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Mar 29th, 2018
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  1.  
  2. 2.1. Interference Concerns
  3. Wi-Fi channels are spaced 5 MHz apart. However, a channel typically requires up to 20
  4. MHz bandwidth for operation. This results in interference when devices operate in adjacent
  5. channels in the same airspace. Therefore, when two transmitters are operating in the same
  6. airspace with a possibility of interference, it is good design practice to space the
  7. operational channels by at least 20 MHz (or 25 MHz for best results). For example, when
  8. one 802.11 transmitter is using channel 1, the other may use channel 5 or 6. Using channel
  9. 2 or 3 is not recommended.
  10. 2.2. Legal Considerations
  11. While spacing channels widely is better from a system design point of view—there are legal
  12. considerations that must be given priority. It is important that the transmitter falls well within
  13. the allowed limits in the country of operation. In most countries, the initial channels are
  14. usually allowed. For example, channels 1 through 11 may be used safely in most of the
  15. countries in the world.
  16. Care must be taken when using the last channels of the spectrum. Using channel 13 and
  17. 14 may be prohibited by local authorities in most countries. Also, using channel 13 and 14
  18. must be done carefully as there are chances of interference with the adjacent licensed/
  19. restricted bands, should the transmitter drift away from the specified channel frequency for
  20. some reason.
  21. Espressif
  22. /! 5
  23. 2
  24. 2017.042. Channel Selection Considerations
  25. Also, note that the last few channels are generally used in low power, low range
  26. applications and spread spectrum applications (subject to limitations). Please consult the
  27. FCC rules for such applications.
  28. Table 2-1. Legal 802.11 Channels
  29. Channel 
 Channel Center Regulatory
  30. No.
  31. Frequency (MHz) Domain Channel 
 Channel Center 
 Regulatory
  32. No.
  33. Frequency (MHz) Domain
  34. 1 2412 FCC/WORLD/TELEC 1 8 2447 FCC/WORLD/TELEC
  35. 2 2417 FCC/WORLD/TELEC 9 2452 FCC/WORLD/TELEC
  36. 3 2422 FCC/WORLD/TELEC 10 2457 FCC/WORLD/TELEC
  37. 4 2427 FCC/WORLD/TELEC 11 2462 FCC/WORLD/TELEC
  38. 5 2432 FCC/WORLD/TELEC 12 2467 WORLD/TELEC
  39. 6 2437 FCC/WORLD/TELEC 13 2472 WORLD/TELEC
  40. 7 2442 FCC/WORLD/TELEC 14 2484 TELEC 2
  41. 1. Regulatory domains are FCC for the United States, TELEC for Japan, and WORLD for all other countries.
  42. 2. Channel 14 for 802.11g is not supported in Japan.
  43. Note that this is general information and developers should consult specifications by
  44. regulatory authorities in their area before implementation.
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