@ARTICLE {19001,
author={N.S. Souto and M.  Ribeiro and P. Sebastião},
doi={10.1109/LSP.2016.2576640},
journal={IEEE Signal Processing Letters},
title={Semidefinite Relaxations for MIMO Transmissions With High-Order QAM Constellations},
year={2016},
month={July},
volume={23},
number={7},
pages={984-988},
ISSN={1070-9908}
}