Physics:Weissberger's model

From HandWiki

Weissberger’s modified exponential decay model, or simply, Weissberger’s model, is a radio wave propagation model that estimates the path loss due to the presence of one or more trees in a point-to-point telecommunication link. This model belongs to the category Foliage or Vegetation models.

Applicable to/under conditions

  • This model is applicable to the cases of line of sight propagation. Example is microwave transmission.
  • This model is only applicable when there is an obstruction made by some foliage in the link. i.e. In between the transmitter and receiver.
  • This model is ideal for application in the situation where the LOS path is blocked by dense, dry and leafy trees.

Coverage

Frequency: 230 MHz to 95 GHz[1]

Depth of foliage: up to 400 m

History

Formulated in 1982, this model is a development of the ITU Model for Exponential Decay (MED).

Mathematical formulation

Weissberger’s model is formally expressed as

[math]\displaystyle{ L = \begin{cases} 1.33 \, f^{0.284} \, d^{0.588} \,\mbox{, if } 14 \lt d \le 400 \\ 0.45 \, f^{0.284} \, d \, \, \, \, \, \, \, \, \, \, \mbox{, if } 0 \lt d \le 14 \end{cases} }[/math]

where,

L = The loss due to foliage. Unit: decibels (dB)

f = The transmission frequency. Unit: gigahertz (GHz)

d = The depth of foliage ‘’’along’’’ the path. Unit: meters (m)

Points to note

  • The equation is scaled for frequency specified in GHz range.
  • Depth of foliage must be specified in meters (m).

Limitations

  • This model is significant for frequency range 230 MHz to 95 GHz only, as pointed out by Blaunstein.
  • This model does not define the operation if the depth of vegetation is more than 400 m.
  • This model predicts the loss due to foliage. The path loss must be calculated with inclusion of the free space loss.[2]

See also

References

  1. Radio propagation in cellular networks, N. Blaunstein
  2. Introduction to RF propagation, John S. Seybold

Further reading

External links