Spring 2005Data Communications, Kwangwoon University9-1 Chapter 9. High-Speed Digital Access 1.DSL...

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Spring 2005 Data Communications, Kwangwoon Unive rsity 9-1 Chapter 9. High-Speed Digital Access 1. DSL Technology 2. Cable Modem 3. SONET

Transcript of Spring 2005Data Communications, Kwangwoon University9-1 Chapter 9. High-Speed Digital Access 1.DSL...

Page 1: Spring 2005Data Communications, Kwangwoon University9-1 Chapter 9. High-Speed Digital Access 1.DSL Technology 2.Cable Modem 3.SONET.

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Chapter 9. High-Speed Digital Access

1. DSL Technology

2. Cable Modem

3. SONET

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ADSL

• Asymmetrical Digital Subscriber Line

• ADSL is an asymmetric communication technology designed for residential users; it is not suitable for businesses

• The existing local loop can handle bandwidths up to 1.1 MHz

• ADSL is an adaptive technology. The system uses a data rate based on the condition of the local loop line.

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DMT (Discrete Multitone Technique)

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DMT: Bandwidth Division

• There is no set way that the bandwidth is divided

• Upstream– 24 channels * 4 Kbaud/sec * 15 bits/baud = 1.44 Mbps

• Downstream

– 224 channels * 4 Kbaud/sec * 15 bits/baud = 13.4 Mbps

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DSL: Actual Bit Rate

• Because of the high signal/noise ratio

• Upstream– 64 Kbps to 1 Mbps

• Downstream– 500 Kbps to 8 Mbps

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Customer Site: ADSL Modem

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Telco Site: DSLAM

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Other DSL Technologies: xDSL

• SDSL (Symmectric DSL)– For businesses that send and receive data in large volues in both di

rections

• HDSL (High-bit-rate DSL)– Designed as an alternative to the T-1 line

• VDSL (Very-high-bit-rate DSL)– Alternative to ADSL

– Uses coaxial, fiber-optic, twisted-pair cable for short distances (300-1800m)

– Uses DMT with a bit rate of 50-55 Mbps (downstream) and 1.5-2.5 Mbps (upstream)

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Traditional Cable TV Network

• Started to distribute video signals to locations with poor or no reception in the late 1940s: Unidirectional

• It was called Community Antenna TV

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HFC (Hybrid Fiber Coaxial) Network

• RCH (Regional Cable Head) feeds the distribution hubs

• Fiber node splits the signal to each coaxial cable

• Communication in an HFC network can be bidirectional

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Coaxial Cable Bands

• Video band: 6 MHz per TV channel

• Downstream data band: 64-QAM with TCM– Theoretical rate is 30 Mbps (6 Mbaud/sec * 5 bits/baud)

• Upstream data band: QPSK– Theoretical rate is 12 Mbps (6 Mbaud/sec * 2 bits/baud)

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CM (Cable Modem)

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CMTS (Cable Modem Transmission System)

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SONET/SDH

• Digital transmission standards for fiber-optic cable

• Independently developed in USA & Europe

– SONET(Synchronous Optical Network) by ANSI

– SDH(Synchronous Digital Hierarchy) by ITU-T

• Multiplexed transport mechanism

• Carrier for ATM and B-ISDN

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Interesting Features of SONET/SDH

• SONET/SDH is a synchronous network

– A single clock is used across the entire network

• It contains the standards for fiber-optic equipments

• Very flexible to carry other transmission systems (DS-0, DS-1, etc)

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SONET/SDH Rates

• SONET defines a signal hierarchy– STS (Synchronous Transport Signals)

• A hierarchy of signaling levels

– OC (Optical Carriers)

• Physical links defined for optical signals

– STS(OC)-1 (51Mbps) STS(OC)-192 (10Gbps)

• SDH specifies a similar hierarchy– STM (Synchronous Transport Module)

– STM-1 (155Mbps) STM-64 (10Gbps)

• OC-1, OC-3, OC-12, OC-48, OC-192

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SONET

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Frame Format: STS-1

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SONET Frames: STS-1

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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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Virtual Tributaries

• Partial payload that is inserted into an STS-1 frame

• Each component of subdivided SPE

• Provides backward compatibility

• Four types of VTs

– VT1.5 : For DS-1(T-1: 1.544Mbps)

– VT2: For CEPT-1(E-1: 2.048Mbps)

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VT Types

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STS Multiplexing

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STS-n