A Low ML-Decoding Complexity, High Coding Gain, Full-Rate, Full-Diversity STBC for 4 × 2 MIMO System

This paper proposes a full-rate, full-diversity spacetime block code (STBC) with low maximum likelihood (ML) decoding complexity and high coding gain for the 4 transmit antenna, 2 receive antenna (4×2) multiple-input multiple-output (MIMO) system that employs 4/16-QAM. For such a system, the best code known is the DjABBA code and recently, Biglieri, Hong and Viterbo have proposed another STBC (BHV code) for 4-QAM which has lower ML-decoding complexity than the DjABBA code but does not have full-diversity like the DjABBA code. The code proposed in this paper has the same ML-decoding complexity as the BHV code for any square M -QAM but has fulldiversity for 4and 16-QAM. Compared with the DjABBA code, the proposed code has lower ML-decoding complexity for square M -QAM constellation, higher coding gain for 4and 16-QAM, and hence a better codeword error rate (CER) performance. Simulation results confirming this are presented.