and the reflection wave may strengthen the signal, or weaken the signal, which is known as multi-path effect. Diffraction wave is the main radio wave signal source for shadow areas such building interior.
Ionosphere reflection propagation:
When the wavelength of the radio wave is less than 1m (frequency is greater than 300MHz), the ionosphere is the reflector. There may be one or multiple hops in the radio wave reflected from the ionosphere, so this propagation is applicable to long-distance communication. Like the troposphere, the ionosphere also presents the continuous fluctuation feature.