1 Kyung Hee University High-Speed Digital Access: DSL, Cable Modems, and SONET

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Kyung Hee University

High-Speed Digital Access: High-Speed Digital Access: DSL, Cable Modems, and DSL, Cable Modems, and

SONETSONET

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9.1 Digital Subscriber Line (DSL)9.1 Digital Subscriber Line (DSL) uses a newer technology that used the existing telecommunication

s networks such as the local loop telephone line.

is an asymmetric communication technology designed for residen

tial users; it is not suitable for business.

xDSL: where x can be replaced by A, V, H, or S

The existing local loops can handle bandwidths up to 1.1 MHz

by removing the filter at the end of line of telephone company

but, limitation because of distance between the residence and the switching office, size of cable

ADSL is an adaptive technology. The system uses a date rate base

d on the condition of the local loop line

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DSLDSLDMT

Modulation technique that has become standard for ADSL is called the discrete multitone technique (DMT) which combines QAM and FDM.

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DSLDSL

voice : channel 0 is reserved for voice

Idle : channel 1 to 5 are not used; gap between voice a

nd data communicaiton

Upstream data and control : channels 6 to 30 (25channe

ls); one channel for control

Downstream data and control : channels 31 to 255(225

channels); 13.4 Mbps; one channel for control

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DSLDSL

Actual Bit Rate

Upstream : 64 Kbps to 1 Mbps

Downstream : 500 Kbps to 8 Mbps

* Because of the high signal/noise ratio

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DSLDSL

Customer site : ADSL modem

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DSLDSL

Telephone Company Site : DSLAM

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DSLDSL

Other DSL Technologies

SDSL: Symmetric Digital Subscriber Line

HDSL: High-bit-rate digital subscriber line

an alternative to the T-line (1.544 Mbps) using 2B1Q encoding up to 3.6 Km using 2 twisted-pair wires for full-duplex transmission

VDSL : Very-high-rate digital subscriber

using coaxial cable, fiber-optic, or twisted pair cable for short distances (300 to 1800 m)

using DMT with a bit rate of 50 to 55 Mbps downstream and 1.5 to 2.5 Mbps upstream

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9.2 Cable Modem9.2 Cable Modem

Traditional cable Networks

community antenna TV (CATV)

Communication in the traditional cable TV network is unidirectional.

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Cable ModemCable Modem HFC Network

RCH : Regional cable head; serving 400,000 subscribers;

Distribution hub: serving 40,000 subscribers

Coaxial cable : serving 1,000 subscribers

Communication in HFC cable TV network can be bidireactional.

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Cable ModemCable Modem

Bandwidth

video band

54 to 550 MHz TV channels : 6 Mhz x 80 channels

Data downstream band : dividing into 6Mhz channels

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Modulation

Downstream data are modulated using 64-QAM

Data rate

6 bits for each baud in 64-QAM (1bit : control bit) Theoretically, 5bits/Hz x 6 Mhz = 30 Mbps

Upstream data band

Modulation

upstream data band uses lower frequencies that are more susceptible to noise and interference

for this reason, using QPSK instead of QAM

Data rate : 2 bits/hz x 6 Mhz = 12 Mbps

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CM is installed inside the distribution hub by the cable

company.

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Cable ModeCable Mode

Cable modem transmission system(CMTS)

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9.3 SONET9.3 SONET

Synchronous Optical Network : ANSI standard

Synchronous Digital Hierarchy :SDH

SONET is a synchronous TDM system controlled by a

master clock

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SONETSONET

SONET Frame

* SPE : synchronous payload envelope

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SONETSONET

SONET rates

STS

OC Rate (Mbps) SPE (Mbps) User (Mbps)

STS-1STS-1 OC-1 51.84 50.12 49.536

STS-3STS-3 OC-3 155.52 150.336 148.608

STS-9STS-9 OC-9 466.56 451.008 445.824

STS-12STS-12 OC-12 622.08 601.344 594.432

STS-18STS-18 OC-18 933.12 902.016 891.648

STS-24STS-24 OC-24 1244.16 1202.688 1188.864

STS-36STS-36 OC-36 1866.23 1804.032 1783.296

STS-48STS-48 OC-48 2488.32 2405.376 2377.728

STS-192STS-192 OC-192 9953.28 9621.604 9510.912

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SONETSONET

Date Rates

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SONETSONET

STS Multiplexing

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1 Kyung Hee University High-Speed Digital Access: DSL, Cable Modems, and SONET