Hata-Okumura Model

Introduction

The Hata-Okumura computation model was first described by Yoshihisa Okumura in 1968 in his publication "Field Strength and Its Variability in VHF and UHF Land-Mobile 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 Hata-Okumura 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 Hata-Okumura 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 Hata-Okumura.

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:

Knife-Edge Diffraction Extension

To increase the accuracy of this prediction model, WinProp offers the Knife-Edge 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.