1. A method for space-time encoding multicarrier signals comprising: linearly transforming input symbols of a constellation set with a selected transformation matrix to generate linearly transformed symbols; forming a complex symbol for each of a plurality of transmit antennas from the linearly transformed symbols; forming code matrices from the complex symbols; and generating a quasi-orthogonal space-time matrix from the code matrices for use in generating multicarrier signals for transmission by the transmit antennas.