Coded MIMO With Asymmetric Constellation Sizes

An asymmetric constellation scheme for coded multiple-input–multiple-output (MIMO) transmission is proposed, which applies different constellation mappings to different transmit streams and carefully selects the coding rates for different transmit streams. An improved power allocation is derived to naturally incorporate with the coding rate selection and to further enhance the achievable performance. The proposed scheme provides more flexible choices of data rate selection, and by employing fixed-complexity sphere decoding (FSD) detection, it achieves better performance with reduced detection complexity in comparison with the conventional MIMO using the FSD-based detection with the same constellation set for all streams.