Hata Model

In this model, an empirical formula for propagation loss is derived from Okumura’s tests in order to put his prediction method to computational use [1]. This model tries to put Okumura’s observations into a simple form as A+ BlogR, where A and B are frequency and antenna height functions and R is the distance. All formulas derived by Hata are given in terms of Path Loss. Hata’s approach involves dividing the prediction area into a series of clutter and terrain categories, namely open, suburban and urban area. These could be defined as [2]:

Urban Area: Large town with large buildings and houses with two or more floors, or larger villages with close houses.

Suburban Area: Village or highway scattered with trees and houses, some obstacles near the mobile but not very congested.

                               Hata’s formulas:

                                              (1)

* Correction factor for mobile station antenna height

medium –small city

                                                  (2)

                                       large city 

for  f<=200 MHz

                                                            (3)

                              for f>400MHz

                                                                         (4)

             (5)

           (6)

The introduced formula doesn’t cover all conditions proposed in the Okumura’s report. Hata’s approach is valid for restrictions given in Table 1

 Table 1. Limitations in Hata’s formula

By using Wireless Simulator Programâ  following study is done to give an idea how Hata approach works.

                                                              Figure 1 Hata Study Example

Study Parameters: Frequency: 900 MHz, TX Height (hb)=50m Mobile Height (hm)=1.5m TX Gain: 13 dBi City Size: Small/Medium

Terrain Parameters: Average Width: 50.19 m Average Building Height: 16.1m Percentage of Buildings: 62%

Since Hata model is valid for distances greater than 1 km, Wireless Simulator program applies free space propagation up to distance 1km. Therefore, up to that distance, both study have the same results.

As seen in the figure 1, path loss in urban area has about 28.5 dB differences from path loss in Open Area. Actually, this difference is caused by the formula (6). The parameters

yield the same value.

For the frequency between 200 MHz and 400 MHz (formula 3 and 4), the model doesn’t recommend anything. However, some sources propose solution to the problem by applying the formulas for f>300 MHz, and f<300 MHz respectively [3].  For the mobile height hm=1.5m, formulas (3) and (4) yield

  These values imply that solution mentioned above will deviate in small differences from Hata’s actual results and could be accepted in practical applications.

This model works sufficiently for large cell mobile systems, but not for cells with radius in order of 1 km.

  [1] M.Hata, “Empirical Formula for Propagation Loss in Land Mobile Radio Services”, IEEE Trans, Veh. Technol.,Vol.VT-29,pp.317-325,1980

  [2] Siwiak, Kazimierz., “Radiowave Propagation and Antennas for Personal Communications”, Artech House, Boston-London,1995

  [3] Allsebrook, K. and J.D. Parsons., “Mobile Radio Propagation in British Cities at Frequencies in the VHF and UHF Bands,” IEEE Proc. Vol.124,No.2,1997, pp.95-102