A transceiving system using a joined modulation alphabet A having a size M the symbols of which are distributed on a plurality N of orthogonal dimensions, the symbols carried by a dimension belonging to a linear sub-alphabet An having a size P, with M=NP. The transmitter performs a turbocoding of a block of information bits, the code words provided by the turbocoder being mapped to symbols of the joined modulation alphabet before modulating the signal to be transmitted. The receiver performs turbodecoding from the projection of the symbols received on the orthogonal dimensions of the alphabet.