xDSL,CATV,FTTH.pdf

8/10/2019 xDSL,CATV,FTTH.pdf

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Access Network is

the part (xDSL, FTTH etc.) which connects

between user’s network (LAN etc.) and the building of the carrier.

At present, the progress of technology fordiversification of service and high speed is

most remarkable.

Iwao Sasase, Keio University 2



Various Access Networks

Cable communicationsystem

Home user

Metallic xDSL

Optical FTTx FTTH

Cable broadcasting

systemCATV HFC+Cable modem

LANOptical High speed

Business user

HUB center

Company etc.

Various Access Networks




Technology cooperation among

communication, computer and broadcast

Joint region

•High-speed CPU

•Memory with large capacity

•Expansion of LAN

•Appearance of

IP routing Network

•Standardization of MPEG1

and MPEG2

Digital processing is possible.)•Processing Accumulation

Transmission.

Communication

BroadcastComputer

•Downsizing and cost down of

communication equipment

(Optical fiber transmission system,Optical connector, PLC optical device, etc.)

Completion of network DigitizationCommunication, computer and

broadcast developed independently.

Technologies of 3 fields

begin to be cooperatedin access network.




Difference between voice/image service

and computer communication service

The service of voice/ image is a connection-oriented

communication --- Guaranteed type

real time transmission, almost constant rate

Computer communication is connectionless communication

which can accept reasonable network delay --- Best-effort type

burst data transmission




xDSL (x Digital Subscriber Line)

Modem technologies which realize Mbps transmission

using ordinary telephone subscriber line


Internet

Public line network

User’s Home Local communication

equipment center of the carrier

Ordinary

telephone

subscriber line

xDSL Modem

splitter

xDSL

DSLAMRouter

splitter Subscriber

switching board

20k 1.1MHz



Concept of xDSL

Internet

xDSL

DSLAM Router

Local communication

equipment center of the

carrier

Existing telephone

subscriber lines are

used

xDSL

MODEM

Low speed

Telephone network provider




Structure of xDSL

Voice signal less than 4kHz

Ordinary data transmission of dial-up MODEM usesonly the frequency bands up to 4kHz for voice in the

subscriber telephone line.

xDSL modem 20k 1.1MKHz

Although a subscriber line is a copper wire, high-speed data transmission is possible by using higher

frequency bands.




Items of xDSL

Item CableUplink

Downlink Communication speed

Maximum

distance

HDSL 2 pairs Symmetric 1.5M 2Mbps 7km

SDSL 1 pair Symmetric 160k 2Mbps 7km

ADSL 1 pair Asymmetric16k 1Mbps (Up)

1.5M 9Mbps (Down)5.5km

RADSL 1 pair Asymmetric128k 1Mbps (Up)

1M 12Mbps (Down)5.5km

VDSL 1 pair Symmetric

Asymmetric

1.8k 2.3Mbps (Up)

13M 52Mbps

(Down)

1.5km




ADSLDigital communication by 1 pair metallic copper wire.

Uplink/Downlink speeds between users and local communication

equipment center are asymmetric.

Main Coding Technology

DMT(Discrete Multi-Tone), CAP(Carrierless Amplitude)

Rate Variable ADSL

Depending on the loss of copper wire and interference/noise,the optimum transmission rate is varied automatically.

Features

• ADSL transfers high-speed digital service signal

in addition to the conventional telephone (voice).

• asymmetric, downlink is faster due to wideband allocation




ADSLDownlink transmission is faster than uplink transmission

Asymmetric data transmission suitable for download.

CAP system DMT system


frequency

30k 200k 1M4k

Upload Download Upload Download

Parallel data

transmission by using

many subcarriers

30k

frequency

138k 1M4k

Both are QAM



HDSL

Digital communication by 2 pair(or 3 pair) copper wires.Uplink and Downlink are symmetric.

Simultaneous service of providing telephone (voice) and high-

speed digital is not thought.

SDSL

Symmetric data transmission using 1 pair copper wire.Transmission speed is lower than HDSL.

VDSLVDSL can make higher data rate up to 50 Mbps.

Transmission distance is restricted to hundreds of meter.

Combination between VDSL and FTTC is promising.




Features of xDSL

• High data rate transmission – ADSL is 10-50 times higher than

ISDN

• Home wiring is easy. – by sing existing telephone line

• Low cost – Telephone company and user do not

have to invest line equipments except

xDSL modems.

