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Modems, Modems, and more Modems Oct 24, 2002

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  • Modems, Modems, and more ModemsOct 24, 2002

  • AnnouncementsTest #2 Oct 31It will cover Chapters 8, 11, 12, 13, and 17

  • Class ObjectivesModems-PastBell FamilyModems-PresentITU RecommendationsCable ModemADSL

  • FIGURE 13-2 Acoustically coupled modem. (Reprinted with permission from Racal-Vadic.)Warren HiokiTelecommunications, Fourth EditionCopyright 2001 by Prentice-Hall, Inc.Upper Saddle River, New Jersey 07458All rights reserved.

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

  • FIGURE 13-4 Typical direct-connection installation. (Reprinted with permission from Racal-Vadic.)Warren HiokiTelecommunications, Fourth EditionCopyright 2001 by Prentice-Hall, Inc.Upper Saddle River, New Jersey 07458All rights reserved.

  • FIGURE 13-5 Modulation techniques employed by modems.Warren HiokiTelecommunications, Fourth EditionCopyright 2001 by Prentice-Hall, Inc.Upper Saddle River, New Jersey 07458All rights reserved.

  • Transmission ModesSimplexData is sent in only one directionHalf-DuplexData sent in both directions, but only one at a timeFull-DuplexData sent both directions simultaneously

  • FIGURE 13-6 Bell 103/113 frequency assignment. (Courtesy of Racal-Vadic.)Warren HiokiTelecommunications, Fourth EditionCopyright 2001 by Prentice-Hall, Inc.Upper Saddle River, New Jersey 07458All rights reserved.

  • FIGURE 13-7 Bell 202 frequency assignment. (Courtesy of Racal-Vadic.)Warren HiokiTelecommunications, Fourth EditionCopyright 2001 by Prentice-Hall, Inc.Upper Saddle River, New Jersey 07458All rights reserved.

  • 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 HiokiTelecommunications, Fourth EditionCopyright 2001 by Prentice-Hall, Inc.Upper Saddle River, New Jersey 07458All rights reserved.

  • M-aryApplies for PSK or Quadrature Amplitude Modulation (QAM)M = log2(n)where M is the number of encoded bitsand n is the number of state changesSee Example 13.1 in textbook

  • Phasor DiagramBased on geometry and the unit circleWe use it to give us a visual representation of how the modulated signal behavesUsed mainly to represent phase and amplitude relationshipCommonly called a Constellation Diagram

  • Unit Circle45901802700

  • FIGURE 13-10 Phasor diagram for the Bell 212A modem.Warren HiokiTelecommunications, Fourth EditionCopyright 2001 by Prentice-Hall, Inc.Upper Saddle River, New Jersey 07458All rights reserved.

  • FIGURE 13-12 Phasor diagram for the Bell 208A modem.Warren HiokiTelecommunications, Fourth EditionCopyright 2001 by Prentice-Hall, Inc.Upper Saddle River, New Jersey 07458All rights reserved.

  • FIGURE 13-13 Phasor diagram for the Bell 209A modem depicting 9600-bps QAM.Warren HiokiTelecommunications, Fourth EditionCopyright 2001 by Prentice-Hall, Inc.Upper Saddle River, New Jersey 07458All rights reserved.

  • ITU RecommendationsITU 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.

  • See Table 15-1 of textbook

  • Internal PCI Modem CardFeatures:Internal Modem PCI Slot required 56K v.90 Voice Capable

  • FIGURE 13-14 V.22bis 16-point signal constellation.Warren HiokiTelecommunications, Fourth EditionCopyright 2001 by Prentice-Hall, Inc.Upper Saddle River, New Jersey 07458All rights reserved.

  • FIGURE 13-15 V.32 trellis 32-point signal constellation.Warren HiokiTelecommunications, Fourth EditionCopyright 2001 by Prentice-Hall, Inc.Upper Saddle River, New Jersey 07458All rights reserved.

  • FIGURE 13-16 V.33 128-point signal constellation.Warren HiokiTelecommunications, Fourth EditionCopyright 2001 by Prentice-Hall, Inc.Upper Saddle River, New Jersey 07458All rights reserved.

  • ITU-TS V.90Is the basis of our advertised 56 kbps modemsHas different data rate for transmit and receiveTransmits: 33.6 kbpsReceives: 40-53 kbpsUses the characteristics of telephone company infrastructure to optimize the receivers specs. Look at example in textbook.

  • 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 HiokiTelecommunications, Fourth EditionCopyright 2001 by Prentice-Hall, Inc.Upper Saddle River, New Jersey 07458All rights reserved.

  • Cable ModemShares coax cable with television programmingUses DOCSIS: Data Over Cable Service Interface SpecificationBandwidths are shared with other usersDownstream rates are the most affected by high use Effective if cable infrastructure is already in place

  • FIGURE 13-19 Cable modem setup in relation to CATV system.Warren HiokiTelecommunications, Fourth EditionCopyright 2001 by Prentice-Hall, Inc.Upper Saddle River, New Jersey 07458All rights reserved.

  • www.cable-modems.org

  • www.cable-modems.org

  • www.cable-modems.org

  • www.cable-modems.org

  • Asymmetric Digital Subscriber Line (ADSL)Uses the subscriber loop Uses equalizer-based design to improve bandwidth of subscriber loop cableDedicated serviceData rates between Central Office and user does not depend on the other users vs the Cable Modem

  • FIGURE 13-20 ADSL (digital subscriber line) modem connection.Warren HiokiTelecommunications, Fourth EditionCopyright 2001 by Prentice-Hall, Inc.Upper Saddle River, New Jersey 07458All rights reserved.

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

  • FIGURE 13-22 Analog loopback test setup. (Reprinted with permission from Racal-Vadic.)Warren HiokiTelecommunications, Fourth EditionCopyright 2001 by Prentice-Hall, Inc.Upper Saddle River, New Jersey 07458All rights reserved.

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

  • Read the following13.1213.14-13.14.713.15-13.18