In Wireless communications, two types of diversities are used.
1 . Frequency Diversity: Here signal is transmitted on two different frequencies and signals from both carriers combined at receiver end to recover it. Space attenuation is different for different frequencies. If one frequency is attenuated, the other one is strong enough to be used at receiver end and addition of two produces good signal.
2 . Space Diversity: Due to changes in the environment, signal is bent in the vertical direction. On receiver side two antennae are installed on tower with a space between them receiving same frequency and their signals are combined together for good quality.