LTE System Principle 20110525

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Security Level: Internal Use

Copyright @ 2010 Huawei Technologies Co.,Ltd. All rights reserved

LTE system principle

2010-09

Copyright 2010 Huawei Technologies Co., Ltd. All rights reserved.

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Page 2

Upon completion of this course, you will be able

to

Know the backgrounds of evolution

Know system architecture of LTE

Know key features of LTE

Objectives


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3GPP TS 36.401

3GPP TS 36.101

3GPP TS 36.211

Page 3

References


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1. Overview

2. LTE system architecture

3. LTE key features

Contents

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1. Overview


3. LTE key features

Contents

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Mobile communications standards landscape


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3GPP is working on two approaches for 3G evolution: the LTE and

the HSPA Evolution

HSPA Evolution is aimed to be backward compatible while LTE do not

need to be backward compatible with WCDMA and HSPA

By the end of 2007, 3GPP R8 is released as the first specs of LTE

Page 7

3GPP Releases

GSM

9.6kbit/s

Phase 1

GPRS

171.2kbit/s

Phase 2+

(Release 97)

EDGE

473.6kbit/s

Release 99

UMTS

2Mbit/s

Release 99

HSDPA

14.4Mbit/s

Release 5

HSUPA

5.76Mbit/s

Release 6

HSPA+

28.8Mbit/s

42Mbit/sRelease 7/8

LTE

+300Mbit/s

Release 8

Release 9/10

LTE Advanced


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Copyright @ 2010 Huawei Technologies Co.,Ltd. All rights reserved Page 8

LTE will be the Single Global Standard

FDD LTE

TDD LTE

UMTS

CDMA

TD-SCDMA

GSM

WiMAX

700M

800M

850M

900M

1500M

1700M

1800M

1900M

2100M

2300M

2600M

LTE will be the natural migration choice for mobile operators.

84Mbps

/10MHz

21Mbps

/5MHz

42Mbps

/5MHz

64QAM 64QAM

2x2

MIMO

DC

64QAM

2x2

MIM

O 2x2

MIMO

28Mbps

/5MHz

Spectral Efficiency

Title

64QAM

>1.2Gbps

/80MHz

64QAM

300Mbps

/20MHz

OFDM OFDM

4x4

MIMO

New

Key

Tech

.

4x4

MIMO

Relay

2x2

MIMO

64QAM

OFD

M

150Mbps

/20MHz


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SDR Facilitating Smooth Evolution

Pag

e 9

Technolog

y

800M 900M 1800M 2100M 2.6G

GSM

UMTS

LTE

GSM+UMTS

GSM+LTE

LTE

mRRU MRFU

SDR SDR

SDR SDR

GSM

2600MHz LTE

2100MHz UMTS

1800MHz GSM

900MHz

800MHz

2010 2011 2012

LTE

LTE

LTE

LTE UMTS

GSM

Spectrum refarming starts from 900M/1800M, which can be utilized for

LTE deployment.

SDR technology supports flexible and smooth transition from 2G/3G to LTE.

Spectrum for LTE Smooth Transition to LTE


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Reduced delays, in terms of both connection establishment (less then

100ms) and transmission latency (less then 10ms)

Increased user data rates: (Peak data-rate requirements are 100 Mbit/s

and 50 Mbit/s for downlink and uplink respectively, when operating in

20MHz spectrum allocation)

Improved spectral efficiency

Seamless mobility, including between different radio-access technologies

Supporting flexible spectrum allocation (1.4, 3, 5, 10, 15 and 20 MHz) to

meet the complicated spectrum situation requirement

Simplified network architecture

Reasonable power consumption for the mobile terminal.

