7_wireless propagation theory and propagation model(v0_1)
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8/13/2019 7_Wireless Propagation Theory and Propagation Model(V0_1)
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CDMAWireless Propagation Theory and
Propagation Model
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Contents
Ø Characters of Wireless Propagation
Ø Classification of Propagation ModelsØ Free Space Propagation Model
Ø The Application of Propagation
Models in Cellular Design
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Radio Propagation on the Open Land
The received signals are the sum of the direct
wave and reflected wave.
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Radio Propagation in the Dense Urban
Mobile telephone is hard to receive direct wave. In general,
the received signals are the sum of reflected, diffracted and
scattered waves.
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Reflection Reflection occurs when the propagation electromagneticwave encounters an object which has very largedimensions compared to the wavelength of the
propagation wave. Reflection normally occurs on the surfaces of the earth buildings and walls.
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Reflection
t coefficien on Transmissi 1 ! E
E
t coefficien Reflection E
E
i
t
i
r
+==
=
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Diffraction
Diffraction occurs when the radio path between the
transmitter and receiver is obstructed by the edges of
the objects.
Diffraction allows radio signals to propagate around the
curved surface of the earth beyond the horizon, and to
propagate behind obstructions.
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Diffraction Loss
The obstructions position and height
decide the diffraction loss .
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Diffraction Arithmetic
Step one!calculate the diffraction factor
( )
21
212
d d
d d
hv λ
+
=
( ) ( )
( )dx x j
jv F
v
∫
∞
−
+
=2/exp
2
1 2π
( ) ( )v F Log E
E Log dBG d 2020
0
==
Step two!calculate the diffraction loss
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Approximation of the Diffraction Loss
( )
=
v Log dBG
225.020
( ) ( )
−−−= 2
1.038.01184.04.020 v Log dBG
( ) ( )( )v Log dBG 95.0exp5.020 −=
( ) ( )v Log dBG 6.05.020 −=
( ) 0=dBG v"#1
-1"v"0
0"v"1
1"v"2.4
2. 4"v
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Multiple obstructions
The Epstein-Peterson technique is based on the assumptionthat the total loss can be evaluated as the sum of the
attenuation due to each respective significant obstruction.
Epstein Peterson method
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ScatteringScattering occurs when the medium through which the wave travels
consists of objects with dimensions that are small compared to the
wavelength, and where the number of obstacles per unit volume is
large.
Scattering waves are produced by rough surfaces, small objects, or byother irregularities. In practice, foliage, street signs, and lamp posts can
cause scattering in the mobile communication system.
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Characters of Wireless PropagationRadio propagation is related to terrain and clutter around
the base station. Increasing the antennas height can
enlarge the propagation distance of the transmitter.
Radio transmission is very complex which is impacted by
reflection, diffraction and scattering. Sometimes they will
cause serious fading.
Radio propagation is also related to the frequency. The
higher the frequency is used, the shorter the propagation
distance is.
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Wireless Propagation in Dense Urban
Mobile telephone is hard to receive direct wave. In general, the
received signals are the sum of reflected, diffracted and scattered
waves
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Wireless Propagation in Dense Urban
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!"#$%&
-./012345678"#*+,9:0;<0
#=>
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Contents
Ø Characters of Wireless Propagation
Ø
Classification of Propagation ModelsØ Free Space Propagation Model
Ø The Application of Propagation
Models in Cellular Design
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Classification of the Propagation Models(1)Empirical Models
Empirical models are equations derived from the statistic and analysis
based on a great deal of measured data.
Okumura # Hata
Model,
COST231-Hata Model,
Lee Model, etc.
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Classification of the Propagation Models (2)
Deterministic models
Methods that directly use electromagnetic theory to calculate the field in the
surroundings. The description of surroundings can be gotten from the terrain
and clutter database. The accuracy of the description determines the models
resolution.
Ray Tracing ModelGeometrical theory of
diffraction$GTD%, physicaloptics$PO%method and finite
difference time domain
method(FDTD),etc.
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Classification of the Propagation Models (3)Semi-empirical or Semi-deterministic Models
The semi-empirical or semi-deterministic models are some equations
derived from the deterministic models used in urban or indoor
surroundings. Often we correct them based on test data to make them
more accurate.
Ikegami Model,
COST
Walfish-IkeganiModel,
ZTE models,
etc.
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Application of different type of Models
Empirical Models and Semi-empirical Models are suitable for
predicting the area where the environment is uniform and the
coverage radius is large.
