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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
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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
Iwao Sasase, Keio University 3
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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.
Iwao Sasase, Keio University 4
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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
Iwao Sasase, Keio University 5
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xDSL (x Digital Subscriber Line)
Modem technologies which realize Mbps transmission
using ordinary telephone subscriber line
Iwao Sasase, Keio University 6
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
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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
Iwao Sasase, Keio University 7
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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.
Iwao Sasase, Keio University 8
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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
Iwao Sasase, Keio University 9
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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
Iwao Sasase, Keio University 10
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ADSLDownlink transmission is faster than uplink transmission
Asymmetric data transmission suitable for download.
CAP system DMT system
Iwao Sasase, Keio University 11
frequency
30k 200k 1M4k
Upload Download Upload Download
Parallel data
transmission by using
many subcarriers
30k
frequency
138k 1M4k
Both are QAM
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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.
Iwao Sasase, Keio University 12
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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
Iwao Sasase, Keio University 13
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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
Iwao Sasase, Keio University 14
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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
Iwao Sasase, Keio University 15
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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
Iwao Sasase, Keio University 16
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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
Iwao Sasase, Keio University 17
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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
Iwao Sasase, Keio University 18
Di
Dq
LPF1
LPF1 LPF2
LPF2
Di
Dq
QAM transmission and reception
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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
Iwao Sasase, Keio University 19
Transmission and reception in DMT system
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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
Iwao Sasase, Keio University 20
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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
Iwao Sasase, Keio University 21
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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
Iwao Sasase, Keio University 22
switch
Buffer
Memory
Buffer
Memory
Receiver circuit
(upload)
Transmitter circuit
(downlink)
switch
Receiver circuit
(downlink)
Uplink signal
Downlink signal
Ping-pong system
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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
Iwao Sasase, Keio University 23
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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
Iwao Sasase, Keio University 24
DBM D l Bit M t
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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.
Iwao Sasase, Keio University 25
transmission transmission
ISDN
ADSL
uplink data
ADSL
downlink data
DBM
upload upload download
Near-endcrosstalk noise
Far-endCrosstalk noise
Crosstalk
Principle of DBM system
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Downlink Speed of DBM-ADSL
D o
w n
l i n
k s
p e e
d
Line length
Iwao Sasase, Keio University 26
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Iwao Sasase, Keio University 27
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
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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
Iwao Sasase, Keio University 28
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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
Iwao Sasase, Keio University 29
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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.
Iwao Sasase, Keio University 30
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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)
Iwao Sasase, Keio University 31
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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.
Iwao Sasase, Keio University 32
i i i i f
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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.
Iwao Sasase, Keio University 33
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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.
Iwao Sasase, Keio University 34
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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
Iwao Sasase, Keio University 35
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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
Iwao Sasase, Keio University 36
C iti f
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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
Iwao Sasase, Keio University 37
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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
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
P h y s i c a l l a y e r
E t h
e r n e t
P h y s i c a l l a y e r
Outer interface equipment Cable transmission line PC etc.
Iwao Sasase, Keio University 38
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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
Iwao Sasase, Keio University 39
FTTH (Fib t th H )
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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.
Iwao Sasase, Keio University 40
Fiber cable in access network
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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
Iwao Sasase, Keio University 41
5 section of access network cable
FTTH
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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
Iwao Sasase, Keio University 42
FTTB (Fiber to the Building)
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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
Iwao Sasase, Keio University 43
FTTC (Fiber to the Curb) + VDSL
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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.
Iwao Sasase, Keio University 44
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Single starSS composition
Active double star
ADS composition
Passive double starPDS composition
DSU
Star type
Communication center
Metallic cable
User
DSU
Communication center
Metallic cable
user
RT
Star type
Optical
fiber
Star type
Double star type
ONU
Communication center
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
Iwao Sasase, Keio University 47