What does the term 'echo' refer to in wireless communication?

In wireless communication, the term 'echo' specifically refers to a reflected signal that arrives back at the receiver after a delay. This phenomenon occurs when a transmitted signal bounces off a surface, such as a building or terrain, and travels back to the receiver. The delayed return of this reflected signal can cause confusion in communication systems, as it adds to the original signal and may create distortions or overlapping of information. Therefore, understanding echoes is crucial for improving signal clarity and reducing interference in various wireless applications.

Other options relate to different concepts in communication. Redundant transmission refers to sending the same data multiple times for reliability, interference pertains to the disruption caused by competing signals, and amplification involves increasing the power of a signal rather than reflecting it. In contrast, the core aspect of 'echo' is its nature as a delayed reflection of a signal.