Wave Propagation Model Principles - AWE-Communications

Wave Propagation Models 

Principles & 

Scenarios 

© 2012 by AWE Communications GmbH 

www.awe-com.com

Contents 

• Wave Propagation Model Principles 

- Multipath propagation 

-Reflection 

- Diffraction 

- Scattering 

- Antenna pattern 

© by AWE Communications GmbH 2


Multipath Propagation 

• Multiple propagation paths 

between Tx and Rx 

• Different delays and attenuations 

• Destructive and 

constructive interference 

Tx 

Rx 

Superposition of multiple paths 

No line of sight (Rayleigh fading) 

Line of sight (Rice fading) 



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) 



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) 

• Considering topography 

• Evaluating additional obstacles 

Tx 

2D Vertical plane 

3D Paths 

Rx1 

Rx2 



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 

E 

i 

E 

i 

 

i 

 

i 

 

r 

E 

r 

E 

n 

 

r 

r 

Material 1 

, , 

1 

1 

1 

Q R 

 

t 

E 

E t t 

t 

Material 2 

, , 

2 

2 

2 



Basic Principle – Reflection II 

• Fresnel coefficients for modelling the reflection: 

Polarisation parallel to 

plane of incidence 

Polarisation perpendicular to 

plane of incidence 



Basic Principle – Breakpoint 

• Free space: 

received power ~ 1 / d 2 

20 dB / decade 

130 

120 

Two path model 

Free space model 

• No longer valid from 

a certain distance on 

• After breakpoint: 

received power ~ 1 / d 4 

40 dB / decade 

Path Loss [dB] 

110 

100 

90 

• Deduced from 

two-path model, i.e. 

80 

superposition of direct 

and ground-reflected rays: 

BP = 4h tx h rx / 

70 

0,1 

0,3 

1,0 3,16 10,0 

Distance [km] 

Loss for 900 MHz and Tx height of 30m (Rx height 1.5m) 

breakpoint distance = 1.7 km 



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 


- Fresnel coefficients for modelling the transmission 

E 

i 

E 

i 

 

i 

 

i 

 

r 

E 

r 

E 

n 

 

r 

r 

Material 1 

, , 

1 

1 

1 

Q R 

 

t 

E 

E t t 

t 

Material 2 

, , 

2 

2 

2 



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 



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 


- UTD coefficients with Luebbers extension for modelling the diffraction 

Q D 

i 

k 



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 



Basic Principle – Diffraction III 

• Uniform Geometrical Theory of Diffraction (3 zones: NLOS, LOS, LOS + Refl.) 

Diffractions are relevant 

in shadowed areas 



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 



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 



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 

• Example: Ground properties 

Low attenuation if incident angle 

equals scattered angle: 

Specular reflection 

Absorber 

Measurement results: RCS with respect to incident 

angle alpha and scattered angle beta 

(independent of azimuth) 

Measurement setup 

Ground 



Consideration of Antenna Patterns 

• Manufacturer provides 3D antenna pattern 

• Manufacturer provides antenna 

gains in horizontal and vertical plane 

Kathrein K 742212 

G 

Z 

Theta 

Bilinear interpolation of 3D antenna characteristic 

 

 

G , 

 

1 2 1 2 

1G2 2G1 1G2 2G1 

 

2 2 

1 2 1 2 

 

 

1 2 1 2 

12 12 

 

2 2 

1 2 1 2 

 

G 

-Y 

 

2 

1 

G 

1 

2 

G 

Phi 

X

Wave Propagation Model Principles - AWE-Communications

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