1. Chapter 9 High-Speed Digital Access: DSL, Cable Modem, and SONET

2. 9.1 DSL Technology ADSL Other DSL Technologies

3. ADSL is an asymmetric communication technology designed for residential users; it is not suitable for businesses. Note:

4. The existing local loops can handle bandwidths up to 1.1 MHz. Note:

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

6. Figure 9.1 DMT

7. Figure 9.2 Bandwidth division Theoratical Upstream Speed=1.44Mbps but actual is less than 1Mbps Theoratical Downstream speed=13.4Mbps but actual is less than 8Mbps

8. Figure 9.3 ADSL modem

9. Figure 9.4 DSLAM

10. SDSL:-Symmetric DSL provides equal speed in both the directions whether upstream or downstream. HDSL:-IT is full duplex and uses two twisted pair cables and provides almost the double the speed of ADSL VDSL:-It uses generally fiber optic cable for data transmission for long distances.it provides 25-55Mbps upstream and 3Mbps downstream.

11. 9.2 Cable Modem Traditional Cable Networks HFC Network Sharing CM and CMTS DOCSIS

12. Figure 9.5 Traditional cable TV network

13. Communication in the traditional cable TV network is unidirectional. Note:

14. Figure 9.6 HFC network

15. Communication in an HFC cable TV network can be bidirectional. Note:

16. Figure 9.7 Coaxial cable bands Each channel in the video band requires 6MHz of bandwidth so it can have upto 80 channels.

17. Downstream data are modulated using the 64-QAM modulation technique. Note:

18. . The theoretical downstream data rate is 30 Mbps. Note:

19. Upstream data are modulated using the QPSK modulation technique. Note:

20. The theoretical upstream data rate is 12 Mbps. Note:

21. Figure 9.8 Cable modem

22. Figure 9.9 CMTS

23. 9.3 SONET SONET Devices SONET Frame Frame Transmission Synchronous Transport Signals STS-1 Virtual Tributaries Higher-Rate Service

24. SONET is a synchronous TDM system controlled by a master clock. Note:

25. Figure 9.10 A SONET

26. Figure 9.11 Frame format

27. Table 9.1 SONET rates STSOCRate (Mbps)SPE (Mbps)User (Mbps) STS-1OC-151.8450.1249.536 STS-3OC-3155.52150.336148.608 STS-9OC-9466.56451.008445.824 STS-12OC-12622.08601.344594.432 STS-18OC-18933.12902.016891.648 STS-24OC-241244.161202.6881188.864 STS-36OC-361866.231804.0321783.296 STS-48OC-482488.322405.3762377.728 STS-192OC-1929953.289621.6049510.912

28. Figure 9.12 Data rate

29. Figure 9.13 VT types

30. Figure 9.14 STS multiplexing