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By-
Dr. Jesmin Akhter
Professor
Institute of Information Technology
Jahangirnagar University
Wireless and Mobile Communication
ICT-4203
Fading Distributions
• Describes how the received signal amplitude changes with time.
• Remember that the received signal is combination of multiple signals
arriving from different directions, phases and amplitudes.
• With the received signal we mean the baseband signal, namely the
envelope of the received signal (i.e. r(t)). (The envelope of
an oscillating signal is a smooth curve outlining its extremes)
• Fading Distribution is a statistical characterization of the multipath fading.
This fading characteristics of a mobile radio signal are described by the
following three statistical distributions -
• Rician Distribution
• Rayleigh Distribution
• Lognormal Distribution
Rayleigh Distributions
• Describes the received signal envelope distribution for channels,
where all the components are non-LOS:
• i.e. there is no line-of–sight (LOS) component.
Rayleigh Fading Distribution
• The Rayleigh distribution is commonly used to describe the statistical time
varying nature of the received envelope of a flat fading signal, or the
envelope of an individual multipath component.
• The Rayleigh distribution is given as:
•  is the rms value of the received voltage before envelope detection, 2 is
the time-average power/local average power of the received signal before
envelope detection and r2 is instantaneous power.
p r
r r
r
r
( )
exp( )

   






 
2
2
2
2
0
0 0
Ricean Distributions
• Describes the received signal envelope distribution for
channels where one of the multipath components is LOS
component.
• i.e. there is one LOS component.
Ricean Fading Distribution
• When there is a dominant stationary signal component present, the small-scale
fading envelope distribution is Ricean. The effect of a dominant signal arriving
with many weaker multipath signals gives rise to the Ricean distribution.
• The Ricean distribution degenerates to a Rayleigh distribution when the
dominant component fades away.
• The Ricean distribution is often described in terms of a parameter K which is
defined as the ratio between the deterministic signal power and the variance of
the multipath.
• K is known as the Ricean factor
• As A0, K  - dB, Ricean distribution degenerates to Rayleigh distribution.













0
0
0
,
0
)
(
]
2
)
(
exp[
)
( 2
0
2
2
2
2
r
A
r
Ar
I
A
r
r
r
p 


K
A

2
2
2
PDF
• Probability density function of Ricean distributions: K=-∞dB
(Rayleigh) and K=6dB. For K>>1, the Ricean pdf is approximately
Gaussian about the mean.
• Propagation path-loss models play an important role in the design
of cellular systems to specify key system parameters such as
transmission power, frequency, antenna heights, and so on.
• Several models have been proposed for cellular systems operating in
different environments (indoor, outdoor, urban, suburban, rural).
• Okumura Model
• Hata Model
• Cost 231 Model
Propagation Path-Loss Models
• The Okumura model is a Radio propagation model that was built
using the data collected in the city of Tokyo, Japan.
• The model is ideal for using in cities with many urban structures but
not many tall blocking structures.
• The model served as a base for the Hata Model.
• Okumura model was built into three modes.
• Urban, suburban and open areas.
• The model for urban areas was built first and used as the base for
others.
Okumura model
50% of measured
values lie above
this threshold and
50% of measured
values lie below
this threshold value
Thank You

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Lecture 11

  • 1. By- Dr. Jesmin Akhter Professor Institute of Information Technology Jahangirnagar University Wireless and Mobile Communication ICT-4203
  • 2. Fading Distributions • Describes how the received signal amplitude changes with time. • Remember that the received signal is combination of multiple signals arriving from different directions, phases and amplitudes. • With the received signal we mean the baseband signal, namely the envelope of the received signal (i.e. r(t)). (The envelope of an oscillating signal is a smooth curve outlining its extremes) • Fading Distribution is a statistical characterization of the multipath fading. This fading characteristics of a mobile radio signal are described by the following three statistical distributions - • Rician Distribution • Rayleigh Distribution • Lognormal Distribution
  • 3. Rayleigh Distributions • Describes the received signal envelope distribution for channels, where all the components are non-LOS: • i.e. there is no line-of–sight (LOS) component.
  • 4. Rayleigh Fading Distribution • The Rayleigh distribution is commonly used to describe the statistical time varying nature of the received envelope of a flat fading signal, or the envelope of an individual multipath component. • The Rayleigh distribution is given as: •  is the rms value of the received voltage before envelope detection, 2 is the time-average power/local average power of the received signal before envelope detection and r2 is instantaneous power. p r r r r r ( ) exp( )              2 2 2 2 0 0 0
  • 5. Ricean Distributions • Describes the received signal envelope distribution for channels where one of the multipath components is LOS component. • i.e. there is one LOS component.
  • 6. Ricean Fading Distribution • When there is a dominant stationary signal component present, the small-scale fading envelope distribution is Ricean. The effect of a dominant signal arriving with many weaker multipath signals gives rise to the Ricean distribution. • The Ricean distribution degenerates to a Rayleigh distribution when the dominant component fades away. • The Ricean distribution is often described in terms of a parameter K which is defined as the ratio between the deterministic signal power and the variance of the multipath. • K is known as the Ricean factor • As A0, K  - dB, Ricean distribution degenerates to Rayleigh distribution.              0 0 0 , 0 ) ( ] 2 ) ( exp[ ) ( 2 0 2 2 2 2 r A r Ar I A r r r p    K A  2 2 2
  • 7. PDF • Probability density function of Ricean distributions: K=-∞dB (Rayleigh) and K=6dB. For K>>1, the Ricean pdf is approximately Gaussian about the mean.
  • 8.
  • 9. • Propagation path-loss models play an important role in the design of cellular systems to specify key system parameters such as transmission power, frequency, antenna heights, and so on. • Several models have been proposed for cellular systems operating in different environments (indoor, outdoor, urban, suburban, rural). • Okumura Model • Hata Model • Cost 231 Model Propagation Path-Loss Models
  • 10. • The Okumura model is a Radio propagation model that was built using the data collected in the city of Tokyo, Japan. • The model is ideal for using in cities with many urban structures but not many tall blocking structures. • The model served as a base for the Hata Model. • Okumura model was built into three modes. • Urban, suburban and open areas. • The model for urban areas was built first and used as the base for others. Okumura model
  • 11. 50% of measured values lie above this threshold and 50% of measured values lie below this threshold value
  • 12.
  • 13.
  • 14.
  • 15.
  • 16.
  • 17.

Editor's Notes

  1. 2
  2. 3
  3. 4
  4. 5
  5. 6
  6. 7
  7. Clutter is a term used for unwanted echoes in electronic systems, particularly in reference to radars. Such echoes are typically returned from ground, sea, rain, animals/insects, chaff and atmospheric turbulences, and can cause serious performance issues with radar systems.
  8. If a child's weight is at the 50th percentile line, that means that out of 100 normal children her age,  50 will be bigger than she is and 50 smaller. Similarly, if she is in the 75th percentile, that means that she is bigger than 75 children and smaller than only 25, compared with 100 children her age
  9. Quasi-public space" is land that is open to all comers but which is under private ownership – classically, the public areas of shopping centres. As the law stands, owners of quasi-public space have absolute discretion over who can enter their property and what they can do there. Empirical studies: It is a way of gaining knowledge by means of direct and indirect observation or experience.