Soft versus Hard Interference Cancellation in MMSE OSIC MIMO Detector: A Comparative Study

There are two schemes to perform interference cancellation in soft-out minimum mean square error (MMSE) ordering successive interference cancellation (OSIC) detector for channel coded multiple-input multiple-output (MIMO) system, i.e., soft interference cancellation (SIC) and maximal likelihood (ML) hard decision based interference cancellation (HDIC). In this paper, we investigated these two schemes. At first, we discussed the basic principles of soft-output MMSE OSIC MIMO detector and proposed a reduced-complexity implementation. Then, based on the post-detection effective signal-to-interference and noise ratio (SINR) of MMSE filter at each detection stage, these two schemes are compared analytically. Finally, extensive simulations are performed to validate the analysis. The results show that the SIC based soft-output MMSE OSIC MIMO detector is superior to HDIC based one and all of them are much better than the MMSE detector and conventional MMSE OSIC detector, which assumes perfect interference cancellation.