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COMPARATIVE STUDY OF PATH LOSS MODELS DEPENDS ON VARIOUS PARAMETERS

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COMPARATIVE STUDY OF PATH LOSS MODELS DEPENDS
ON VARIOUS PARAMETERS
Purnima K Sharma
Research Scholar, UTU, Dehradun (INDIA)
purnima_kadali@rediffmail.com
R. K. Singh
OSD (Professor), UTU, Dehradun (INDIA)
rksinghkec12@rediffmail.com
Abstract:
Wireless system designing is not only an expensive process but it also takes lots of time for establishment. So before
going for the establishment of such type of expensive systems mathematical model analysis is necessary to estimate
channel environment, frequency band and the desired radio coverage range. That type of modeling plays an
important role in cell coverage prediction, received signal strength estimation and link budget analysis of mobile
radio systems. To acquire more efficiency in the system design using the frequency reuse concept in current cellular
systems one has to eliminate the interference at the cell boundaries. Determining the cell size correctly can be
calculated by using an accurate path loss model. So the study of path loss models is important. In this paper we
compare the different path loss propagation models depends on various parameters like frequency & height of
antenna at the transmitter side. For comparative analysis we use the Stanford University Interim (SUI) Model, Hata
model, COST231 Extension to Hata Model, Walfisch - Bertoni model and ECC-33 model in three different
environments (urban, suburban, & rural environments).
1. Introduction
Understanding and predicting electromagnetic radio-propagation characteristics in different environments is
important in the implementation of wireless system designing. As the volatile growth of cellular communication
systems continues, it is very important to have the ability of determining minimum base-station locations, obtaining
suitable data rates, and estimating their coverage, without conducting a series of propagation measurements, which
are very expensive and time consuming [1]. It is therefore important to develop effective propagation models for
mobile communications, in order to provide design guidelines for mobile systems. The path loss propagation models
have been an active area of research in recent years because pathloss model analysis provides a good initial estimate
of the signal characteristics. Path loss is an unwanted introduction arises when an electromagnetic wave propagates
through space from transmitter to receiver. The strength of signal reduces due to various parameters like path
distance, reflection, diffraction, scattering, free-space loss, type of environments (i.e. urban, suburban and rural),
variation of transmitter antenna heights, variation of receiver antenna heights and absorption by the objects of
environment.
There are number of propagation models available to predict the path loss (e.g. Hata Model, Walfisch - Bertoni
model etc.), but some of the models are limited to the lower frequency bands. In this paper we compare and analyze
different path loss models (e.g. COST 231, Hata model, ECC-33 model, SUI model, Betroni and xia model) in three
different environments at different frequencies, & at different transmitter antenna heights in different receiver
antenna heights [2].
2. PROPAGATION PATH LOSS MODELS
In wireless communication systems, transfer of information between the transmitting antenna and the receiving
antenna is achieved by means of electromagnetic waves. The interaction between the electromagnetic waves and the

