Communication method and system using multi-antenna in network including transmitter, receiver and relay

A communication method of a relay using a multi-antenna in a network which has a transmitter, a receiver and a relay includes: a step of performing singular value decomposition for a channel matrix which includes a first channel matrix between the transmitter and relay and a second channel matrix between the transmitter and receiver; a step of obtaining a first matrix which corresponds to the first channel matrix and a second matrix which corresponds to the second channel matrix from a left singular matrix calculated from the singular value decomposition; a step of controlling a power amplification factor of the relay using the first and second matrices; and a step of amplifying a first transmission signal received from the transmitter using the power amplification factor. [Reference numerals] (310) Decomposing a channel matrix feature value; (320) Acquiring the first and second matrices; (330) Controlling the amplification factor; (340) Amplifying the first transmission signal