Diversity gain is the increase in signal-to-interference ratio due to some diversity scheme, or how much the transmission power can be reduced when a diversity scheme is introduced, without a performance loss. Diversity gain is usually expressed in decibels, and sometimes as a power ratio. An example is soft handoff gain. For selection combining N signals are received, and the strongest signal is selected. When the N signals are independent and Rayleigh distributed, the expected diversity gain has been shown to be ∑ k = 1 N 1 k {\displaystyle \sum _{k=1}^{N}{\frac {1}{k}}} , expressed as a power ratio.
See also Array gain Diversity combining
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