Semi-empirical Models are also suitable for the uniform
environment but the coverage radius is relative small.
Deterministic Models are suitable for the atactic environmentand indoor situation. The coverage radius is very small.
Meanwhile, it asks for high resolution of the digital map.
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Contents
Ø Characters of Wireless Propagation
Ø
Classification of Propagation Models
Ø Free Space Propagation Model
Ø The Application of Propagation
Models in Cellular Design
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The free space propagation model is used to predict
the received signal strength when there is a clear and
unobstructed line-of-sight path between thetransmitter and receiver. It is a standard used to
evaluate the propagation performance of other
environment.
Satellite communication systems and microwave
line-of-sight radio links typically undergo the free
space propagation.
Free Space Propagation Model
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The path loss for the free space model
included the antenna gains is given by
−==
22
2
)4(log10log10)(
d
GG
P
P dB PL r t
r
t
π
λ
Path Loss of the Free Space Model
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Path Loss of the Free Space Model
MHz mi
MHz km
f d dB
f d dB
log20log2058.36
log20log2045.32
++=++=
−==
22
2
)4(log10log10)(
d P
P dB PL
r
t
π
λ
When antenna gains are excluded, the antennas areassumed to have unity gain, and path loss is given
by
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Path Loss of the Free Space Model
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Contents
Ø Characters of Wireless Propagation
Ø
Classification of Propagation ModelsØ Free Space Propagation Model
Ø The Application of Propagation
Models in Cellular Design
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Okumura-Hata Model
Okumura-Hata is an empirical formulation
of the graphical path loss data provided by
Okumura.
This Model presents the urban area
propagation loss as a standard formula and
supplied correction equations for applicationto other situations.
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Okumura-Hata Model is restricted to the following
conditions:
Frequency f150&1500 MHz
Effective height of the Base station antenna!30&200 m
Height of the Mobile antenna!1&10 m
Communication distance!1&35km
Okumura-Hata Model
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The standard formula for mean path loss in urban
areas is given by
Okumura-Hata Model
d hhah f L
b
mbb
lg)lg55.69.44( )(lg82.13lg16.2655.69
⋅−+−−+=
d!Distance from the base station(km)
f!Frequency(MHz)
L b!Mean path loss in urban areas (dB)
hb!h
m!Base station and mobile antenna effective height.
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The mobile antenna height correction factor
=
<<−<<−
−−−
=
mh
MHz f h
MHz f h
f h f
ha
m
m
m
m
m
5.10
cityLarge150040097.4)75.11(lg2.3
2001501.1)54.1(lg29.8
citymediumandSmall)8.0lg56.1()7.0lg1.1(
)(2
2
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Okumura-Hata'(
Base station height 150m
mobile antenna 1.5m
Frequency 900MHz
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COST231-Hata Model
COST231-Hata Model is also based on Okumuras test data.
Its an empirical formulation via Okumuras high frequency
graphical path loss data.
This Model is restricted to the following conditions:
Frequency f : 1500&2000 MHz
Effective height of the Base station antenna :30&200 m
Height of the Mobile antenna : 1&10 m
Communication distance: 1&35km
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COST231-Hata Model
γ
))(lglg55.69.44(
)(lg82.13lg9.333.46
d h
hah f L
b
mbb
−+
−−+=
d :Distance from base station(km)
f :Frequency(MHz)
L b :Mean path loss in urban areas (dB)
hb!hm:Base station and mobile antenna effective
height.
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General Model
The model is given by
K1K2K3K4K5K6 are correction
factors' is a series of clutter correction factors.
These correction factors can be corrected based on
the practical test data.
Clutter
K
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ZTE Models for Extended Coverage
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The Application of the Propagation Model in
Cellular Design
In order to predict the base stations coverage radius and
received power we can use this function:
bf r t r t t r L L LGG P P +−−++=
received power, transmitting power
receive antenna gain , transmitting antenna gain
forward and reverse link feed line loss
path loss
)(dBm P r )(dBm P t
)(dBGr )(dBGt
)(dB Lr )(dB Lt
)(dB Lbf
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Propagation Model Correction
The propagation decay rate in different
environment is different, such as in urban,suburban
and rural. We can choose different model and
correction factors. The prediction software provides
a model that we can correct its parameters using the
test data. The corrected model can improve the
simulation precision greatly.
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A citys digital map
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Propagation Model Applications
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Simulation results of the coverage
forward received power by mobile telephone reverse transmitting power by mobile telephone
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Simulation Results of the Extended Coverage
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