This model is based on the Okumura-Hata method for predicting signal value at one point, thus offering the same applications and the same restrictions. It is therefore a hybrid model especially useful to analyze mobile services propagation.
The original method is rather vague since does not take into account the effects of deterministic elements (terrain, buildings, streets, etc width). To solve this, the modulated Okumura-Hata method includes a correction. This correction depends on the terrain, using diffraction losses calculated with ITU-R Rec. 526 as reference.
It is considered that average error value offered by Okumura-Hata is 0. The aim will be to change this value in an environment of ±σ based on the error made with diffraction losses. For this the method uses the normal distribution function, with a standard deviation σ, turning error values between -∞ and +∞ into values between -σ and +σ.
In this way we obtain an Okumura Hata result adjusted in a precise way to the studied environment. In the following figures a comparison of a base station coverage calculated with both methods is shown.
•The same as Okumura-Hata, it is recommended for mobile services.
•Recommended when the user has detailed buildings information.