Editing Radio propagation (section)

==Empirical models{{anchor|Models}}==
A '''radio propagation model''', also known as the '''radio wave propagation model''' or the '''radio frequency propagation model''', is an [[empirical]] [[mathematical]] [[formulation]] for the characterization of [[radio wave]] propagation as a [[Function (mathematics)|function]] of [[frequency]], [[distance]] and other conditions. A single model is usually developed to predict the behavior of propagation for all similar links under similar constraints. Created with the goal of formalizing the way radio waves are propagated from one place to another, such models typically predict the [[path loss]] along a link or the effective coverage area of a [[transmitter]].

The inventor of radio communication, [[Guglielmo Marconi]], before 1900 formulated the first crude empirical rule of radio propagation: the maximum  transmission distance varied as the square of the height of the antenna.

As the path loss encountered along any radio link serves as the dominant factor for characterization of propagation for the link, radio propagation models typically focus on realization of the path loss with the auxiliary task of predicting the area of coverage for a transmitter or modeling the distribution of signals over different regions.

Because each individual telecommunication link has to encounter different terrain, path, obstructions, atmospheric conditions and other phenomena, it is intractable to formulate the exact loss for all telecommunication systems in a single mathematical equation. As a result, different models exist for different types of radio links under different conditions. The models rely on [[Reference distance|computing the median path loss]] for a link under a certain probability that the considered conditions will occur.

Radio propagation models are empirical in nature, which means, they are developed based on large collections of data collected for the specific scenario. For any model, the collection of data has to be sufficiently large to provide enough likeliness (or enough scope) to all kind of situations that can happen in that specific scenario. Like all empirical models, radio propagation models do not point out the exact behavior of a link, rather, they predict the most likely behavior the link may exhibit under the specified conditions.

Different models have been developed to meet the needs of realizing the propagation behavior in different conditions. Types of models for radio propagation include:

;Models for free space attenuation
* [[Free-space path loss]]
* [[Dipole field strength in free space]]
* [[Friis transmission equation]]

;Models for outdoor attenuation
*Terrain models
**[[ITU terrain model]]
**[[Egli model]]
**[[Longley–Rice model|Longley–Rice irregular terrain model (ITM)]]
**[[Two-ray ground-reflection model]]
*City models
**[[Okumura model]]
**[[Hata model]]
**[[COST Hata model]]

;Models for indoor attenuation
*[[ITU model for indoor attenuation]]
*[[Log-distance path loss model]]