The invention relates to a sending method for multiple users requiring to transmit digital data over a frequency-selective channel with a plurality of send antennas and a plurality of receive antennas, characterized in that it applies to coded and interleaved data (d[n]): demultiplexing (105) into K channels, where K is strictly greater than the number T of send antennas, and modulation (107) of the demultiplexed data; internal linear coding (108) defined by an N×K generator matrix (W,Wn) where N is strictly greater than T, this internal coding being applied to the K-dimensional vectors of the modulated data. The invention also relates to a sending system for implementing said method.