1. Comparative Use of Unlicensed Spectrum Training materials for wireless trainers

2. 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. 3 These considerations are important to keep in mind when using devices that operate using unlicensed spectrum. Sharing the air ‣ 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. 4 Electromagnetic Spectrum Approximate range for WiFi

5. 5 802.11 Channels

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

7. 7 Non-overlapping channels: others

8. 8 Adjacent channel interference

9. 9 Non-adjacent channel interference

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

11. 11 Bluetooth: frequency hopping

12. 12 Cordless phones: wide channels

13. 13 Video senders: extreme interference

14. 14 Other sources of interference 14

15. 15 Microwave Ovens

16. 16 Power Supplies

17. 17 Radar stations

18. 18 Other high-power radio sources

19. 19 Seeing the noise 19

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

21. 21 Chanalyzer

22. 22 Spectools

23. 23 EaKiu

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

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

26. 26 Using a spectrum analyzer

27. 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/ 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/ Thank you for your attention