Reflection Diffraction and Scattering in wireless communication
Reflection in wireless communication
- Reflections Occurs when a wave impinges upon a smooth surface.
- Dimensions of the surface are large relative to l.
- Reflections occur from the surface of the earth and from buildings and walls.
Diffraction in wireless communication
- Diffraction Occurs when the path is blocked by an object with large dimensions relative to l and sharp irregularities (edges).
- Secondary “wavelets” propagate into the shadowed region.
- Diffraction gives rise to bending of waves around the obstacle.
Scattering in wireless communication
- Scattering Occurs when a wave impinges upon an object with dimensions on the order of l or less, causing the reflected energy to spread out or“scatter” in many directions.
- Small objects such as street lights, signs, & leaves cause scattering
MultiPath in wireless communication
- Multiple Waves Create “Multipath”
- Due to propagation mechanisms, multiple waves arrive at the receiver
- Sometimes this includes a direct Line-of-Sight (LOS) signal
Multipath Propagation in wireless communication
- Multipath propagation causes large and rapid fluctuations in a signal
- These fluctuations are not the same as the propagation path loss.
Multipath causes three major things in wireless communication
- Rapid changes in signal strength over a short distance or time.
- Random frequency modulation due to Doppler Shifts on different multipath signals.
- Time dispersion caused by multipath delays
- These are called “fading effects
- Multipath propagation results in small-scale fading.
Now you understand diffraction has what affect on a wireless signal’s propagation?.