Multipath distortion

In applications where more than one propagation path will exist, the interaction of the signals from these multiple paths at the receiver (multipath propagation) gives rise to significant distortion of the received data symbols.

The same source signal, arriving by a different route, will experience a different path length and hence a different propagation delay. This difference in delay will result in different phases between the two received signals. If the phase difference approaches 180o then the signals will in fact partially cancel each other, while if the phase difference approaches 0o they will reinforce.