Quasi-Orthogonal Space-Frequency Block Codes for MIMO OFDM Channels

In this paper, we propose a novel class of Space-Frequency and Space-Time-Frequency block codes based on Quasi-Orthogonal designs, over a frequency selective Rayleigh fading channel. The proposed codes are able to achieve rate one and full diversity by exploiting the space and multipath diversity gains available in the MIMO-OFDM channel. As the simulation results show, our codes outperform the existing Space-Frequency block codes in terms of bit error rate performance. Additionally, the proposed Space-Time-Frequency code benefits from a reduced maximum likelihood decoding complexity, which is a huge simplification compared to the existing codes. We also discuss the conditions under which the maximum likelihood decoding for our proposed Quasi-Orthogonal Space-Frequency code is simplified as well.