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This paper deals with low maximum-likelihood (ML)-decoding complexity, full-rate and full-diversity space-time block codes (STBCs), which also offer large coding gain, for the 2 transmit antenna, 2 receive antenna (2 Ã 2) and the 4 transmit antenna, 2 receive antenna (4 Ã 2) MIMO systems. Presently, the best known STBC for the 2 Ã 2 system is the Golden code and that for the 4 Ã 2 system is the DjABBA code. Following the approach by Biglieri, Hong, and Viterbo, a new STBC is presented in this paper for the 2 Ã 2 system. This code matches the Golden code in performance and ML-decoding complexity for square QAM constellations while it has lower ML-decoding complexity with the same performance for non-rectangular QAM constellations. This code is also shown to be information-lossless and diversity-multiplexing gain (DMG) tradeoff optimal. This design procedure is then extended to the 4 Ã 2 system and a code, which outperforms the DjABBA code for QAM constellations with lower ML-decoding complexity, is presented. So far, the Golden code has been reported to have an ML-decoding complexity of the order of M 4 for square QAM of size M. In this paper, a scheme that reduces its ML-decoding complexity to M 2Â¿(M) is presented.
Selected Topics in Signal Processing, IEEE Journal of (Volume:3 , Issue: 6 )
Date of Publication: Dec. 2009