Okumura-Hata Model• The okumura and Hata Model is good but more complex

propagation model that is based on extensive empirical measurements taken in urban environments and was further approximated by Hata

The model includes parameters such as frequency, frequency range, heights of the transmitter and receiver and building density.The model is the most popular model for macrocell loss prediction

10 10

10 10

( ) (69.55 26.16log 13.82log )(44.9 6.55log ) log

c t

t

L dB f hh d C

= + −

+ − −

• Where d – distance between transmitter and receiver in km

• ht – height of the transmitter antenna in meter• Ht – height of the receiver antenna in meter• Fc – Carrier frequency

2102 log ( ) 5.4

28cfC = +

210 104.78 log 18.33log 40.94c cC f f= + +

210

210

10 10

3.2 log (11.75 ) 4.97

8.29log (1.54 ) 1.1(1.1log 0.7) (1.56log 0.8)

r

r

c c

h

C hf f

⎧ −⎪

= −⎨⎪ − − −⎩

, large cities, fc >= 300MHz

, large cities, fc < 300MHz

, Medium or small cities

For Suburban area

For Open area

For Urban area

• The model was intended for macrocells and is applicable over distance of 1-100km, frequency range 150-1500MHz, Base station height 30-200m and MS height 1-10m

• The model is satisfactory in Urban and Suburban areas but not suitable for rural areas

• The model is suitable for 1G cellular systems but is not applicable to current cellular systems which have smaller cell sizes and higher frequency

• This model is also not applicable for indoor wireless communication systems

COST-231 Hata Model

• The COST-231 Hata model is an extension of the Okumura-Hata Model to 2GHz

• It is also an empirical model and is suitable for micro cells and small macro cells.

• This model is suitable for fc within 1.5GHz – 2GHz, ht is within 1-10m and d is within 1 – 20km range

• It is used by the ITU-R IMT-2000 standards for the outdoor case

10 10

10 10

( ) (46.3 33.9 log 13.82log )(44.9 6.55log ) log ( )urban c t

t M

L dB f hh d C C

= + −

+ − − +

• Where C – Correction factor for mobile antenna heightCM - is 0dB for medium sized cities and Suburban areas,

is 3dB for metropolitan areas • Both the Okumura-Hata and COST-231Hata models

are specified to have a BS height above 30m, they can be used when ht is less than 30m, as long as surrounding buildings are well below this height.

• They are not suitable for microcells like urban canyons

Example

• Determine the path loss using Hata model at a frequency of 1GHz with ht=50meter, hr= 2meter and distance d = 2km

• Answer: 170.75dB

Other empirical models• In most of the models received power can be

estimated using the following equation

Where• d0 - reference distance • d – distance at which power to be find out• n – path loss exponent

00

P ( )n

r rdP dd

−⎛ ⎞

= ⎜ ⎟⎜ ⎠⎝

00

P ( ) ( ) 10 logr rddB P d nd

⎛ ⎞= − ⎜ ⎟⎜ ⎠⎝

• Lee’s Model:

• Lee’s model is used topredict the path loss over flat terrain. It also takes into account the influence of the heights of the transmit and receive antenna ht and hr

• But it is based on measurement at 900MHz, for suburban areas it has a d3.84 power law.

COST-231-Walfisch-Ikegami Model(WI-model)

• In most of the cases diffraction is a major propagation mechanism.

• Diffraction: Diffraction occurs when the radio path between transmitter and receiver is obstructed by sharp edges.

• A number of physical models based available for diffraction analysis like Ikegami model, the flat-edge model, and Walfisch-Bertoni model

• The COST-231-Walfisch-Ikegami model combines the Walfisch-Bertoni and Ikegami Model plus some empirical correction factors.

d

hroof

h rϕ

Incident wave

Building

br l w

ht

As shown into the diagram model defines more parameters like

• height of buildings hroof ,

•width of roads w ,

•building separation b,

•road orientation with respect to direct radio path φ

• Restrictions :• Frequency f between 800 MHz and 2000

Mhz• TX height hBase between 4 and 50 m• RX height hMobile between 1 and 3 m• TX - RX distance d between 0.02 and 5 km

2 cases : LOS and NLOSLOS :

LLOS [dB] = 42.6 + 26 log10 d[km] + 20 log10 f [MHz]

NLOS :• LNLOS [dB] = LFS + Lrts (wr, f, ∆hMobile , Φ ) +

LMSD (∆hBase, hBase, d, f, bS )where

LFS = free space path loss = 32.4 + 20 log10 d[km] + 20 log10 f [MHz]Lrts= roof-to-street loss

LMSD= multi-diffraction loss

Example

• Lfs =98.42dB• Lrts =37.63dB• Lbsh =-23.79dB• Kf =-3.94• Lmsd = 9.39• Lnos = 145.44dB