A method of processing signals in a distributed antenna system, the method comprising: receiving, by a Base Station, BS, Channel State Information, CSI, from N Mobile Stations, MSs, located within a coverage area of the BS or a coverage area of Relay Stations, RSs, connected to the BS; selecting a set of M MSs from among the N MSs that minimises a transmission capacity loss due to inter-signal interference; multiplying signals for transmission to the selected MSs by beamforming vectors by using the received CSI; transmitting, by the BS, the multiplied signals for transmission to the selected MSs; and simultaneously transmitting, by the RSs, respective multiplied signals to the selected MSs; wherein selecting the set of M MSs and multiplying the signals by the beamforming vectors comprise: selecting an MS with a largest sum of channel power; generating a beamforming vector for the MS with the largest sum of channel power by using CSI thereof; generating a beamforming vector orthogonal to the generated beamforming vector for the MS with the largest sum of channel power; detecting an MS for simultaneous signal transmission using the orthogonal beamforming vector; multiplying a signal to be transmitted to the MS with the largest sum of channel power by the beamforming vector; and multiplying a signal to be transmitted to the MS for simultaneous signal transmission by the orthogonal beamforming vector. receiving, by a Base Station, BS, Channel State Information, CSI, from N Mobile Stations, MSs, located within a coverage area of the BS or a coverage area of Relay Stations, RSs, connected to the BS; selecting a set of M MSs from among the N MSs that minimises a transmission capacity loss due to inter-signal interference; multiplying signals for transmission to the selected MSs by beamforming vectors by using the received CSI; transmitting, by the BS, the multiplied signals for transmission to the selected MSs; and simultaneously transmitting, by the RSs, respective multiplied signals to the selected MSs; wherein selecting the set of M MSs and multiplying the signals by the beamforming vectors comprise: selecting an MS with a largest sum of channel power; generating a beamforming vector for the MS with the largest sum of channel power by using CSI thereof; generating a beamforming vector orthogonal to the generated beamforming vector for the MS with the largest sum of channel power; detecting an MS for simultaneous signal transmission using the orthogonal beamforming vector; multiplying a signal to be transmitted to the MS with the largest sum of channel power by the beamforming vector; and multiplying a signal to be transmitted to the MS for simultaneous signal transmission by the orthogonal beamforming vector. selecting an MS with a largest sum of channel power; generating a beamforming vector for the MS with the largest sum of channel power by using CSI thereof; generating a beamforming vector orthogonal to the generated beamforming vector for the MS with the largest sum of channel power; detecting an MS for simultaneous signal transmission using the orthogonal beamforming vector; multiplying a signal to be transmitted to the MS with the largest sum of channel power by the beamforming vector; and multiplying a signal to be transmitted to the MS for simultaneous signal transmission by the orthogonal beamforming vector.