Random Binary Phase Offset Scheme for CDD Based MIMO-OFDM System

In this paper, random binary phase offsets are induced into the transmitting symbols to mitigate the spatial correlation effects in a cyclic delay diversity (CDD) based MIMO-OFDM system. Our analysis reveals that depending on the channel spatial correlation, some of the sub-carriers have substantially lower average capacity than others and may, therefore, deteriorate the system performance. In such cases, the proposed scheme enables those sub-carriers to recover from correlation effects and reinstates all the sub-carriers with the same upper bound of the average capacity as offered by the uncorrelated channel. Our analysis of pairwise error probability (PEP) demonstrates the effects of spatial correlation on the squared Euclidean distance between any two codewords and shows how the proposed scheme mitigates those effects without the knowledge of the channel spatial correlation. We observe in simulation that depending on the channel spatial correlation, our proposed scheme can yield a dramatic performance improvement.