The

ITU The International Telecommunication Union (ITU)In the other common languages of the ITU: * * is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established ...

terrain loss model is a

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 affect ...

that provides a method to predict the

median The median of a set of numbers is the value separating the higher half from the lower half of a Sample (statistics), data sample, a statistical population, population, or a probability distribution. For a data set, it may be thought of as 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. ...

for a

telecommunication Telecommunication, often used in its plural form or abbreviated as telecom, is the transmission of information over a distance using electronic means, typically through cables, radio waves, or other communication technologies. These means of ...

link. Developed on the basis of

diffraction Diffraction is the deviation of waves from straight-line propagation without any change in their energy due to an obstacle or through an aperture. The diffracting object or aperture effectively becomes a secondary source of the Wave propagation ...

theory, this model predicts the path loss as a function of the height of path blockage and the First

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 size of the calculated Fresnel zone at any particular di ...

for the transmission link.

Applicable to / under conditions

This model is applicable on any terrain. This model accounts for obstructions in the middle of the telecommunication link, and therefore, is suitable to be used inside cities as well as in open fields.

Coverage

Frequency: Any Distance: Any

Mathematical formulation

The model is mathematically formulated as: :

A \; = \; 10 \; - \; 20 \; C_N

C_N \; = \; \frac

h \; = \; h_L \; - \; h_O

F_1 \; = \; 17.3 \; \sqrt

Where, :

A \;

= Additional loss (in excess of free-space loss) due to diffraction (dB) :

C_N \;

Normalized Normalization or normalisation refers to a process that makes something more normal or regular. Science * Normalization process theory, a sociological theory of the implementation of new technologies or innovations * Normalization model, used in ...

terrain clearance :

h \;

= The height difference (negative in the case that the LOS path is completely obscured) (m) :

h_L \;

= Height of the line-of-sight link (m) :

h_O \;

= Height of the obstruction (m) :

F_1 \;

= Radius of the first Fresnel zone (m) :

d_1 \;

= Distance of obstruction from one terminal (km) :

d_2 \;

= Distance of obstruction from the other terminal (km) :

f \;

= Frequency of transmission (GHz) :

d \;

= Distance from transmitter to receiver (km) To use the model, one computes the additional loss to each path obstruction (A). These losses are summed and then added to the predicted line of sight path loss which is calculated using

Friis transmission equation The Friis transmission formula is used in telecommunications engineering, equating the power at the terminals of a receive antenna as the product of power density of the incident wave and the effective aperture of the receiving antenna under i ...

or a similar theoretical or empirical model.

Limitations

This model is considered valid for losses over 15 dB and may be valid for losses as low as 6 dB. In the event that the loss is less than 6 dB or is negative (i.e., gain), this A-value should be discarded. This model's output is only as good as the data on which it is based and the LOS model it is used to correct.

References

{{DEFAULTSORT:Itu Terrain Model Radio frequency propagation model

Applicable to / under conditions

Coverage

Mathematical formulation

Limitations

See also

References