Page 10

LTE requirements and targets


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The LTE downlink transmission scheme is based on downlink

OFDMA and uplink SC-FDMA

LTE adopts shared-channel transmission, in which the time-

frequency resource is dynamically shared between users. This is

similar to the approach taken in HSDPA

Fast hybrid ARQ with soft combining is used in LTE

MIMO is supported by LTE, basically this is Spatial multiplexing

which can increase data rate prominently

LTE supports flexible spectrum allocation in terms of duplex

arrangement which support both FDD and TDD and bandwidth

allocations which ranges 1.4, 3, 5, 10, 15 and 20 MHz

Support SON

Page 11

LTE technical features


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LTE is designed to operate in these frequency bands

2.1GHz, 1.9GHz, 1.7GHz, 2.6GHz, 900 MHz, 800 MHz, 450 MHz,

etc , refer to 36.101 for details.

Transmission bandwidth could be:

Channel bandwidth BWChannel [MHz] 1.4 3 5 10 15 20

Transmission bandwidth configuration NRB 6 15 25 50 75 100

Transmission

Bandwidth [RB]

Transmission Bandwidth Configuration [RB]

Channel Bandwidth [MHz]

Res

ou

rce

blo

ck

Ch

an

nel e

dg

e

Ch

an

nel e

dg

e

DC carrier (downlink only)Active Resource Blocks Page 12

LTE frequency bands


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LTE Release 8 Bands Band Duplex FDL_low

(MHz)

FDL_high

(MHz)

NOffs-DL NDL FUL_low

(MHz)

FUL_high

(MHz)

NOffs-UL NUL

1 FDD 2110 2170 0 0-599 1920 1980 18000 18000-18599

2 FDD 1930 1990 600 600-1199 1850 1910 18600 18600-19199

3 FDD 1805 1880 1200 1200-1949 1710 1785 19200 19200-19949

4 FDD 2110 2155 1950 1950-2399 1710 1755 19950 19950-20399

5 FDD 869 894 2400 2400-2649 824 849 20400 20400-20649

6 FDD 875 885 2650 2650-2749 830 840 20650 20650-20749

7 FDD 2620 2690 2750 2750-3449 2500 2570 20750 20750-21449

8 FDD 925 960 3450 3450-3799 880 915 21450 21450-21799

9 FDD 1844.9 1879.9 3800 3800-4149 1749.9 1784.9 21800 21800-22149

10 FDD 2110 2170 4150 4150-4749 1710 1770 22150 22150-22749

11 FDD 1475.9 1500.9 4750 4750-4999 1427.9 1452.9 22750 22750-22999

12 FDD 728 746 5000 5000-5179 698 716 23000 23000-23179

13 FDD 746 756 5180 5180-5279 777 787 23180 23180-23279

14 FDD 758 768 5280 5280-5379 788 798 23280 23280-23379

17 FDD 734 746 5730 5730-5849 704 716 23730 23730-23849

33 TDD 1900 1920 26000 36000-36199 1900 1920 36000 36000-36199

34 TDD 2010 2025 26200 36200-36349 2010 2025 36200 36200-36349

35 TDD 1850 1910 26350 36350-36949 1850 1910 36350 36350-36949

36 TDD 1930 1990 26950 36950-37549 1930 1990 36950 36950-37549

37 TDD 1910 1930 27550 37550-37749 1910 1930 37550 37550-37749

38 TDD 2570 2620 27750 37750-38249 2570 2620 37750 37750-38249

39 TDD 1880 1920 28250 38250-38649 1880 1920 38250 38250-38649

40 TDD 2300 2400 28650 38650-39649 2300 2400 38650 38650-39649

Page 13


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eNB

UE

Carrier Frequency EARFCN

Calculation

FDL = FDL_low + 0.1(NDL - NOffs-DL)

FUL = FUL_low + 0.1(NUL - NOffs-UL)

Page 14


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Example

Frequency

Uplink Downlink

100kHz Raster

2127.4MHz1937.4MHz

FDL = FDL_low + 0.1(NDL - NOffs-DL)

(FDL - FDL_low)

0.1+ NOffs-DL

(2127.4 - 2110)

0.1+ 0

NDL =

NDL = = 174

Page 15


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Huawei mirror site for 3GPP specifications.