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environment reduces the signal strength send from transmitter to receiver that causes path loss. Different models are
there to calculate the path loss. Some of them are described and compared in this paper [1].
2.1. Stanford University Interim (SUI) Model
The proposed standards for the frequency bands below 11 GHz contain the channel models developed by Stanford
University, namely the SUI models. Note that these models are defined for the Multipoint Microwave Distribution
System (MMDS) frequency band which is from 2.5 GHz to 2.7 GHz. Their applicability to the 3.5 GHz frequency
band that is in use in the UK has so far not been clearly established [6]. The SUI models are divided into three types
of terrains1, namely A, B and C. Type A is associated with maximum path loss and is appropriate for hilly terrain
with moderate to heavy foliage densities. Type C is associated with minimum path loss and applies to flat terrain
with light tree densities. Type B is characterized with either mostly flat terrains with moderate to heavy tree densities
or hilly terrains with light tree densities. The basic path loss equation with correction factors is presented in [4, 5].
10
0
10 log
f h
d
PL A X X s
d
γ
= + + + +
for
0
>dd
(1)
where, d is the distance between the Access Points (AP) and the Customer Premises Equipment (CPE) antennas in
meters, d0 = 100 m and s is a log normally distributed factor that is used to account for the shadow fading owing to
trees and other clutter and has a value between 8.2 dB and 10.6 dB [4]. The other parameters are defined as,
10
4
20log
o
d
A
π
λ
=
÷
(2)
b
b
c
a bh
h
γ
= +
(3)
where, the parameter h
b
is the base station height above ground in metres and should be between 10 m and 80 m.
The constants used for a, b and c are given in Table II. The parameter γ in (3) is equal to the path loss exponent. For
a given terrain type the path loss exponent is determined by h
b
.
Table I: The parameters of SUI model in different types of environments
Model
parmeter
Terrain
A
Terrain
B
Terrain
C
a
1
( )b m
C(m)
4.6
0.0075
12.6
4.0
0.0065
17.1
3.6
0.005
20
The correction factors for the operating frequency and for the CPE antenna height for the model are [4,6].
10
6.0log
2000
f
f
X
=
÷
(4)
10
10.8log
2000
r
h
h
X
=
÷
for Terrain types A and B (5)
=
10
20.0 log
2000
r
h
÷
for Terrain type C (6)
Where, f is the frequency in MHz and hr is the CPE antenna height above ground in meters. The SUI model is used
to predict the path loss in all three environments, namely rural suburban and urban.

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2.2. Hata Model
The Hata model [7] is an empirical formulation of the graphical path loss data provided by Okumura and is valid
over roughly the same range of frequencies, 150-1500 MHz. This empirical model simplifies calculation of path loss
since it is a closed-form formula and is not based on empirical curves for the different parameters. The standard
formula for median path loss in urban areas under the Hata model is
(7)
The parameters in this model are the same as under the Okumura model, and a(hre) is a correction factor for the
mobile antenna height based on the size of the coverage area. For small to medium sized cities, this factor is given
by [3,7]:
r 10 c r 10 c
a(h ) = (1.1 log (f ) - 0.7)h - (1.56 log (f ) -0.8)dB
(8)
& for larger cities at frequencies
c
f
> 300 MHz by
2
r 10 r
a(h ) = 3.2(log (11.75h ) - 4.97 dB.
(9)
Corrections to the urban model are made for suburban and rural propagation, so that these models are, respectively,
2
50,suburban 50,urban 10 c
L (dB) = L (dB) - 2[log (f /28)] - 5.4
(10)
2
50,rural 50,urban 10 c
10 c
L (dB) = L (dB) - 4.78[log (f )] +
18.33log (f ) - K
(11)
Where K ranges from 35.94 (countryside) to 40.94 (desert). Hata’s model does not provide for any path specific
correction factors, as is available in the Okumura model. The Hata model well-approximates the Okumura model for
distances d > 1 Km. Thus, it is a good model for first generation cellular systems, but does not model propagation
well in current cellular systems with smaller cell sizes and higher frequencies. Indoor environments are also not
captured with the Hata model.
2.3. COST231 Extension to Hata Model
A model that is widely used for predicting path loss in mobile wireless system is the COST-231 Hata model [6,8].
The COST-231 Hata model is designed to be used in the frequency band from 500 MHz to 2000 MHz. It also
contains corrections for urban, suburban and rural (flat) environments. Although its frequency range is outside that
of the measurements, its simplicity and the availability of correction factors has seen it widely used for path loss
prediction at this frequency band. The basic equation for path loss in dB is [3],
10 10
10 10
PL=46.3+33.9log ( ) 13.82log ( )
(44.9 6.55log ( ))log
b m
b m
f h ah
h d c
+ +
(12)
where, f is the frequency in MHz, d is the distance between AP and CPE antennas in km, and hb is the AP antenna
height above ground level in metres. The parameter cm is defined as 0 dB for suburban or open environments and 3
dB for urban environments. The parameter ah
m
is defined for urban environments as [9]
2
m 10
ah = 3.20(log (11.75hr)) -4.97, for f > 400 MHz
(13)

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