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CMPE 150 Fall 2005 Lecture 6

CMPE 150 Fall 2005 Lecture 6. Introduction to Networks and the Internet. Announcements. Labs: 1 slot either M or W 4-6pm. Other slot? T or Th 6-8pm? First lab is next week. TA office hours: T 6-7pm and Th 1-2pm in BME 314. Last Class. PHY. Analog and digital technology/communication.

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CMPE 150 Fall 2005 Lecture 6

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  1. CMPE 150Fall 2005Lecture 6 Introduction to Networks and the Internet

  2. Announcements • Labs: • 1 slot either M or W 4-6pm. • Other slot? T or Th 6-8pm? • First lab is next week. • TA office hours: T 6-7pm and Th 1-2pm in BME 314.

  3. Last Class • PHY. • Analog and digital technology/communication. • Digitization. • Sampling period and sampling rate. • Bit rate. • Signal and systems. • Periodic signals. • Fourier series. • Bandwidth limitation. • Channel capacity.

  4. Today • PHY (cont’d). • T1 demo.

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

  6. Magnetic Media • Examples? • Advantages? • Disadvantages?

  7. Twisted Pair • Oldest but still very common. • Telephone system. • Cheap and effective for long ranges. • Bundles of twisted pairs. • Can transmit both analog and digital signals. • Bandwidth depends on thickness of wire and distance traveled. • Mb/s for few kilometers.

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

  9. Twisted Pair http://searchnetworking.techtarget.com/sDefinition/0,,sid7_gci211752,00.html

  10. Coaxial Cable • Better performance than twisted pair, i.e., higher bandwidth and longer distances. • Good noise immunity. • But… • Bandwidths close to 1GHz. • Used widely in telephone networks for longer distances; but gradually being replaced by fiber. • Used for CATV!

  11. Coaxial Cable

  12. Fiber Optics • Optical transmission. • Optical transmission system: light source, medium, and detector. • Pulse of light = “1”. • No light = “0”. • Transmission medium: ultra thin fiber of glass. • Detector: generates electrical pulse when perceives light.

  13. Transmitting Light • (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.

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

  15. Fiber Optic Networks • A fiber optic ring.

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

  17. Fiber versus Copper Wire • Fiber can handle much higher bandwidths. • Low attenuation: 50km without repeater. • Unaffected by power surges/outages, and interference. • Fiber is thin and lightweight: easy to deploy and add new capacity. • Difficult to tap. • But…

  18. Fiber versus Copper (cont’d) • Fiber can be damaged easily. • Optical transmission is unidirectional, so need 2 fibers or 2 frequencies for 2-way communication. • Fiber and fiber interfaces is more expensive.

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

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

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

  22. Major Components of the Telephone System • Local loops: • Connection from subscriber to end office. • Trunks • Outgoing lines connecting offices. • Toll office: • Connects end offices. • Switching offices • Where calls are moved from one trunk to another.

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