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For a turbo coded BLAST (Bell LAbs Space-Time architecture) system with Nt transmit antennas and Nr receive antennas, there is a significant gap between its detection threshold and the capacity in case Nt > Nr. In this paper, we show that by introducing a convolutional interleaver with block delay between the BLAST mapper and the turbo encoder, the threshold can be improved. Near-capacity thresholds can be achieved for some cases. To take advantage of the low detector complexity in Alamouti STBC (space-time block code), we also investigate a STBC system, which is the concatenation of the Alamouti STBC with a turbo trellis coded modulation. By using a proper labelling and adding a convolutional interleaver with block delay to such a STBC system, we achieve both lower error floors and lower thresholds.
Date of Publication: August 2009