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Introduction to LTE (Part 1)

The webinar will start shortly

2

About the Presenters

Graham Whyley Technical Master Trainer

AIRCOM Technical Master Trainer since 2005

Currently responsible for all LTE training

course creation and delivery

Over 20 years of training experience at

companies including British Telecom and

Fujitsu

Adam Moore Learning & Development Manager With AIRCOM since 2006

Member of CIPD

3

Webinar - Introduction to LTE (Part 1)

Approximate Duration – 1 hour

Agenda

Comparison between GSM, UMTS & LTE

Motivation for LTE

4

Interference

Interference in cellular networks is one of the most common problems in the

radio access network (RAN).

What is Interference?

Anything at the same

frequency at the same time

Same frequency

High interference between the cells

Same frequency

To reduce levels of

Interference we have more

frequencies. Frequency

Planning

Frequency F1

High interference between the cells

Different

frequency F2

5

Global System for Mobile Communications (GSM)

The total number of frequencies used is termed the frequency reuse factor.

A high frequency reuse factor gives good isolation between cells

Same

Frequency

F2 F1 F1

Low interference between the cells. Poor Capacity

F1 F1

High interference between the cells

8 Timeslots/freq

6

C/I ratio

CARRIER (f1) INTERFERER (f1)

C

I

C/I = 10 log

100/10 =+10

C/I = 0dB

C/I = 10 log

10/10 =0

C/I = 10 log

10/100 =-10

Co-channel

Interfering Cell

RATES DEPENDANT ON C/I RATIO

CS1- Data Rate = 181 payload bits per 20mS sample = 9.05kbps

CS2-Data Rate = 268 payload bits per 20mS sample = 13.4kbps

CS3-Data Rate = 312 payload bits per 20mS sample = 15.6kbps

CS4-Data Rate = 428 payload bits per 20mS sample = 21.4kbps

CS1

CS4

7

Coding Scheme Performance

C / I

CS-2

CS-3

CS-4

CS-1

Average Data Throughput per TS vs Average Connection C/I

Da

ta t

hro

ug

hp

ut

4 levels of channel coding schemes

(CS-1 to CS-4)

Scheme selected according to

interference level (C/I)

Very poor data rates

CS1- Data Rate = 181 payload bits per 20mS sample =

9.05kbps

CS2-Data Rate = 268 payload bits per 20mS sample =

13.4kbps

CS3-Data Rate = 312 payload bits per 20mS sample =

15.6kbps

CS4-Data Rate = 428 payload bits per 20mS sample =

21.4kbps

8

Circuit/Packet Data Separation

BTS BSC PCU

Visited

MSC/VLR

Serving

GSN

Gateway

MSC

Gateway

GSN

HLR

Circuit Switched

Packet Switched

PSTN

PDN

A

Gb Gb interface LAYER TWO-FRAME

RELAY

NO QoS

THIS IS NOT AN ALL IP

NETWORK:

Lots of SS7 links

UMTS uses Ethernet or ATM (depends

on Release) both give good QoS

LTE is an ALL IP NEWORK. You can set QOS at Network layer(Layer) DSCP, or at

Ethernet layer (Layer2)

LTE DOES NOT SUPPORT CIRCUIT SWITCHED. But CS fallback

9

Frequency reuse

The use of CDMA/LTE requires a fundamental change in cellular network

planning and deployment strategies, largely resulting from the fact that it

enables a frequency reuse factor of 1 to be used.

GSM900/1800: 3G (WCDMA):

