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Comparative Use of Unlicensed Spectrum

Comparative Use of Unlicensed Spectrum. Training materials for wireless trainers. Goals. To see the issues related with the use of a shared medium, like the unlicensed radio spectrum (specifically the 2.4 GHz ISM band).

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Comparative Use of Unlicensed Spectrum

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  1. Comparative Use ofUnlicensed Spectrum Training materials for wireless trainers

  2. Goals • To see the issues related with the use of a shared medium, like the unlicensed radio spectrum (specifically the 2.4 GHz ISM band). • To identify the most common sources of interference when operating a WiFi network. • To introduce software and hardware tools that can help identify sources of interference.

  3. Sharing the air These considerations are important to keep in mind when using devices that operate using unlicensed spectrum. • All devices must share the available radio bandwidth.Devices that use different protocols are typically unaware of each other.This competition leads to contention, retries, noise, dropped packets, delays, or static.The effect and amount of interference depends on how the devices make use of the spectrum.

  4. Approximate range for WiFi Electromagnetic Spectrum

  5. 802.11 Channels

  6. Non-overlapping channels: 1, 6, 11

  7. Non-overlapping channels: others

  8. Adjacent channel interference

  9. Non-adjacent channel interference

  10. Other 2.4 GHz communications devices • Which common communication devices operate at 2.4 GHz? • 802.11 b/g networks • Bluetooth devices • Cordless phones • Video senders • Baby monitors 10

  11. Bluetooth: frequency hopping

  12. Cordless phones: wide channels

  13. Video senders: extreme interference

  14. Other sources of interference 14

  15. Microwave Ovens

  16. Power Supplies

  17. Radar stations

  18. Other high-power radio sources

  19. Seeing the noise 19

  20. Wi-Spy spectrum analyzer • http://www.metageek.net/

  21. Chanalyzer

  22. Spectools

  23. EaKiu

  24. Ubiquiti AirView • http://www.ubnt.com/

  25. Spectrum Analyzer • A good spectrum analyzer is usually the best (and most expensive) tool for detecting sources of interference.

  26. Using a spectrum analyzer

  27. Thank you for your attention For more details about the topics presented in this lecture, please see the book Wireless Networking in the Developing World, available as free download in many languages at: http://wndw.net/

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