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Survey of Radio Propagation Models forMobile Communication
Presented bySalini Patnaik
Roll# EC200157231
AtNIST,Berhampur
Under the guidance of
Mr. Rowdra Ghatak
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High-tier
Low-tier
Satellite
High Mobility Low MobilityWide Area
Regional Area
Local Area
Different Communication System
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INTRODUCTION:
Various propagationmodels can actually address
both problems.
BAS E
STATIONRADIO
TOWER
The objective here is to
design a suitable receiver
that
will receive the transmitted
signal, distorted due to themultipath and dispersion
effects of the channel, and
that will decode the
transmitted signal.
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DEFINITIONS AND TERMINOLOGIES
Path Loss:
Where Ptand P
rthe transmitted and received power
Power Delay Profile:
Where h(t) = impulse response
Time-Delay Spread
Coherence Bandwidth: Bc=1/50 RMS
Where BC = Coherence bandwidth
RMS = RMS Delay
r
t
PPlog10)dB(PL =
=dt|)t(h|
|)t(h|)t(P
2
2
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TYPES OF FADING:
Large-scale fading Frequency-selective fading Flat fading Fast fading and slow fading
BASIC PROPAGATION MECHANISMS :
Reflection
Diffraction Scattering
Transmissionthrough a
dielectric slab
TR
1st Fresnel zone
ObstructionDiffraction
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OUTDOOR CASE
OKUMURA et al MODEL
L50
(db) = LF
+Amu
(f,d)-G(hte) - G(h
re)-G
AREA
Where
L50
is the median value of the propagation path loss
LF
is the free-space propagation loss
Amu, is the median attenuation in the medium relative to free space at frequencyf
dcorresponds to the distance between the base and the mobile unit.G(h
te) and G(h
re) are the gain factors for the BTS antenna and the MS antenna.
hte
and hre
are the effective heights (in meters )of the BTS and the MS antennae.
GAREA
is the gain generated by the environment in which the system is operating.
EMPIRICAL OR STATISTICAL MODELS FOR PATH LOSS
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HATA MODEL
L50 (urban)(dB) = 69.55 + 26.16log fc - 13.82 log hre -a(hre,)
+ (44.9 - 6.55 log hre)logd
Where
fcis the frequency (in MHz), which varies from 150 MHz to 1500MHz.
hte
and hre
are the effective heights of the base-station and the mobile
antennas (in meters), respectively.
d is the distance from the base station to the mobile antenna,
a(hre) is the correction factor for the effective antenna height of the mobile
unit, which is a function of the size of the area of coverage.
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COST-231-Walfisch-lkegami Model
Where
L0
represents the free-space loss.
Lrts is the roof-top-to-street diffraction andscattering loss.
Lmsd
is the multi-screen diffraction loss.
+>+++
=0LLL
0LLLLLL
msdrts0
msdrtsmsdrts0b
for
for
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INDOOR CASE
It can be affected by the layout in a building.
When electromagnetic radiation is incident on a wall or
a flow in an oblique fashion, less power will be
transmitted through the wall than would occur at normal
incidence .
Transmitter
Propagation in Indoor Case
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SITE-SPECIFIC MODELS FOR PATH LOSS
RAY-TRACING TECHNIQUE Technique based on Geometrical Optics (GO) Fermat principle and the principle of the local field are two
basic concepts extensively used by the ray models . The Fermat principle states that a ray follows the shortest path
from a source point to a field point. The principle of the local field states that the high-frequency
rays produce reflection, refraction, and diffraction when
hitting a surface.
Two types of ray-tracing methods :Image methodBrute-force ray-tracing method
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Image Method
This method generates the images
of a source at all planes These images then serve as
secondary sources for thesubsequent points of reflections.
It can only handle simpleenvironments.
Ground reflections and rays overrooftops are neglected .
A threshold must be set with
respect to the number and order ofreflection and diffraction rays thatcan be considered.
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Brute-Force Ray-Tracing Method
This method considers a
bundle of transmitted rays
that may or may not reach
the receiver.
A finite sample of the
possible directions of the
propagation from the
transmitter is chosen. A
ray is launched for each
such direction.
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There are two kinds of methods to obtain the rays at the sourcepoint.
2D ray tracing approach:At the source, rays are launched along
different directions with the same sector angle, , in a plane . An intersection with a surface of an object is represented by a
node in the tree. The incident ray is decomposed into an object-reflected ray and
an object-penetrated ray . 3D ray tracing approach:The transmitter and receiver are
modeled as point sources . In order to determine all possible rays that may leave the
transmitter and arrive at the receiver in three dimensions, all
possible angles of departure and arrival at the transmitter and
receiver are considered.
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Applicable when transmitting and receiving antennas are
often inevitably installed close to structures with complex
material .
properties for which no asymptotic solutions are available.
Advantages of the FDTD method are its accuracy. It also
gives signal-coverage information throughout a given area
Disadvantage of FDTD is that it requires large amounts of
computer memory.
FDTD modelFDTD model
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Moment-Method Models
Method of Moments(MOM) model is better when higher
precision is required and when the size of the buildings is
smaller.
Due to limitations of computer memory and CPU time,the
MOM is usually applied for analyzing objects that are tens of
wavelengths in size.
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Artificial Neural-Network Models
Key feature of the neural network is the intrinsic parallelism,allowing for fast evaluation of the solutions .
The inputs were the frequency, the heights of the antenna forthe base and mobile stations, respectively, and the distances
between them. The output was the field strength. Multilayered ANN suffers from slow convergence and
unpredictable solutions during learning . Radial-basis function (RBF) neural networks that have a
linear-in-the parameters representation were proposed to
overcome multilayered ANN problem.
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Vector Parabolic-Equation Model As a parabolic version of Maxwells equations, it allows
a full treatment of three-dimensional electromagnetic
scattering . Fast Far-Field Approximation Model
The method has been applied to gently undulating
terrains and more hilly terrain. Waveguide Model
In large metropolitan areas the city streets act as a type of
wave-guiding structure for the propagating signal . the statistical propagation characteristics in such a
Waveguide are expressed in terms of multiple ray fields
approaching the observer.
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Boltzmann Model
It describes a physical system in terms of the motion of
fictitious microscopic particles on a lattice . MODELS FOR SMALL SCALE FADING
Ricean Distribution:
Where
ris the amplitude of the envelope of the received signal,
2 2 is the predicted mean power of the multipath signalA denotes the peak amplitude of the dominant signal, and
Io (Ar/ 2) is the modified Bessel function of the first kind
Rayleigh Distribution:
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