Space-time block codes (STBCs) is a known approach for using multiple transmit antennas to provide higher data rates and better reliability by exploiting spatial diversity. Existing STBCs use independent two-dimensional constellations. Methods and systems for using multidimensional constellations to improve the performance of orthogonal STBCs are disclosed. Methods for finding optimized multidimensional constellations for orthogonal STBCs are also disclosed.