
Introduction


The
HataOkumura computation model was first described by
Yoshihisa Okumura in 1968 in his publication "Field
Strength and Its Variability in VHF and UHF LandMobile
Radio Service". In 1980, Masaharu Hata simplified the
considerations from Okumura ("Empirical formula for
propagation loss in Land Mobile Radio Services"). These
simplifications led to the restriction that only regions
with less than 20 km distance to the transmitter can be
predicted.
As only four parameters are required, the computation
time is very short. This is an advantage of this model.
However, the model neglects the terrain profile between
transmitter and receiver, i.e. hills or other obstacles
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 phenomena like reflection
and shadowing are not included. 
An example prediction with the HataOkumura Model


Parameters


The four
parameters with their limits are:

Frequency
f (150...1500 MHz)

Distance
between transmitter and receiver d (1...20 km)

Antenna
height of the transmitter hTX (30...200 m)

Antenna
height of the receiver hRX (1...10 m)

Definition
of parameters (click
here
to enlarge)

As the height
of the transmitter and the receiver is measured relative
to the ground, an effective antenna height heff is
additionally used and added to the antenna height of the
transmitter (see figure on the right). This also
improves the accuracy of the prediction.
The items
marked green in the figure show the parameters of the
HataOkumura model. In this example the prediction would
be too optimistic, because the model assumes LOS (line
of sight), but the actual path is obstructed by two
hills. 

Computation


The following
equations show the computation of the basic path loss a
(in dB) with the model of HataOkumura.
Additionally
to the basic loss, there are correction terms which
characterize different environments:
Some
modifications to the equations for rural or open
environment are necessary. They are taken into account
in the following formulas:


KnifeEdge Diffraction Extension


To increase
the accuracy of this prediction model, WinProp offers
the KnifeEdge Diffraction Extension. More about this
feature can be found on the
Knife Edge Diffraction Page. 




Download a brochure with all rural prediction
models.



See a comparison between
different rural prediction models.



Read more
about the Knife Edge Diffraction Extension to
this prediction model.


See the
overview over all rural prediction models.



The figure illustrates the
variation of the correction terms depending on the frequency (relative
to the basic path loss)  Click
here to
enlarge picture.