http://szxmir01-in.huawei.com/www.3gpp.org/www.3gpp.org

The specification document for LTE is 36 series, inherits the

structure of UTRAN 25 series:

36.1xx series is about the physical layer general aspect

36.2xx series is about radio interface physical layer

36.3xx series is about the radio interface layer 2 and 3

36.4xx series is about the terrestrial interfaces (S1, X2 )

Page 16

LTE standardization and specifications


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1. Overview


3. LTE key features

Contents

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LTE System architecture

LTE: simplified IP flat architecture

Less equipment node and easier deployment

Less transmission delay and easier O&M

S1 and X2 interfaces are based on a full IP transport stack

eNB

MME / S-GW MME / S-GW

eNB

eNBS1 S1

S1 S1

X2

X2

X2

E-UTRAN

UMTS LTE

Page 18


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Page 19

LTE-SAE System architecture

SAE

Control plane

User plane

Operator's

IP ServiceSGi

Rx

UE

S-GW P-GW

PCRF

Gx

S5

MME

HSS

S1-U

S11

S6a

LTE

S1-MME

LTE

-UuX2 S1-U

S1-MME

eNodeB

eNodeB

Gxc

An evolved core network, the Evolved Packet Core is at the same time

developed, which generally is called System Architecture Evolution.

The philosophy of the SAE is to focus on the packet-switched domain, and

migrate away from the circuit-switched domain


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Transfer of user data

Radio channel ciphering

and deciphering

Integrity protection

Header compression

Mobility control functions

Handover

Paging

Positioning

Inter-cell interference coordination

Connection setup and release

Load Balancing

Distribution function for NAS

messages

NAS node selection function

Synchronization

Radio access network sharing

MBMS function

Page 20

E-UTRAN functions


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1. Overview

2. TE system architecture

3. LTE key features

Contents

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Transmission by means of OFDM can be seen as a kind of multi-carrier

transmission.

Due to the fact that two modulated OFDM subcarriers are mutually

orthogonal, multiple signals could be transmitted in parallel over the

same radio link, the overall data rate can be increased up to M times.

Page 22

Basic principles of OFDM

Frequency

Guard Band

Channel

Bandwidth

Subcarrier

Frequency

Channel

Bandwidth


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Efficient use of radio spectrum includes placing modulated carriers as close as

possible without causing Inter-Carrier Interference (ICI)

In order to transmit high data rates, short symbol periods must be used, In a

multi-path environment, a shorter symbol period leads to a greater chance for

Inter-Symbol Interference (ISI).

Orthogonal Frequency Division Multiplexing (OFDM) addresses both of these

problems:

OFDM provides a technique allowing the bandwidths of modulated carriers

to overlap without interference (no ICI).

It also provides a high date rate with a long symbol duration, thus helping to

eliminate ISI.

Page 23

Why use OFDM?


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OFDM modulation implementation in LTE

Normally ,assume LTE sub carrier frequency f =1/Tu=15khz, and

IFFT bin size N=2048, the sampling rate is fs =1/Ts

=N f=30720000Hz

Page 24

OFDM implementation by IFFT/FFT

Coded

BitsIFFT

Serial

to

Parallel

Subcarrier

Modulation

RF

Inverse Fast

Fourier

Transform

Complex

Waveform

Coded

Bits

Parallel

to

Serial

FFT

Subcarrier

Demodulation

Receiver

Fast Fourier

Transform


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LTE Channel and FFT Sizes

Channel Bandwidth

FFT Size Subcarrier Bandwidth

Sampling Rate

1.4MHz 128

15kHz

1.92MHz

3MHz 256 3.84MHz

5MHz 512 7.68MHz

10MHz 1024 15.36MHz

15MHz 1536 23.04MHz

20MHz 2048 30.72MHz

Page 25


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Cyclic-prefix insertion


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Time dispersion on the radio channel may cause ISI

To deal with this problem, cyclic-prefix insertion is typically used in

case of OFDM transmission

The last NCP samples of the IFFT output block of length N is copied

and inserted at the beginning of the block, increasing the block

length from N to N +NCP. At the receiver side, the corresponding

samples are discarded before OFDM demodulation

Subcarrier orthogonality will then be preserved also in case of a

time-dispersive channel, as long as the span of the time dispersion is

shorter than the cyclic-prefix length.