Telephone office

Home

M e t a l l i c l i n e s c a n b e u s e d c on t i n u o u s l y

L

i n e e q ui pm e n t s

Home wiring

Backbone network

Access system

POTS

POTS

Pair cable




Communication System Model

Transmitter Channel Receiver

Noise

Message

signal signal

Message

Sender

ReceiverTelephone lineCoaxial cable

Optical fiber

Mod ulator

Error corr ecting cod er

Full-du plex K ind s of cod ec

Demod ulator

Error corr ecting d ecoder

Full-du plexK ind s of cod ec

Transmission performance is determined by channel, noise,

transmitter and receiver

Communication system model




Distortion and Noise of xDSLDistortion is caused basically by signal loss

characteristic of metallic cable and crosstalk noise.

Transmission quality

degradation factor

Distortion

Linear distortion

Nonlinear distortion

Regular broadband

Random noise

Direct current interception

of Line trans

Metallic cable

Signal attenuation

Phase distortion

Other noise-140dBm/Hz

Near-end

Crosstalk noise

Far-end

Crosstalk noise

Broadcasting induced noise

Amateur radio

Power line induced noise

impulse noise

induced by metallic cable

Distortion of AFE amplification

Distortion of line trans

Noise

Amplitude distortion

Phase distortion

White noise

Colored Noise

Irregular broadband

Impulse noise

Crosstalk noise

Distortion and noise of DSL transmission system

General distortion

noise

Noise of metallic

noise

Regular narrowband noise

Tone noise




Transmission characteristic of

metallic cable• Higher frequency signals are attenuated more.

• Longer metallic cable attenuates the signal more.

Transmission loss is large

Noise of metallic cable• Crosstalk noise

• Impulse noise

• Electromagnetic wave broadcasting wave, Amateur radio

induced noise




Transmission technologies in xDSL

• Transmission coding and modulation

– 2B1Q Code

– CAP/QAM System single carrier

– DMT system multi carrier

• Full-duplex system

– FDM (frequency division multiplexing) system

– Echo canceller system

– TDD Ping-pong system

• Noise level measures

• Variable rate transmission




QAM (Quadrature Amplitude Modulation)Typical modulation technique used in xDSL

)cos( t c

ω

)sin( t c

ω

LPF

LPF

)cos( t c

ω

)sin( t c

ω

LPF

LPF

MultiplicationAddition

Transmission line


Di

Dq

LPF1

LPF1 LPF2

LPF2

Di

Dq

QAM transmission and reception



DMT(Discrete Multi-Tone) system

Dividing frequency bands into some sub bands (sub channels).In each sub channel, QAM transmission is carried out.

Sub channel 1

Subchannel N

Sub channel 1

Sub channel N

Transmission line

Multiplication

Addition

)cos( t c

ω )cos( t c

ω

)cos( t N c

ω )cos( t N c

ω

)sin( t N c

ω )sin( t N c

ω

)sin( t c

ω )sin( t c

ω


Transmission and reception in DMT system



FDM (frequency division multiplexing)

Full-duplex FDM system using different frequency band between uplink and downlink.

Metallic

cable

Uplink signal

Downlink signal

Send/receiveseparation

filter

Send/receiveseparation

filter

QAM demodulator

(downlink)

QAM modulator

(downlink)

QAM demodulator

(uplink)

FDM Multiplex FDM Demultiplex

Carrier frequency

QAM modulator

(uplink)

Carrier frequency

2

Carrier frequency

2

Carrier frequency

FDM system




Echo canceller systemBy making pseudo echo waveform using ADF

and subtracting pseudo echo signal from actual

echo signal, echo signal is removed.

Metallic

cable

Uplink signal

Downlink signal

Hybrid

circuit

Hybrid

circuit

Transmitter circuit

(uplink)

Receiver circuit

(uplink)

ADF ADF

Transmitting circuit

(downlink)

Receiver circuit

(downlink)

Echo canceller system




Ping-pong system

By transmitting and receiving uplink/downlink signal alternately,

overlap of signals in the transmission line is avoided.

