Summary of Path Loss in Propagation Narayan Mandayam
- Slides: 12
Summary of Path Loss in Propagation Narayan Mandayam
Understanding RF Propagation Goals 1. Estimate radio coverage area 2. Estimate link performance 3. Estimate network design parameters 1. Transmitters and their location 2. Transmit power 3. Antenna type
Interesting Scenarios At which locations will correct reception take place?
Antenna Basics Isotropic 0 d. Bi Dipole 2. 2 d. Bi High gain directional 14 d. Bi
Free Space Propagation Model PR PT Isotropic power density d Power density along the direction of maximum radiation Power received by Antenna Predict received signal strength when the transmitter and receiver have a clear line-of-sight path between them Also known as Friis free space formula
Path Loss (relative measure) PR Pt f is in MHz d is in Km Path Loss represents signal attenuation (measured on d. B) between the effective transmitted power and the receive power (excluding antenna gains)
Path Loss (Example) PR Pt Assume that antennas are isotropic. Calculate receive power (in d. Bm) at free space distance of 100 m from the antenna. What is PR at 10 Km? 50 W = 47 d. Bm 59 -20 (for d = 0. 1) 20 (for d = 10)
Path Loss (another example)
Path Loss (another example)
Radio propagation: path loss near field path loss in 2. 4 Ghz band Pr r 8 m Pt near field r Pr r 2 path loss = 10 log (4 r 2/ ) = 58. 3 + 10 log (r 3. 3 /8) r > 8 m far field r 3. 3 r 8 m r > 8 m
Indoor Signal Measurement
Outdoor P 2 P Link Signal Measurement
