An apparatus for transmitting packet data in a wireless communication system that receives channel status information between multiple transmission antennas (304 - 308) and multiple reception antennas (311 - 314) as feedback information, comprising: a feedback signal receiver for receiving a basis transform matrix indication information and a channel quality information, CQI, for each basis being fed back from each of a number K of receivers, where K is an integer larger than 0; a user classifier for classifying users having transmission data streams, the users preferring the same basis, into groups using preferred basis transform information output from the feedback signal receiver and classifying the transmission data streams according to the classified groups; a scheduling and demultiplexing block for receiving an output of the user classifier and the feedback information from the feedback signal receiver, for demultiplexing the transmission data streams into substreams, for selecting at least one of a group according to a priority of the group, for selecting at least one of a demultiplexed substream according to a priority of the substreams or a priority of the user, and for outputting the selected substream, per-basis adaptive modulation and coding, AMC, information for the selected substream, and power allocation information; an AMC block (504, 505) for modulating and coding the selected substream output from the scheduling and demultiplexing block according to the AMC information; a power allocator (506, 507) for allocating transmission power to the AMC-processed substream according to the power allocation information; and a transmitter for transmitting the power-allocated substream through each of the transmission antennas (304 - 308), wherein the transmitter is adapted to perform basis transform such that each substream is transmitted through the corresponding basis. a feedback signal receiver for receiving a basis transform matrix indication information and a channel quality information, CQI, for each basis being fed back from each of a number K of receivers, where K is an integer larger than 0; a user classifier for classifying users having transmission data streams, the users preferring the same basis, into groups using preferred basis transform information output from the feedback signal receiver and classifying the transmission data streams according to the classified groups; a scheduling and demultiplexing block for receiving an output of the user classifier and the feedback information from the feedback signal receiver, for demultiplexing the transmission data streams into substreams, for selecting at least one of a group according to a priority of the group, for selecting at least one of a demultiplexed substream according to a priority of the substreams or a priority of the user, and for outputting the selected substream, per-basis adaptive modulation and coding, AMC, information for the selected substream, and power allocation information; an AMC block (504, 505) for modulating and coding the selected substream output from the scheduling and demultiplexing block according to the AMC information; a power allocator (506, 507) for allocating transmission power to the AMC-processed substream according to the power allocation information; and a transmitter for transmitting the power-allocated substream through each of the transmission antennas (304 - 308), wherein the transmitter is adapted to perform basis transform such that each substream is transmitted through the corresponding basis.