Disclosed is a method of transmitting signals by a transmitting side device having multiple antennas. In this method, the transmitting side device spatially modulates information to be transmitted, where the information is spatially modulated to be represented based on which antennas among the N antennas are selected to be used for transmission. And, the transmitting side device transmits the spatially modulated information through the selected antennas. Here, the number of the selected antennas for transmitting one transmission information unit (hereinafter, ‘M’ where M≤N) is plural. And, different sequence of the selected antennas represents different information to be transmitted.