Gain
Cisco measures gain in dBi, which stands for decibel isotropic and is a
measure of decibels relative to an isotropic source in free space. A decibel is
the ratio between two signal levels. An isotropic antenna is a theoretical one
in which the signal spreads out evenly in all directions from one point. Thus,
dBi is the ratio of an antenna’s signal to that of an isotropic antenna.