A forecast model allows to avoid long and expensive measure campaigns. An efficient forecast model represents a valid tool to obtain attenuation estimates.
Okumura's model was developed using measurement data taken at several frequencies in the Tokyo urban and suburban area.
This method is most appropriate for urbanized areas where the study distance is relatively short (less than 30 km), the effective transmit antenna height is less than 200 meters, the effective receive antenna height is less than 10 meters, and the terrain is relatively flat.
In 1980 Masaharu Hata simplified the consideration from Okumura (Empirical formula for propagation loss in Land Mobile Radio Services).
These simplifications led to the restriction that only region with less than 20 km distance to the transmitter can be predicted.
As only four parameter are require, the computation time is very short.
This is an advantage of this model. However, the model neglects the terrain profile between the transmitter and the receiver are
not considered. As Hata and Okumura made the assumption, that the transmitter would normally be located on hills, this was no disadvantage.
Also phemomena like reflection nd shadowing are not included.
The four input parameters are :
- Frequency
- Distance between transmitter and receiver
- Antenna height of the transmitter
- Antenna height of the receiver
The following equations shows the computation of the basic path loss :
L = 69.55 + 26.16Log10(f) - 13.82Log10(hb) - a(hm) + (44.9 - 6.55Log10(hb))Log10(d)
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