1. ECE637 : Fundamentals of Wireless Communications
Lecture 2:
Wireless propagation
Aliazam Abbasfar

2. Outline Class arrangements Radio propagation and fading
Path loss models

3. Radio propagation and fading
Rays coming from different paths
Reflections
Refractions
scattering
Large scale fading
Path loss
shadowing
Small scale fading
Multi-path fading
Slow
Pr/Pt
Very slow
Fast d

4. Path loss models Maxwell’s equations Ray tracing Empirical models
Too complex
Ray tracing
Site-specific
Empirical models
Simplified model

5. Free space model (LOS) For each ray free space model applies
Signal attenuation and delay
Electric far field is inversely proportional to distance and proportional to l
Path loss :

6. Two-path propagation Ground reflection
Ground bounce approximately cancels LOS path above critical distance
RX power
Power falls off Proportional to d4 and independent of l (f)

7. Ray tracing Models all signal components Reflections Scattering
Diffraction
More info needed
detailed geometry
dielectric properties
Simpler than Maxwell’s equations

8. Empirical models Statistical models Based on measurements
Predicts local mean signal power
Based on measurements
Okumura
Hata …
Simplified model
d < d0 : near-field
g : path loss exponent

9. Shadowing Variation in large scale path loss Statistical modeling
Blockage
Reflection, refraction, and scattering
Statistical modeling
Log-normal distribution
Verified empirically for both indoor and outdoor
Two parameters : m and s

10. Outage probability/Cell coverage
Outage probability ( at a given distance)
Probability received power below given minimum
pout( Pmin, d) = p(pr(d) <Pmin ) = p(PL > pt-Pmin )
Cell coverage

11. Reading
Ch. 2 Goldsmith
Ch. 2 Tse