Survey of Radio Propagation Models for Mobile Communication

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Technical Seminar Presentation - 2004

Presented by :-Salini Patnaik(EC 200157231)

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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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Survey of Radio Propagation Models for Mobile Communication

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