This document discusses wireless communication propagation mechanisms and propagation models. It explains that when a signal hits an obstacle, it can be reflected, diffracted, or scattered depending on the surface properties. Propagation models are used to predict the average received signal power and design wireless systems by characterizing radio wave propagation based on factors like frequency and distance. Small-scale fading models predict power fluctuations over short ranges, while large-scale models predict average power decreases over large distances between transmitter and receiver.

1. WIRELESS COMMUNICATION
SERIES
Propagation Mechanisms
&
Propagation Models

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3. • Channel – Medium through which the signal is transferred from
one point to another
• Propagation – Tendency of EM Wave to travel from one place to
another place.
TRANSMITTER RECEIVER

4. -
When a Signal Hits the obstacle there are 3 possible effects that would happen
to the signal based on the surface on which the signal impinges, they are:
Reflection – Reflection occurs when the a propagating
wave impinges on a smooth objects that has a very
large wavelength when compared to the wavelength of
the wave. Eg:. Earth and Buildings
Diffraction – Diffraction occurs when there are sharp
edges between the transmitter and the receiver. The
diffracted wave spreads all over the space and creates
bending of signal
Scattering – Scattering occurs when the propagating
wave impinges on a rough surface or irregular
surfaces that have more number of obstacles per unit
volume.

5. • All these propagation mechanisms have different effects on the
propagating radio waves.
What
amount of
Signal do I
receive?

6. • Basically there are two ways to predict the amount of received
signal after propagation at the receiver side.
An empirical
method involves the
use of objective,
quantitative observation
in a systematically
controlled, replicable
situation, in order to
test or refine a theory.
EMPERICAL METHOD PROPAGATION MODEL
mathematical formula
tion for the
characterization
of radio
wave propagation as
a function of frequency,
distance and other
conditions.

7. -
• With Propagation models it is easy to design, simulate and Plan
the wireless systems.
• Propagation models reflect the properties of the propagation
channel
• Since the wireless channel characteristics are dynamic in nature
one single model cannot be defined for estimating the wireless
systems.
• Modelling a radio channel decides the coverage area,
modulation schemes to be used to optimize communication
parameters

8. • Different models have been developed to meet the needs of
realizing the propagation behaviour in different fading conditions.
FADING
SMALL SCALE
FADING
LARGE SCALE
FADING
When the user moves over a
small distance, the
instantaneous received
signal strength fluctuates
rapidly giving raise to Small
Scale Fading.
Small Scale Fading Models
are used to predict the Avg.
Received power at the
receiver when the receiver
moves over a short range,
(Within a room)
When the user moves over
a large distance, the
average received signal
strength gradually
decreases. This
phenomenon is referred to
as Large Scale Fading.
Large Scale Fading
Models are used to predict
the Avg. Received power at
the receiver when the
distance between the Tr.
And Rx. Increases.

9. SMALL SCALE FADING
LARGE SCALE FADING

10. Introduction
Propagation Mechanisms
Propagation Models
Uses of Prop. Models
Small & Large Scale Fading
S U B S C R I B E