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Signal propagation

2 min read

Signal propagation refers to the movement of electromagnetic waves from a transmitter to a receiver through a medium, influenced by environmental interactions. These interactions cause phenomena like shadowing, reflection, refraction, scattering, and multipath propagation, which significantly impact communication quality.

Types of Signal Propagation Ranges:

  1. Transmission Range: The range within which the signal is strong enough for the receiver to decode it accurately with a low error rate.
  2. Detection Range: The range beyond the transmission range where the receiver can sense the signal’s presence but cannot decode the data.
  3. Interference Range: The range where the signal is too weak to be detected or decoded by a receiver but still strong enough to interfere with other ongoing transmissions.

Key Effects in Signal Propagation

  1. Shadowing
    • Occurs when large obstacles like buildings or hills block the signal.
    • Causes a significant drop in signal strength behind the obstacle (known as a shadow region).
    • Results in slow variations in signal strength over distance.
  2. Reflection
    • Happens when signals bounce off large surfaces like walls, buildings, or the ground.
    • Creates multiple copies of the signal arriving at the receiver.
    • Can either strengthen or weaken the overall signal depending on phase alignment.
  3. Refraction
    • Bending of the signal as it passes through materials with different densities (e.g., from air to glass or air layers with different temperatures).
    • Can cause signal distortion and path deviation.
  4. Scattering
    • Caused by small objects or rough surfaces (e.g., trees, lampposts, street signs).
    • Signal is diffused in many directions.
    • Especially significant at higher frequencies like in 5G.
  5. Multi-path Propagation
    • A combination of reflection, scattering, and diffraction.
    • Multiple versions of the signal reach the receiver via different paths, each with different delays.
    • Can cause constructive or destructive interference leading to:
      • Fading (signal drops)
      • Inter-symbol interference (symbols overlap)

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