Weissberger’s modified exponential decay model, or simply, Weissberger’s model, is a
radio wave propagation model that estimates the
path loss
Path loss, or path attenuation, is the reduction in power density (attenuation) of an electromagnetic wave as it propagates through space. Path loss is a major component in the analysis and design of the link budget of a telecommunication system. ...
due to the presence of one or more trees in a point-to-point
telecommunication
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...
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
[Radio propagation in cellular networks, N. Blaunstein]
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
:
where,
''L'' = The loss due to foliage. Unit:
decibel
The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a po ...
s (dB)
''f'' = The transmission frequency. Unit:
gigahertz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one h ...
(GHz)
''d'' = The depth of foliage along the path. Unit:
meter
The metre (British spelling) or meter (American spelling; see spelling differences) (from the French unit , from the Greek noun , "measure"), symbol m, is the primary unit of length in the International System of Units (SI), though its prefi ...
s (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.
[Introduction to RF propagation, John S. Seybold]
See also
*
Fresnel zone
A Fresnel zone ( ), named after physicist Augustin-Jean Fresnel, is one of a series of confocal prolate ellipsoidal regions of space between and around a transmitter and a receiver. The primary wave will travel in a relative straight line from ...
*
Radio propagation model
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere.
As a form of electromagnetic radiation, like light waves, radio waves are affected ...
References
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
*
{{Radio frequency propagation models
Radio frequency propagation model