QPSK Balanced Space Time Trellis Codes

All 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. Introduction: The concept of space-time trellis codes (STTCs) was introduced by Tarokh et al. in [1]. Several design criteria to search the optimal STTCs have been proposed in [1, 2]. All the published codes which achieve the best performance have the same property : they use the points of the constellation with the same probability if the data are generated by a binary memoryless source with equally probable symbols. Therefore, we call these codes “Balanced STTC” (B-STTC). To overcome the difficulties of exhaustive codes search in terms of computer resources for a high number of transmit antennas and a high number of states of the encoder, the first method to design this new B-STTCs class 1 ha l-0 03 48 79 0, v er si on 1 22 D ec 2 00 8 Author manuscript, published in "Electronics Letters (2008) 983-985"