A distributed space-time coding method for a UWB pulse telecommunication system, wherein a source terminal transmits a signal to a destination terminal during a transmission interval constituted by K frames, K≧1, each frame being divided into a first and a second half-frame, the signal transmitted in each first half-frame being received, then retransmitted after amplification during the next second half-frame by a distinct relay terminal among K relay terminals of the system. The source terminal codes 4K data symbols belonging to a PPM modulation alphabet or a composite PPM-PAM modulation alphabet including a plurality of time positions, to provide a sequence of four transmission symbols per frame, the transmission symbols being obtained from 4K linear combinations of the data symbols using a plurality of coefficients belonging to a real algebraic extension of degree 2K of the field of rational numbers and, for one of the transmission symbols, a permutation of its PPM components.