1. Wave Propagation Models
Principles &
Scenarios
© 2012 by AWE Communications GmbH
www.awe-com.com

2. Contents
• Wave Propagation Model Principles
- Multipath propagation
- Reflection
- Diffraction
- Scattering
- Antenna pattern
© by AWE Communications GmbH 2

3. Wave Propagation Models
Multipath Propagation
• Multiple propagation paths Rx
between Tx and Rx
Tx
• Different delays and attenuations
• Destructive and
constructive interference
Superposition of multiple paths
No line of sight (Rayleigh fading) Line of sight (Rice fading)
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4. Wave Propagation Models
Multipath Propagation
• Superposition of multiple paths leads to fading channel
• Fast fading due to random phase variations
• Slow fading due to principle changes in the propagation channel (add. obstacles)
Example of a
measurement
route
• Fast fading (green)
• Slow fading (red)
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5. Wave Propagation Models
Propagation Model Types
• Empirical models (e.g. Hata-Okumura)
• Only consideration of effective antenna height (no topography between Tx and Rx)
• Considering additional losses due to clutter data
• Semi-Empirical models (e.g. Two-Ray plus Knife-Edge diffraction)
• Including terrain profile between Tx and Rx
• Considering additional losses due to diffraction
• Deterministic models (e.g. Ray Tracing) 2D Vertical plane
• Considering topography Tx 3D Paths
• Evaluating additional obstacles
Rx1
Rx2
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6. Wave Propagation Models
Basic Principle – Reflection I
• Reflections are present in LOS regions and rather limited in NLOS regions
• Refection loss depending on:
- angle of incidence
- properties of reflecting material: permittivity, conductance, permeability
- polarisation of incident wave
- Fresnel coefficients for modelling the reflection
Ei
r
Ei i Er
Er
i r
Material 1
1 , 1 , 1
n
QR Material 2
 2 ,  2,  2
Et
t
Et t
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7. Wave Propagation Models
Basic Principle – Reflection II
• Fresnel coefficients for modelling the reflection:
Polarisation parallel to Polarisation perpendicular to
plane of incidence plane of incidence
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8. Wave Propagation Models
Basic Principle – Breakpoint
130
• Free space: Two path model
Free space model
received power ~ 1 / d2
120
 20 dB / decade
• No longer valid from 110
a certain distance on Path Loss [dB]
• After breakpoint:
100
received power ~ 1 / d4
 40 dB / decade
90
• Deduced from 80
two-path model, i.e.
superposition of direct 70
and ground-reflected rays:
0,1 0,3 1,0 3,16 10,0
BP = 4htxhrx/ Distance [km]
Loss for 900 MHz and Tx height of 30m (Rx height 1.5m)
breakpoint distance = 1.7 km
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9. Wave Propagation Models
Basic Principle – Transmission I
• Transmissions are relevant for penetration of obstacles (as e.g. walls)
• Transmission loss depending on:
- angle of incidence
- properties of material: permittivity, conductance, permeability
- polarisation of incident wave
- Fresnel coefficients for modelling the transmission
Ei
r
Ei i Er
Er
i r
Material 1
1 , 1 , 1
n
QR Material 2
 2 ,  2,  2
Et
t
Et t
© by AWE Communications GmbH 9

10. Wave Propagation Models
Basic Principle – Transmission II
• Fresnel coefficients for modelling the transmission:
• Penetration loss includes two parts:
- Loss at border between materials
- Loss for penetration of plate
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11. Wave Propagation Models
Basic Principle – Diffraction I
• Diffractions are relevant in shadowed areas and are therefore important
• Diffraction loss depending on:
- angle of incidence & angle of diffraction
- properties of material: epsilon, µ and sigma
- polarisation of incident wave
- UTD coefficients with Luebbers extension for modelling the diffraction
k
QD
i
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12. Wave Propagation Models
Basic Principle – Diffraction II
• UTD coefficients with Luebbers extension for modelling the diffraction
• Fresnel function F(x)
• Distance parameter L(r) depending on type of incident wave
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13. Wave Propagation Models
Basic Principle – Diffraction III
• Uniform Geometrical Theory of Diffraction (3 zones: NLOS, LOS, LOS + Refl.)
Diffractions are relevant
in shadowed areas
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14. Wave Propagation Models
Basic Principle – Knife-Edge Diffraction I
• According to Huygens-Fresnel principle the obstacle acts as secondary source
• Epstein-Petersen: Subsequent evaluation from Tx to Rx (first TQ2 then Q1R)
• Deygout: Main obstacle first, then remaining obstacles on both sides
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15. Wave Propagation Models
Basic Principle – Knife-Edge Diffraction II
• Additional diffraction losses in shadowed areas are accumulated
• Determination of obstacles based on Fresnel parameter
• Similar procedure as for Deygout model (start with main obstacle)
• Example:
Height in m
Distance in 50m steps
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16. Wave Propagation Models
Basic Principle – Scattering
• Scattering occurs on rough surfaces
• Subdivision of terrain profile into numerous scattering elements
• Consideration of the relevant part only to obtain acceptable computation effort
Low attenuation if incident angle
• Example: Ground properties equals scattered angle: Specular
reflection
Absorber
Ground
Measurement results: RCS with respect to incident Measurement setup
angle alpha and scattered angle beta (independent
of azimuth)
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17. Wave Propagation Models
Consideration of Antenna Patterns
• Manufacturer provides 3D antenna pattern
• Manufacturer provides antenna
gains in horizontal and vertical plane
Kathrein K 742212
Z
G 

1
Bilinear interpolation of 3D antenna characteristic G G


  1
2
 12  
 G   2G1   G  2G1  1 2 2
2  1  2
2
 1  2  1   2 
1 2  X
G  ,   
 
   
G
1  2  1 2 2  1  2  1 2 2 -Y
1  2  1  2 
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