Differential unitary space-time-frequency coding for MIMO OFDM systems

Incorporating subcarrier grouping and differential unitary space-time modulation, we develop a differential unitary space-time-frequency (DUSTF) coding scheme for MIMO OFDM systems over frequency selective fading channels. We derive the design criteria for the DUSTF codes to maximize diversity advantage and coding advantage. We adopt Abelian group codes and show that for DUSTF coded MIMO OFDM systems with M/sub T/ transmit antennas and L resolvable multipaths in the channel, the optimal Abelian group in the sense of maximizing the coding advantage is actually the optimal Abelian group for a flat fading channel with M/sub T/L transmit antennas with the same rate. Simulation results are given to show the merits of the proposed scheme.