1. Modems, Modems, and more Modems March 12, 2002

2. Announcements Test #2 - March 26 –It will cover Chapters 8, 11, 12, 13, and 17 Class Web Page –No change yet, hope for next week.

3. Class Objectives Modems-Past –Bell Family Modems-Present –ITU Recommendations –Cable Modem –ADSL

4. FIGURE 13-2 Acoustically coupled modem. (Reprinted with permission from Racal-Vadic.) Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

5. FIGURE 13-3 Common modem voice and data jacks. (Reprinted with permission from Racal-Vadic.) Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

6. FIGURE 13-4 Typical direct-connection installation. (Reprinted with permission from Racal-Vadic.) Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

7. FIGURE 13-5 Modulation techniques employed by modems. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

8. Transmission Modes Simplex –Data is sent in only one direction Half-Duplex –Data sent in both directions, but only one at a time Full-Duplex –Data sent both directions simultaneously

9. FIGURE 13-6 Bell 103/113 frequency assignment. (Courtesy of Racal-Vadic.) Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

10. FIGURE 13-7 Bell 202 frequency assignment. (Courtesy of Racal-Vadic.) Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

11. FIGURE 13-9 Bell 212A frequency assignment for the high-speed mode. Frequency assignment for the low-speed mode is identical to the Bell 103 specification (See Figure 13-6). Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

12. M-ary Applies for PSK or Quadrature Amplitude Modulation (QAM) M = log 2 (n) where M is the number of encoded bits and n is the number of state changes See Example 13.1 in textbook

13. Phasor Diagram Based on geometry and the unit circle We use it to give us a visual representation of how the modulated signal behaves Used mainly to represent phase and amplitude relationship Commonly called a “Constellation” Diagram

14. Unit Circle 45 90 180 270 0

15. FIGURE 13-10 Phasor diagram for the Bell 212A modem. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

16. FIGURE 13-12 Phasor diagram for the Bell 208A modem. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

17. FIGURE 13-13 Phasor diagram for the Bell 209A modem depicting 9600-bps QAM. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

18. ITU Recommendations ITU sets standards for the international community. As a practical matter, most of the standards are compatible with the US Bell standards. Present modems can reconfigure themselves to be compatible with many V. recommendations through software options and upgrades.

19. See Table 15-1 of textbook

20. Internal PCI Modem Card Features: Internal Modem PCI Slot required 56K v.90 Voice Capable

21. FIGURE 13-14 V.22bis 16-point signal constellation. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

22. FIGURE 13-15 V.32 trellis 32-point signal constellation. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

23. FIGURE 13-16 V.33 128-point signal constellation. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

24. ITU-TS V.90 Is the basis of our “advertised” 56 kbps modems Has different data rate for transmit and receive –Transmits: 33.6 kbps –Receives: 40-53 kbps –Uses the characteristics of telephone company infrastructure to optimize the receiver’s specs. –Look at example in textbook.

25. FIGURE 13-17 Comparison of a V.34 and V.90 modem connection: (a) V.34 connection showing analog-to-digital conversions in both directions; (b) V.90 connection to an ISP showing only one analog-to-digital conversion. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

26. Cable Modem Shares coax cable with television programming Uses “DOCSIS”: Data Over Cable Service Interface Specification Bandwidths are shared with other users –Downstream rates are the most affected by high use – Effective if cable infrastructure is already in place

27. FIGURE 13-19 Cable modem setup in relation to CATV system. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

28. www.cable-modems.org

32. Asymmetric Digital Subscriber Line (ADSL) Uses the subscriber loop Uses equalizer-based design to improve bandwidth of subscriber loop cable Dedicated service –Data rates between Central Office and user does not depend on the other users vs the Cable Modem

33. FIGURE 13-20 ADSL (digital subscriber line) modem connection. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

34. FIGURE 13-21 The ADSL modem uses frequency-division multiplexing (FDM) in the subscriber loop. Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

35. FIGURE 13-22 Analog loopback test setup. (Reprinted with permission from Racal-Vadic.) Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

36. FIGURE 13-23 (a) Local DLB test setup; (b) remote DLB test setup. (Reprinted with permission from Racal-Vadic.) Warren Hioki Telecommunications, Fourth Edition Copyright ©2001 by Prentice-Hall, Inc. Upper Saddle River, New Jersey 07458 All rights reserved.

37. Read the following 13.12 13.14-13.14.7 13.15-13.18