Constellation Expansion Free Quasi-Orthogonal Space-Time Block Codes on Square Lattice Constellations with Full Diversity and High Coding Gains

This article presents a set of quasi-orthogonal spacetime block codes for four transmit antennas that achieves full diversity and high coding gain whenever a square lattice constellation is adopted. From the simulation results, the new designs perform very closely to quasi-orthogonal codes with constellation rotations. Without a search of the optimal rotation angle and any constellation expansion, our new codes yield an advantageous transmission scheme for QPSK and 16-QAM modulations.