Understanding the Impact of RF Interference

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In Association with
Interference Hunting Techniques
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RF Interference What is it and Why all the Hype?

• As Wireless services grow, Interference
  (previously Uncommon) is on the rise
• Interference naturally affects reception first
  where signal levels are normally small.
• First Indicators include Noisy Links (Analog),
  Dropped Calls, Low Data-rate, High RX Noise Floor
  (Mobile Cellular), Poor Reception (Broadcasting)
• All of the above problems equate to loss of
  revenue to the service provider who often pay a
  premium for their allocated spectrum.

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Types of Interference

• On-Band Interference (Antenna tilts and
  reflection)
• In-Band Interference (Carriers from Other
  Services, Intermodulation Products, Harmonics of
  other Signals)
• Impulse Noise (Lightening suppression devices,
  Motors, Ovens, Welding, Electric Fences, Power
  Lines, Light Dimmers, Diode Display Screens)
• Harmonics
• Passive Intermodulation (PIM)
• Near-Far Problem
• Intentional Interference

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Spotting Interference in the field

• Once the tell-tale signs are established from
  First indicators it is now time to bring out a
  spectrum analyser to take a look.
• Once an interfering signal is characterized and
  detected using the tower antenna the next step is
  to use a ground level antenna to find the same
  signal.
• This allows us the opportunity to search for the
  signal source by direction finding and signal
  strength.
• For burst-type interferers the use of a max-hold
  or waterfall feature on a spectrum analyser
  which aids in determining the transmission
  pattern of a signal.

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Spectrum Max-Hold Display
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Spectrum Waterfall Display
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Spectrum Waterfall 3D View
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Locating the source

• After determining the frequency of interest we
  use our spectrum analyser with settings on the
  desired frequency we need to track using an
  Omni-directional antenna. Reason being that we
  determine the signal strength without direction.
  (Due consideration should be given using any gain
  factors)
• We then use a directional antenna at the same
  input we used the Omni- directional antenna and
  note the bearing of the strongest signal strength
  using a signal strength meter.
• Plotting this bearing on a map over multiple
  points (at least 3) will point to the source at
  interception points. (Care should be taken in
  built up areas where possibility of reflections
  can distort results).

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Locating the source

• Modern spectrum analysers have built-in mapping
  software electronic compasses and GPS receivers
  that can aid in time saving and plotting
  direction on maps easily.

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Fixing The Problems

• Once interference issues are identified. We
  propose resolution to the party breaching the
  spectrum.
• In most cases the party in breach are unaware of
  their infringements and are willing to compromise
  especially if the methodology in determining the
  interference is properly documented.
• Often lowering signal strength, filtering,
  cleaning/re-torque of connectors, removing
  environmental diodes, adjusting tilt and removing
  illegal TRXs can immediately resolve issues.
• Reporting the issue to authorities for resolution
  or legal action is often the final recourse.

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Conclusion

• With the push for modern society to go wireless,
  it brings with it more challenges as we struggle
  to maximise the spectrum at our disposal.
• The advancements in digital technology and filter
  design allows us to maximise on the spectrum
  usage.
• To determine and locate failure fast and
  accurately in modern systems is crucial for
  harmonious usage of our spectrum resource.
• It is therefore most important to adopt the
  latest technology at hand to maximise on benefit
  in tracking down interferers.

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Thank YouQA