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CMPE 150 – Winter 2009

CMPE 150 – Winter 2009. Lecture 4 January 15, 2009 P.E. Mantey. CMPE 150 -- Introduction to Computer Networks. Instructor: Patrick Mantey mantey@soe.ucsc.edu http://www.soe.ucsc.edu/~mantey/ Office: Engr. 2 Room 595J Office hours: Tuesday 3-5 PM TA: Anselm Kia akia@soe.ucsc.edu

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CMPE 150 – Winter 2009

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  1. CMPE 150 – Winter 2009 Lecture 4 January 15, 2009 P.E. Mantey

  2. CMPE 150 -- Introduction to Computer Networks • Instructor: Patrick Mantey mantey@soe.ucsc.edu http://www.soe.ucsc.edu/~mantey/ • Office: Engr. 2 Room 595J • Office hours: Tuesday 3-5 PM • TA: Anselm Kia akia@soe.ucsc.edu • Web site: http://www.soe.ucsc.edu/classes/cmpe150/Winter09/ • Text: Tannenbaum: Computer Networks (4th edition – available in bookstore, etc. )

  3. Syllabus

  4. Assignment #2 Available on the web site: http://www.soe.ucsc.edu/classes/cmpe150/Winter09/ Due Thursday, January 22, 2009

  5. Today’s Agenda • Physical Layer • Data Communications • (Where the data really get moved) • Theoretical Basis for Data Communications • Nyquist • Shannon • Various Data Channels

  6. The Theoretical Basis for Data Communication • Fourier Analysis • Bandwidth-Limited Signals • Maximum Data Rate of a Channel

  7. Bandwidth-Limited Signals • A binary signal and its root-mean-square Fourier amplitudes. • (b) – (c) Successive approximations to the original signal.

  8. Bandwidth-Limited Signals (2) • (d) – (e) Successive approximations to the original signal.

  9. Bandwidth-Limited Signals (3) • Relation between data rate and harmonics.

  10. Maximum Data Rate • Nyquist (1924) (Noiseless capacity) capacity C = 2H log2V where H = bandwidth of channel V = number of discrete levels

  11. Maximum Data Rate • Nyquist (1924) (Noiseless capacity) capacity C = 2H log2V where H = bandwidth of channel V = number of discrete levels • Shannon (1948) (“error free” capacity) • capacity C < H log2 [ 1 + S/N ] • where S/N = signal / noise

  12. Guided Transmission Data • Magnetic Media • Twisted Pair • Coaxial Cable • Fiber Optics

  13. Twisted Pair • (a) Category 3 UTP. • (b) Category 5 UTP.

  14. http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci211752,00.htmlhttp://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci211752,00.html

  15. Coaxial Cable • A coaxial cable.

  16. Fiber Optics • (a) Three examples of a light ray from inside a silica fiber impinging on the air/silica boundary at different angles. • (b) Light trapped by total internal reflection.

  17. Transmission of Light through Fiber • Attenuation of light through fiber in the infrared region.

  18. Fiber Cables • (a) Side view of a single fiber. • (b) End view of a sheath with three fibers.

  19. Fiber Cables (2) • A comparison of semiconductor diodes and LEDs as light sources.

  20. Fiber Optic Networks • A fiber optic ring with active repeaters.

  21. Fiber Optic Networks (2) • A passive star connection in a fiber optics network.

  22. Wireless Transmission • The Electromagnetic Spectrum • Radio Transmission • Microwave Transmission • Infrared and Millimeter Waves • Lightwave Transmission

  23. The Electromagnetic Spectrum • The electromagnetic spectrum and its uses for communication.

  24. Radio Transmission • (a) In the VLF, LF, and MF bands, radio waves follow the curvature of the earth. • (b) In the HF band, they bounce off the ionosphere.

  25. Politics of the Electromagnetic Spectrum • The ISM bands in the United States.

  26. Lightwave Transmission • Convection currents can interfere with laser communication systems. • A bidirectional system with two lasers is pictured here.

  27. Communication Satellites • Geostationary Satellites • Medium-Earth Orbit Satellites • Low-Earth Orbit Satellites • Satellites versus Fiber

  28. Communication Satellites • Communication satellites and some of their properties, including altitude above the earth, round-trip delay time and number of satellites needed for global coverage.

  29. Communication Satellites (2) • The principal satellite bands.

  30. Communication Satellites (3) • VSATs using a hub.

  31. Low-Earth Orbit SatellitesIridium • (a) The Iridium satellites from six necklaces around the earth. • (b) 1628 moving cells cover the earth.

  32. Globalstar • (a) Relaying in space. • (b) Relaying on the ground.

  33. Public Switched Telephone System • Structure of the Telephone System • The Politics of Telephones • The Local Loop: Modems, ADSL and Wireless • Trunks and Multiplexing • Switching

  34. Structure of the Telephone System • (a) Fully-interconnected network. • (b) Centralized switch. • (c) Two-level hierarchy.

  35. Structure of the Telephone System (2) • A typical circuit route for a medium-distance call.

  36. Major Components of the Telephone System • Local loops • Analog twisted pairs going to houses and businesses • Trunks • Digital fiber optics connecting the switching offices • Switching offices • Where calls are moved from one trunk to another

  37. The Politics of Telephones • The relationship of LATAs, LECs, and IXCs. All the circles are LEC switching offices. Each hexagon belongs to the IXC whose number is on it.

  38. The Local Loop: Modems, ADSL, and Wireless • The use of both analog and digital transmissions for a computer to computer call. Conversion is done by the modems and codecs.

  39. (a) A binary signal (b) Amplitude modulation (c) Frequency modulation (d) Phase modulation Modems

  40. Modems (2) • (a) QPSK. • (b) QAM-16. • (c) QAM-64.

  41. Modems (3) • (a) V.32 for 9600 bps. • (b) V32 bis for 14,400 bps. (b) (a)

  42. Digital Subscriber Lines • Bandwidth versus distanced over category 3 UTP for DSL.

  43. Digital Subscriber Lines (2) • Operation of ADSL using discrete multitone modulation.

  44. Digital Subscriber Lines (3) • A typical ADSL equipment configuration.

  45. Wireless Local Loops • Architecture of an LMDS system.

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