A communication system comprising: at least one first communication device configured to spatially multiplex a plurality of data signals and to transmit the plurality of data signals spatially multiplexed from a plurality of antennas; and a plurality of second communication devices configured to receive the plurality of data signals spatially multiplexed through an antenna, wherein the first communication device comprises: a determining unit configured to determine whether each of the plurality of second communication devices is a Tomlinson-Harashima Precoding, THP, -complaint second communication device which can perform a modulo arithmetic method on a received signal or non-THP-compliant second communication device which cannot perform the modulo arithmetic method, based on a received signal from each of the plurality of second communication devices, respectively; a converting device configured to perform equivalent conversion by applying a modulo arithmetic method or a vector perturbation method only on a data signal addressed to the THP-compliant second communication device; and a weighting device configured to cancel at least a part of interferences among the plurality of data signals spatially multiplexed by weighting the converted and non-converted signals by a weighting matrix generated based on a channel matrix between the first and second communication devices, wherein the weighting matrix is the Q matrix of a QR decomposition of the channel matrix if the modulo arithmetic method is performed and wherein the weighting matrix is the inverse of the channel matrix if the vector perturbation method is performed. at least one first communication device configured to spatially multiplex a plurality of data signals and to transmit the plurality of data signals spatially multiplexed from a plurality of antennas; and a plurality of second communication devices configured to receive the plurality of data signals spatially multiplexed through an antenna, wherein the first communication device comprises: a determining unit configured to determine whether each of the plurality of second communication devices is a Tomlinson-Harashima Precoding, THP, -complaint second communication device which can perform a modulo arithmetic method on a received signal or non-THP-compliant second communication device which cannot perform the modulo arithmetic method, based on a received signal from each of the plurality of second communication devices, respectively; a converting device configured to perform equivalent conversion by applying a modulo arithmetic method or a vector perturbation method only on a data signal addressed to the THP-compliant second communication device; and a weighting device configured to cancel at least a part of interferences among the plurality of data signals spatially multiplexed by weighting the converted and non-converted signals by a weighting matrix generated based on a channel matrix between the first and second communication devices, wherein the weighting matrix is the Q matrix of a QR decomposition of the channel matrix if the modulo arithmetic method is performed and wherein the weighting matrix is the inverse of the channel matrix if the vector perturbation method is performed. a determining unit configured to determine whether each of the plurality of second communication devices is a Tomlinson-Harashima Precoding, THP, -complaint second communication device which can perform a modulo arithmetic method on a received signal or non-THP-compliant second communication device which cannot perform the modulo arithmetic method, based on a received signal from each of the plurality of second communication devices, respectively; a converting device configured to perform equivalent conversion by applying a modulo arithmetic method or a vector perturbation method only on a data signal addressed to the THP-compliant second communication device; and a weighting device configured to cancel at least a part of interferences among the plurality of data signals spatially multiplexed by weighting the converted and non-converted signals by a weighting matrix generated based on a channel matrix between the first and second communication devices, wherein the weighting matrix is the Q matrix of a QR decomposition of the channel matrix if the modulo arithmetic method is performed and wherein the weighting matrix is the inverse of the channel matrix if the vector perturbation method is performed.