  This paper proposes a low decoding complexity, full-diversity and full-rate
space-time block code (STBC) for 4 transmit and 2 receive ($4\times 2$)
multiple-input multiple-output (MIMO) systems. For such systems, the best code
known is the DjABBA code and recently, Biglieri, Hong and Viterbo have proposed
another STBC (BHV code) which has lower decoding complexity than DjABBA but
does not have full-diversity like the DjABBA code. The code proposed in this
paper has the same decoding complexity as the BHV code for square QAM
constellations but has full-diversity as well. Compared to the best code in the
DjABBA family of codes, our code has lower decoding complexity, a better coding
gain and hence a better error performance as well. Simulation results
confirming these are presented.
