonalities with3G UMTS

TDD mode has commonalities withTD-SCDMA (developed in China)

In this course both FDD andTDD modes will be

discussed

LTE FDD and TDD modes have been harmonized in the sense that both modes share thesame underlaying framework including the radio access schemes (OFDM in DL and SC-FDMA in UL for both), basic frame formats and protocols.

As a clear indication of harmonisation the TDD mode is included together with the FDDmode in the same set of specifications . Protocols and procedures are kept the same forFDD and TDD and therefore it is expected a high level of commonalities for theimplementation. This will make possibile to implement FDD and TDD in the same mobileterminal with a big potential for roaming between FDD and TDD and the other wayarround. However the scenarios for coexistences still need to be further investigated.

Another key feature of TDD mode is the commonality with TD-SCDMA. This is a bigadvantege since China is already having TD-SCDMA so the gloabal roaming will bepossibile.


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Introduction

Overview

Requirements

Delay & QoS


Spectrum



LTE Air Interface

Specification


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Requirement Input for LTE/EPC

Demand for higher

data rates

Demand for higher

data rates

Demand for quality of

service, lower delay

Demand for quality of

service, lower delay

Expected new spectrum

allocations

Expected new spectrum

allocations

Request for flexible

bandwidth usage

Request for flexible

bandwidth usage

Demand for reduced

terminal complexity

Demand for reduced

terminal complexity

Requirements Input

significantly increased downlink bit rates (>150Mbps);

significantly increased uplink bit rates (>50 Mbps);

increased cell edge bit rates;

low delay;

higher spectrum efficiency;

scalable bandwidth per cell (operator choice);

acceptable terminal complexity and costs (lower thanWCDMA);

optimization for low speed (0-15 km/h) but support forhigh and highest speed (up to 500 km/h);

.

Requirements Excerpt

Generic:

The requirements input list for LTE/EPC contains the following crucial elements:

higher data rates: Obviously this is a general requirement requested from any newsystem.

quality of service, lower delay: To enable true convergence between real-time and non-real-time services quality of service awareness is of absolute importance. This mustalready be paid attention to during the design of the physical layer. So LTE/EPC will beQoS aware from the very beginning on and not have QoS as an add-on, which is usuallynot very efficient.

expected new spectrum allocation: It is expected to get some new frequency bandsassigned to 3G. LTE should be ready to use these bands.

flexible bandwidth usage: LTE should be able to deal with frequency bands of differentsize. So a fixed bandwidth ultra-wideband system is not of big use. Rather LTE should beable to scale the frequency requirements dependent on the operators choice.

reduced terminal complexity: 3G terminals are very complex and thus suffer often frompoor performance due to hardware limitations and very often also software limitations (orbugs). LTE terminals should have essentially lower complexity. This would also offer thepossibility to implement other performance enhancement techniques later on.

These points result in a long list of requirements for LTE/EPC. So 3GPP/ETSI demand tohave downlink bit rates of greater than 100 Mbps and uplink bit rates of 50 Mbps. Of highimportance is also to increase the cell edge bit rates compared to HSPA.


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Requirement: Latency and Signal Performance

User Plane Latency

cell

Gateway

IP NetworkIP Network

< 5 ms (unloaded condition)

Control Plane Latency

IDLE

(no resources)

ACTIVE

< 100 ms

No resourceResource

Allocated

< 50 ms

The transition times between different levels of activity are also named C-plane latency.The one-way transit time can be seen as U-plane latency.

Furthermore for the C-plane capacity targets are stated as number of active users:

200 (5 MHz) and at least 400 for wider bands.

The UL/DL resource scheduling of course requires that the scheduler can handle anddistinguish different quality of service classes.


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Requirement: Spectrum Usage

LTE/SAE Targets

UL DL

Peak Bit Rate(Mbps)

> 50 > 150

SpectralEfficiency

(bps/Hz/s)

2..3 timesHSUPA

3..4 timesHSDPA

Cell EdgeThroughput(bps/Hz/s)

2..3 timesHSUPA

2..3 timesHSDPA

DOWNLINK

UPLINKUPLINK

Targets are defined related to the Rel. 6 baseline.

TIP!Note, bit rates are defined for 20 MHz bandwidth and for smaller bands proportionalscaling applies.

2 Tx antennas at the Node B and 2 Rx antennas at the UE are assumed for DL. For ULthe targets are set considering a single Tx antenna at the UE and 2 Rx antennas at theeNB.