Cyclic-prefix insertion

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Downlink CP Parameters

Configuration CP Length (Ts) Time Delay Spread

Normal Cyclic

Prefix

f = 15kHz 160 for slot 0 ~ 5.208s ~ 1.562km

144 for slot 1, 2, 6 ~ 4.688s ~ 1.406km

Extended Cyclic

Prefix

f = 15kHz 512 for slot 0, 1, 5 ~16.67s ~ 5km

f = 7.5kHz 1024 for 0, 1, 2 ~ 33.33 s ~ 10km

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High spectrum efficiency - the bandwidth of each subcarrier would be

adjacent to its neighbors, so there would be no wasted spectrum

With multiple subcarriers transmitting in parallel, long symbol duration is

used, thus OFDMA is more tolerant to multi-path environment and

better entitled to eliminate ISI (inter symbol interference)

Especially with a cyclic prefix, inter-symbol interference could be

minimized

OFDM is flexible in allocating power and rate optimally among

narrowband sub-carriers (scheduling)

Frequency diversity could be enabled due to the wide spectrum

Page 29

Advantage of OFDM


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Peak to Average Power Ratio

Amplitude

Time

OFDM

Symbol

PAPR (Peak to Average

Power Ratio) Issue

Peak

Average

The drawback of OFDM is the high peak-to-average ratio of the

transmitted signal, which greatly decrease the efficiency of the linear

amplifiers

This is especially critical for the uplink, due to the high importance of

low mobile-terminal power consumption and cost.

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SC-FDMA, which has much in common with OFDMA, such as multi-

carrier technology and guard interval protected symbol, but much higher

power amplifier efficiency (lower PAPR) is adopt in uplink.

SC-FDMA is just the DFT-S-OFDM, which can be seen as an OFDM

system with a DFT pre-coding. The localized RB distribution makes each

user occupy consecutive part of the whole bandwidth, which looks like a

single carrier.

Page 31

SC-FDMA in uplink

Time Domain

CP

Insertion

Subcarrier

Mapping

Frequency Domain

DFTSymbols

Time Domain

IDFT

0

0

0

0

0

0

0


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eNB

UE

OFDM used in LTE

OFDM

(OFDMA)

OFDM

(SC-FDMA)

eNB

UE

Radio

Channel

FDD Radio

Channel

UE

TDD

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Frequency

PowerTime

Orthogonal Frequency Division Multiple

Access

OFDMA

Each user allocated a

different resource

which can vary in

time and frequency.

Page 33

HUAWEI TECHNOLOGIES CO., LTD. Huawei Confidential

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Page 34

OFDMA used in LTE.

DL: OFDMA (Orthogonal Frequency Division Multiple Access)

Anti multi-path interference

Anti frequency selective fading

Higher spectrum efficiency

Easy to cooperate with MIMO for higher

throughput

Flexible multi-users scheduling

UL: SC-FDMA (Single Carrier - FDMA)

Save terminals cost & power consumption

Lower PAPR modulation technology: DFT-S-OFDM,

which is similar to OFDM

Higher spectral efficiency compare with traditional

single carrier technology.


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Downlink PRB Parameters

Configuration NSCRB NSymbDL

Normal Cyclic Prefix f = 15kHz 12

7

Extended Cyclic

Prefix f = 15kHz 6

f = 7.5kHz 24 3

0

OFDM Symbols (= 7 for Normal CP)

21 3 4 5 6

NsymbDL

160 144 144 144 144 144 1442048 2048 2048 2048 2048 2048 2048

Larger first CP when

Normal CP is configured

E.g. NCP = 144,

TCP= 144 x Ts = 4.6875s

Normal CP Configuration

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OFDM Symbol Mapping

Time

Frequency

Amplitude

OFDM

Symbol

Cyclic

Prefix

Modulated

OFDM

Symbol

OFDMA

Each user allocated a

different resource

which can vary in

time and frequency.

