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9. Shadowing

9. Shadowing


Shadowing – Video: Register for Course

Shadowing – Transcript:

Shadowing Introduction

  • So when we take an omnidirectional antenna, and our example, with the signal values and pathloss models and assume line of sight (that tx and rx antennas „see each other”), we should expect that the received signal level will be the same at thhe same distance wherever the receiver goes.
  • While the reality it is not that „rose” i.e. in reality we have obstacles – e.g. in our case a house – so that the receiver at the same distance, but a different location from the receiver, (different angle) is experiencing much worse signal level, due to additional obstruction. This is known to as shadowing.

Shadowing Map

  • This is the same example but on a simulated environment – where we have different signal levels put on a map with different colours – the warmer the colour the higher the received signal level
  • We see the „fluctuation of the colours on the right figure

Shadowing Map 3

  • So lets see that from different perspective (the same example)
  • We have a nice clean figure when there is no signal fading ,
  • then we have a shadofading itself – that is a variation of the attenuation of the signal depending on the position, frequency and time – and is modeled as a random proces, but is pretty long – i.e. the building is there always (therfore we call it slow fading)
  • We could actually see a better or worse changes of the signal – when we have in one place of the same distance we have a building and on the other a mountain that imrpvoes a signal level
  • So the „good”/bad” signal level additions/subtractions are added to the nice / clean signal levels coming from pathloss formulas and give in result a more „hilly” terrain