WCDMA GSM

Carrier spacing 5 MHz 200 kHz

Frequency reuse

factor

1 yes

In LTE networks there

are number of ways of

reducing interference

More frequencies the

better

10

CELL-DCH

REL’99

Variable SF YES

Soft handover YES

TTI times 10,20,40,80 mS

Maximum channel Rate 2 Mbps –Typical 384kb/s

Modulation QPSK

Comparison Rel’99

same

WCDMA carrier

R

N

C

This has transmission implications

Soft Handover Region

384kb/s

Data

Active

Set =1

Active

Set =2

Active

Set =1

LTE/HSDPA NO Soft Handover

11

CELL-DCH

REL’99

HSDPA

REL’5

Variable SF YES NO

Soft handover YES NO

TTI times 10,20,40,80 mS 2mS

Maximum channel Rate 2 Mbps –Typical 384kb/s

14.4 Mbps

Modulation QPSK QPSK/16-QAM

Comparison Rel’99 /Rel’5

12

CELL-DCH

REL’99

HSDPA

REL’5

LTE

Variable SF YES NO NO

Soft handover YES NO NO

TTI times 10,20,40,80 mS 2mS 1mS

Maximum channel Rate

2 Mbps –Typical 384kb/s

14.4 Mbps With 4x4 MIMO

About 300Mb/s

Modulation QPSK QPSK/16-QAM QPSK/16-QAM/64-QAM

Comparison Rel’99 /Rel’5/LTE

13

HSDPA-Rel’5 M

ax

imu

m

po

we

r 4

3d

bm

CPICH

RSCP

Ec/Io

HSDPA

Po

we

r fo

r

HS

DP

A HSDPA-

REL 5 16 QAM

QPSK

Shared with Rel’99 –

Typically 5 codes

REL 99 – Circuit Switched

PS Data –Typical 384kbit/s

REL 99 – Circuit Switched

PS Data –Typical 384kbit/s

HSDPA-REL 5

Same Frequency

F1- Shared

Power/Share Codes

REL 99 – Circuit Switched

PS Data –Typical 384kbit/s

Frequency

F1

Frequency

F2 HSDPA-REL 5

Different coding

Rates

The benefit of 16 QAM

is that 4 bits of data are

transmitted in each

radio symbol as

opposed to 2 bits with

QPSK.

Under good radio conditions, an advanced

modulation scheme—16 QAM

Maximum channel Rate

14.4 Mbps

WILL NOT GET

Maximum channel Rate

14.4 Mbps - SHARED

14

0 20 40 60 80 100 120 140 160-2

02468

10121416

Time [number of TTIs]

QPSK1/4

QPSK2/4

QPSK3/4

16QAM2/4

16QAM3/4

Inst

an

tan

eou

s EsN

o [

dB

] C/I received by UE

Link adaptation

mode

C/I varies with fading

BTS adjusts link adaptation mode with a few ms delay based on channel quality

reports from the UE

Fast Link Adaptation in HSDPA

Mobile devices report the quality of the downlink channel via channel quality indicator (CQI) reports to

the mobile network. Using these reports, the system continuously optimises performance (at 10%

BLER) by choosing the best transmission speed for the next TTI.

channel quality reports

15

HSPA Evolution- HSPA+

Three main benefits of HSPA+

• Higher-order modulation (64 QAM, 16QAM, QPSK)

• Advanced multiple-antenna techniques

• Multi-carrier operation

Dual-carrier HSDPA was introduced, whereby two adjacent

5-MHz radio channels can be used simultaneously to a single UE

QPSK 16QAM 64QAM

QPSK 16QAM 64QAM

TX

TX

5 MHz

41.00 Mbps

channel quality reports

channel quality reports

16

• Bit Rates after accounting for the overheads generated by Reference

Signals, Synchronisation Signals and other Physical Channels

• Coding rate hasn’t been included

LTE compared to HSPA+ - Downlink

Channel Bandwidth

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

QPSK 1.61 4.27 7.23 14.63 22.03 29.43

16QAM 3.21 8.54 14.46 29.26 44.06 58.86

64QAM 4.82 12.81 21.69 43.89 66.09 88.29

64QAM (2+2 MIMO) 9.08 24.20 41.00 83.00 125.00 167.00

64QAM (4+4 MIMO) 17.07 45.58 77.26 156.46 235.66 314.86

Figures in Mbps

Compare with the

equivalent HSPA+

bit rate

17

Question

What is Interference?

18

Questions

Do you require Frequency planning in GSM?

YES

Why?

To improve C/I ratio

What happens if improve C/I ratio?

Increased coverage. Increased data rate

The use of CDMA/LTE requires a

fundamental change in cellular network

planning and deployment strategies,

largely resulting from the fact that it

enables a frequency reuse factor of 1

to be used. (Rel’99 & Rel’5 may use

different frequencies)

RATES DEPENDANT ON C/I RATIO

CS1-Data Rate = 181 payload bits per 20mS sample = 9.05kbps

CS2-Data Rate = 268 payload bits per 20mS sample = 13.4kbps

CS3-Data Rate = 312 payload bits per 20mS sample = 15.6kbps

CS4-Data Rate = 428 payload bits per 20mS sample = 21.4kbps

Privileged and confidential. The information contained in this material is privileged and confidential, and is intended

only for the use of the individual to whom it is addressed and others who have been specifically authorized to receive

it. If you are not the intended recipient, you are hereby notified that any dissemination, distribution or copying of this

material is strictly prohibited. If you have received this material in error, please destroy it immediately.