Buffer

Memory

Transmitter circuit

(uplink)

Metallic

Cable

Buffer

Memory


switch

Buffer

Memory

Buffer

Memory

Receiver circuit

(upload)

Transmitter circuit

(downlink)

switch

Receiver circuit

(downlink)

Uplink signal

Downlink signal

Ping-pong system



Variable rate transmission

When we assume Internet service, variable rate transmission

according to application such as file download is preferred.

Against signal loss and noise characteristic of subscriber line,

setup functions of transmitting speed and transmitting delayquantity at any time is expected.

Many realization methods exist,

but best usage has not been established yet.However




Interference between ADSL and ISDN

When ADSL and ISDN lines co-exit in the same cable,

crosstalk noise occurs and may cause serious performance

degradation

DBM Dual Bit Map technology is developed,and interference problem is solved.

ADSL and ISDN Lines

ISDN

ASDL


DBM D l Bit M t



DBM Dual Bit Map system• Interference between ADSL and ISDN lines can be reduced

by using DBM.

• Standardized on ITU-T as AnnexC (for Japan)

• When near-end crosstalk noise occurs and noise becomes

large, DBM reduces the quantity of data transmission.• When far-end noise occurs, DBM transmits more data.


transmission transmission

ISDN

ADSL

uplink data

ADSL

downlink data

DBM

upload upload download

Near-endcrosstalk noise

Far-endCrosstalk noise

Crosstalk

Principle of DBM system



Downlink Speed of DBM-ADSL

D o

w n

l i n

k s

p e e

d

Line length





CATV (Cable Television)

High-speed TV transmissiontechnology by coaxial cable

HUB center receives TV signals from radio wave towers andsatellites. These signals are distributed through cable to each

home and companies.Satellite

Radio wave tower

HUB center

Home, Company

Main line



History of CATV(1)

1948 First operation (U.S.A)

1953 First experiment on joint reception (Ikaho, Gunma Pref.)

Development in fringe area of terrestrial broadcasting and

region having no broadcasting station.

1960s Development in cities against multi path obstacle by high-

rise buildings

Role as a “complement” to terrestrial broadcasting




History of CATV(2)

1980s Examination of realization of various services and

applications as interactive region media (partly realized)

1990s Spread of Internet strengthens movement making

CATV Internet enterprise

Now Examination of digital CATV technology

Role as a key of other than broadcasting service




Broadband

transmission technology(1)CATV transmission technology concerning

broadband TV (moving picture )

many TV channels on high-frequency bands

•Cheap coaxial cable with stable transmitting characteristic

•Broadband amplifier

are needed.




Broadband

transmission technology(2)• Coaxial cable

Appearance of Polyethylene covering

•Broadband amplifier

Development of transistor : 70 1000MHz amplifier.

Center conductor (annealed copper single track )

Outer conductor(Aluminum pipe)

Insulator(Foamed polyethylene) Protection covering(Black polyethylene)




Deployment to broadband CATV•250MHz/20ch : 1960 1970s

Negative return (Feedback) amplifier system is generalized.

•450MHz/60ch : 1980s

Interactive amplifier becomes standard.

•770MHz/110ch : 1990s

All television band(VHF UHF) are covered.


i i i i f



Digitization of CATVLatter of 1990s 2000s: a period of digital broadcasting.

Using MPEG2, SDTV can transmit 4ch standard programs

with 6MHz per 1ch.

In case of 770MHz system, 440ch SDTV transmission is

possible.

•Program supply expansion exceeds that of transmission quantity.

•Simulcast broadcasting is duty in the fixed period.

More channel may be required.




Construction of interactive

CATVCATV transmits interactively by making a set of uplink and

downlink transmission line. Broadband LAN(B-LAN)

Construction of interactive CATV = Construction of B-LAN

1990s Internet spread explosively packet switching system solved the problem of traffic switching

At present by development real-time IPv6 technologies, speech

service through CATV is though to be promising.




SCM(Sub Carrier Multiplex)

transmissionIn transmitter side, FDM signal transmission on coaxial

cable and distributed in optical fiber by using E/O.

In receiving side, FDM signals are sent on coaxial cable

after O/E.

Image 1

Image 2

Image n

F DM M ul t i pl e x

Di s t r i b

u t i on

E/O

E/O

E/O

O/E

O/E

O/E

FDM signals(coaxial cable)

1 1

2 2FDM signals

(coaxial cable)Single mode

Optical fiber

Coaxial

cable

C

o a xi a l c a b l e

Optical modulator Optical demodulator

n n

Transmitting side Receiving side




HFC(Hybrid Fiber and Coaxial)Combination of optical fiber and coaxial cable.

