L6 Flashcards
What are the two ways a propagation path can vary?
The propagation path can vary from line-of-sight (LOS) to obstructed indoor space (OBS)
Which wireless communication model is applicable for a case where the receiver is in the far-field of the transmitting antenna?
Free space propagation model
What is the difference between the free space propagation model and generic log-distance path loss model?
Generic Log-Distance Path Loss Model: The signal strength drops logarithmically with distance
Free Space Propagation: power falls off based on a power law function
What is the reflection model?
Two-ray ground reflection model
What affects propagation?
Reflection: waves are reflected partially or fully
Diffraction: caused by sharp objects that intervene in the path
Scattering: when incident on a rough surface a wave is scattered not just reflected, due to energy being diffused in all directions
What is the broad use of the knife-edge model?
Knife-edge model is broadly used to determine the order of magnitude of diffraction loss
How much power loss is expected when the receiver moves away by a few meters?
30db to 40db
What is the radio channel capacity theorem?
Radio channel capacity (Shannon’s theorem): C = B log 2 ( 1 + S/N)
o C is in bps
o B is the RF bandwidth
o S/N is the signal to noise ratio
Why is the free space model useful?
It sets the minimum power required
How can noise be combatted for radio channels?
By tuning the signal to balance out the signal noise ratio, assuming the power limit is not used
