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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

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

$L=\{\begin{array}{l}1.33f^{0.284}{d}^{0.588}\text{, if }14<d\le 400\\ 0.45f^{0.284}d\text{, if }0<d\le 14\end{array}$

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.

Further reading

• Introduction to RF Propagation, John S. Seybold, 2005, John Wiley and Sons.
• Radio Propagation in Cellular Networks, N. Blaunstein, 2000, Artech House
• The Mobile Radio Propagation Channel, J. D. Parsons, 2000, Wiley
• Template:Cite paper

See also

• Fresnel zone
• Radio propagation model