The motivation for LTE

20

Average Revenue per User (ARPU)

ARPU has been flat in recent years

LTE promises to reverse these declines by accelerating adoption of high-

speed data services and innovative new content and applications

Higher-bandwidth and lower-latency will significantly improve the user

experience for bandwidth-hungry content and applications.

Jumpy, stuttering YouTube videos and waiting for things to buffer will be

consigned to the past.

Application and content developers will need to create services that take

advantage of LTE’s capabilities. Applications such as real-time multi-user

video gaming and multi-media remote health monitoring are just two

examples.

Release 8 Evolved

Node B

(eNB)

For Rel’8

up to

20Mhz

21

Evolved Node B(eNB)

Bandwidth (MHz)

1.4 3 5 10 15 20

# of RBs

6 15 25 50 75 100

Subcarriers

72 180 300 600 900 1200

Evolved

Node B

(eNB)

20MHz

15MHz

10MHz

5MHz

3MHz

1.4MHz E-UTRA Band

Bandwidth UL (MHz)

Bandwidth DL (MHz)

Duplex Mode

1 1920-1980 2110-2170 FDD

60Mhz 60Mhz

22

Evolved Node B(eNB) Evolved

Node B

(eNB)

modulation and coding scheme

64QAM 6bits/Hz

16QAM 4bits/Hz

OPSK 2bits/Hz

Max Data

Rate

20MHz

15MHz

10MHz

5MHz

3MHz

1.4MHz

Max Data Rate

23

What limits Bit Rate?

Limitations-Bandwidth.

Each phone tower has a given

total width of frequencies it can

transmit on, with each person that

connects being allocated a small

channel of a certain width. This

means that each tower has a

limited number of customers it can

service before becoming

congested. So the most obvious

way to increase speed would be

to give each customer a wider

range of frequencies to transmit

on, but this means less people per

phone tower, which means

building more phone towers,

which is expensive!

Evolved

Node B

(eNB)

20MHz

15MHz

10MHz

5MHz

3MHz

1.4MHz

Channel Bandwidth (20MHz)

Transmission Bandwidth Configuration (RB)

100 x 180khz= 18Mhz

24

What limits bit rate?

Limitations- SINR.

Speed is also limited by Signal-to-Noise ratio, to which we can increase the

power (or loudness) of the transmission

Evolved

Node B

(eNB)

Packet Scheduling

64QAM 6bits/Hz 16QAM

4bits/Hz QPSK 2bits/Hz

SINR = 19db SINR

SINR=-4.46dB

SINR ave = S

I + N

I = Iown + Iother

Limitations- symbol rate.

3G technologies like HSPA take advantage

of digital modulation techniques like

Quadrature Phase Shift Keying to increase

the symbol rate, which is the second major

factor that limits speed!

25

Increasing the data rate

Increasing the data rate –spatial multiplexing

Spatial multiplexing increases the data rate. Data is divided into separate streams,

which are then transmitted simultaneously over the same air interface resources.

.

TX

TX

2bits/Hz

2bits/Hz

26

Polarisation diversity

LTE MIMO waves are polarised where each wave is

rotated

Allows your UE to distinguish two independent streams of

data over the same PRB allocated by the cell tower

polarisation diversity

27

Multiple-Input Multiple-Output (MIMO)

The propagation channel is the air interface, so that transmission antennas

are handled as input to the channel, whereas receiver antennas are the

output of it

MIMO (Multiple Input Multiple Output)

2x2

4x4

SISO (Single Input Single Output)

Transmission

antenna

(input )

receiver antenna

output 1x1

28

Evolved Node B(eNB)

Evolved

Node B

(eNB)

modulation and coding scheme

64QAM 6bits/Hz

20MHz

SISO

(Single Input Single Output)

Transmission antenna

(input ) receiver antenna

output

1x1

Maximum data rate for 1x1:

• 20 Mhz BW

• Cat 5 UE

• 64 QAM

Approximately 100Mb/s –

25% overhead

29

Evolved Node B(eNB)

Evolved

Node B

(eNB)

modulation and coding scheme

64QAM 6bits/Hz

20MHz

1x1

Maximum data rate for 1x1:

• 20 Mhz BW

• Cat 5 UE

• 64 QAM

Approximately 100Mb/s –

25% overhead SISO

(Single Input Single Output)

ONLY

Cat 5

30

Evolved

Node B

(eNB)

modulation and coding scheme

64QAM 6bits/Hz

20MHz

Maximum data rate for 2x2:

• 20 Mhz BW

• Cat 5 UE

• 64 QAM

Approximately 200Mb/s –

25% overhead modulation and coding scheme

64QAM 6bits/Hz

SU-MIMO

2x2 Doubles peak

rate compared to 1x1

MIMO (Multiple Input Multiple Output)

31

MIMO (Multiple Input Multiple Output)

Evolved

Node B

(eNB)

modulation and coding scheme

64QAM 6bits/Hz

20MHz

Maximum data rate for 4x4:

• 20 Mhz BW

• Cat 5 UE

• 64 QAM

Approximately 400Mb/s –

25% overhead

modulation and coding scheme

64QAM 6bits/Hz

modulation and coding scheme

64QAM 6bits/Hz

modulation and coding scheme

64QAM 6bits/Hz

32

Services

LTE’s all-IP architecture.

TCP UDP

IP

SERVICES SERVICES

LTE is really important to people who want to stay

connected at excellent browsing speeds

Smartphone users to stream

music, videos and other

multimedia content directly

from the internet faster than

ever before.

Evolved

Node B

(eNB)

Serving

Gateway

PDN

Gateway

IP Multimedia Subsystem

PSTN

INTERNET

INTERNET

VoIP

Improved Browsing

Providing download speeds of up to and

beyond 300Mbps. This will make for a

vastly improved mobile browsing

experience, so no more waiting for images

to load

33

Services

In addition, the high bandwidth and low latency will drive the development and

uptake of real-time services with added mobility yet to be conceived.

TCP UDP

IP

NON REAL

TIME

SERVICES REAL TIME

SERVICES

Http

FTP

SMTP

VoIP

streaming

Seamless mobility experience

subscribers to remain connected via any access technology

Serving

Gateway

DATA

MME: Mobility Management Entity

SGSN

RNC

3G

LTE

34

Global Appeal

Because LTE devices will be backward compatible with GSM and UMTS,

even at early stage of LTE deployment, LTE subscribers will be able to roam

worldwide irrespective of the country they are in.

850, 900, 1900, 2100 MHz

Interworking with existing UTRAN/GERAN systems and non-3GPP

systems

35

Services

Gaming

The increased connectivity brought into the

equation by 4G will hopefully be a boon to

gamers as true multiplayer online gaming

will finally be enabled.

Watch TV,

play live multiplayer games

or stream a film

on the move

TCP UDP

IP

NRT

SERVICES

RT

SERVICES

Waiting for things to buffer will be consigned to the pass.

LTE Broadcast will give operators an

opportunity to achieve new revenues

Broadcast Management Centre

Multicast-broadcast single-

frequency network (MBSFN)

Unicast

Data

36

MBSFN (Multicast Broadcast Single Frequency

Network)

A eNodeB can transmit the same data (idential data) to multiple UE

simulteneously. In some case, multiple eNodeB can transmit the identical data

simultaneously so that UE can receive the same data from multiple eNodeBs.

The physical multicast

channel (PMCH) was

fully specified in Release

8, to carry data from the

multicast channel, but is

not usable until Release

9.

37

Services

Waiting for things to buffer will be

consigned to the pass.

LTE Broadcast Area

broadcast across this

stadium between 2pm

and 4pm

With this app the consumer would have the

possibility to access live camera angles

which they can have access to when they

are actually in the stadium and on a mobile

enabled device

38

Channels for Multimedia Broadcast Multicast

Services (MBMS) 3GPP Release 9

• There could be up to 256 different

MBSFN areas defined, each one

with an own identity.

• Cells can belong to more than one

MBSFN area

MBSFN area 1

MBSFN area 2

MBSFN area 3

BM-SC

Content Provider

(MBMS GW)

Evolved

Node B

(eNB)

IP Multimedia Subsystem

39

Technology Evaluation

GSM – CSD

9.6Kbps

GSM –HSCSD

14.4kbit/s

HSCSD-Uses multiple GSM channel coding

schemes to give 4.8 kb/s, 9.6 kb/s or 14.4

kb/s per timeslot

GPRS-21kb/s GPRS-21.4 Kb/s per Timeslot

EDGE-48kb/s Edge -About 48 kb/s per timeslot

3G –

REL 99

3G – Max 2 Mb/s Typical

384 kb/s

3G – REL 5-

HSDPA HSDPA – 14.4 Mbps

3G – REL 6-

HSUPA HSUPA-UP Link(5.76 Mbps)

Up to 44 Mbit/s on the

downlink and 22 Mbit/s on

the uplink

3G – REL 7-

HSPA+ Long Term Evolution (LTE)

REL 8-

300Mbps Downlink (4x4)

75Mbps Uplink

ALL IP NETWORK

40