C cf radio propagation theory and propagation models

Radio Propagation Theory
ISSUE 2.1

The radio propagation theory is an important
lesson in the radio communication
curriculum. This lesson answers the following
questions:
How are radio waves transmitted from one
antenna to the other antenna?
What features does the radio wave have
during the propagation? Which factors affect
the propagation distance?
What fruits are achieved by predecessors in
the radio wave propagation theory? How to
apply the theory to practice?

Target
By learning this lesson, you would understand:
 Propagation modes of radio waves
 Classification of radio propagation environment
 Radio propagation models

Chapter 1 Radio Propagation TheoryChapter 1 Radio Propagation Theory
Chapter 2 Radio Propagation Environment
Chapter 3 Radio Propagation Models

300-3000GHz
EHFExtremely High
Frequency
30-300GHz
SHFSuper High Frequency3-30GHz
UHFUltra High Frequency300-3000MHz
VHFVery High Frequency30-300MHz
HFHigh Frequency3-30MHz
MFMedium Frequency300-3000KHz
LFLow Frequency30-300KHz
VLFVery-low Frequency3-30KHz
VFVoice Frequency300-3000Hz
ELFExtremely Low
Frequency
30-300Hz
3-30Hz
DesignationClassificationFrequency
Frequencies in different bands have
different propagation features.
Spectrum AllocationSpectrum Allocation

Irradiated wave and ground reflected wave
(most common propagation mode)
Tropospheric reflected wave
(The propagation is random to a great extent)
Diffracted wave (signal source for shaded
area)
Ionospheric reflected wave
(trans-horizon communication mode)
Propagation ModesPropagation Modes

① Building reflected wave
② Diffracted wave
③ Direct wave
④ Ground reflected wave

 Slow fading
 Slow fading occurs as the user moves and due to
shadowing by local obstructions. Power control will
overcome slow fading.
 Rapid fading
 Rapid fading occurs as signals received from
many paths drift into and out of phase.
− The fades are roughly
− 2 apart in space: 7 inches apart at 800 MHz, 3
inches apart at 1900 MHz
− Fades also appear in the frequency domain
and time domain
− Fades are typically 10-15 db deep,
occasionally deeper
− Rayleigh distribution is a good model for these
fades
Fading TypeFading Type

 Space diversity
 The main and diversity antennas are used
for reception.
 The fading of signals in the two ways is
irrelevant and is counted independently.
 The diversity distance D ranges from
wavelength 10 to 20
− 800M system, greater than 4 m
Key Technologies for CDMAKey Technologies for CDMA SystemSystem toto RelieveRelieve Fast FadingFast Fading

 Polarization diversity
 The dipole antenna which integrates two
directions of polarization is used.
 The multi-path A and B in two ways with
irrelevant fading feature are integrated into one
way signals. Two multi-path fingers A and B are
finally integrated into one path signals.
 Compared with the space diversity, the
polarization diversity saves the installation
space.
 Frequency diversity
 The bandwidth of the CDMA system is 1.23M.
It has the function of frequency diversity.
Key Technologies for CDMA System to Relieve Fast FadingKey Technologies for CDMA System to Relieve Fast Fading

 Rake receiver
Key Technologies for CDMA SystemKey Technologies for CDMA System to Relieve Fast Fadingto Relieve Fast Fading

Receiver
Finger 1
Finger 2
Finger 3
Searcher Delay
calculation
Combiner The combined
signal
tt
s(t) s(t)
 Rake receiver
 The RAKE receiver can relieve the multi-path fading and improve
the reception performance
Key Technologies for CDMA to Relieve Fast FadingKey Technologies for CDMA to Relieve Fast Fading

 Time diversity
 Interleave, detect and rectify codes. The continuous bit errors caused by
fading become incontinuous after interleaving, which makes it easy to
rectify errors.
Key Technologies for CDMA to Relieve Fast FadingKey Technologies for CDMA to Relieve Fast Fading

Problems
 Which are the key technologies for relieving multi-path?

Chapter 1 Radio Propagation Theory
Chapter 2 Radio Propagation EnvironmentChapter 2 Radio Propagation Environment
Chapter 3 Radio Propagation Models

Actual Coverage PlanningActual Coverage Planning
Radio Propagation Environment
What is different?
Please compare
with the following
knowledge points

The radio wave propagation is influenced by terrain and
artificial factors. The radio propagation environment
determines the propagation model directly.
 Main factors that influence the radio propagation environment:
 Terrain (Mountain, foothill, plain and water area)
 Number, distribution, material of artificial buildings (Artificial
environment)
 Vegetation of an area
 Weather
 Natural and artificial electromagnetic noises
 Artificial environment
 Urban areas, suburbs and rural areas

