Improved quasi-orthogonal space-time block codes with hexagonal lattice modulation

This paper addresses the improvement of performance of one class of quasi-orthogonal space-time block codes, for four transmit antennas, by taking the constituent code symbols from hexagonal lattices. This improvement is obtained over quasi-orthogonal block codes without constellation rotation. Due to full transmitter diversity there is similar performance to those codes with optimal constellation rotation, without the inherent constellation expansion occurred through the use of constellation rotated symbols. The improvement does not extend to other classes of quasi-orthogonal space-time block codes.