CATV system divides service area into cells by placing a node ineach cell, and connects nodes and center by optical fiber.

Optical HUB node

Optical fiber cable

center Coaxial cable


C iti f



Composition of

HFC transmission systemDownlink …optical modulator(E/O) optical fiber cable

optical demodulator(O/E)Uplink …Contrary of downlink

E/O O/E

O/E E/O

Single mode optical fiber

Downlink

Uplink

Coaxial cable

Center side Node side




Protocol of CATV systems

CMTS Cable modem

IP

Data

link layer

Physical

layer

Forwarding

D a t a l i nk l a y e r

P h y s i c a l l a y e r

IEEE

802.2

LLC

MAC

(CSMA

/CD)

IEEE

802.2

LLCE t h e r n e t

TC(down)

PMD

IP

10BASE

-T MAC

IEEE

802.2

LLCE t h e r n e t

Trans

parent

bridge

D a t a l i nk l a y e r

P h y s i c

a l l a y e r


TC(down)

PMD

Linksecurity

IEEE

802.2

LLC

E t h e r n e t

MAC

10B

A S E -T


E t h

e r n e t


Outer interface equipment Cable transmission line PC etc.




Specification of physical layer Item Uplink Downlink

Frequency

band

5 42MHz 88 860MHz

Modulation QPSK 16QAM 64QAM 256QAM

Band wide 200/400/800/

1600/3200kHz

6MHz

Transmission

speed

160/320/640/

1280/2560kbps

30.342/42.884Mbps


FTTH (Fib t th H )



FTTH (Fiber to the Home)

High-speed digital transmissiontechnology by optical cable

FFTH wires optical fiber in houses, makes accessnetwork between users and access node optical and provides high-speed and broadband service.

FFTH can carry multiple service signals (servicemultiplex) in a optical fiber, because it has low losscharacteristic

Because optical fiber has low loss characteristic which can be input to divergence loss by optical splitter,multiplexing of plural users (service multiplexing) is possible.


Fiber cable in access network



Fiber cable in access network • Important point of optical fiber cable technology in access

network is to raise mount density of optical fiber. That is

multi core technology which is how many optical fibers

are bundled against outer diameter of given cable.

• At present, cable which has 3000 optical fiber is developed

distribution pointAccess point

PEC cable

(more than hundreds

Distribution cable

more than tens

Siding cable

1 or 2 core

Access network cable

Communication

Equipment center

User building

User’s house


5 section of access network cable

FTTH



FTTH

ONU (Optical Network Unit) is placed at user full optical

system.

•User Merits

User can receive high speed service because

high speed system is connected to the user directly.

Extension by service multiplexing

•Network Meritscost reduction by user multiplexing

•Applied technology

low speed - STM (Synchronous Transfer Mode) technologyimage - SCM (Sub Carrier Multiplex) technology

high speed – ATM (Asynchronous TM) technology


FTTB (Fiber to the Building)



FTTB (Fiber to the Building)

Buildings, for instance tenant building and apartment

introduce optical fiber, and place ONU in common

spaces, communication room etc.

• One ONU accommodates some users.

• Existing metallic cable is used between ONU and

user, so wiring construction in buildings is needless.

It becomes economical


FTTC (Fiber to the Curb) + VDSL



FTTC (Fiber to the Curb) + VDSL

VDSL Modem is placed in Curb of FTTC.

Optical and Metallic systems cooperate.

• VDSL transmission distance is short, and it can provide high-speed digital service.

By connecting FTTC, problem about distance

from communication equipment center is solved

• Because of two composition by optical system and

metallic systems in access network, cost-up of

equipment part can be not avoided.








Single starSS composition

Active double star

ADS composition

Passive double starPDS composition

DSU

Star type

Communication center

Metallic cable

User

DSU


Metallic cable

user

RT

Star type

Optical

fiber

Star type

Double star type

ONU


Optical fiber cable

user

Optical divergence

Star type

Optical

fiber

Star type

Double star type

Optical divergence

element

passive element

O/E translation

multiplexing

active element

Fig.5-6 network composition of access netwprk


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