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All categories support 20 MHz 64QAM mandatory in downlink, but not in uplink (except Class 5)

2x2 MIMO mandatory in other classes except Class 1

Class 1 Class 2 Class 3 Class 4 Class 5

10/5 Mbps 50/25 Mbps 100/50 Mbps 150/50 Mbps 300/75 MbpsPeak rate DL/UL

20 MHzRF bandwidth 20 MHz 20 MHz 20 MHz 20 MHz

64QAMModulation DL 64QAM 64QAM 64QAM 64QAM

16QAMModulation UL 16QAM 64QAM16QAM 16QAM

YesRx diversity Yes YesYes Yes

1-4 TxBTS Tx diversity

OptionalMIMO DL 2x2 4x42x2 2x2

1-4 Tx 1-4 Tx 1-4 Tx 1-4 Tx

LTE UE Categories

Functionality:

eNB obtains the UE radio capabilities via:

- The S1AP initial setup request message- The X2AP in case of handover

- The RRC in any other cases

eNB sends the UE radio capabilities to:

- The MME if it has been retrieved from RRC signalling

- The neighbour eNB in case of handover

UE category determines:

- MIMO settings

- PRB allocation and AMC limitation (e.g. 64QAM in UL)

- ROHC (Robust Header Compression) profile

- Inter RAT handover support


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LTE Paired Frequency Bands in 3GPP (FDD)

1800

2600

900

US AWS

UMTS core

US PCS

US 850

Japan 800

Japan 1700

Japan 1500

Extended AWS*

!"# $ %"'(

UHF (TV)

US700

))

US700

US700

*AWS = Advanced Wireless Spectrum , in Canada


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LTE Unpaired Frequency Bands in 3GPP (TDD)

**

US 1900 UL

UMTS TDD

2300

US 1900 DL

UMTS TDD1

UMTS TDD2

US 1900

2600

+* ,--.


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Frequency Deployment Possible Scenarios

Urban

Rural

or

2.6 GHz

2.1 GHz

2.6 GHz

2.1 GHz

900 MHz

900 MHz

or


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LTE/EPC Key Features

EPS ( Evolved Packet System ) /

SAE ( System Architecture Evolution ) /

LTE ( Long Term Evolution )

EPC ( Evolved Packet Core )EPC ( Evolved Packet Core )

EUTRAN

( Evolved UTRAN )

EUTRAN

( Evolved UTRAN )




OFDMA/SC-FDMA

MIMO ( beam-forming/

spatial multiplexing)

HARQ

Scalable bandwidth

(1.4, 2.5, 5, 10, .. 20 MHz)

Evolved Node B /

No RNC

UL/DL resource

scheduling

IP Transport Layer

QoS Aware

Self Configuration

PS Domain only,

No CS Domain

IP Transport Layer

QoS Aware

3GPP (GTP) or

IETF (MIPv6)

Prepared for

Non-3GPP Access

Mobile IPversion 6

(Was initially 1.25, 2., now1.4 and 3 MHz bandwidths) to give a goodmatch for both GSM and cdma2000 refarming cases)

BASED ON THE REQUIREMENTS 3GPP AGREED UPON STANDARD FEATURES:

OFDMA/SC-FDMA.MIMO (Multiple Input Multiple Output)

HARQ (Hybrid Automatic Retransmission on reQuest)

Scalable bandwidth

Evolved Node B

IP transport layer

UL/DL resource scheduling

QoS awareness

Self configuration

Self optimization

Packet Switched Domain only

3GPP (GTP) or IETF (MIPv6) option

Non-3GPP access


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Introduction

Overview

Requirements

Delay & QoS


Spectrum



LTE Air Interface

Specification


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Network Architecture Evolution

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Direct tunnel

I-HSPA

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$ '

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(

)

1

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(

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1

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(

)

1 3 4

6

3 4 63 4 6

3 4

6

Node B +RNC

Functionality

EvolvedNode B(eNB)

! #

! #! #

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HSPA

(

)

7

(

)

7(

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(

)

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LTE

User plane

Control Plane

Flat architecture: single network element in user plane inradio network and core network

SAE: System Architecture Evolution

SAE GW: Serving Gateway +PDN Gateway


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Evolved Packet System (EPS) Architecture -Subsystems The EPS architecture goal is to optimize the system for packet data transfer.

There are no circuit switched components. The EPS architecture is made up of: EPC: Evolved Packet Core, also referred as SAE

eUTRAN: Radio Access Network, also referred as LTE

LTE or eUTRAN SAE or EPC

EPC provides access toexternal packet IP networksand performs a number ofCN related functions (e.g.QoS, security, mobility andterminal context

management) for idle andactive terminals

eUTRAN performs all radiointerface related functions

EPS Architecture

FDD and TDD ArchitectureHarmonisation:

No difference between FDDand TDD mode regarding the

network architecture!

The LTE/EPC architecture is driven by the goal to optimize the system for packet datatransfer.

TIP!

There are no circuit switched components in LTE/EPC

There is a new approach in the inter-connection between radio access network and corenetwork. The EPS architecture is made up of an EPC (Packet Core Network, alsoreferred as EPC) and an eUTRAN Radio Access Network (also referred as LTE)

The CN provides access to external packet IP networks and performs a number of CNrelated functions (e.g. QoS, security, mobility and terminal context management) for idle(camped) and active terminals. The RAN performs all radio interface related functions.

The LTE/EPC radio access network - Evolved UTRAN (E-UTRAN) - will only containNode Bs. No RNC is provided anymore. This means, that the evolved Node Bs take overthe radio management functionality.

This will make radio management faster and the network architecture simpler. E-UTRANexclusively uses IP as transport layer. Behind the EPC follow one or more IP networks. Amajor example will be IMS, that can benefit especially from the QoS awareness of LTE.


