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Chapter 9. High-Speed Digital Access

Chapter 9. High-Speed Digital Access. DSL Technology Cable Modem SONET. 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

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Chapter 9. High-Speed Digital Access

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  1. Chapter 9. High-Speed Digital Access DSL Technology Cable Modem SONET Data Communications, Kwangwoon University

  2. 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. Data Communications, Kwangwoon University

  3. DMT (Discrete Multitone Technique) Data Communications, Kwangwoon University

  4. 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 Data Communications, Kwangwoon University

  5. DSL: Actual Bit Rate • Because of the high signal/noise ratio • Upstream • 64 Kbps to 1 Mbps • Downstream • 500 Kbps to 8 Mbps Data Communications, Kwangwoon University

  6. Customer Site: ADSL Modem Data Communications, Kwangwoon University

  7. Telco Site: DSLAM Data Communications, Kwangwoon University

  8. Other DSL Technologies: xDSL • SDSL (Symmectric DSL) • For businesses that send and receive data in large volues in both directions • 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) Data Communications, Kwangwoon University

  9. 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 Data Communications, Kwangwoon University

  10. 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 Data Communications, Kwangwoon University

  11. 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) Data Communications, Kwangwoon University

  12. CM (Cable Modem) Data Communications, Kwangwoon University

  13. CMTS (Cable Modem Transmission System) Data Communications, Kwangwoon University

  14. 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 Data Communications, Kwangwoon University

  15. 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) Data Communications, Kwangwoon University

  16. 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 Data Communications, Kwangwoon University

  17. SONET Data Communications, Kwangwoon University

  18. Frame Format: STS-1 Data Communications, Kwangwoon University

  19. SONET Frames: STS-1 Data Communications, Kwangwoon University

  20. SONET Rates Data Communications, Kwangwoon University

  21. 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) Data Communications, Kwangwoon University

  22. VT Types Data Communications, Kwangwoon University

  23. STS Multiplexing Data Communications, Kwangwoon University

  24. STS-n Data Communications, Kwangwoon University

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