Controller Based WLANs

802.11b and 802.11a Channels

by ‎02-08-2016 10:18 AM - edited ‎02-08-2016 10:18 AM
Q:

Briefly describe the 802.11b (2.4GHz) and 802.11a (5GHz) frequency ranges with respect to the channels available in them to transmit wireless data.



A:

2.4Ghz Band

  • Only channels 1-11 are used in US. It gives us a range 72Mhz (2.401- 2.473) to transmit data in the 2.4GHz spectrum.
  • Only channels 1,6 and 11 are non overlapping and hence used when we deploy the Access Points.
  • Channel Width of each channel is 22MHz.
  • 2.4GHz is also used by microwave ovens, cordless phones, baby monitors and wireless video cameras.
  • This frequency range is heaviliy used and is the potential for interference.

 

5GHz Band

 

  • 5GHz have 4 UNII bands (Unlicensed National Information Infrastructure Bands).
  • UNII-1 (lower) band ranges from 5.15-5.25 GHz and has 4 channels. All the channels are non-overlapping. (Range: 100MHz)
  • UNII-2 (Middle) band ranges from 5.25-5.35 GHz and has 4 channels. All the channels are non-overlapping. (Range: 100MHz)
  • UNII-2 Extended (Extended) band ranges from 5.470-5.725 GHz and has 11 channels. All the channels are non-overlapping. (Range: 255MHz)
  • UNII-3 (Upper) band ranges from 5.725-5.825 GHz and has 4 channels. All the channels are non-overlapping. (Range: 100MHz)
  • Total of 23 channels are present in the 5GHz range and all the channels are non-overlapping and we get a range of 550MHz to transmit data.
  • Channel Width of each channel is 20Mhz.

 

Note: In 2.4ghz we get a frequency range of 72Mhz whereas in 5GHz we get a frequency range of 555Mhz to transmit data.

 

 

 

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