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LTE/SAE Network Elements

Main references to architecture in 3GPP specs.: TS23.401,TS23.402,TS36.300

NOTE: Interface names are from draft specification and may not be the final in terface names.

LTE-UE

Evolved UTRAN (E-UTRAN)

MME S10

S6a

ServingGateway

S1-U

S11

PDNGateway

PDN

Evolved Packet Core (EPC)

S1-MME

PCRF

S7 Rx+

SGiS5/S8

Evolved Node B(eNB)

X2

LTE-Uu

HSS

MobilityManagement

EntityPolicy & Charging

Rule Function

SAEGateway

eNB

Gx

S7 is Gx


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Introduction

Overview

Requirements

Delay & QoS


Spectrum



LTE Air Interface

Specification


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LTE Air Interface Key Features

OFDM is the state-of-the-art and most efficient and robust airinterface and could be used for both FDD and TDD modes

Fast Link Adaptation

due to channel behaviour

Short TTI = 1 ms

Transmissiontime interval

Advanced SchedulingTime & Freq.

TX RX

Tx RxMIMO

Channel

DL: OFDMA

UL: SC-FDMA

scalable

ARQ AutomaticRepeat Request

64QAMModulation

The state-of-the-art design of the LTE air interface is characterised by OFDMA (DL) andSC-FDMA (UL) together with MIMO.

The downlink modulation is based on OFDMA (Orthogonal Frequency Division MultipleAccess). OFDMA is a variant of OFDM which has the advantage that receiver complexityis at a reasonable level, it can handle scalable bandwidth requirements and it supportsvarious modulation schemes from BPSK, QPSK, 16QAM to 64QAM. This allows adaptivemodulation on a per user base. In uplink direction a variant of OFDMA called SC-FDMA(Single Carrier Frequency Division Multiple Access) is used. It has the advantage againstOFDMA to have a lower PAPR (Peak-to-Average Power Ratio), which leads to lowerpower consumption and less expensive RF amplifiers in the terminal.

LTE will support MIMO. It describes the possibility to have multiple transmitter andreceiver antennas in a system. Other names are beam-forming or smart antennas. Up tofour antennas can be used by a single LTE cell. This allows having spatial multiplexing

and beam-forming. MIMO is considered to be the core technology to increase spectralefficiency. Currently the performance of MIMO for high mobility cases is still underinvestigation.

HARQ implements a protocol on layer 1/layer 2 that allows for fast retransmission.Furthermore blocks can be retransmitted with increased coding.

In contrast to UMTS where physical resources are either shared or dedicated, theEvolved Node B in EUTRAN handles all physical resource via a scheduler and assignsthem dynamically to users and channels. This provides greater flexibility than the oldersystem


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Introduction

Overview

Requirements

Delay & QoS


Spectrum



LTE Air Interface

Specification


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3GPP List ofSpecification Series

36 Series contains mostpart of LTE relatedspecifications for Radio

FDD and TDD SpecificationHarmonisation:

The TDD mode is includedtogether with the FDD mode

in the same set ofspecifications !

The specification of LTE/EPC starts with UMTS release 7 for the studies and reports andUMTS release 8 contains the first complete set of technical specifications.

E-UTRAN which takes the biggest part will be specified in series TS/TR 36.xxx.

In TS 23.401/402 one will find the network architecture.

All 3GPP specifications have a specification number consisting of 4 or 5 digits. (e.g. 09.02or 29.002).

The first two digits define the series, followed by 2 further digits for the 01 to 13 series or3 further digits for the 21 to 55 series.


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The LTE radio interface is standardised in the 36-series of 3GPP

Release 8. The detailed physical layer structure is described in fivephysical layer specifications.

LTE is standardised in the 36-series of 3GPP Release 8:TS 36.1xx Equipment requirements (terminals, eNodeB)TS 36.2xx Layer 1 (physical layer) specificationsTS 36.3xx Layer 2 and 3 specificationsTS 36.4xx Network signalling specificationsTS 36.5xx User equipment conformance testing

LTE is standardised in the 36-series of 3GPP Release 8:TS 36.1xx Equipment requirements (terminals, eNodeB)TS 36.2xx Layer 1 (physical layer) specificationsTS 36.3xx Layer 2 and 3 specificationsTS 36.4xx Network signalling specificationsTS 36.5xx User equipment conformance testing

Physical layer specifications:

TS 36.201 Physical layer; General descriptionTS 36.211 Physical channels and modulationTS 36.212 Multiplexing and channel codingTS 36.213 Physical layer proceduresTS 36.214 Physical layer; Measurements

Physical layer specifications:

TS 36.201 Physical layer; General descriptionTS 36.211 Physical channels and modulationTS 36.212 Multiplexing and channel codingTS 36.213 Physical layer proceduresTS 36.214 Physical layer; Measurements

Frequency

eNodeB

Subcarriers

OFDMAOFDMASC-FDMASC-FDMA

LTE Air Interface Specifications

01 Introduction v04

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