Disclosed is a signal transmission method. The signal transmission method includes the steps of: setting a default value for generating a beamforming vector to be used for precoding; performing a calculation process of an outer layer for determining whether an accuracy of an energy efficiency satisfies a first threshold value range during a dual layer calculation process for maximizing an energy efficiency of a base station; performing a calculation process of an inner layer for calculating a predetermined second threshold value on which deterministic equivalence of a channel gain matrix coverage; generating a beamforming vector on the basis of values used in the calculation process of the outer layer and the calculation process of the inner layer, when the accuracy of the energy efficiency satisfies the first threshold value range in the calculation process of the outer layer; generating a transmission signal using the beamforming vector; and transmitting the generated transmission signal.