Embodiments of quasi-orthogonal space-time encoder, decoder and method for space-time encoding and decoding orthogonal frequency division multiplexed (OFDM) signals in a multiple-input multiple-output (MDMO) system are generally described herein. Other embodiments may be described and claimed. In some embodiments, a method of decoding received multicarrier signals comprises deriving objective functions from a received signal matrix, minimizing the objective functions to generate decoded hard bits, and solving a set of linear equations of the objective functions to generate decoded soft bits.