Page 36


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Basically LTE uses shared-channel transmission, similar to HSDPA,

the time-frequency resource is dynamically shared between users

LTE can take channel variations into account not only in the time

domain, as HSPA, but also in the frequency domain

For LTE, scheduling decisions can be taken as often as once every 1

ms and the granularity in the frequency domain is 180 kHz

Page 37

Channel-dependent scheduling


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Multi-Antenna Technique MIMO

Fundamentals of MIMO:

The data to be sent will be divided into multiple concurrent data streams.

The data streams are simultaneously transmitted from multiple antennas

through the spatial dimensions, through different radio channels, and

received by multiple antennas.

And then can be restored to the original data according to the spatial

signature of each data stream.

Receive diversity:

SIMO

Transmit diversity:

MISO

Multi-antenna reception

and transmission: MIMO

Page 38


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MIMO Modes

8 MIMO modes specified in 3GPP LTE standard

Transmission

Mode

Transmission scheme Reference

Mode 1 single-antenna port (port 0) It is compatible with single-antenna transmission

Mode 2 transmit diversity It weakens the interference caused by channel fading and is

applicable within low SINR environment

Mode 3 open-loop space division

multiplexing

It increases the peak rate and is applicable within high rate and

SINR environment

Mode 4 Closed-loop spatial

multiplexing

It is weighted according to the channel characteristics,

increases the peak rate, and is applicable within low rate but

high SINR environment

Mode 5 Multi-user MIMO It improves cell throughput

Mode 6 Closed-loop precoding with

rank of 1

It increases cell coverage

Mode 7 Beamforming, single-

antenna port (port 5)

It weakens interference and increases cell coverage

Mode 8 Dual-antenna port: Dual-

stream BF

It increases cell throughput

Page 39


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Array gain: It increases the transmit power and can be used for beamforming.

Diversity gain: It weakens the interference caused by channel fading.

Spatial multiplexing gain: It doubles the rate within the same bandwidth after

spatial orthogonal channels are constructed.

MIMO

Channel

Data

Streaming

Advantages of MIMO

Page 40


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UL Virtual MIMO

Features Benefits

Improve the overall uplink cell throughput.

Increase the UL spectrum efficiency.

The uplink channels of paired users

must be with good orthogonality to

each other to prevent interference.

Multi-users use the same time-

frequency resource.

Page 41


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2x2 MIMO

eNodeB UE 1

1x2 SIMO

eNode

B UE 1

Thro

ughput (M

bps)

28.34%

18.15%

ISD:500m

Speed:3km/h

13.88

16.4

9.42

12.09

12.36

14.23

15.12%

MIMO

SIMO xx.xx%: Gain

ISD:500m

Speed:30km/h

ISD:1732m

Speed:30km/h

Thro

ughput (M

bps)

46.40% 46.94%

Outdoor-to-Indoor

Speed: 3km/h

23.24

34.15

56.68%

MIMO SIMO xx.xx%: Gain

24.03

35.18

17.15

26.87

Outdoor-to-Outdoor

Speed: 3km/h

Outdoor-to-Outdoor

Speed: 30km/h

In typical urban

area: 15%~28% gain over SIMO @ Macro

~50% gain over SIMO @ Micro

L

T

E

L

T

E

L

T

E

Macr

o

Micro

MIMO--the Key to Improve Cell Throughput

Page 42


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More Gains through Higher-order MIMO

23%~90% increasing in edge user

throughput

4x4 MIMO v.s. 2x2 MIMO:

~ 50% gain in average cell

throughput

23%~90% increasing in edge user

throughput

2x4 MU-MIMO v.s. 1x2 SIMO:

~50% gain in average cell

throughput

eNodeB UE 1

UE 1

UE 2

eNodeB

UL 24 MU-MIMO DL 44 MIMO

Page 43


Slide title :32-35pt

Color: R153 G0 B0

Corporate Font :


Font to be used by customers and

partners :

Arial

Slide text :20-22pt

Bullets level 2-5:

18pt

Color:Black

Corporate Font :


Font to be used by customers and

partners :

Arial

Top right corner for

field-mark,

customer or

partner logotypes.

