802.11a - 5 GHz Frequency Band

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Every Wi-Fi device operates on a specific radio frequency range within an overall frequency band. Each frequency band is split into a series of smaller ranges referred to as channels.

IEEE 802.11a and 5 GHz Channel Layout

• IEEE 802.11a standard specifies use of:
  • 5 GHz frequency band
  • Orthogonal Frequency Divisions Multiplexing (OFDM)
    • a multiplexed carrier scheme
• The data encoding method allows a maximum data rate of 54 Mbps
• 5 GHz band is subdivided into 25 non-overlapping channels
  • each is 20 MHz wide
• exact use of channels can be subject to different regulation in different countries
  • include a limit on power output, constraining the range of Wi-Fi devices
  • some channels are used by radar

802.11h

• 802.11h specifies a Dynamic Frequency Selection (DFS) method
  • devices operating on 5 GHz band must use DFS
  • to scan for radar signals and prevent an access point from using channels that would cause interference
  • Traffic Power Control allows devices to adjust their transmitting power levels
    • crucial in areas with dense wireless traffic and strict regulatory oversight
      • helps minimize interference with other devices by reducing power to the necessary level for communication