Locating and identifying RF interference sources

  • Spectrum analyzers monitor the RF signal itself.
  • Before conducting the coverage analysis survey, locating sources of potential interference is a must.
  • To conduct a proper 802.11 spectrum analysis survey, the spectrum analyzer needs to be capable of scanning both the 2.4 GHz ISM band and the 5 GHz U-NII bands.
  • If the background noise level exceeds –85 dBm in either the 2.4 GHz ISM band or the 5 GHz U-NII bands, the performance of the wireless network can be severely
    degraded.
  • A noisy environment can cause the data in 802.11 transmissions to become corrupted.
  • Most data applications in a Wi-Fi network can handle a layer 2 retransmission rate of up to 10 percent without any noticeable degradation in performance.
  • Voice over Wi-Fi (VoWiFi) networks need to limit retransmissions at layer 2 to about 10 percent or less to guarantee the timely delivery of VoIP packets.
  • After locating the sources of interference, the best and simplest solution is to eliminate them entirely.

 

2.4 GHz Interferers

  • Microwave ovens
  • 2.4 GHz cordless phones, DSSS and FHSS
  • Fluorescent bulbs
  • 2.4 GHz video cameras
  • Elevator motors
  • Cauterizing devices
  • Plasma cutters
  • Bluetooth radios
  • Nearby 802.11, 802.11b, 802.11g, or 802.11n (2.4 GHz) WLANs

5 GHz Interferers

  • 5 GHz cordless phones
  • Radar
  • Perimeter sensors
  • Digital satellite
  • Nearby 5 GHz WLANs
  • Outdoor wireless 5 GHz bridges
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