A method of transmitting data by a multi-user multiple input multiple output (MU-MIMO) transmitter in a wireless local area network system. The method includes transmitting by the MU-MIMO transmitter, a physical layer convergence procedure (PLCP) protocol data unit (PPDU), the PPDU including a bundled interface field, a modulation and coding scheme (MCS) index field and a data field; and transmitting, by the MU-MIMO transmitter, the PPDU to a receiving station. The bundled interface field indicates a number of a plurality of spatial streams allocated to the receiving station. The MCS index field indicates a same MCS index used for modulating and coding all of the plurality of spatial streams indicated by the bundled interface field. The data field is modulated and coded by an MCS scheme indicated by the MCS index field and transmitted via the plurality of spatial streams indicated by the bundled interface field.