----------------

The following nine

groups of colors

are an example of

how our design

colors can be used,

please take note

that you should

only use one

design color group

per slide.

For specific usage

details, refer to the

Typesetting Standard.

Page44

AMC & 64QAM

AMC, Adaptive Modulation and Coding

Radio-link data rate is controlled by adjusting the modulation scheme and/or the

channel coding rate

Modulations: QPSK, 16QAM, and 64QAM

Turbo code

Provide higher-data-rate services

Significantly improve the system

throughput

Improve users experience

High-order modulation scheme used

within excellent channel condition

Features


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Antenna

Ports

OFDM Signal Generation

Codewords

Scrambling

Scrambling

Modulation

Mapper

Modulation

Mapper

Layer

MapperPrecoding

Layers

Resource

Element

Mapper

Resource

Element

Mapper

OFDM

Signal

Generation

OFDM

Signal

Generation

Page 45


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By restricting the transmission power of parts of the spectrum in one

cell, the interference seen in the neighbouring cells in this part of the

spectrum will be reduced, This part of the spectrum can then be used

to provide higher data rates for users in the neighbouring cell

Page 46

Inter-cell interference coordination

2

3

6

5

7

4

2

3

5

9

1 1

4

7

8

6

Frequency

Cell 1,4,7 Power

Frequency

Cell 2,5,8 Power

Frequency

Cell 3,6,9

Power

Different subband allocated for different cell edge users among cells

Reducing the DL inter-cell interference among neighbor cells

30~50% throughput increased for cell edge users (


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Page 47

LTE Key Technologies SON

Self-Optiz. & Maintenance

Network Performance

Improvement Network Planning &

Design

Installation &

Initial Tuning

Network Operation &

Maintenance Network Upgrade and

evolution

Self-Planning Self-Config. Self-optimiz.

Deployment Stage

Operation & Maintenance Stage

eNB 3

eNB 1

eNB 2

Self-Organising Network (SON)

SON effectively reduces human intervention in deployment and operation stage. Thus, SON saves both CAPEX & OPEX.

SON with ICIC : SON helps inter-cell interference coordination to improve cell edge throughput and user experience


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SON Improving Operation Efficiency

Planning

Phase

Deploymen

t

Phase

Maintenance

Phase Optimization

Phase

Inventory Management

Sleeping Cell detection

Antenna Fault Detection

Cell/interface/sub. trace

Automatic Network Planning

Automatic Config. Planning

Automatic Parameter Planning

Automatic PCI/TA Optimization

Automatic Neighbor Relation

Inter-RAT ANR,MRO, System Load

Balance, RACH Optimization

Self- configuration (Plug & Play)

Auto Software Management

SON makes LTE network more efficient and solves new challenges when network architecture changes

Page 48


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Typical SON Features at Initial Stage

MLB: Mobility Load Balancing

ANR: Automatic Neighbor

Relation

Self-Config.: Quick Deployment

Save cost & Improve exactness Avoid first HO failure due to missing neighbor relation

New

Optimizing cell reselection and handover

parameters

Reduce call drop rate, handover failure rate,

Reduce unnecessary redirection

MRO: Mobility Robust

Optimization

unnecessary HO Rate

HO successful rate

Va

lue

eNodeB

EMS + DHCP

File Server

Config Config Config

S/W

Config S/W

More reliable

Improve network KPI by HO optimization

Plug & Play Installation

Shorten deployment duration

Cell A Cell B Cell C

Cell C Cell B Cell A

Cell B

Page 49

Thank you www.huawei.com

Documents

LTE System Principle 20110525