Add to ORKGInternational audienceAll the best known space-time trellis codes (STTCs) belong to the Balanced STTCs class. The first method to design balanced STTCs is proposed in this letter. The exhaustive code search of optimal codes can then be reduced to this class. Finally, the proposed method is used to construct new QPSK codes for 3 and 4 transmit antennas which outperform the best previously published codes of the same complexity