IQ Space Frequency Time Codes for MIMO-OFDM Systems

In this paper, we study concatenated coding for MIMO-OFDM systems. The proposed concatenated system achieves full spatial and frequency diversity at much lower complexity in terms of number of states without any bandwidth expansion. In general, coding for MIMO-OFDM systems is known as space frequency time (SFT) coding. This paper focuses on applying a powerful class of trellis codes known as IQ-TCM. We illustrate the benefits of IQ-TCM in concatenated SFT codes. The results of this study show the performance improvements of IQ-TCM over conventional TCM at the same number of states and spectral efficiency. The reason for that is the larger effective length of IQ-TCM. Also, the simulation results emphasize the importance of an appropriate interleaver design since there is a great loss in performance and diversity if the block interleaver is not designed carefully