Propagation loss in free space
Ploss =32.4+20lgf(MHz)+20lgd(km)
If the frequency is specified, the formula can
be:
Ploss=L0+10lgd,  =2 path loss slope. In the
actual situation,  ranges from 3 to 5.
Propagation loss in even area
Ploss = L0+10lgd -20lghb - 20lghm
 =4 path loss slope
hb: height of base station antenna
hm: height of mobile station antenna
Propagation LossPropagation Loss

Propagation loss for quasi-flat terrain and anomalistic terrain
Quasi-flat terrains
The terrains ripple mildly and the ripple height is
less than 20 m.
Anomalistic terrains
The terrains exclude the quasi-flat terrains and
can be divided into the following:
Foothill, isolated mountain, versant and
terraqueous terrain
R
T
T
R

T
R
T
R
• Diffraction loss
• Penetration loss

¦ È
¦ È
¦ Å0¦ Ì 0 ¦ Å¦ Ì ¦ Å0¦ Ì 0
d
Dw1 w2
E1
E2
XdBmWdBm
Penetration LossX-W=B dBPenetration LossX-W=B dB Reflection and refraction of radio waves
after penetrating walls
Penetration LossPenetration Loss
 Indoor signal propagation depends on the penetration loss of buildings.
 The building materials have a great influence on the penetration loss.
 The angle of incidence of radio waves has a great influence on the
penetration loss.
 The higher the frequency is, the higher the penetration is.

penetrationpenetration LossLoss
 Object barrier/penetration loss:
 Wall partition barrier: 5–20dB
 Floor barrier: >20dB
 The indoor loss is the function of building height. The loss
decreases by 1.9dB for each ascending floor.
 Barrier of furniture and other obstacles: ： 2–15dB
 Thick glass: 6–10dB
 Penetration loss of the carriage: 15–30dB
 Penetration loss of the elevator: about 30dB
 Loss of flourishing leaves: 10dB

Chapter 1 Radio Propagation Theory
Chapter 2 Radio Propagation Environment
Chapter 3 Radio Propagation ModelsChapter 3 Radio Propagation Models

 The propagation models are used to forecast the
influences of terrains and artificial environments on
path loss
 The propagation models are the basis of
coverage planning. Good models ensure the
precision of planning.
 The radio propagation modules are affected by
the system working frequency. Different models
have different working frequency ranges, and the
ranges differ for indoor propagation models and
outdoor propagation models.
 When using the propagation models, pay
attention to the value set for each parameter.
Radio Propagation Models
Significance of radio Propagation ModelsSignificance of radio Propagation Models

Model Applicable Range
Okumura-Hata Macro cell forecast, 150-1500 MHz,
distance, 1-20km
Cost231-Hata 1500-2000 MHz, macro cell forecast
Walfish-lkegami 800-2000MHz (urban area), micro cell
forecast for urban areas with a dense
population
Keenan-Motley 800-2000MHz, indoor environment
forecast
One used in the
planning software
400-2000MHz, macro cell forecast
Common Propagation ModelCommon Propagation Model
Typical models are gradually studied out by scientists through the CW test dataTypical models are gradually studied out by scientists through the CW test data

Lp=69.55 + 26.16logf - 13.82loghb+(44.9 -6.55loghb)logd – A(hm)
For small and medium cities: A(hm)=(1.1logf - 0.7)hm - (1.56logf - 0.8)
For metropolises: A(hm)=3.2(log11.75hm) 2
－ 4.97
Okumura/Hata model
Lp f
bh
mh
d
mhA
Path loss (dB)
BS antenna height (m)
MS antenna height (m)
Carrier frequency (MHz)
Distance between BS and MS
(Km)
Correction factor of MS
antenna (dB)
The frequency ranges from 150MHZ to 1500MHZ

Cost231-Hata Model
mhbbp CAdhhfL m
+−−+−+= log)log55.69.44(log82.13log9.333.46
Cm ＝ 0dB Medium cities and central areas in suburbs
Cm ＝ 3dB Metropolises
The frequency ranges from 1500MHZ to 2000MHZ

Ordinary Planning Software Model ：
Lp=K1+K2lgd+K3(hm)+K4lg(hm)
+K5lg(Heff) +K6lg(Heff)lgd ＋
K7diffn+Kclutter
K1—Constant related to frequency (MHz) K2—Constant related to distance (km)
K3,K4—Correction factor of MS antenna height (m)
K5,K6—Correction factor of BS antenna height (m)
K7—Diffraction correction factor
Kclutter—Correction factor of clutter attenuation
d—Distance between BS and MS (km)
hm,Heff—Valid height of BS antenna and MS antenna (m)
The initial K factor is resulted from typical modulesThe initial K factor is resulted from typical modules

Problems
 What is the applicable range of the Okumura-Hata model?
 What are the differences between Okumura-Hata and Cost231-Hata?
 What is the significance of propagation models?

Conclusion
 Basic theory of radio propagation
 Classification of radio environments
 Traditional radio propagation models
SummarySummary

C cf radio propagation theory and propagation models

C cf radio propagation theory and propagation models

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