The present invention relates to a transmission method for a transmitter having Nt transmit antennas. The method (1) spreads symbols in two dimensions by means of a spreading code, the symbols coming from a signal for transmission over Nfft sub-carriers via the Nt transmit antennas. The signal is transmitted with a power pem(k) that is determined per symbol m, per user k=1, . . . , Nu, and per transmit antenna. The principle of the method (1) is to determine (2) a set of powers pem(k) that is constant over a symbol frame, with the distribution of power amongst the users minimizing an overall error criterion under the constraint that the sum of the powers pem(k) in the set is equal to the product of the number of users multiplied by the average power emitted per symbol over the users.