Wave propagationmodels
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The document discusses principles of wave propagation models. It covers topics like multipath propagation, reflection, diffraction, scattering, and antenna patterns. Multipath propagation results in fading due to multiple signal paths combining constructively and destructively. Reflection, transmission, and diffraction losses are determined by factors like the incident angle and material properties. Scattering occurs on rough surfaces. Antenna patterns are considered using data from manufacturers.
![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• No longer valid from 110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 = 4htxhrx/ Distance [km]
Loss for 900 MHz and Tx height of 30m (Rx height 1.5m)
breakpoint distance = 1.7 km
© by AWE Communications GmbH 8](https://image.slidesharecdn.com/wavepropagationmodels-120920010922-phpapp01/85/Wave-propagationmodels-8-320.jpg)
Wave propagationmodels
- 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) © by AWE Communications GmbH 3
- 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) © by AWE Communications GmbH 4
- 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 © by AWE Communications GmbH 5
- 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 © by AWE Communications GmbH 6
- 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 © by AWE Communications GmbH 7
- 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 = 4htxhrx/ Distance [km] Loss for 900 MHz and Tx height of 30m (Rx height 1.5m) breakpoint distance = 1.7 km © by AWE Communications GmbH 8
- 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 © by AWE Communications GmbH 10
- 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 © by AWE Communications GmbH 11
- 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 © by AWE Communications GmbH 12
- 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 © by AWE Communications GmbH 13
- 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 © by AWE Communications GmbH 14
- 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 © by AWE Communications GmbH 15
- 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) © by AWE Communications GmbH 16
- 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 12 G 2G1 G 2G1 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 © by AWE Communications GmbH 17