A communication system that has two or more paths or channels. The outputs of these are combined to give a single received signal and thus reduce the effects of fading. The diversity gain is the gain in reception achieved by using a diversity system.

Frequency diversity employs independent transmission channels on neighbouring frequencies. Space diversity employs several receiving antennas spaced several wavelengths from each other. In both cases each antenna supplies its own receiver; the demodulated outputs are then combined. Polarization diversity uses antennas that are arranged to receive oppositely polarized waves. Time diversity transmits the signal more than once at different times.