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S kills : none

The physical layer. S kills : none C oncepts : wired hardware characteristics , wireless hardware characteristics (frequency and power), modulation schemes. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License. Where does this topic fit?.

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S kills : none

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  1. The physical layer Skills: none Concepts: wired hardware characteristics, wireless hardware characteristics (frequency and power), modulation schemes This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License.

  2. Where does this topic fit? • Internet concepts • Applications • Technology (communication) • Implications • Internet skills • Application development • Content creation • User skills

  3. The physical layer

  4. Copper and fiber

  5. Frequency

  6. Frequency range examples

  7. Electromagnetic radiation applications

  8. What is power?

  9. Radio power

  10. Estimated coverage for 600 watt KPCC

  11. Wolfman Jack, 250,000 watt XERF Click to hear the Wolfman

  12. 15-20 Mbps 20-22 Mbps 10-15 Mbps 5-10 Mbps Coverage 802.11g WiFi access point, < 1 watt 200 feet 125 feet

  13. Inside my house

  14. In the back yard

  15. Antenna focus

  16. Modulation mehtod or

  17. Modulation – transmit ones and zeros

  18. AM and FM modulation Signal AM FM 1 1 0 http://som.csudh.edu/fac/lpress/presentations/Amfm.gif

  19. Summary We saw that the two major functions of the physical layer are defining the hardware and the modulation method. We discussed both wired and wireless hardware specifications, noting that wireless links are characterized by their frequency and transmission power level.

  20. Self study questions We mentioned two wired technologies, what were they? WiFi is commonly used for wireless network links. Can you think of other wireless technologies that are used for network links? In our modulation example, the AM transmitter and receiver could differentiate two different frequencies – one high the other low. In other words, we could transmit one bit during each clock cycle. If a more sensitive radios could differentiate between four different frequencies, how many bits could we transmit during a clock cycle? Why isn’t the signal strength at a given distance the same in all directions? What is the unit of measure for radio power? What is the unit of measure for radio signal frequency? The FCC allows WiFi radios with narrowly focused antennae to transmit at higher power levels than WiFi radios which transmit In all directions. Why is that?

  21. Resources Locate radio stations and unused FM frequency bands: http://www.radio-locator.com/

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